Exchange of matters, energies and termoregulation. Role Exchange of matters, energies and termoregulation. Role of cavity of mouth in these reactions. State of hunger, of cavity of mouth in these reactions. State of hunger,

appetite and satiation.appetite and satiation.

The absorbed materialsThe absorbed materials

Digested molecules of food, water Digested molecules of food, water and minerals from the diet, are and minerals from the diet, are absorbed from the cavity of the absorbed from the cavity of the upper small intestine. upper small intestine. The absorbed materials cross the The absorbed materials cross the mucosa into the blood, and are mucosa into the blood, and are carried off in the bloodstream to carried off in the bloodstream to other parts of the body for storage or other parts of the body for storage or further chemical change.further chemical change.

ProteinProtein

Foods such as meat, eggs, and beans consist of Foods such as meat, eggs, and beans consist of large molecules of protein that must be digested large molecules of protein that must be digested by enzymes before they can be used to build and by enzymes before they can be used to build and repair body tissues. repair body tissues.

Digestion of proteinsDigestion of proteins

An enzyme in the juice of the stomach starts the An enzyme in the juice of the stomach starts the digestion of swallowed protein. Further digestion digestion of swallowed protein. Further digestion of the protein is completed in the small intestine. of the protein is completed in the small intestine. Here, several enzymes from the pancreatic juice Here, several enzymes from the pancreatic juice and the lining of the intestine carry out the and the lining of the intestine carry out the breakdown of huge protein molecules into small breakdown of huge protein molecules into small molecules called amino acids. molecules called amino acids. These small molecules can be absorbed from the These small molecules can be absorbed from the hollow of the small intestine into the blood and hollow of the small intestine into the blood and then be carried to all parts of the body to build then be carried to all parts of the body to build the walls and other parts of cells.the walls and other parts of cells.

Protein MetabolismProtein Metabolism

The first step in protein metabolism is to break it into The first step in protein metabolism is to break it into its constituent amino acids. These are absorbed into its constituent amino acids. These are absorbed into the blood stream. the blood stream. The second step is to break down the amino acids The second step is to break down the amino acids into their constituent parts - catabolism. This into their constituent parts - catabolism. This removes the nitrogen or amino group from the removes the nitrogen or amino group from the amino acids. The process is called deamination. amino acids. The process is called deamination. Deamination breaks the amino group down into Deamination breaks the amino group down into ammonia and what is termed the carbon skeleton. ammonia and what is termed the carbon skeleton. Ammonia is converted to urea, filtered through the Ammonia is converted to urea, filtered through the kidneys, and excreted in urine. The carbon skeleton--kidneys, and excreted in urine. The carbon skeleton--which is composed of carbon, hydrogen, and which is composed of carbon, hydrogen, and oxygen--can then by used either for protein oxygen--can then by used either for protein synthesis, energy production (ATP), or converted to synthesis, energy production (ATP), or converted to glucose by gluconeogenesis. glucose by gluconeogenesis.

Amino acids stimulate the release of Amino acids stimulate the release of both glucagon and insulinboth glucagon and insulin

In a healthy person, a rise in blood amino In a healthy person, a rise in blood amino acid concentration stimulates the acid concentration stimulates the secretion of both glucagon and insulin, so secretion of both glucagon and insulin, so their blood sugar remains stable. their blood sugar remains stable. The insulin is secreted to stimulate protein The insulin is secreted to stimulate protein synthesis - the uptake of amino acids into synthesis - the uptake of amino acids into muscle cells - making them less available muscle cells - making them less available for gluconeogenesis. The glucagon is for gluconeogenesis. The glucagon is secreted to stimulate the uptake of amino secreted to stimulate the uptake of amino acids into the cells of the liver for acids into the cells of the liver for gluconeogenesis. gluconeogenesis.

Why are these two hormones battling for Why are these two hormones battling for opposing uses of the same amino acids? opposing uses of the same amino acids?

Isn't that non-productive?Isn't that non-productive?

Actually, the phenomenon serves an important Actually, the phenomenon serves an important purpose. The release of these two opposing purpose. The release of these two opposing hormones ensures that the amino acids are used hormones ensures that the amino acids are used for protein synthesis (because of the extra for protein synthesis (because of the extra insulin) but the blood sugar doesn't drop to insulin) but the blood sugar doesn't drop to dangerously low levels, even if the meal was low dangerously low levels, even if the meal was low in carbohydrate. in carbohydrate. As a result, blood glucose concentration remains As a result, blood glucose concentration remains reasonably stable during protein metabolism. reasonably stable during protein metabolism. The insulin and glucagon essentially cancel each The insulin and glucagon essentially cancel each other out in terms of their effect on blood other out in terms of their effect on blood glucose, while the insulin is still able to promote glucose, while the insulin is still able to promote protein synthesis. protein synthesis.

Protein digestibilityProtein digestibility

An important aspect of protein metabolism is how An important aspect of protein metabolism is how well or how poorly a given protein is digested by the well or how poorly a given protein is digested by the human body. Claims are sometimes made that human body. Claims are sometimes made that protein powders (especially predigested or protein powders (especially predigested or hydrolyzed proteins) are digested more efficiently hydrolyzed proteins) are digested more efficiently than whole food proteins. than whole food proteins. Protein digestibility is measured by seeing how much Protein digestibility is measured by seeing how much nitrogen is excreted in the feces compared to the nitrogen is excreted in the feces compared to the amount of nitrogen which is ingested. A correction is amount of nitrogen which is ingested. A correction is made for the amount of nitrogen which is normally made for the amount of nitrogen which is normally lost in the feces. Therefore, digestibility research lost in the feces. Therefore, digestibility research examines how much more nitrogen is lost over examines how much more nitrogen is lost over normal levels when a given protein is fed.normal levels when a given protein is fed.If an individual were fed 6,25 grams of protein, 1 If an individual were fed 6,25 grams of protein, 1 gram of nitrogen was excreted in the feces.gram of nitrogen was excreted in the feces.

Digestibility of common Digestibility of common

proteins foodsproteins foods

Food sourceFood source Protein digestibility (%)Protein digestibility (%)

EggEgg 9797

Milk and cheeseMilk and cheese 9797

Mixed US dietMixed US diet 9696

Peanut butterPeanut butter 9595

Meat and fishMeat and fish 9494

Whole wheatWhole wheat 8686

OatmealOatmeal 8686

SoybeansSoybeans 7878

RiceRice 7676

Protein qualityProtein quality

Protein quality is a topic of major debate, both in Protein quality is a topic of major debate, both in the research world, as well as in the realm of the research world, as well as in the realm of protein supplements. Arguments have been made protein supplements. Arguments have been made that one protein is of higher quality than another, that one protein is of higher quality than another, or that protein powders are superior to whole or that protein powders are superior to whole food protein. food protein. Protein quality refers, in a general sense, to how Protein quality refers, in a general sense, to how well or poorly a given protein will be used by the well or poorly a given protein will be used by the body. body. More specifically, it refers to how well the More specifically, it refers to how well the indispensable amino acid (AA) profile of a protein indispensable amino acid (AA) profile of a protein matches the requirements of the body. However, matches the requirements of the body. However, this should not suggest that the content of this should not suggest that the content of dispensable AAs in a protein is irrelevant to dispensable AAs in a protein is irrelevant to protein quality as the body. protein quality as the body.

Methods of measuring Methods of measuring protein qualityprotein quality

There most spread methods available to measure There most spread methods available to measure protein quality are: chemical score, biological protein quality are: chemical score, biological value, protein efficiency ratio, and protein value, protein efficiency ratio, and protein digestibility corrected amino acid score.digestibility corrected amino acid score.The quality of a protein is directly related to the The quality of a protein is directly related to the physiological needs of the subject being studied.physiological needs of the subject being studied.Diet and activity can affect how AAs are used in Diet and activity can affect how AAs are used in the body. For example, long-duration endurance the body. For example, long-duration endurance activity tends to oxidize high quantities of the activity tends to oxidize high quantities of the branch-chain amino acids (BCAAs). In all branch-chain amino acids (BCAAs). In all likelihood, there is no single protein that can be likelihood, there is no single protein that can be rated as the highest quality for all situations.rated as the highest quality for all situations.

