chapter 35: the digestive and endocrine systems · the digestive and endocrine systems • review...

916

Visit to• study the entire chapter

online• access Web Links for more

information and activities onthe digestive and endocrinesystems

• review content with theInteractive Tutor and self-check quizzes

The Digestive and Endocrine SystemsThe Digestive and Endocrine Systems

Barium sulfate, a compoundthat absorbs X rays, providescontrast in this color-enhancedX ray of the large intestine andpart of the small intestine.

Understandingthe Photo

What You’ll Learn■ You will interpret the func-

tions of the digestive system.■ You will outline the journey

of a meal through the diges-tive system.

■ You will identify differentnutrients and their uses in the body.

■ You will describe how internalfeedback mechanisms regu-late the release of hormones.

■ You will analyze how endo-crine hormones control inter-nal body processes and helpmaintain homeostasis of the body.

Why It’s ImportantBy examining the functions ofyour digestive and endocrinesystems, you will understandhow your body obtains energyfrom food and how it controlsyour behavior and development.

Susan Leavines/Science Source/Photo Researchers

ca.bdol.glencoe.comca.bdol.glencoe.com

916-923 C35S1 BDOL-829900 8/5/04 2:19 AM Page 916

http://ca.bdol.glencoe.com

35.1 FOLLOWING DIGESTION OF A MEAL 917

Following Digestion of a Meal35.1

Digestive System Make the following Foldable to help you learn more about the structures and functions of the digestive system.

Label each tab as shown.

Draw a mark at the midpoint of a sheet of paper along the side edge. Then fold the top and bottom edges in to touch the midpoint.

Fold in half from side to side.

Open and cut along theinside fold lines to form four tabs.

STEP 1

STEP 3

STEP 2

STEP 4

SECTION PREVIEWObjectivesInterpret the differentfunctions of the digestivesystem organs.Outline the pathway foodfollows through the diges-tive tract.Identify the role of enzymes in chemical digestion.

Review Vocabularyenzyme: type of protein

found in all living thingsthat increases the rateof chemical reactions (p. 161)

New Vocabularyamylaseesophagusperistalsisepiglottisstomachpepsinsmall intestinepancreasliverbilegallbladdervilluslarge intestinerectum

Mouth

SmallIntestine

LargeIntestine

Stomach

Identify As you read Chapter 35, list the functions of each of these digestivesystem structures beneath the appropriate tab.

Functions of the Digestive SystemThe main function of the digestive system is to disassemble the food

you eat into its component molecules so that it can be used as energy foryour body. In this sense, your digestive system can be thought of as a sortof disassembly line.

Digestion is accomplished through a number of steps. First, the systemtakes ingested food and begins moving it through the digestive tract. Asit does so, it digests—or breaks down mechanically and chemically—thecomplex food molecules. Then, the system absorbs the digested food anddistributes it to your cells. Finally, it eliminates undigested materials fromyour body. As you read about each digestive organ, use Figure 35.1 onthe next page to locate its position within the system.

The MouthThe first stop along the digestive disassembly line is your mouth.

Suppose it’s lunchtime and you have just prepared a bacon, lettuce, andtomato sandwich. The first thing you do is bite off a piece and chew it.

Standard 9f* Students know the individual functions and sites of secretionof digestive enzymes (amylases, proteases, nucleases, lipases), stomach acid, and bile salts.

California Standards

916-923 C35S1 BDOL-829900 8/5/04 2:22 AM Page 917

918 THE DIGESTIVE AND ENDOCRINE SYSTEMS

Table 35.1 Digestive Enzymes

Organ Enzyme Molecules Digested Product

Salivary glands Salivary amylase Starch Disaccharide

Stomach Pepsin Proteins PeptidesPancreas Pancreatic amylase Starch Disaccharide

Trypsin Proteins PeptidesPancreatic lipase Fats Fatty acids and glycerolNucleases Nucleic acids Nucleotides

Small intestine Maltase Disaccharide MonosaccharideSucrase Disaccharide MonosaccharideLactase Disaccharide MonosaccharidePeptidase Peptides Amino acidsNuclease Nucleotides Sugar and nitrogen bases

What happens as you chew?As you chew, your tongue moves

the food around and helps position itbetween your teeth. Chewing is aform of mechanical digestion, thephysical process of breaking foodinto smaller pieces. Mechanicaldigestion prepares food particles forchemical digestion. Chemical diges-tion is the process of changing foodon a molecular level through the

action of enzymes. What purpose dothe different structures inside yourmouth serve? Find out by examiningFigure 35.2.

Chemical digestion begins in the mouth

Some of the nutrients in your sand-wich are starches, large moleculesknown as polysaccharides. As youchew your bite of sandwich, salivaryglands in your mouth secrete saliva.Saliva contains a digestive enzyme,called amylase, which breaks downstarch into smaller molecules such asdi- or monosaccharides. In the stom-ach, amylase continues to digeststarch in the swallowed food for about30 minutes. Table 35.1 lists somedigestive enzymes that act to breakfood molecules apart.

Swallowing your foodOnce you’ve thoroughly chewed

your bite of sandwich, your tongueshapes it into a ball and moves it to theback of your mouth to be swallowed.Swallowing forces food from yourmouth into your throat and from thereinto your esophagus, a muscular tubethat connects your mouth to yourstomach. Food moves down the esoph-agus by way of peristalsis. Peristalsis(per uh STAHL sus) is a series of invol-untary smooth muscle contractionsalong the walls of the digestive tract.

TeethMouthTongue

Esophagus

Diaphragm

Gallbladder

Liver

Largeintestine

Appendix

Anus

Salivaryglands

Pharynx

Stomach

Pancreas

Smallintestine

Rectum

PhysicalScience

Connection

Physical andchemical changesin matter Diges-tion involves bothphysical andchemical changes inmatter. Describethe digestiveprocesses thatoccur in the mouth.Classify each as aphysical or achemical change.

Figure 35.1All the digestive organswork together to breakdown food into simplercompounds that can beabsorbed by the body.Describe Interpret thefunctions of the diges-tive system.

916-923 C35S1 BDOL-829900 8/5/04 2:23 AM Page 918


Incisors

Gums

Soft palate

Opening of salivary gland duct

Cuspids orcanines

Bicuspidsor premolars

Molars

Uvula

Hard palate

Teeth The incisors are adaptedfor cutting food. The cuspids, orcanines, tear or shred food.The three sets of molarscan crush and grindfood. Often, there isnot enough room for the third set ofmolars, calledwisdom teeth, which then must be removed.

TongueThe tongue is attached to the floor of the mouth. It is made of numerous skeletal muscles covered with a mucous membrane.

Enamel

Dentin

Nerve

Pulp

Rootcanal

Vascular supplyBone

CROWN

NECK

ROOT Structure of a tooth Teeth are made mainly of dentin, a bonelikesubstance that gives a tooth its shape and strength. The dentin encloses aspace filled with pulp, a tissue that contains blood vessels and nerves. Thedentin of the crown is covered with an enamel that consists mostly ofcalcium salts. Tooth enamel is the hardest substance in the body.

Tonsils A pair oftonsils is located at theback of the mouth. Theyplay a role in preventinginfections in the noseand mouth by helpingto eliminate foreignbacteria.

The tongue is covered by projectionsthat contain numerous taste receptorcells like the ones shown here.

Color-enhanced SEMMagnification: 245�

Your MouthFigure 35.2Your mouth houses many structures involved in other functions besides digestion. Someof these structures protect against foreign materials invading your body; others help youtaste the food you eat. Critical Thinking Why is it important that the tongue is com-posed of skeletal muscles?