Chemical scoreChemical score

Chemical score is method of rating proteins based on it's Chemical score is method of rating proteins based on it's chemical composition (more specifically it's indispensable AA chemical composition (more specifically it's indispensable AA levels). To determine chemical score, a protein is picked as a levels). To determine chemical score, a protein is picked as a reference and other proteins are rated relative to that reference and other proteins are rated relative to that reference protein. reference protein. Typically, egg protein has been used as the reference protein, Typically, egg protein has been used as the reference protein, but this assumes that the amino acid profile of egg is the ideal but this assumes that the amino acid profile of egg is the ideal for humans. for humans. Since chemical score is a relative, and not an absolute scale, it Since chemical score is a relative, and not an absolute scale, it is possible to have values greater than 100. If 5 grams of the is possible to have values greater than 100. If 5 grams of the reference protein contains 800 mg of a certain amino acid, and reference protein contains 800 mg of a certain amino acid, and 5 grams of the test protein contains 1000 mg of that same 5 grams of the test protein contains 1000 mg of that same amino acid, the second protein would be rated as 125% for amino acid, the second protein would be rated as 125% for that amino acid.that amino acid.The chemical score has little to do with how a food protein will The chemical score has little to do with how a food protein will be used in the body and is rarely the only measure of protein be used in the body and is rarely the only measure of protein quality used to rate a protein.quality used to rate a protein.

Biological value (BV)Biological value (BV)

Biological value (BV) is probably one of the most commonly Biological value (BV) is probably one of the most commonly used measures of a protein's quality. The BV of a protein is used measures of a protein's quality. The BV of a protein is given as the amount of nitrogen retained in the body given as the amount of nitrogen retained in the body divided by the amount of nitrogen absorbed from that divided by the amount of nitrogen absorbed from that protein. Therefore, digestibility of that protein is taken into protein. Therefore, digestibility of that protein is taken into account. Thus:account. Thus:BV = (nitrogen retained / nitrogen absorbed) * 100 %BV = (nitrogen retained / nitrogen absorbed) * 100 %A BV of 100 would indicate complete utilization of a given A BV of 100 would indicate complete utilization of a given dietary protein, in that 100% of the protein ingested was dietary protein, in that 100% of the protein ingested was stored in the body with none lost.stored in the body with none lost.To measure BV, subjects are typically fed a zero protein To measure BV, subjects are typically fed a zero protein diet so that baseline losses of nitrogen can be measured diet so that baseline losses of nitrogen can be measured (i.e. the amount of nitrogen that is lost normally). Then the (i.e. the amount of nitrogen that is lost normally). Then the test protein is fed at varying levels (generally 0.6, 0.5, 0.4 test protein is fed at varying levels (generally 0.6, 0.5, 0.4 and 0.3 g/kg are fed) and a nitrogen balance study is done. and 0.3 g/kg are fed) and a nitrogen balance study is done. Some studies use longer periods of starvation and this is an Some studies use longer periods of starvation and this is an important consideration in evaluating the data.important consideration in evaluating the data.

BV of some BV of some common common proteinsproteins

Table 2 presents the BV of Table 2 presents the BV of some common proteins.some common proteins.Considering the high protein Considering the high protein intakes of most strength intakes of most strength athletes (2.0 g/kg or higher) athletes (2.0 g/kg or higher) it is hard to see how BV will it is hard to see how BV will play a meaningful role in play a meaningful role in rating proteins in this rating proteins in this population. In all likelihood, population. In all likelihood, any decent quality protein any decent quality protein will be as good as any other will be as good as any other at these types of protein at these types of protein intakes. intakes.

ProteinProtein BVBV

wheywhey 100100

eggegg 100100

milkmilk 9393

ricerice 8686

casein, casein, fish and fish and beefbeef

7575

corncorn 7272

peanut peanut flourflour

5656

wheat wheat glutengluten

4444

Protein efficiency ratio (PER)Protein efficiency ratio (PER)

PER is sometimes used to rate proteins and PER is sometimes used to rate proteins and represents the amount of weight gained (in grams) represents the amount of weight gained (in grams) relative the amount of protein consumed (in grams). relative the amount of protein consumed (in grams). For example, a PER of 2.5 would mean that 2.5 grams For example, a PER of 2.5 would mean that 2.5 grams of weight was gained for every gram of protein of weight was gained for every gram of protein ingested. ingested. A recent animal study found that combinations of A recent animal study found that combinations of animal (30% of total) and plant based proteins (70% animal (30% of total) and plant based proteins (70% of total) had a higher PER value than the animal or of total) had a higher PER value than the animal or vegetable proteins eaten alone. This may have to do vegetable proteins eaten alone. This may have to do with the proteins 'combining' to decrease the impact with the proteins 'combining' to decrease the impact of the limiting AA. of the limiting AA. Individuals who wish to decrease their intake of Individuals who wish to decrease their intake of animal-based proteins may be able to achieve higher animal-based proteins may be able to achieve higher PER values with a combination of animal and plant PER values with a combination of animal and plant based proteins than someone eating only animal based proteins than someone eating only animal based proteins.based proteins.

Protein digestibility corrected Protein digestibility corrected amino acid score (PDCAAS)amino acid score (PDCAAS)

PDCAAS is the newest method of protein quality to PDCAAS is the newest method of protein quality to be developed. It has also been suggested as the be developed. It has also been suggested as the ideal scale to rate proteins for their ability to meet ideal scale to rate proteins for their ability to meet human requirements. Similar to chemical score, it human requirements. Similar to chemical score, it rates protein foods relative to a given reference rates protein foods relative to a given reference protein. In this case, the AA profile used is that one protein. In this case, the AA profile used is that one determined to be ideal for children two to five years determined to be ideal for children two to five years old as its reference protein for adults. old as its reference protein for adults. Using the PDCAAS method, along with the proposed Using the PDCAAS method, along with the proposed AA reference patter, proteins which were previously AA reference patter, proteins which were previously rated at poor quality, such as soy, have obtained rated at poor quality, such as soy, have obtained higher quality ratings. This is more in line with higher quality ratings. This is more in line with studies showing that certain purified soy proteins, studies showing that certain purified soy proteins, such as Supro (tm) which is found in Twinlab Vege-such as Supro (tm) which is found in Twinlab Vege-fuel, can maintain adults in nitrogen balance. fuel, can maintain adults in nitrogen balance.

Summary of protein Summary of protein qualityquality

Although a variety of methods of measuring protein Although a variety of methods of measuring protein quality have been proposed, none are perfect in rating quality have been proposed, none are perfect in rating proteins for human use. While some methods of rating proteins for human use. While some methods of rating protein are based on how well (or poorly) an animal protein are based on how well (or poorly) an animal grows (or the nitrogen balance which is attained), grows (or the nitrogen balance which is attained), these methods provide no information on specific these methods provide no information on specific amino acid requirements or protein synthesis at a amino acid requirements or protein synthesis at a given tissue. Rather, only data regarding growth in the given tissue. Rather, only data regarding growth in the whole body are obtained.whole body are obtained.Another strategy to rate proteins is to compare the AA Another strategy to rate proteins is to compare the AA profile in food protein to some reference protein. profile in food protein to some reference protein. Previously, food proteins such as egg or milk were Previously, food proteins such as egg or milk were used as a reference but there has been a recent move used as a reference but there has been a recent move toward the use of an idealized reference pattern of toward the use of an idealized reference pattern of AAs to rate proteins. This assumes that the true AAs to rate proteins. This assumes that the true requirements for a given AA are known.requirements for a given AA are known.