AA

BB

CC

DD

Omikron/Photo Researchers

916-923 C35S1 BDOL-829900 8/5/04 2:24 AM Page 919

Figure 35.3 shows how the food ismoved along from the mouth to thestomach. The contractions occur inwaves: first, circular muscles relax andlongitudinal muscles contract; then cir-cular muscles contract and longitudinalmuscles relax.

When you swallow, the food entersthe esophagus. Usually, a flap of carti-lage called the epiglottis (ep uh GLAH

tus) closes over the opening to the respiratory tract as you swallow, pre-venting food from entering. After thefood passes into your esophagus, theepiglottis opens again. But if you talkor laugh as you swallow, the epiglottismay open, allowing food to enter theupper portion of the respiratory tract.Your response, a reflex, is to choke andcough, forcing the food out of the res-piratory tube.

The StomachWhen the chewed food reaches the

end of your esophagus, it enters thestomach. The stomach is a muscular,pouchlike enlargement of the diges-tive tract. Both physical and chemicaldigestion take place in the stomach.

Muscular churningThree layers of involuntary mus-

cles, lying across one another, arelocated within the wall of the stom-ach. When these muscles contract, asshown in Figure 35.4, they work tophysically break down the swallowedfood, creating smaller pieces. As themuscles continue to work the foodpieces, they mix them with digestivejuices produced by the stomach.

Chemical digestion in the stomach

The inner lining of the stomachcontains millions of glands thatsecrete a mixture of chemicals calledgastric juice. Gastric juice contains

Frommouth

Contraction

Contractionof circularmusclesbehindfood mass

Longitudinalmuscle

Food massTo stomach

Contractionin circularmuscle layerforces foodmass forward

Contraction oflongitudinalmuscles aheadof food mass

Circularmuscle

Esophagus

Stomach

Small intestine

Figure 35.3Smooth muscle contractions are responsible formoving food through the digestive system.

Figure 35.4Smooth muscle contrac-tions churn the food inthe stomach until itbecomes a thin liquid.


916-923 C35S1 BDOL-829900 8/5/04 2:25 AM Page 920

pepsin and hydrochloric acid. Pepsinis an enzyme that begins the chemicaldigestion of proteins in food. Pepsinworks best in the acidic environmentprovided by hydrochloric acid, whichincreases the acidity of the stomachcontents to pH 2.

How is the stomach lining pro-tected from powerful digestive en-zymes and strong acids? The stomachlining secretes mucus that forms aprotective layer between it and theacidic environment of the stomach.

Food remains in your stomach forapproximately two to four hours.When food is ready to leave the stom-ach, it is about the consistency oftomato soup. Peristaltic waves gradu-ally become more vigorous and beginto force small amounts of liquid outof the lower end of the stomach andinto the small intestine.

The Small IntestineFrom your stomach, the liquid food

moves into your small intestine, amuscular tube about 6 m long. Thissection of the intestine is called smallnot because of its length, butbecause of its narrow diameter—only 2.5 cm. Digestion of your mealis completed within the small intes-tine. Muscle contractions contributeto further mechanical breakdown ofthe food. At the same time, carbohy-drates and proteins undergo furtherchemical digestion with the help ofenzymes produced and secreted bythe pancreas and liver.

Explain which typesof digestion occur in the smallintestine.

Chemical actionThe first 25 cm of the small intes-

tine is called the duodenum (doo ahDEE num). Most of the enzymes and

chemicals that function in the duode-num enter it through ducts that col-lect juices from the pancreas, liver,and gallbladder. These organs, shownin Figure 35.5, play important rolesin digestion, even though food doesnot pass directly through them.

Secretions of the pancreasThe pancreas is a soft, flattened

gland that secretes both digestiveenzymes and hormones, which you willlearn more about in the last section ofthis chapter. The mixture of enzymes itsecretes breaks down carbohydrates,proteins, and fats. Alkaline pancreaticjuices also help to neutralize the acidityof the liquid food, stopping any furtheraction of pepsin.

Secretions of the liverThe liver is a large, complex

organ that has many functions. One of its functions is to producebile. Bile is a chemical substancethat helps break down fats. Oncemade in the liver, bile is stored in asmall organ called the gallbladder.


Esophagus

Pancreas

Pancreaticduct

Stomach

Diaphragm

Duodenum

Bile duct

Smallintestine

Liver

Gallbladder

Figure 35.5Both the pancreas andthe liver produce chemi-cals needed for digestionin the small intestine.

916-923 C35S1 BDOL-829900 8/5/04 2:25 AM Page 921

From the gallbladder, bile passes intothe duodenum. Bile causes furthermechanical digestion by breakingapart large drops of fat into smallerdroplets. If bile becomes too concen-trated due to high levels of cholesterolin the diet, or if the gallbladderbecomes inflamed, gallstones canform, as seen in Figure 35.6. Can aperson live without a gallbladder?Find out in the Problem-Solving Lab onthis page.

Absorption of foodLiquid food stays in your small

intestine for three to five hours and isslowly moved along its length by peri-stalsis. As digested food moves throughthe intestine, it passes over thousandsof tiny fingerlike structures called villi.A villus (plural, villi) is a single projec-tion on the lining of the small intestinethat functions in the absorption ofdigested food. The villi greatly increasethe surface area of the small intestine,allowing for a greater absorption rate.Because the digested food is now in theform of small molecules, it can beabsorbed directly into the cells of thevilli, as shown in Figure 35.7. Thefood molecules then diffuse into theblood vessels of the villus and enter the bloodstream. The villi are the linkbetween the digestive system and thecirculatory system.

What happens to indigestible mate-rials that remain in the digestive tract?


Figure 35.6Gallstones, seen in this color-enhanced X ray,can form in the gallbladder or bile duct.They consist mainly of crystallized bile salts.

Gallstones

SequenceHow is digestion affected if the gallbladder is removed?Many people have had their gallbladders surgically removed.What changes take place in digestion if the gallbladder isremoved?

Solve the ProblemThe following diagrams show the appearance of a normal liverand gallbladder (diagram A) and the appearance when thegallbladder has been removed (diagram B).

Thinking Critically1. Identify Where is bile produced? Where is bile stored?2. Explain How does bile affect fat?3. Sequence Identify the pathway for bile from the liver to

the duodenum in a person with a gallbladder and compare it to the sequence in a person with no gallbladder.

4. Infer The gallbladder is a muscular sac. It squeezes anddischarges a large quantity of bile when fats are present in the duodenum. Explain why a person without a gall-bladder is unable to digest fats as efficiently as someonewho has a gallbladder.

Hepatic duct

Bile duct

Hepatic duct

Bile duct

AA BB

Department of Clinical Radiology, Salisbury District Hospital/Science Photo Library/Photo Researchers

916-923 C35S1 BDOL-829900 8/5/04 2:26 AM Page 922

Understanding Main Ideas1. Describe the functions of the digestive system and

sequence the organs according to the order inwhich food passes through them.

2. Identify the effects of enzymes on food molecules.Which enzymes act on proteins?

3. How do villi of the small intestine increase therate of nutrient absorption?

4. What role does the pancreas play in digestion?

Thinking Critically5. How would chronic diarrhea affect homeostasis of

the body?

6. Get the Big Picture Prepare a circle graph rep-resenting the time food remains in each part ofthe digestive tract. For more help, refer to Get theBig Picture in the Skill Handbook.

SKILL REVIEWSKILL REVIEW


The LargeIntestine

The indigestible materialfrom your meal now passesinto your large intestine, amuscular tube that is alsocalled the colon. Althoughthe large intestine is onlyabout 1.5 m long, it is muchwider than the small intes-tine—about 6.5 cm in dia-meter. The appendix, atubelike extension off thelarge intestine thought to bean evolutionary remnantfrom our herbivorous ances-tors, seems to serve no func-tion in human digestion.

Water absorptionAs the indigestible mixture passes

through the large intestine, water andsalts are absorbed by the intestinalwalls, leaving behind a more solidmaterial. In this way, the water is notwasted. A secondary function of thelarge intestine is vitamin synthesis.Anaerobic bacteria in the large intes-tine synthesize some B vitamins andvitamin K, which are absorbed asneeded by the body. The presence ofcertain bacteria in the large intestineis beneficial in another way. Undernormal conditions, these bacteria stop

harmful bacteria from colonizing, re-ducing the risk of intestinal infections.

Identify anddescribe the roles that bacteria play in maintaining health.

Elimination of wastesAfter 18 to 24 hours in the large

intestine, the remaining indigestiblematerial, now called feces, reaches therectum. The rectum is the last part ofthe digestive system. Feces are elimi-nated from the rectum through theanus. Your meal’s entire journeythrough the digestive tract has takenbetween 24 and 33 hours.

Fatty acids

Amino acids

Monosaccharides

Columnarepithelium Lymph

vesselBlood vesselnetwork

Figure 35.7Once food has beenfully digested in thesmall intestine, it is in the form of mole-cules small enough to enter the body’sbloodstream throughprojections called villi.

ca.bdol.glencoe.com/self_check_quiz

916-923 C35S1 BDOL-829900 8/5/04 2:27 AM Page 923

http://ca.bdol.glencoe.com/self_check_quiz

35.2SECTION PREVIEWObjectivesRecognize the contribu-tion of the six classes of nutrients to body nutrition.Identify the role of theliver in food storage.Relate caloric intake toweight loss or gain.

Review Vocabularycarbohydrate: organic

compound used by cellsto store and releaseenergy (p. 158)

New VocabularymineralvitaminCalorie


You Are What You EatUsing Prior Knowledge In this section, you will learn about nutrition and the different molecules that your body uses for energy and those it needs to function properly. List the foods you eat in a day. Using the food pyramid as a guide, categorize them into different groupsaccording to food type. Evaluate How do your meals fit into this pyramid?

The Vital NutrientsSix basic kinds of nutrients can be found in foods: carbohydrates, fats,

proteins, minerals, vitamins, and water. These substances are essential toproper body function. You supply your body with these nutrients whenyou eat foods from the five main food groups shown in Figure 35.8.

CarbohydratesPerhaps your favorite food is pasta, fresh-baked bread, or corn on the cob.

If so, your favorite food contains carbohydrates, important sources of energyfor your body cells. Recall that carbohydrates are starches and sugars.Starches are complex carbohydrates found in bread, cereal, potatoes, rice,

corn, beans, and pasta. Sugars aresimple carbohydrates foundmainly in fruits, such as plums,strawberries, and oranges.

During digestion, complexcarbohydrates are broken downinto simple sugars, such as glu-cose, fructose, and galactose.Absorbed into the bloodstreamthrough the villi of the smallintestine, these sugar moleculescirculate to fuel body functions.

Nutrition

USE SPARINGLY

2–3 SERVINGS 2–3 SERVINGS

2–4 SERVINGS3–5 SERVINGS

6–11 SERVINGS

Includes butter,oils, salad dressings,and soft drinks

FatSugar

The food pyramid

Figure 35.8Select foods from each ofthe five food groups everyday and you’ll have ahealthful diet that sup-plies the six essentialnutrients your body needs.

Aaron Haupt

924-928 C35S2 BDOL-829900 8/5/04 3:06 AM 24

Some sugar is carried to the liverwhere it is stored as glycogen.

Cellulose, another complex carbo-hydrate, is found in all plant cell wallsand is not digestible by humans.However, cellulose (also known asfiber) is still an important item toinclude in the diet as it helps in theelimination of wastes. Sources of fiberinclude bran, beans, and lettuce.

FatsMany people think that eating fat

means getting fat; however, fats are an essential nutrient. They provideenergy for your body and are alsoused as building materials. Recall thatfats are essential building blocks ofthe cell membrane. They are alsoneeded to synthesize hormones, pro-tect body organs against injury, andinsulate the body from cold.

Sources of fat in the diet includemeats, nuts, and dairy products, aswell as cooking oils. In the digestivesystem, fats are broken down intofatty acids and glycerol and absorbedby the villi of the small intestine.Eventually, some of these fatty acidsend up in the liver. The liver convertsthem to glycogen or stores them as fatthroughout your body.

ProteinsYour body has many uses for pro-

teins. Enzymes, antibodies, manyhormones, and substances that helpthe blood to clot, are all proteins.Proteins form part of muscles andmany cell structures, including thecell membrane.

During digestion, proteins are bro-ken down into amino acids. After theamino acids have been absorbed by thesmall intestine, they enter the blood-stream and are carried to the liver. The liver can convert amino acids tofats or glucose, both of which can beused for energy. However, your body

uses amino acids for energy only ifother energy sources are depleted.Most amino acids are absorbed by cellsand used for protein synthesis. Thehuman body needs 20 different aminoacids to carry out protein synthesis, but it can make only 12 of them. The remaining 8 must be consumed in the diet and so are called essen-tial amino acids. Sources of essentialamino acids include meats, dried beans,whole grains, eggs, and dairy products.

35.2 NUTRITION 925

Function Source

Fluorine (F)Dental cavityreductionFluoridated water

Iodine (I)Formation ofthyroid hormoneSeafood, eggs,iodized salt,milk group

Copper (Cu)Development ofred blood cells,formation of somerespiratoryenzymesGrain group, liver

Iron (Fe)Formation ofhemoglobin(carries oxygen tobody cells) andcytochromes (ATPformation)Liver, egg yolk,grain and meatgroups, leafyvegetables

Sodium (Na)Nerve activity,body pHregulationBacon, butter,table salt,vegetable group

Magnesium (Mg)Muscle and nerveactivity, boneformation,enzyme functionFruit, vegetable, and grain groups

Calcium (Ca)Teeth and boneformation, muscleand nerve activity,blood clottingMilk and graingroups

Phosphorus (P)Teeth and boneformation, bloodpH, muscle andnerve activity, partof enzymes andnucleic acidsMilk, grain, andvegetable groups

Potassium (K)Nerve and muscleactivityVegetable group,bananas

Sulfur (S)Builds hair, nails, andskin, componentof insulinGrain and fruitgroups, eggs, cheese

Figure 35.9Minerals serve manyvital functions. DescribeWhat are the func-tions of iron in thebody?

924-928 C35S2 BDOL-829900 8/5/04 3:07 AM Page 925


vitamin from theLatin word vita,meaning “life”;Vitamins are neces-sary for life.

Minerals and vitaminsWhen you think of minerals, you

may picture substances that peoplemine, or extract from Earth. Asshown in Figure 35.9 on the previouspage, the same minerals can also beextracted from foods and put to useby your body.

A mineral is an inorganic substancethat serves as a building material ortakes part in a chemical reaction in thebody. Minerals make up about fourpercent of your total body weight, mostof it in your skeleton. Although theyserve many different functions withinthe body, minerals are not used as anenergy source.