CarbohydratesCarbohydratesAn average American adult eats about half a An average American adult eats about half a pound of carbohydrate each day. Some of our pound of carbohydrate each day. Some of our most common foods contain mostly most common foods contain mostly carbohydrates. Examples are bread, potatoes, carbohydrates. Examples are bread, potatoes, pastries, candy, rice, spaghetti, fruits, and pastries, candy, rice, spaghetti, fruits, and vegetables. Many of these foods contain both vegetables. Many of these foods contain both starch, which can be digested, and fiber, which starch, which can be digested, and fiber, which the body cannot digest.the body cannot digest.The digestible carbohydrates are broken into The digestible carbohydrates are broken into simpler molecules by enzymes in the saliva, in simpler molecules by enzymes in the saliva, in juice produced by the pancreas, and in the lining juice produced by the pancreas, and in the lining of the small intestine. Glucose and other of the small intestine. Glucose and other monocaccharides is carried through the monocaccharides is carried through the bloodstream to the liver, where it is stored or bloodstream to the liver, where it is stored or used to provide energy for the work of the body.used to provide energy for the work of the body.

Fates of dietary glucoseFates of dietary glucose

The major source of dietary carbohydrate for humans The major source of dietary carbohydrate for humans is is starchstarch from consumed plant material. This is from consumed plant material. This is supplemented with a small amount of supplemented with a small amount of glycogenglycogen from from animal tissue, animal tissue, disaccharidesdisaccharides such as sucrose from such as sucrose from products containing refined sugar and lactose in milk. products containing refined sugar and lactose in milk. Digestion in the gut converts all carbohydrate to Digestion in the gut converts all carbohydrate to monosaccharides which are transported to the liver monosaccharides which are transported to the liver and converted to glucose. The liver has a central role and converted to glucose. The liver has a central role in the storage and distribution within the body of all in the storage and distribution within the body of all fuels, including glucose. fuels, including glucose. Glucose in the body undergoes one of three metabolic Glucose in the body undergoes one of three metabolic fates: it is catabolised to produce fates: it is catabolised to produce ATPATP; ; it is stored as it is stored as glycogen in liver and muscleglycogen in liver and muscle; ; it is converted to it is converted to fattyfatty acidsacids. . Once converted to fatty acids, these are stored Once converted to fatty acids, these are stored in adipose tissue as in adipose tissue as triglyceridestriglycerides..

Extracting Energy from Extracting Energy from GlucoseGlucose

Two different pathways are involved in the Two different pathways are involved in the metabolism of glucose: one anaerobic and one metabolism of glucose: one anaerobic and one aerobic. aerobic. The anaerobic process occurs in the cytoplasm The anaerobic process occurs in the cytoplasm and is only moderately efficient. and is only moderately efficient. The aerobic cycle takes place in the mitochondria The aerobic cycle takes place in the mitochondria and is results in the greatest release of energy. and is results in the greatest release of energy. As the name implies, though, it requires oxygen. As the name implies, though, it requires oxygen.

Anaerobic MetabolismAnaerobic Metabolism

Glucose in the bloodstream diffuses into the Glucose in the bloodstream diffuses into the cytoplasm and is locked there by cytoplasm and is locked there by phosphorylation. A glucose molecule is then phosphorylation. A glucose molecule is then rearranged slightly to fructose and rearranged slightly to fructose and phosphorylated again to fructose diphosphate. phosphorylated again to fructose diphosphate. These steps actually require energy, in the form These steps actually require energy, in the form of two ATPs per glucose. The fructose is then of two ATPs per glucose. The fructose is then cleaved to yield two glyceraldehyde phosphates cleaved to yield two glyceraldehyde phosphates (GPs). (GPs). Finally, two more ATPs are produced as the Finally, two more ATPs are produced as the phosphoglycerates are oxidized to pyruvate. phosphoglycerates are oxidized to pyruvate.

Aerobic Aerobic MetabolismMetabolism

Pyruvate is the Pyruvate is the starting starting molecule for molecule for oxidative oxidative phosphorylation phosphorylation via the Krebb's via the Krebb's or citric acid or citric acid cycle. cycle. In this process, In this process, all of the C-C all of the C-C and C-H bonds and C-H bonds of the pyruvate of the pyruvate will be will be transferred to transferred to oxygen. oxygen.

Summary of Summary of metabolism of glucosemetabolism of glucose

Basically, the pyruvate is Basically, the pyruvate is oxidized to acetyl coenzyme oxidized to acetyl coenzyme A, which can then bind with A, which can then bind with the four carbon oxaloacetate the four carbon oxaloacetate to generate a six carbon to generate a six carbon citrate. citrate. Carbons and hydrogens are Carbons and hydrogens are gradually cleaved from this gradually cleaved from this citrate until all that remains citrate until all that remains is the four carbon is the four carbon oxaloacetate we started oxaloacetate we started with. In the process, four with. In the process, four NADHsNADHs, one FADH and one , one FADH and one GTP are generated for each GTP are generated for each starting pyruvate. starting pyruvate.

AnaerobicAnaerobic

ConsumedConsumed::

2 ATP2 ATP

Produced:Produced: 8 ATP8 ATP

Net:Net: 6 ATP6 ATP

AerobicAerobic

ConsumeConsumed:d: 0 ATP0 ATP

Produced:Produced: 2x 15 ATP2x 15 ATP

Net:Net: 30 ATP30 ATP

GluconeogenesisGluconeogenesis

The process of conversion of lactate to The process of conversion of lactate to glucose is called gluconeogenesis, uses glucose is called gluconeogenesis, uses some of the reactions of glycolysis (but in some of the reactions of glycolysis (but in the reverse direction) and some reactions the reverse direction) and some reactions unique to this pathway to re-synthesise unique to this pathway to re-synthesise glucose. glucose. This pathway requires an energy input (as This pathway requires an energy input (as ATP) but hasATP) but has, due to kidneys,, due to kidneys, the role of the role of maintaining a circulating glucose maintaining a circulating glucose concentration in the bloodstream (even in concentration in the bloodstream (even in the absence of dietary supply) and also the absence of dietary supply) and also maintaining a glucose supply to fast twitch maintaining a glucose supply to fast twitch muscle fibres. muscle fibres.

FatsFats

Fat molecules are a rich source of energy for Fat molecules are a rich source of energy for the body. The first step in digestion of a fat is the body. The first step in digestion of a fat is to dissolve it into the watery content of the to dissolve it into the watery content of the intestinal cavity. intestinal cavity.

Fat digestionFat digestion

The bile acids produced by the liver act as natural The bile acids produced by the liver act as natural detergents to dissolve fat in water and allow the detergents to dissolve fat in water and allow the enzymes to break the large fat molecules into smaller enzymes to break the large fat molecules into smaller molecules, some of which are fatty acids and molecules, some of which are fatty acids and cholesterol. The bile acids combine with the fatty cholesterol. The bile acids combine with the fatty acids and cholesterol and help these molecules to acids and cholesterol and help these molecules to move into the cells of the mucosa. In these cells the move into the cells of the mucosa. In these cells the small molecules are formed back into large molecules, small molecules are formed back into large molecules, most of which pass into vessels (called lymphatics) most of which pass into vessels (called lymphatics) near the intestine. near the intestine. These small vessels carry the reformed fat to the These small vessels carry the reformed fat to the veins of the chest, and the blood carries the fat to veins of the chest, and the blood carries the fat to liver and than to storage depots in different parts of liver and than to storage depots in different parts of the body.the body.