Unlike minerals, vitamins areorganic nutrients that are required in

small amounts to maintain growthand metabolism. The two maingroups of vitamins are fat-soluble and water-soluble, as shown inTable 35.2. Although fat-solublevitamins can be stored in the liver,the accumulation of excess amountscan prove toxic. Water-soluble vita-mins cannot be stored in the bodyand so must be included regularly inthe diet. Table 35.2 lists foods thatcontain fat-soluble and water-solublevitamins.

Vitamin D, a fat-soluble vitamin, issynthesized in your skin. Vitamin Kand some B vitamins are made by bacteria in your large intestine. Therest of the vitamins must be con-sumed in your diet.

Table 35.2 Vitamins

Vitamin Function Source

Fat-soluble

A Maintain health of epithelial cells; formation of light- Liver, broccoli, green and yellow absorbing pigment; growth of bones and teeth vegetables, tomatoes, butter, egg yolk

D Absorption of calcium and phosphorus in digestive Egg yolk, shrimp, yeast, liver, fortified milk;tract produced in the skin upon exposure to

ultraviolet rays in sunlight

E Formation of DNA, RNA, and red blood cells Leafy vegetables, milk, butter

K Blood clotting Green vegetables, tomatoes, produced byintestinal bacteria

Water-soluble

B1 Sugar metabolism; synthesis of neurotransmitters Ham, eggs, green vegetables, chicken, raisins, seafood, soybeans, milk

B2 (riboflavin) Sugar and protein metabolism in cells of eyes, Green vegetables, meats, yeast, eggsskin, intestines, blood

Niacin Energy-releasing reactions; fat metabolism Yeast, meats, liver, fish, whole-grain cereals, nuts

B6 Fat metabolism Salmon, yeast, tomatoes, corn, spinach, liver, yogurt, wheat bran, whole-grain cereals and bread

B12 Red blood cell formation; metabolism of amino acids Liver, milk, cheese, eggs, meats

Pantothenic Aerobic respiration; synthesis of hormones Milk, liver, yeast, green vegetables, whole-acid grain cereals and breads

Folic acid Synthesis of DNA and RNA; production of red and Liver, leafy green vegetables, nuts, white blood cells orange juice

Biotin Aerobic respiration; fat metabolism Yeast, liver, egg yolkC Protein metabolism; wound healing Citrus fruits, tomatoes, leafy green

vegetables, broccoli, potatoes, peppers

924-928 C35S2 BDOL-829900 8/5/04 3:09 AM Page 926

WaterWater is the most abundant sub-

stance in your body—between 45 and75 percent of your total body mass.Water facilitates the chemical reac-tions in your body and is necessary forthe breakdown of foods during diges-tion. Water is also an excellent sol-vent; oxygen and nutrients from foodcould not enter your cells if they didnot first dissolve in water.

Recall that water absorbs andreleases heat slowly. It is this charac-teristic that helps water maintain yourbody’s internal temperature. A largeamount of heat is needed to raise thetemperature of water. Because thebody contains so much water, it takes alot of added energy to raise its internaltemperature. Your body loses about2.5 L of water per day through exhala-tion, sweat, and urine. As a result,water must be replaced constantly.

Calories andMetabolism

The energy content of food ismeasured in units of heat calledCalories, each of which represents akilocalorie, or 1000 calories (writtenwith a small c). A calorie is theamount of heat required to raise thetemperature of 1 mL of water by 1°C.Some foods, especially those withfats, contain more Calories than oth-ers. In general, 1 g of fat contains nineCalories, while 1 g of carbohydrate orprotein contains four Calories. Tolearn more about Calories in meals,complete the MiniLab on this page.

The number of Calories neededeach day varies from person to per-son, depending on metabolism, orrate at which energy is burned. Asyou will see in the next section, amajor regulator of metabolic rate is ahormone from the thyroid gland.

A person’s body mass, age, gender,and level of physical activity alsoaffect metabolic rate. Generally,males need more Calories per daythan females, teenagers need morethan adults, and active people needmore than inactive people.

List factors that canaffect metabolic rate.

35.2 NUTRITION 927

Interpret DataEvaluate a Bowl of Soup As a consumer, you are bom-barded by advertising that promotes the nutritional benefitsof specific food products. Choosing a food to eat on the basisof such ads may not make nutritional sense. By examining theproduct labels that list the ingredients of processed foods, youcan learn about their actual nutritional content.

Procedure! Examine the information in the table listing the daily

value (DV) of various nutrients. DV expresses what percentof Calories should come from certain nutrients.

@ Examine the nutritional information on the soup can label,and compare it with the DV table.

Analysis1. Analyze Does your bowl of soup provide more than

30 percent of any of the daily nutrients? Which ones?2. Use Numbers Calculate the percentage of Calories in

soup that are provided by saturated fat.3. Evaluate Is this soup a nutritious meal? Explain.

NUTRITION FACTS

Amount Per ServingCalories 140 Calories from Fat 54

% Daily Value*

Total Fat 8g 12%Saturated Fat 6g 30%

Cholesterol 20mg 7%Sodium 1640 mg 68%Total Carbohydrate 22g 7%

Dietary Fiber 5g 20%Sugars 5g

Protein 6gVitamin A 50% Vitamin C 4%Calcium 2%

Percent Daily Values are based on a 2,000calorie diet. Your daily values may be higher orlower depending on your calorie needs:

Calories 2,000 2,500Total Fat Less than 65g 80g Sat Fat Less than 20g 25gCholesterol Less than 300mg 300mgSodium Less than 2,400mg 2,400mgTotal Carbohydrate 300g 375gFiber 25g 30g

Calories per gram:Fat 9 * Carbohydrates 4 * Protein 4

Iron 2%

Serving Size: 2 cups (452g)Servings Per Container: 1

*

Data Table

Percentage of Daily Value (DV)

Carbohydrates 60%

Fat 30%Saturated fats 10%

Cholesterol 1.5%

Protein 10%

Total Calories 2000

924-928 C35S2 BDOL-829900 8/5/04 3:09 AM Page 927

Understanding Main Ideas1. Compare the functions of carbohydrates, fats, and

proteins in the body.

2. Describe the role of the liver in the storage of car-bohydrates, fats, and proteins.

3. Compare and contrast vitamins and minerals. Whichvitamins and minerals can be found in milk?

4. What happens when a person takes in more foodenergy than his or her body needs?

Thinking Critically5. Describe two effects dehydration can have on

homeostasis of the body.

6. Make and Use Tables Using Table 35.2 on page926, analyze how a lack of vitamins A, D, K, and Cin a person’s diet could affect his or her health.For more help, refer to Make and Use Tables inthe Skill Handbook.



Calories and healthWhat happens if a person consumes

more Calories than his or her bodycan metabolize? When the energytaken in is greater than the energyexpended, the extra energy is stored asbody fat and a person gains weight.However, if a person eats fewerCalories than the body can metabo-lize, some of the body’s stored energyis used and weight is lost.

Physicians have determined thatmany Americans are overweight.Being overweight or obese increases aperson’s risk for developing healthproblems such as high blood pressure,diabetes, and heart disease. Beingunderweight is also associated withhealth problems such as anemia,fatigue, and decreased ability to fightinfection and disease. A simple way todetermine if a person is at a healthyweight is to calculate his or her BodyMass Index (BMI). Calculate a sampleBMI by doing the Problem-Solving Labon this page.

Millions of people put themselveson diets every year in hopes of losingweight. While many diets are nutri-tionally sound, others prescribe eatinghabits that are not sensible and usuallyfail to produce the desired result.Read more about weight-loss prod-ucts in the Biology and Society section atthe end of this chapter.

Use NumbersWhat is BMI? BMI is a reliable indicator of a healthy bodyweight for adult men and women based on height andweight. Approximately sixty percent of adults in the UnitedStates are considered overweight. Use the following equationto calculate a sample BMI.

Solve the ProblemCompute BMI, or Body Mass Index, using the following formula:

The guidelines for adults from the National Institutes of Healthare as follows:

A BMI• 18.5 to 24.9 = normal weight• 25 to 29.9 = overweight • 30 or over = obese

Thinking Critically1. Evaluate Calcuate the BMI for a person who is 5 feet

4 inches tall and weighs 132 pounds. According to theguidelines, is this person of normal weight, overweight, or obese?

2. Recognize Cause and Effect How might a person with aBMI of 27 reduce his or her BMI? Consider both nutritionalintake and physical activity.

3. Infer Fred has a BMI of 22. How do you suppose hisCalorie intake compares to his Calorie expenditure?

4. Think Critically What limits does the BMI test have?(Hint: A 6 foot tall, well-muscled athlete weighing200 pounds would have a BMI of 27.)

weight (in pounds)height (in inches )2

� 704.5 = BMI


924-928 C35S2 BDOL-829900 8/5/04 3:10 AM Page 928


35.3SECTION PREVIEWObjectivesDescribe the internalfeedback mechanism con-trolling hormone levels inthe body. Contrast the actions ofsteroid and amino acidhormones.Identify and interpret thefunctions of some of thehormones secreted byendocrine glands.

Review Vocabulary gland: in mammals, a cell

or group of cells thatsecretes fluid (p. 842)

New Vocabularyendocrine glandshypothalamuspituitary glandtarget cellreceptornegative feedbacksystem

adrenal glandthyroid glandparathyroid glands

endocrine fromthe Greek wordsendo, meaning“within,” andkrinein, meaning“to separate”; Theendocrine glandssecrete hormonesinto the blood.

35.3 THE ENDOCRINE SYSTEM 929

Internal FeedbackConcept Map Copy the concept map onto a separate sheet of paper.

Organize Information As you read this section, complete the concept mapabout internal feedback in the endocrine system.

detects low watercontent in blood

and stimulates the

The

to reabsorb

to release which cantarget

hypothalamus

1.

4.

2. 3.

The Endocrine System

Control of the BodyInternal control of the body is directed by two systems: the nervous

system, which you will learn more about later, and the endocrine system.The endocrine system is made up of a series of glands, called endocrineglands, that release chemicals directly into the bloodstream. Thesechemicals act as messengers, relaying information to other parts of thebody. Ultimately, the functions of all body systems are controlled by theinteraction between the nervous and endocrine systems.

Interaction of the nervous system and endocrine systemMuch of the time, the endocrine system and the nervous system work

together to maintain homeostasis within the body. Because there are twocontrol systems within the body, coordination between the two systems isneeded. The hypothalamus (hi poh THA luh mus) is the portion of thebrain that connects the endocrine and nervous systems. The hypothala-mus receives messages from other areas of the brain and from internalorgans. When a change in homeostasis is detected, the hypothalamusstimulates the pituitary (pih TEW uh ter ee) gland. The pituitary gland,the main gland of the endocrine system, is located in the skull just beneaththe hypothalamus. The pituitary gland is controlled by the hypothalamus,and the two are connected by nerves and blood vessels. In response tomessages received by the hypothalamus, the pituitary gland releases itsown chemicals or stimulates other glands to release theirs. Otherendocrine glands under the control of the pituitary include the thyroidgland, the adrenal glands, and glands associated with reproduction.

Standard 9c Students know how feedback loops in the nervous andendocrine systems regulate conditions in the body.

California Standards

929-941 C35S3 BDOL-829900 8/5/04 3:19 AM Page 929

Endocrine control of the bodyThe chemicals secreted by endo-

crine glands into the bloodstream are called hormones. Recall that a hor-mone is a chemical released in one partof an organism that affects another

part. Hormones convey information toother cells in your body, giving theminstructions regarding your metabo-lism, growth, development, and behav-ior. Once released by the glands, thehormones travel in the bloodstreamand then attach to specific binding sitesfound on the plasma membranes, or inthe nuclei, of target cells. These bind-ing sites on cells are called receptors.Figure 35.10 summarizes the action ofdifferent endocrine glands.

Example of endocrine control Human growth hormone (hGH) is

a good example of an endocrine sys-tem hormone. When your body isactively growing, blood glucose levelsare slightly lowered as the growingcells use up the sugar. This low bloodglucose level is detected by the hypo-thalamus, which stimulates the pro-duction and release of hGH from thepituitary into the bloodstream. hGHbinds to receptors on the plasmamembranes of liver cells, stimulatingthe liver cells to release glucose intoyour blood. Your cells need the glu-cose in order to continue growing.Figure 35.11 summarizes the controlof hGH by the pituitary gland. Thisdiagram also shows the types of hor-mones secreted by other humanendocrine glands and some of theeffects they have on the body.

Negative Feedback Control

If homeostasis is disrupted, endo-crine glands can be stimulated by thenervous system, changes in bloodchemistry, or by other hormones.Regulation of the endocrine system iscontrolled most often through onetype of internal feedback mechanismcalled a negative feedback system.In a negative feedback system, the

PituitaryAmino acidhormonesControls adrenalgland, thyroidgland, ovaries,testes, mammaryglands, storeshypothalamushormones, andsecretesgrowth hormone

ParathyroidglandAmino acidhormonesSecretes para-thyroid hormone

AdrenalmedullaAmino acidhormonesSecretesepinephrine andnorepinephrine

Adrenal cortexSteroid hormonesSecretes gluco-corticoid andaldosterone

HypothalamusAmino acidhormonesControls pituitaryand synthesizesantidiuretichormone andoxytocin for uteruscontraction duringbirth

Thyroid glandAmino acidhormonesSecretes thyroxinto stimulategrowth andmetabolism andsecretes calcitonin

Ovary in femaleSteroid hormonesSecretes femalesex hormones

Testis in maleSteroid hormonesSecretes malesex hormonesType of hormones

released

Function of gland

Figure 35.10 This diagram shows the principal human endocrine glands, the type of hormone(s) they secrete, and the action of the gland/hormone. List What are the hormones secreted by the adrenal medulla?


929-941 C35S3 BDOL-829900 8/5/04 3:21 AM Page 930

hormones, or their effects, are fedback to inhibit the original signal.Once homeostasis is reached, the sig-nal is stopped and the hormone is nolonger released. The thermostat inyour home is controlled by a similarnegative feedback system. It main-tains the room at a set temperature.When the temperature drops, thethermostat senses the reduction ofthermal energy and signals the heaterto increase its output. When the ther-mal energy of the room rises again toa certain point, the thermostat nolonger stimulates the heater, whichshuts off. When the temperaturedrops again, the process repeats itself.In this negative feedback system, theincrease in temperature “feeds back”to signal the thermostat to stop stim-ulating thermal energy production.

Relate negativefeedback systems to the mainte-nance of homeostasis.

Feedback control of hormonesThe majority of endocrine glands

operate under negative feedback sys-tems. A gland synthesizes and secretesits hormone, which travels in theblood to target cells where the appro-priate response occurs. Informationregarding the hormone level or itseffect on target cells is fed back, usu-ally to the hypothalamus or pituitarygland, to regulate the gland’s produc-tion of the hormone.