Fat metabolism and Fat metabolism and gluconeogenesisgluconeogenesis

Fatty acids cannot be used directly to Fatty acids cannot be used directly to produce glucose. However, gycerol, a produce glucose. However, gycerol, a product of fat metabolism, can and does product of fat metabolism, can and does go through the gluconeogenic pathway to go through the gluconeogenic pathway to produce glucose. Glycerol is a minor produce glucose. Glycerol is a minor component in fats, and accounts for only 9 component in fats, and accounts for only 9 to 15% of the total mass. to 15% of the total mass. Fats are much less important than proteins Fats are much less important than proteins in the gluconeogenic processin the gluconeogenic process

Vitamins, water and saltVitamins, water and salt

Another important part of our food that is absorbed Another important part of our food that is absorbed from the small intestine is the class of chemicals we from the small intestine is the class of chemicals we call vitamins. There are two different types of call vitamins. There are two different types of vitamins, classified by the fluid in which they can be vitamins, classified by the fluid in which they can be dissolved:water-soluble vitamins (all the B vitamins dissolved:water-soluble vitamins (all the B vitamins and vitamin C) and fat-soluble vitamins (vitamins A, D, and vitamin C) and fat-soluble vitamins (vitamins A, D, and K).and K).Most of the material absorbed from the cavity of the Most of the material absorbed from the cavity of the small intestine is water in which salt is dissolved. The small intestine is water in which salt is dissolved. The salt and water come from the food and liquid we salt and water come from the food and liquid we swallow and the juices secreted by the many digestive swallow and the juices secreted by the many digestive glands. In a healthy adult, more than a gallon of water glands. In a healthy adult, more than a gallon of water containing over an ounce of salt is absorbed from the containing over an ounce of salt is absorbed from the intestine every 24 hours.intestine every 24 hours.

Oxydation and ATPOxydation and ATP

Food energy is released through a chemical reaction with Food energy is released through a chemical reaction with oxygen in a process called oxidation. When this occurs oxygen in a process called oxidation. When this occurs outside the body - for example the burning of oil (a fat) in a outside the body - for example the burning of oil (a fat) in a lamp or the use of a flaming sugar cube (a carbohydrate) as lamp or the use of a flaming sugar cube (a carbohydrate) as a decoration in a dessert - this energy is released as heat a decoration in a dessert - this energy is released as heat and light. In the body however, food energy needs to be and light. In the body however, food energy needs to be released more slowly and in a form that can be harnessed released more slowly and in a form that can be harnessed for basic cell functions and transformed into mechanical for basic cell functions and transformed into mechanical movement by the muscle cells. movement by the muscle cells. This is accomplished by "refining" the three basic food This is accomplished by "refining" the three basic food materials (carbohydrate, fat, and protein), converting them materials (carbohydrate, fat, and protein), converting them into a single common chemical compound adenosine into a single common chemical compound adenosine triphosphate (ATP). It is this ATP, synthesized as the cell triphosphate (ATP). It is this ATP, synthesized as the cell metabolizes (or breaks down) these three basic foods that metabolizes (or breaks down) these three basic foods that transfers the energy content of all foods to muscle action. transfers the energy content of all foods to muscle action.

Isodinamia of substancesIsodinamia of substances

The energy contained in equal weights of The energy contained in equal weights of carbohydrate, fat, and protein is not the same. carbohydrate, fat, and protein is not the same. Energy content is measured in Calories. Energy content is measured in Calories. Carbohydrates and protein both contain 4.1 Carbohydrates and protein both contain 4.1 Calories per gram (120 Calories per ounce) while Calories per gram (120 Calories per ounce) while the energy "density" of fat is more than double at the energy "density" of fat is more than double at 9 Calories per gram. 9 Calories per gram. The disadvantage of fat as a fuel for exercise is The disadvantage of fat as a fuel for exercise is that it is metabolized through pathways that that it is metabolized through pathways that differ from carbohydrates and can only support differ from carbohydrates and can only support an exercise level equivalent to 50% VO2 max. It an exercise level equivalent to 50% VO2 max. It is an ideal fuel for endurance events, but is an ideal fuel for endurance events, but unacceptable for high level aerobic (or sprint) unacceptable for high level aerobic (or sprint) type activities. type activities.

Energy Requirements Energy Requirements for Daily Activitiesfor Daily Activities

An average man of 70 kilograms who lies in bed all day uses An average man of 70 kilograms who lies in bed all day uses about 1650 Calories of energy. The process of eating and about 1650 Calories of energy. The process of eating and digesting food increases the amount of energy used each day by digesting food increases the amount of energy used each day by an additional 200 or more Calories, so that the same man lying in an additional 200 or more Calories, so that the same man lying in bed and eating a reasonable diet requires a dietary intake of bed and eating a reasonable diet requires a dietary intake of aboul 1850 Calories per day. If he sits in a chair all day without aboul 1850 Calories per day. If he sits in a chair all day without exercising, his total energy requirement reaches 2000 to 2250 exercising, his total energy requirement reaches 2000 to 2250 Calories. Therefore, the approximate daily en- ergy requirement Calories. Therefore, the approximate daily en- ergy requirement for a very sedentary man performing only essential functions is for a very sedentary man performing only essential functions is 2000 Calories. 2000 Calories. The amount of energy used to perform daily physical activi- ties The amount of energy used to perform daily physical activi- ties is normally about 25 per cent of the total energy expendi- ture, is normally about 25 per cent of the total energy expendi- ture, but it can vary markedly in different individuals, depend- ing on but it can vary markedly in different individuals, depend- ing on the types and amounts of physical activities. For example, the types and amounts of physical activities. For example, walking up stairs requires about 17 times as much energy as walking up stairs requires about 17 times as much energy as lying in bed asleep. In general, over a 24-hour period, a person lying in bed asleep. In general, over a 24-hour period, a person performing heavy labor can achieve a maxi- mal rate of energy performing heavy labor can achieve a maxi- mal rate of energy utilization as great as 6000 to 7000 Calo- ries, or as much as 3.5 utilization as great as 6000 to 7000 Calo- ries, or as much as 3.5 times the energy used under conditions of no physical activity.times the energy used under conditions of no physical activity.

Notion about basal Notion about basal metabolismmetabolism

Physiology of temperature Physiology of temperature regulation and water-solt balanceregulation and water-solt balance

Poikilothermic Poikilothermic and and

homeothermic homeothermic organismsorganisms

Invertebrates generally Invertebrates generally cannot adjust their body cannot adjust their body temperatures and so are at temperatures and so are at the mercy of the the mercy of the environment. In vertebrates, environment. In vertebrates, mechanisms for maintaining mechanisms for maintaining body temperature by body temperature by adjusting heat production and adjusting heat production and heat loss have evolved. These heat loss have evolved. These species are called "cold-species are called "cold-blooded" blooded" (poikilothermic)(poikilothermic) because their body because their body temperature fluctuates over a temperature fluctuates over a considerable range. considerable range. In birds and mammals , the ' In birds and mammals , the ' 'warm-blooded ' ''warm-blooded ' ' (homeothermic)(homeothermic) animals, a animals, a group of reflex responses that group of reflex responses that are primarily integrated in the are primarily integrated in the hypothalamus operate to hypothalamus operate to maintain body temperature maintain body temperature within a narrow range in spite within a narrow range in spite of wide fluctuations in of wide fluctuations in environmental temperature. environmental temperature.

Temperature Temperature balancebalance

The balance betweenThe balance between heat heat production and heat loss is production and heat loss is continuously beingcontinuously being disturbed, disturbed, either by changes in either by changes in metabolic rate (exercisemetabolic rate (exercise being the most powerful being the most powerful influence) or by changesinfluence) or by changes in in the external environment that the external environment that alter heat loss or gain.alter heat loss or gain. The resulting changes in body The resulting changes in body temperature are detectedtemperature are detected by by thermoreceptors, which thermoreceptors, which initiate reflexes thatinitiate reflexes that change change the output of various effectors the output of various effectors so that heat productionso that heat production and/or loss are changed and and/or loss are changed and body temperaturebody temperature is restored is restored toward normal.toward normal.

Normal Body TemperatureNormal Body Temperature

In homeothermic animals, the actual In homeothermic animals, the actual temperature at which the body is temperature at which the body is maintained varies from species to species maintained varies from species to species and, to a lesser degree, from individual to and, to a lesser degree, from individual to individual. In humans, the traditional individual. In humans, the traditional normal value for the oral temperature is normal value for the oral temperature is 37 °C (98.6 °F), but in one large series of 37 °C (98.6 °F), but in one large series of normal young adults, the morning oral normal young adults, the morning oral tem- perature averaged 36.7 °C, with a tem- perature averaged 36.7 °C, with a standard deviation of 0.2 °C. standard deviation of 0.2 °C.