Control of blood water levelsLet’s look at an example of a hor-

mone that is controlled by a negativefeedback system. After working out inthe gym and building up a sweat, youare thirsty. This is because the watercontent of your blood has beenreduced. The hypothalamus, which isable to sense the concentration of

water in your blood, determines thatyour body is dehydrated. In response, itstimulates the pituitary gland to releaseantidiuretic (AN tih di yuh reh tihk)hormone (ADH).

ADH reduces the amount of waterin your urine. It binds to receptors inkidney cells, promoting the reabsorp-tion of water and reducing theamount of water excreted in urine.Information about blood water levelsis constantly fed back to the hypothal-amus so it can regulate the pituitary’srelease of ADH. If the body becomesoverhydrated, the hypothalamus stopsstimulating release of ADH.


Low blood sugaris detected.

Pituitary

Hypothalamusstimulates pituitaryto release hGH.

hGH stimulates liver to convert glycogen into glucose and releases glucose into blood.

Increased sugar in blood signals back to hypothalamus to slow stimulation of pituitary.

Figure 35.11 The hypothalamus and pituitary gland control the amount of human growth hormone (hGH) in your blood.

A

B

C

D

929-941 C35S3 BDOL-829900 8/5/04 3:21 AM Page 931

Control of blood glucose levelsAnother example of a negative

feedback system involves the regula-tion of blood glucose levels. Unlikemost other endocrine glands, the pan-creas is not controlled by the pituitarygland. When you have just eaten andyour blood glucose levels are high,your pancreas releases the hormoneinsulin. Then, insulin signals liver and

muscle cells to take in glucose, thus lowering blood glucose levels. Whenblood glucose levels become too low,another pancreatic hormone, gluca-gon, is released. Glucagon binds toliver cells, signaling them to releasestored glycogen as glucose. Learnmore about glucose storage andrelease by doing the Problem-SolvingLab on this page.

Hormone ActionOnce hormones are released by an

endocrine gland, they travel to targetcells and cause a change. Hormonescan be grouped into two basic typesaccording to how they act on theirtarget cells: steroid hormones andamino acid hormones.

Action of steroid hormones Hormones that are made from

lipids are called steroid hormones.Steroid hormones are lipid-solubleand therefore diffuse freely into cellsthrough their plasma membranes, asshown in Figure 35.12. There theybind to a hormone receptor inside thecell. The hormone-receptor complexthen travels to the nucleus where itactivates the synthesis of specific mes-senger RNA molecules. The mRNAmolecules move out to the cytoplasmwhere they guide the synthesis of therequired proteins.

Action of amino acid hormonesThe second group of hormones is

made from amino acids. Recall thatamino acids can be strung togetherin chains and that proteins are madefrom long chains of amino acids.Some hormones are short chains ofamino acids and others are largechains. These amino acid hormones,once secreted into the bloodstream,bind to receptors embedded in theplasma membrane of the target cell,


adrenal from theLatin words ad,meaning “to” or“toward” andrenes, meaning“the kidneys”; Theadrenal glands arelocated on top ofthe kidneys.

Insu

lin (

µU/m

L)

Glu

cago

n (p

g/m

L)

5 150

300

450

0 1 2 3 4

10

Hours

Levels of Insulin and Glucagon During Exercise

Insulin

Glucagon

Interpret DataHow does exercise affect levels of insulin and glucagon?Exercise represents an example of rapid fuel mobilization inthe body. The body must gear up to supply great amounts ofglucose and oxygen for muscle metabolism.

Solve the ProblemThe graph here shows the effects of prolonged exercise, suchas running a marathon, on blood insulin and glucagon levels.

Thinking Critically1. Analyze Examine the graph and explain how exercise

affects the concentrations of insulin and glucagon in theblood.

2. Recognize Cause and Effect Relate the changes shownon the graph to what is occurring in muscle cells as well asto blood glucose levels.

3. Sequence Design a flowchart that shows the stepsinvolved in maintaining homeostasis of blood glucose during exercise. Begin your flowchart with muscle cells.

929-941 C35S3 BDOL-829900 8/5/04 3:22 AM Page 932

as shown in Figure 35.13. From there,they open ion channels in the mem-brane, or route signals down from thesurface of the membrane to activateenzymes inside the cell. The enzymes,in turn, alter the behavior of othermolecules inside the cell. In both ofthese ways, the hormone is able to con-trol what goes on inside the target cell.

Adrenal Hormones and Stress

You are sitting in math class and theteacher is about to hand out the semes-ter test. Because this test is an importantone, you have spent many hours study-ing for it. Like most of your classmates,you are a little nervous as the test isbeing passed down the row. Your heartis beating fast and your hands are a little sweaty. As you review the firstproblem, however, you begin to calmdown because you know how to solve it.

The adrenal glands play an impor-tant role in preparing your body forstressful situations. The adrenalglands are located on top of the kid-neys and consist of two parts—aninner portion and an outer portion.

The outer portion secretes steroidhormones, including glucocorticoids(glew ko KOR tuh koydz) and aldos-terone (ahl DOS tuh rohn).

These steroid hormones cause anincrease in available glucose and raiseblood pressure. In this way, they helpthe body combat stresses such as fright,temperature extremes, bleeding, infec-tion, disease, and even test anxiety.


Ions

Ion channel

Enzyme(inactive)

Enzyme(active)

Cellmembrane

Nucleus

Amino acidhormone

Hormonereceptor

11

22

33

33

11

22Ribosome

Nucleus

Steroidhormone

Cell membrane

mRNA

mRNA

DNA

New proteinmolecule

Hormone-receptorcomplex

Figure 35.12 Steroid hormones entera cell (1), bind to areceptor (2), which inturn binds to DNA tostimulate protein synthesis (3).

Figure 35.13 When an amino acidhormone binds to thereceptor on the cellmembrane (1), it canopen ion channels (2),or activate enzymes (3).

929-941 C35S3 BDOL-829900 8/5/04 3:23 AM Page 933

The inner portion of the adrenalgland secretes two amino acid hor-mones: epinephrine (eh puh NEH

frun)—often called adrenaline—andnorepinephrine. Recall the fight-or-flight response discussed in the ani-mal behavior chapter. During such aresponse, the hypothalamus relaysimpulses to the nervous system,which in turn stimulates the adrenalglands to increase their output of epi-nephrine and norepinephrine. Thesehormones increase heart rate, bloodpressure, and rate of respiration;increase efficiency of muscle contrac-tions; and increase blood sugar levels.If you have ever had to perform infront of a large audience, you mayhave experienced these symptoms,often referred to collectively as an“adrenaline rush.” This is how thebody prepares itself to face or flee astressful situation.

Thyroid andParathyroid Hormones

The thyroid gland, located in theneck, regulates metabolism, growth,and development. The main meta-bolic and growth hormone of the thy-roid is thyroxine. This hormoneaffects the rate at which the body usesenergy and determines your foodintake requirements.

The thyroid gland also secretes calcitonin (kal suh TOH nun)—a hor-mone that regulates calcium levels inthe blood. Calcium is a mineral thebody needs for blood clotting, forma-tion of bones and teeth, and normalnerve and muscle function. Calcitoninbinds to the membranes of kidney cellsand causes an increase in calciumexcretion. Calcitonin also binds tobone-forming cells, causing them toincrease calcium absorption and syn-thesize new bone.


Data Table

Name of Hormone(s)Tissue Drawing Produced

Thyroid

Parathyroid

Fred Hossler/Visuals Unlimited

ObserveCompare Thyroid and Parathyroid Tissue Although theirnames seem somewhat similar, the thyroid and parathyroidglands perform rather different functions within the body.