Temperature receptorsTemperature receptorsThere are cold and warmth receptors. There are cold and warmth receptors. Nerve fibers respond differently at Nerve fibers respond differently at different levels of temperature. So a different levels of temperature. So a person determines the different gradation person determines the different gradation of thermal sensation by the relative of thermal sensation by the relative degrees of stimulation. degrees of stimulation. It is believed that the cold and warmth It is believed that the cold and warmth receptors are stimulated by changes in receptors are stimulated by changes in their metabolic rates or from chemical their metabolic rates or from chemical stimulation of the endings as modified by stimulation of the endings as modified by the temperature.the temperature.

Sensory Nerve Endings in the Sensory Nerve Endings in the SkinSkin

CCentral entral and and peripheral peripheral thermoreceptorsthermoreceptors

There are two categories of There are two categories of thermoreceptors,thermoreceptors, one in the skin one in the skin (peripheral thermoreceptors)(peripheral thermoreceptors) and the and the other other (central(central thermoreceptors) thermoreceptors) in deep in deep body structures, includingbody structures, including the the hypothalamus, spinal cord, and abdominal hypothalamus, spinal cord, and abdominal organs.organs.Since it is the core body temperature, not Since it is the core body temperature, not the skin temperature,the skin temperature, that is being that is being maintained relatively constant,maintained relatively constant, the central the central thermoreceptors provide the essentialthermoreceptors provide the essential negative-feedback component of the negative-feedback component of the reflexes.reflexes.

Central control of touch and Central control of touch and temperature sensationtemperature sensation

Almost all sensory information from the somatic Almost all sensory information from the somatic segments of the body enters the spinal cord through the segments of the body enters the spinal cord through the dorsal roots from the spinal nerves. dorsal roots from the spinal nerves. SSensory signals are carried through one or two ensory signals are carried through one or two alternative sensory pathways: 1) the dorsal colomn-alternative sensory pathways: 1) the dorsal colomn-medial lemniscal system; 2) the anterolateral system. medial lemniscal system; 2) the anterolateral system. All these fibers belong to spinothalamic tract. All these fibers belong to spinothalamic tract. Sensory information that must be transmitted rapidly or Sensory information that must be transmitted rapidly or with great spatial fidelity is transmitted mainly in the with great spatial fidelity is transmitted mainly in the dorsal colomn-medial lemniscal system. dorsal colomn-medial lemniscal system. Sensory impulses, which do not need to keep these Sensory impulses, which do not need to keep these conditions, are transmitted mainly in the anterolateral conditions, are transmitted mainly in the anterolateral system. The anterolateral system can transmit pain, system. The anterolateral system can transmit pain, warmth, cold and crude tactile sensation. Because of warmth, cold and crude tactile sensation. Because of the crossing of the medial lemnisci in the medulla, the the crossing of the medial lemnisci in the medulla, the left side of the body is represented in the right side of left side of the body is represented in the right side of the thalamus, and the right side of the body is the thalamus, and the right side of the body is represented in the left part of the thalamus. represented in the left part of the thalamus.

Central processing of impulsesCentral processing of impulsesCerebral cortex processes somatic sensory information in Cerebral cortex processes somatic sensory information in somatosensory area I, and somatosensory area II. somatosensory area I, and somatosensory area II. Somatosensory area I has much more extensive spatial Somatosensory area I has much more extensive spatial orientation of the different parts of the body. orientation of the different parts of the body. Somatosensory area II helps in association of somatic Somatosensory area II helps in association of somatic sensory information with visceral sensation and body sensory information with visceral sensation and body activity. In general, thermal signals are transmitted in activity. In general, thermal signals are transmitted in pathways parallel to those for pain signals. On entering pathways parallel to those for pain signals. On entering the spinal cord the signals travel for a few segments the spinal cord the signals travel for a few segments upward or downward and than terminate in dorsal horns. upward or downward and than terminate in dorsal horns. Then nerve fibers cross to opposite anterolateral sensory Then nerve fibers cross to opposite anterolateral sensory tract and terminate both the reticular areas of the brain tract and terminate both the reticular areas of the brain stem and the ventrobasal complex of thalamus. stem and the ventrobasal complex of thalamus. A few thermal signals are also relayed to the somatic A few thermal signals are also relayed to the somatic sensory cortex from the ventrobasal complex. sensory cortex from the ventrobasal complex. Furthermore, it is known that removal of the postcentral Furthermore, it is known that removal of the postcentral gurus in the human brain being reduced but does not gurus in the human brain being reduced but does not abolish the ability to distinguish gradations of abolish the ability to distinguish gradations of temperature. temperature.

Role Role of the hypothalamusof the hypothalamus

An area of the hypothalamus serves as the An area of the hypothalamus serves as the primaryprimary overall integrator of the reflexes, but overall integrator of the reflexes, but other brain centersother brain centers also exert some control also exert some control over specific componentsover specific components of the reflexes.of the reflexes.

Output from the hypothalamus and the other Output from the hypothalamus and the other brainbrain areas to the effectors is via: (1) areas to the effectors is via: (1) ssympathetic nerves toympathetic nerves to the sweat glands, skin the sweat glands, skin arterioles, and the adrenalarterioles, and the adrenal medulla; and (2) medulla; and (2) motor neurons to the skeletal muscles.motor neurons to the skeletal muscles.

Control of Heat Loss by Control of Heat Loss by EvaporationEvaporation

Even in theEven in the absence of sweating, there is loss of absence of sweating, there is loss of water by diffusionwater by diffusion through the skin, which is not through the skin, which is not waterproof. A similarwaterproof. A similar amount is lost from the amount is lost from the respiratory lining during expiration.respiratory lining during expiration.These two losses are known as These two losses are known as insensible waterinsensible water loss loss and amount to approximately 600 ml/day inand amount to approximately 600 ml/day in human beings. Evaporation of this water accounts human beings. Evaporation of this water accounts forfor a significant fraction of total heat loss. In a significant fraction of total heat loss. In contrast tocontrast to this passive water loss, sweating this passive water loss, sweating requires the active secretionrequires the active secretion of fluid by of fluid by sweat sweat glands glands and its extrusion intoand its extrusion into ducts that carry it ducts that carry it to the skin surface.to the skin surface.

SSympatheticympathetic nervesnerves effect effectProduction of sweat is stimulated by Production of sweat is stimulated by sympatheticsympathetic nerves to the glands. nerves to the glands. These nerves release acetylcholineThese nerves release acetylcholine rather rather than the usual sympathetic than the usual sympathetic neurotransmitterneurotransmitter norepinephrine. norepinephrine. Sweat is a dilute solution containingSweat is a dilute solution containing sodium chloride as its major solute. sodium chloride as its major solute. SweatingSweating rates of over 4 L/h have been rates of over 4 L/h have been reported; the evaporationreported; the evaporation of 4 L of water of 4 L of water would eliminate almost 2400 kcalwould eliminate almost 2400 kcal from the from the bodybody..

Control of Heat Loss by Control of Heat Loss by Radiation and ConductionRadiation and Conduction

For purposes of temperature control, it is For purposes of temperature control, it is convenientconvenient to view the body as a central to view the body as a central core surrounded by acore surrounded by a shell consisting of skin shell consisting of skin and subcutaneous tissue; weand subcutaneous tissue; we shall refer to shall refer to this complex outer shell simply as skin.this complex outer shell simply as skin.

It is the temperature of the central core that It is the temperature of the central core that is beingis being regulated at approximately 37°C. regulated at approximately 37°C. As we shall see, theAs we shall see, the temperature of the temperature of the outer surface of the skin changesouter surface of the skin changes markedly.markedly.