Procedure! Copy the data table.@ Use low-power magnifica-

tion to examine a pre-pared slide of thyroid andparathyroid endocrinegland tissue. (Note: Bothtissues appear on thesame slide.) CAUTION: Usecaution when workingwith a microscope andprepared slides.

# The image on the right isa photograph of thyroidand parathyroid tissue.Use it as a guide in locatingthe two types of endocrinegland tissue under lowpower and in answering certain analysis questions.

$ Now locate each type of gland tissue under high-powermagnification. Draw what you see in the data table. Thenuse what you learned in the chapter to identify the namesof the hormones produced by each gland.

Analysis1. Compare and Contrast Compare and contrast the

microscopic appearance of parathyroid tissue to that ofthyroid tissue.

2. a. Observe Which tissue type contains follicles (large liquid storage areas)?

b. Infer What may be present within the follicles? c. Think Critically Hypothesize what function the thin

layer of tissue that surrounds each follicle may have.3. Explain How might you explain the fact that both thy-

roid and parathyroid tissue can be seen on the same slide?

Parathyroid (A) and thyroid (B) tissue

Color-enhanced LM Magnification: 16�

AA

BB

929-941 C35S3 BDOL-829900 8/5/04 3:23 AM Page 934

Understanding Main Ideas1. Identify and interpret the functions of the

endocrine system.

2. Explain the interrelationship between the nervoussystem and the endocrine system.

3. Describe the relationship between a negative feed-back system and the maintenance of homeostasis.

4. How does a steroid hormone affect its target cell?How does this action differ from how an aminoacid hormone affects its target cell?

Thinking Critically5. Hormones continually make adjustments in blood

glucose levels. Why must blood glucose levels bekept fairly constant?

6. Sequence Create a flowchart that illustrates theinternal feedback system the body uses to main-tain blood glucose homeostasis. For more infor-mation, refer to Sequence in the Skill Handbook.



Another hormone involved inmineral regulation, parathyroid hor-mone (PTH), is produced by theparathyroid glands, which areattached to the thyroid gland. Therelease of PTH leads to an increasein the rate of calcium, phosphate, andmagnesium absorption in the intes-tines. PTH causes the release of cal-cium and phosphate from bonetissue. It also increases the rate atwhich the kidneys remove calciumand magnesium from urine andreturn them to the blood.

The overall effect of parathyroidhormone and calcitonin hormoneinteraction in the body is shown inFigure 35.14. Take a closer look atthyroid and parathyroid tissue by com-pleting the MiniLab on the previouspage.

As you can see, hormones associ-ated with the endocrine system areresponsible for controlling many different functions in your body.Different hormones may play moreimportant roles during some periodsin your life than others. In any case,they remain the principal biologicalinfluence on your behavior anddevelopment.

Describe how bloodcalcium homeostasis is maintainedwithin the body.

Blood calciumlevels decreased

PTHIntestine

Ca2+ absorbedto blood

Ca2+ releasedto blood

Blood calciumlevels increased

Calcitonin

Parathyroids Thyroid

Kidney

Ca2+ absorbedto blood

Ca2+

absorbed

Bone

Ca2+ excreted

Figure 35.14 Calcitonin and parathyroid hormone (PTH) have opposite effects on blood calcium levels.


929-941 C35S3 BDOL-829900 8/5/04 3:24 AM Page 935


Before You Begin


Before You BeginThe enzyme amylase isfound in both salivary and pancreatic secretions.Amylase is used by thebody to digest starch.When you eat foods thatcontain starch, such asbreakfast cereals, salivaryamylase immediatelybegins to digest thesemolecules. How long doesit take for larger mole-cules of starch to be bro-ken down into simplesugars? In this lab, you will investigate the rela-tive rate of starch diges-tion by amylase.

Initial test

0

30

60

Data Table

Time (sec) Presence of Starch

Cereal A Cereal B Cereal C

The Action of the Enzyme Amylase onBreakfast Cereals

ProblemHow long does it take amylase to digest all of the starch inbreakfast cereals?

ObjectivesIn this BioLab, you will:■ Compare the relative rate of starch digestion by amylase on

three breakfast cereals.

Materialsvariety of dry cereals watermortar and pestle Bunsen burner or hot platetest tubes graduated cylindertest tube racks iodine solution in dropper bottlesfilter paper watch glassesfunnel plastic droppersbalance amylase solutionbeaker

Safety Precautions CAUTION: Never eat laboratory materials. Iodine can irritateand will stain skin.

Skill HandbookIf you need help with this lab, refer to the Skill Handbook.

1. Copy the data table.2. Label the breakfast cereals and three corresponding test

tubes A, B, and C.

PROCEDUREPROCEDURE

PREPARATIONPREPARATION

929-941 C35S3 BDOL-829900 8/5/04 3:27 AM Page 936


1. Analyze Did all of the breakfast cereals con-tain starch? What action did the amylase haveon the starch?

2. Observe and Infer Which cereal was con-verted to simple sugars in the least amount oftime? Infer what this indicates about thestarch concentration of this cereal comparedto the other cereals.

3. Think Critically Does the amount of starchversus simple sugars make a difference in theCalorie content of the cereal?

Use Variables, Constants, and ControlsInvestigate the effect of temperature or pHon the action of amylase on one of thebreakfast cereals.

Web Links To find out more about digestive enzymes, visit

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

A B C

3. Grind a small portion of each of the breakfast cereals to apowder using the mortar and pestle.

4. Place a piece of filter paper in the funnel. Place the fun-nel over test tube A.

5. Using the balance, measure out 0.5 g of ground cereal Aand transfer it to the funnel.

6. Filter 10 mL of boiling water over the cereal and allowthe filtrate to collect in the bottom of the test tube.

7. Repeat steps 4, 5, and 6 for cereals Band C. Rinse the funnel and replacethe filter paper before each filtration.

8. Add 2 drops of the iodine solution to awatch glass, followed by 2 drops of fil-trate A. A dark blue/black color indi-cates the presence of starch. Recordyour results.

9. Using a separate eyedropper for eachsolution, repeat step 8 on cereals Band C. Clean the watch glass betweeneach test.

10. Add 2 mL of amylase solution to eachfiltrate. Immediately take a sample, andrepeat steps 8 and 9 to retest for the presence of starch.

11. Test each filtrate every 30 seconds until all of the starchhas been digested to simple sugars in each sample.Record your results.

12. Clean all equipment as instructedby your teacher. Make wise choices as to the disposal orrecycling of materials. Wash your hands thoroughly.

CLEANUP AND DISPOSAL

ca.bdol.glencoe.com/digestive_enzymes

929-941 C35S3 BDOL-829900 8/5/04 3:32 AM Page 937

http://ca.bdol.glencoe.com/digestive_enzymes


The appeal of weight-loss products There are many weight-loss products available to the public. Some of these products arebased on good nutrition and positive lifestyle changes, such as eating a well-balanced dietand incorporating a regularexercise program. Other prod-ucts look like a fast and easysolution to a weight-loss prob-lem. However, these productsmay not provide permanentresults or may have negative sideeffects. How can you evaluate thepromotional claims such as thoseseen in magazine and televisionadvertisements or on a product label?

Read the fine print Many weight-loss prod-ucts make claims in bold letters at the top of anadvertisement or have a quote from someoneclaiming to have successfully lost weight usingthe product. However, in very small print at thebottom may be a qualifying statement such as“Results not typical” or “When used with a bal-anced diet and regular exercise.”