Heat Exchange in the SkinHeat Exchange in the Skin

NNonshiveringonshivering thermogenesisthermogenesis

Muscle contraction is not the only process Muscle contraction is not the only process controlledcontrolled in temperature-regulating reflexes. In in temperature-regulating reflexes. In most experimentalmost experimental animals, chronic cold exposure animals, chronic cold exposure induces aninduces an increase in metabolic rate (heat increase in metabolic rate (heat production) that is notproduction) that is not due to increased muscle due to increased muscle activity and is termed activity and is termed nonshiveringnonshivering thermogenesis. thermogenesis. Its causes are an increasedIts causes are an increased adrenal secretion of adrenal secretion of epinephrine and increased sympatheticepinephrine and increased sympathetic activity to activity to adipose tissue, with some contributionadipose tissue, with some contribution by thyroid by thyroid hormone as well. However, nonshiveringhormone as well. However, nonshivering thermogenesis is quite minimal, if present atthermogenesis is quite minimal, if present at all, in all, in adult human beings, and there is no increasedadult human beings, and there is no increased secretion of thyroid hormone in response to cold. secretion of thyroid hormone in response to cold. NonshiveringNonshivering thermogenesis does occur in infants.thermogenesis does occur in infants.

SShivering thermogenesishivering thermogenesisChanges in muscle activityChanges in muscle activity constitute the major constitute the major control of heat production forcontrol of heat production for temperature temperature regulation. The first muscle changes in responseregulation. The first muscle changes in response to a to a decrease in core body temperature are adecrease in core body temperature are a gradual gradual and general increase in skeletal-muscle contraction.and general increase in skeletal-muscle contraction. This may lead to shivering, which consists ofThis may lead to shivering, which consists of oscillating rhythmical muscle contractions and oscillating rhythmical muscle contractions and relaxationsrelaxations occurring at a rapid rate. During occurring at a rapid rate. During shivering, theshivering, the efferent motor nerves to the skeletal efferent motor nerves to the skeletal muscles are influencedmuscles are influenced by descending pathways by descending pathways under the primary controlunder the primary control of the hypothalamus. of the hypothalamus. Because almost no externalBecause almost no external work is performed by work is performed by shivering, virtually all the energyshivering, virtually all the energy liberated by the liberated by the metabolic machinery appears as internalmetabolic machinery appears as internal heat and is heat and is known as known as shivering thermogenesis. shivering thermogenesis. PeoplePeople also also use their muscles for voluntary heat-producinguse their muscles for voluntary heat-producing activities such as foot stamping and hand clapping.activities such as foot stamping and hand clapping.

Termoregulatory muscular tonusTermoregulatory muscular tonus

PPrimarily onrimarily on the muscle response to the muscle response to cold; cold; the opposite muscle reactionsthe opposite muscle reactions occur in occur in response to heat. Basal muscle response to heat. Basal muscle contractioncontraction is reflexly decreased, and is reflexly decreased, and voluntary movement isvoluntary movement is also diminished. also diminished. These attempts to reduce heat productionThese attempts to reduce heat production are relatively limited, however, both are relatively limited, however, both becausebecause basal muscle contraction is quite basal muscle contraction is quite low to start with andlow to start with and because any because any increased core temperature produced byincreased core temperature produced by the heat acts the heat acts directly directly on cells to increase on cells to increase metabolic rate.metabolic rate.

Scheme of reflex arcScheme of reflex arc

The skin’s effectiveness as an The skin’s effectiveness as an insulatorinsulator

The skin’s effectiveness as an insulator is subjectThe skin’s effectiveness as an insulator is subject to physiological control by a change in the blood to physiological control by a change in the blood flowflow to it. The more blood reaching the skin from to it. The more blood reaching the skin from the core,the core, the more closely the skin’s temperature the more closely the skin’s temperature approachesapproaches that of the core. In effect, the blood that of the core. In effect, the blood vessels diminishvessels diminish the insulating capacity of the skin the insulating capacity of the skin by carrying heat toby carrying heat to the surface to be lost to the the surface to be lost to the external environment.external environment.These vessels are controlled largely by These vessels are controlled largely by vasoconstrictorvasoconstrictor sympathetic nerves, the firing rate sympathetic nerves, the firing rate of which is reflexlyof which is reflexly increased in response to cold increased in response to cold and decreased in responseand decreased in response to heat. There is also a to heat. There is also a population of sympatheticpopulation of sympathetic neurons to the skin neurons to the skin whose neurotransmitters cause active whose neurotransmitters cause active vasodilation. vasodilation. Certain areasCertain areas of skin participate much more than of skin participate much more than others in allothers in all these vasomotor responses, and so these vasomotor responses, and so skin temperaturesskin temperatures vary with location.vary with location.

Loosing heat by pantingLoosing heat by panting

Some mammals lose heat bySome mammals lose heat by panting. panting. This This rapid, shallow breathing greatly increases the rapid, shallow breathing greatly increases the amount of water vaporized in the mouth and amount of water vaporized in the mouth and respiratory passages and therefore the respiratory passages and therefore the amount of heat lost. Because the breathing is amount of heat lost. Because the breathing is shallow, it produces relatively little change in shallow, it produces relatively little change in the composition of alveolar air.the composition of alveolar air.The relative contribution of each of the The relative contribution of each of the processes that transfer heat away from the processes that transfer heat away from the body varies with the environmental body varies with the environmental temperature. At 21 °C, vaporization is a minor temperature. At 21 °C, vaporization is a minor component in humans at rest. As the component in humans at rest. As the environmental temperature approaches body environmental temperature approaches body temperature, radiation losses decline and temperature, radiation losses decline and vaporization losses increase.vaporization losses increase.

Effect of Effect of relativerelative humidityhumidityIt is essential to recognize that sweat must It is essential to recognize that sweat must evaporateevaporate in order to exert its cooling in order to exert its cooling effect. The most importanteffect. The most important factor factor determining evaporation rate is thedetermining evaporation rate is the water-water-vapor concentration of the air—that is, the vapor concentration of the air—that is, the relativerelative humidityhumidity. . The discomfort suffered on humid daysThe discomfort suffered on humid days is is due to the failure of evaporation; the due to the failure of evaporation; the sweat glandssweat glands continue to secrete, but the continue to secrete, but the sweat simply remains onsweat simply remains on the skin or drips the skin or drips off.off.

Head ThermogramHead ThermogramInfraredInfrared ( (IRIR) radiation ) radiation is is electromagnetic radiatioelectromagnetic radiationn of a of a wavelengthwavelength longer longer than that of than that of visible lightvisible light, , but shorter than that of but shorter than that of radio wavesradio waves. The name . The name means "below means "below redred" " (from the (from the LatinLatin infrainfra, , "below"), red being the "below"), red being the colorcolor of visible of visible lightlight of of longest wavelength. longest wavelength. Infrared radiation spans Infrared radiation spans three orders of three orders of magnitude and has magnitude and has wavelengths between wavelengths between approximately approximately 750750  nmnm and 1 and 1 mmmm

Infrared thermographyInfrared thermography

Infrared Infrared thermography is a thermography is a non-contact, non-non-contact, non-destructive test destructive test method that method that utilizes a thermal utilizes a thermal imager to detect, imager to detect, display and record display and record thermal patterns thermal patterns and temperatures and temperatures across the surface across the surface of an object. of an object.

Thermal imagingThermal imaging

ThermographyThermography, or , or thermal imagingthermal imaging, , is a type of infrared is a type of infrared imaging. imaging. Thermographic Thermographic cameras detect cameras detect radiation in the radiation in the infrared range of infrared range of the the electromagnetic electromagnetic spectrum (roughly spectrum (roughly 900–14,000 900–14,000 nanometers or 0.9–nanometers or 0.9–14 µm) and 14 µm) and produce images of produce images of that radiation. that radiation.

ThermologyThermologyThermologyThermology is the medical science that derives is the medical science that derives diagnostic indications from highly detailed and diagnostic indications from highly detailed and sensitive infrared images of the human body. sensitive infrared images of the human body. Thermology is sometimes referred to as medical Thermology is sometimes referred to as medical infrared imaging or tele-thermology and utilizes infrared imaging or tele-thermology and utilizes highly resolute and sensitive infrared highly resolute and sensitive infrared (thermographic) cameras. Thermology is (thermographic) cameras. Thermology is completely non-contact and involves no form of completely non-contact and involves no form of energy imparted onto or into the body. energy imparted onto or into the body. Thermology has recognized applications in breast Thermology has recognized applications in breast oncology, chiropractic, dentistry, neurology, oncology, chiropractic, dentistry, neurology, orthopedics, occupational medicine, pain orthopedics, occupational medicine, pain management, vascular medicine/cardiology and management, vascular medicine/cardiology and veterinary medicine.veterinary medicine.

BBehavioralehavioral mechanismsmechanismsTThere are three here are three behavioral behavioral mechanisms formechanisms for altering altering heat loss by radiation and conduction: changesheat loss by radiation and conduction: changes in in surface area, changes in clothing, and choice of surface area, changes in clothing, and choice of surroundings.surroundings.Curling up into a ball, hunching the shoulders,Curling up into a ball, hunching the shoulders, and and similar maneuvers in response to cold reducesimilar maneuvers in response to cold reduce the the surface area exposed to the environment, therebysurface area exposed to the environment, thereby decreasing heat loss by radiation and conduction. Indecreasing heat loss by radiation and conduction. In human beings, clothing is also an important human beings, clothing is also an important componentcomponent of temperature regulation, substituting for of temperature regulation, substituting for the insulatingthe insulating effects of feathers in birds and fur in effects of feathers in birds and fur in otherother mammals. The outer surface of the clothes forms mammals. The outer surface of the clothes forms thethe true “exterior” of the body surface. true “exterior” of the body surface. The skin loses heatThe skin loses heat directly to the air space trapped by directly to the air space trapped by the clothes, whichthe clothes, which in turn pick up heat from the inner in turn pick up heat from the inner air layer andair layer and transfer it to the external environment. transfer it to the external environment. The insulatingThe insulating ability of clothing is determined ability of clothing is determined primarily by theprimarily by the thickness of the trapped air layer.thickness of the trapped air layer.

ClothingClothing and body and body temperaturetemperature

Clothing is important not only at low temperaturesClothing is important not only at low temperatures but also at very high temperatures. When the but also at very high temperatures. When the environmentalenvironmental temperature is greater than body temperature is greater than body temperature,temperature, conduction favors heat conduction favors heat gain gain rather than rather than heat loss.heat loss.Heat gain also occurs by radiation during exposure toHeat gain also occurs by radiation during exposure to the sun. People therefore insulate themselves in suchthe sun. People therefore insulate themselves in such situations by wearing clothes. The clothing, however,situations by wearing clothes. The clothing, however, must be loose so as to allow adequate movement of must be loose so as to allow adequate movement of airair to permit evaporation. White clothing isto permit evaporation. White clothing is cooler cooler since it reflects more radiant energy, which darksince it reflects more radiant energy, which dark colors absorb. Loose-fitting, light-colored clothes arecolors absorb. Loose-fitting, light-colored clothes are far more cooling than going nude in a hot far more cooling than going nude in a hot environmentenvironment and during direct exposure to the sun.and during direct exposure to the sun.

The third behavioral mechanismThe third behavioral mechanism

The third behavioral mechanism for The third behavioral mechanism for altering heataltering heat loss is to seek out loss is to seek out warmer or colder surroundings, aswarmer or colder surroundings, as for for example by moving from a shady example by moving from a shady spot into the sunlight.spot into the sunlight.

Raising or lowering the thermostat of Raising or lowering the thermostat of a house ora house or turning on an air turning on an air conditioner also fits this category.conditioner also fits this category.

Integration of Effector Integration of Effector MechanismsMechanisms

By altering heat loss, changes in skin blood flow aloneBy altering heat loss, changes in skin blood flow alone can can regulate body temperature over a range of environmentalregulate body temperature over a range of environmental temperatures (approximately 25 to 30°C ortemperatures (approximately 25 to 30°C or 75 to 86°F for a 75 to 86°F for a nude individual) known as the nude individual) known as the thermoneutralthermoneutral zone. zone. At temperatures lower than this, evenAt temperatures lower than this, even maximal maximal vasoconstriction cannot prevent heat lossvasoconstriction cannot prevent heat loss from exceeding heat from exceeding heat production, and the body mustproduction, and the body must increase its heat production to increase its heat production to maintain temperature.maintain temperature. At environmental temperatures above At environmental temperatures above the thermoneutralthe thermoneutral zone, even maximal vasodilation cannot zone, even maximal vasodilation cannot eliminateeliminate heat as fast as it is produced, and another heat-lossheat as fast as it is produced, and another heat-loss mechanism—sweating—is therefore brought stronglymechanism—sweating—is therefore brought strongly into play. into play. Since at environmental temperatures aboveSince at environmental temperatures above that of the body, that of the body, heat is actually added to the body byheat is actually added to the body by radiation and radiation and conduction, evaporation is the soleconduction, evaporation is the sole mechanism for heat loss. mechanism for heat loss. A person’s ability to tolerateA person’s ability to tolerate such temperatures is determined such temperatures is determined by the humidity andby the humidity and by his/her maximal sweating rate. by his/her maximal sweating rate.

Summary of Effector Mechanisms in Summary of Effector Mechanisms in Temperature RegulationTemperature Regulation

Peculiarities of temperature homeostasis in Peculiarities of temperature homeostasis in childrenchildren

Newborns thermoregulatory system is well Newborns thermoregulatory system is well developed, but in newborns different condition of developed, but in newborns different condition of temperature exchange and present some temperature exchange and present some peculiarities of thermoregulation. Children have peculiarities of thermoregulation. Children have another than adults ratio of body surface and another than adults ratio of body surface and weight.weight. Body square is more than body weight that is Body square is more than body weight that is why lost of temperature increase and regime of why lost of temperature increase and regime of temperature comfort change in side of increase of temperature comfort change in side of increase of external temperature to 32-34 °C. Big body external temperature to 32-34 °C. Big body square developed condition for more intensive square developed condition for more intensive cool and heating. Children have more thin thermo cool and heating. Children have more thin thermo isolative layer of subcutaneous fat.isolative layer of subcutaneous fat.

Role of brown fatRole of brown fat

In newborns very important role in thermo regulative In newborns very important role in thermo regulative processes has brown fat. It’s present under the skin of processes has brown fat. It’s present under the skin of neck, between scapulars. That gives condition for blood neck, between scapulars. That gives condition for blood supply of brain, where the cells are very sensate to supply of brain, where the cells are very sensate to disbalance of temperature homeostasis. Brown fat is well disbalance of temperature homeostasis. Brown fat is well innervated by sympathetic nerves and well provided with innervated by sympathetic nerves and well provided with blood. blood. In the cells of brown fat small drops of fat are present. In a In the cells of brown fat small drops of fat are present. In a white cells there is only one drop of fat. Quantity of white cells there is only one drop of fat. Quantity of mitochondria, cytochroms is greater in brown fat. Speed of mitochondria, cytochroms is greater in brown fat. Speed of fat acids oxidation 20 times higher, but absent synthesis fat acids oxidation 20 times higher, but absent synthesis and hydrolysis of ATP, that is why the heat produced and hydrolysis of ATP, that is why the heat produced immediately. That is caused by presents of special immediately. That is caused by presents of special membrane polypeptide – termogenine. When it is membrane polypeptide – termogenine. When it is necessary increase of brown fat oxygenation may be necessary increase of brown fat oxygenation may be added to increase the heat production in 2-3 times. added to increase the heat production in 2-3 times. Children, especially of first year life, do not so sensitive as Children, especially of first year life, do not so sensitive as adult to change of temperature homeostasis. That's why adult to change of temperature homeostasis. That's why they don't cry when they lost heat.they don't cry when they lost heat.

Body fluidsBody fluids

The cells that make up the bodies of all but the simplest The cells that make up the bodies of all but the simplest multicellular animals, both aquatic and terrestrial, exist in multicellular animals, both aquatic and terrestrial, exist in an '''internal sea" of extracellular fluid (ECF) enclosed an '''internal sea" of extracellular fluid (ECF) enclosed within the integument of the animal. From this fluid, the within the integument of the animal. From this fluid, the cells take up 02 and nutrients; into it, they discharge cells take up 02 and nutrients; into it, they discharge metabolic waste products. The ECF is more dilute than metabolic waste products. The ECF is more dilute than present-day sea water, but its composition closely present-day sea water, but its composition closely resembles that of theprimordial oceans in which, resembles that of theprimordial oceans in which, presumably, all life originated.presumably, all life originated.In animals with a closed vascular system, the ECFis divided In animals with a closed vascular system, the ECFis divided into 2 components: the interstitial fluid andthe circulating into 2 components: the interstitial fluid andthe circulating blood plasma. The plasma and thecellular elements of the blood plasma. The plasma and thecellular elements of the blood, principally red bloodcells, fill the vascular system, blood, principally red bloodcells, fill the vascular system, and together they consti-tute the total blood volume.The and together they consti-tute the total blood volume.The interstitial fluid isthat part of the ECF that is outside the interstitial fluid isthat part of the ECF that is outside the vascular system,bathing the cells. The special fluids vascular system,bathing the cells. The special fluids lumped together astranscetlular fluids are discussed below. lumped together astranscetlular fluids are discussed below. About a thirdof the total body water (TBW) is extracellular; About a thirdof the total body water (TBW) is extracellular; theremaining two-thirds are intracellular (intracellularfluid).theremaining two-thirds are intracellular (intracellularfluid).

Size of the Fluid CompartmentsSize of the Fluid Compartments

In the average young adult male, 18% of the In the average young adult male, 18% of the bodyweight is protein and related substances, bodyweight is protein and related substances, 7% is mineral, and 15% is fat. 7% is mineral, and 15% is fat. The remaining 60% is water. The intracellular The remaining 60% is water. The intracellular component of the body wateraccounts for about component of the body wateraccounts for about 40% of body weight and the extracellular 40% of body weight and the extracellular component for about 20%. component for about 20%. Approximately 25% of the extracellular Approximately 25% of the extracellular component is in the vascularsystem (plasma == component is in the vascularsystem (plasma == 5% of5% of body weight) body weight) and and 75% out-side the blood 75% out-side the blood vessels (interstitial fluid = 15% of bodyweight). vessels (interstitial fluid = 15% of bodyweight). TheThe total total blood volume is about 8% of blood volume is about 8% of bodyweight.bodyweight.

Extracellular Fluid VolumeExtracellular Fluid VolumeThe ECF volume isThe ECF volume is difficult difficult to measure because the to measure because the limits of this space are ill defined and because limits of this space are ill defined and because fewsubstances mix rapidly in all parts of the space fewsubstances mix rapidly in all parts of the space while remaining exclusively extracellular. The lymph while remaining exclusively extracellular. The lymph cannot be separated from the ECF and is measured cannot be separated from the ECF and is measured with it. with it. ManyMany substances enter the cercbrospinal substances enter the cercbrospinal fluid (CSF) slowly because of the blood-brain barrier. fluid (CSF) slowly because of the blood-brain barrier. Equilibration is slow with joint fluid and aqueous Equilibration is slow with joint fluid and aqueous humor and with thehumor and with the ECF ECF In relatively avascular In relatively avascular tissues such as dense connective tissue, cartilage, tissues such as dense connective tissue, cartilage, and some parts of bone. Substances that distributeand some parts of bone. Substances that distribute in ECFin ECF appear in glandular secretions and in the appear in glandular secretions and in the contents of the gastrointestinal tract. Because they contents of the gastrointestinal tract. Because they are not strictly part of theare not strictly part of the ECF, ECF, these fluids, as well these fluids, as well asas CSF, CSF, me fluids in the me fluids in the eyeeye, and a few other , and a few other special fluids, are calledspecial fluids, are called transcellular fluids. transcellular fluids. Their Their volume is relatively small.volume is relatively small.

Interstitial Fluid VolumeInterstitial Fluid VolumeThe interstitial fluid space cannot be measured The interstitial fluid space cannot be measured directly, since it is difficult to sample interstitial directly, since it is difficult to sample interstitial fluid and since substances that equilibrate in fluid and since substances that equilibrate in interstitial fluid also equilibrate in plasma. The interstitial fluid also equilibrate in plasma. The volume of the interstitial fluid can be calculated volume of the interstitial fluid can be calculated by subtracting the plasma volume from the ECF by subtracting the plasma volume from the ECF volume. volume. The ECF volume/intracellular fluid volume ratio is The ECF volume/intracellular fluid volume ratio is larger in infants and children than it is in adults, larger in infants and children than it is in adults, but the absolute volume of ECF in children is, of but the absolute volume of ECF in children is, of course, smaller than it is in adults. Therefore, course, smaller than it is in adults. Therefore, dehydration develops more rapidly and is dehydration develops more rapidly and is frequently more severe in children than in adults.frequently more severe in children than in adults.

Intracellular Fluid VolumeIntracellular Fluid VolumeThe intracellular fluid volume cannot be measured The intracellular fluid volume cannot be measured directly, but it can be calculated by subtracting the directly, but it can be calculated by subtracting the ECF volume from the total body water (TBW). TBW ECF volume from the total body water (TBW). TBW can be measured by the same dilution principle can be measured by the same dilution principle used to measure the other body spaces. Deuterium used to measure the other body spaces. Deuterium oxide (D;0, heavy water) is most frequently used. oxide (D;0, heavy water) is most frequently used. D20 has properties that are slightly different from D20 has properties that are slightly different from H20, but in equilibration experiments for H20, but in equilibration experiments for measuring body water it gives accurate results. measuring body water it gives accurate results. Tritium oxide and aminopyrine have also been Tritium oxide and aminopyrine have also been used for this purpose.used for this purpose.The water content of lean body tissue is constant The water content of lean body tissue is constant at 71 -72 mL/100 g of tissue, but since fat is at 71 -72 mL/100 g of tissue, but since fat is relatively free of water, the ratio of TBW to body relatively free of water, the ratio of TBW to body weight varies with the amount of fat present. In weight varies with the amount of fat present. In young men, water constitutes about 60% of body young men, water constitutes about 60% of body weight. The values for women are somewhat lower. weight. The values for women are somewhat lower.

The distribution of electrolytes in the various The distribution of electrolytes in the various compartmentscompartments

The composition of intracellular fluid The composition of intracellular fluid varies somewhat depending upon the varies somewhat depending upon the nature and function of the cell.nature and function of the cell.Eelectrolyte concentrations differ Eelectrolyte concentrations differ markedly in the various compartments. markedly in the various compartments. The most striking differences are the The most striking differences are the relatively low content of protein anions in relatively low content of protein anions in interstitial fluid compared to intracellular interstitial fluid compared to intracellular fluid and plasma, and the fact that Na+ fluid and plasma, and the fact that Na+ and C- are largely extracellular, whereas and C- are largely extracellular, whereas most of the K+ is intracellular.most of the K+ is intracellular.

Size of the Fluid CompartmentsSize of the Fluid Compartments

In the average young adult male, 18 % of the In the average young adult male, 18 % of the body weight is protein and related substances, body weight is protein and related substances, 7 % is mineral, and 15 % is fat. The remaining 7 % is mineral, and 15 % is fat. The remaining 60 % is water60 % is water. . TheThe intracellular component of the body intracellular component of the body water accounts for about 40 % of body water accounts for about 40 % of body weight and the extra cellular component weight and the extra cellular component for about 20 %. for about 20 %. Approximately 10 % of the body water is Approximately 10 % of the body water is inside the blood vessels. inside the blood vessels. Interstitial fluid = 15 % of body weight. Interstitial fluid = 15 % of body weight. The total blood volume is about 6-8 % of The total blood volume is about 6-8 % of body weight.body weight.