Some weight-loss products may help somepeople lose a few pounds temporarily. However,for safe, long-term weight loss, nutritionists rec-ommend a diet based on healthy eating habits:balanced, regular meals rich in fruits and vege-tables, whole grains, sufficient protein, and smallamounts of fat. Making lifestyle changes thatincorporate regular exercise also allow forhealthy weight loss and maintenance.

Evaluate the Promise of Weight Lossas a Promotional Claim

Lose ten pounds in one week!”“Shed weight without going

hungry!” “Burn fat while you sleep!”

Evaluate Collect advertisements and product labelsfor three different weight-loss products that promise“miracle” results. Research how these products con-tribute to weight loss. What effects do these productshave on the body that result in weight loss? Arethere any negative side effects? Evaluate the promo-tional claims of these advertisements and productlabels. Based on what you know about the impor-tance of good nutrition and exercise on health,would you recommend the use of these particularproducts? Why or why not?

To find out more about weight-loss products, visit ca.bdol.glencoe.com/biology_society

Aaron Haupt

929-941 C35S3 BDOL-829900 8/5/04 3:35 AM Page 938

http://ca.bdol.glencoe.com/biology_society

STUDY GUIDESTUDY GUIDESection 35.1

Section 35.2

Section 35.3

Vocabularyamylase (p. 918)bile (p. 921)epiglottis (p. 920)esophagus (p. 918)gallbladder (p. 921)large intestine (p. 923)liver (p. 921)pancreas (p. 921)pepsin (p. 921)peristalsis (p. 918)rectum (p. 923)small intestine (p. 921)stomach (p. 920)villus (p. 922)

VocabularyCalorie (p. 927)mineral (p. 926)vitamin (p. 926)

Vocabularyadrenal gland (p. 933)endocrine glands

(p. 929)hypothalamus (p. 929)negative feedback

system (p. 930)parathyroid glands

(p. 935)pituitary gland (p. 929)receptor (p. 930)target cell (p. 930)thyroid gland (p. 934)

Nutrition

The EndocrineSystem

CHAPTER 35 ASSESSMENT 939

FollowingDigestion of a Meal

Ribosome

Nucleus

Steroidhormone

Cell membrane

mRNA

mRNA

DNA

New proteinmolecule

Hormone-receptorcomplex

USE SPARINGLY

2–3 SERVINGS 2–3 SERVINGS

2–4 SERVINGS3–5 SERVINGS

6–11 SERVINGS

Includes butter,oils, salad dressings,and soft drinks

FatSugar

To help you review thedigestive system, use the Organiza-tional Study Fold on page 917.

Key Concepts■ Digestion begins in the mouth with both

mechanical and chemical action. Theesophagus transports food from the mouthto the stomach.

■ Chemical and mechanical digestion con-tinue in the acidic environment of thestomach.

■ In the small intestine, digestion is com-pleted and food is absorbed. The liver andpancreas play key roles in digestion.

■ The large intestine absorbs water beforeindigestible materials are eliminated.

Key Concepts■ The endocrine glands work with the ner-

vous system to regulate body functions.■ Blood hormone levels are controlled by a

negative feedback system.■ Steroid hormones bind to receptors inside

the target cells, and amino acid hormonesbind to plasma membrane receptors.■ Hormones are involved in the regula-

tion of blood glucose and calcium levels, as well as responses to stress.

Key Concepts■ Carbohydrates are the body’s main source

of energy. Fats are used to store energy.Proteins are used as building materials.

■ Minerals serve as structural materials ortake part in chemical reactions. Vitaminsare needed for growth and metabolism.■ Water facilitates chemical reactions in

the body, acts as a solvent, and helpsmaintain internal body temperature.

ca.bdol.glencoe.com/vocabulary_puzzlemaker

929-941 C35S3 BDOL-829900 8/5/04 3:36 AM Page 939

http://ca.bdol.glencoe.com/vocabulary_puzzlemaker

940 CHAPTER 35 ASSESSMENT ca.bdol.glencoe.com/chapter_test

Review the Chapter 35 vocabulary words listed inthe Study Guide on page 939. Distinguishbetween the vocabulary words in each pair.

1. amylase—bile2. epiglottis—esophagus3. mineral—vitamin4. receptor—target cell5. hypothalamus—pituitary gland6. thyroid gland—parathyroid glands

7. Which of these is NOT a function of thedigestive system?A. eliminating wastesB. absorbing nutrientsC. digesting foodD. regulating metabolism

8. Which structure prevents food from enter-ing the respiratory tract?A. villus C. epiglottisB. pancreas D. stomach

9. Which of the following is located beneath thehypothalamus?A. pituitary glandB. adrenal glandsC. thyroid glandD. parathyroid glands

10. What unit is used to measure the energycontent of food?A. temperature C. CalorieB. gram D. mass

11. The pancreas releases which of the follow-ing hormones?A. epinephrine, norepinephrineB. hGH, ADHC. thyroxine, calcitoninD. glucagon, insulin

12. What is the most abundant substance in thehuman body?A. carbohydrates C. waterB. vitamins D. proteins

13. Which of these enzymes functions best inthe acidic pH of the stomach?A. lipase C. pepsinB. lactase D. amylase

14. Concept Map Complete the concept mapby using the following vocabulary terms:liver, bile, small intestine, stomach, esopha-gus, gallbladder.

15. Open Ended Patients with cystic fibrosiscan have a blocked pancreatic duct. Whateffect will this have on digestion?

16. Open Ended People with Type 1 diabetesdo not produce any insulin. What effectwould this have on cells and metabolism ifleft untreated?

17. Open Ended How would the removal of theparathyroid glands affect muscle contrac-tion? Explain how this could result in a dis-ruption of homeostasis.

18. Recognize Cause and Effect How is therole of pancreatic hormones in glucose regu-lation important for homeostasis?

19. Visitto find out more

about the bacteria that live in the large in-testines of humans. What species of bacteriaare found in the large intestines of humans?How does each organism benefit from thisrelationship?

REAL WORLD BIOCHALLENGE

4.

5.

6.

passesfood to the

which isstored in the

makes

2.

1.

which passes food to the

which deliversbile to the

3.

ca.bdol.glencoe.com

929-941 C35S3 BDOL-829900 8/5/04 3:37 AM Page 940

http://ca.bdol.glencoe.com/chapter_test

http://ca.bdol.glencoe.com

CHAPTER 35 ASSESSMENT 941

20. Predict The thyroid gland needs the min-eral iodine to function properly. Use yourknowledge of the thyroid gland to predictthe effects that an iodine deficiency couldhave on a person’s health.

21. Design an Experiment Design an experi-ment to show that exercise can contribute toweight loss. Identify dependent and inde-pendent variables. What could account forvariations in your results?

Constructed Response/Grid InRecord your answers or fill in the bubbles on your answer document using the correct place value.

27. Grid In For a 2000-Calorie-per-day diet, calculate, in grams, the amount of carbohydrates, fats, and proteins that should be consumed using the Daily Values recommended by the FDA. (Hint: 1 g of carbohydrate � 4 Calories, 1 g of fat � 9 Calories, 1 g of protein � 4 Calories)

28. Open Ended Achlorhydria is a condition in which the stomach fails to secrete hydrochloricacid. How would this condition affect digestion? If left untreated, how could this affect thebody as a whole?

Multiple ChoiceUse the diagram to answer questions 22–24.

22. The diagram shows the control pathway ofhuman growth hormone (hGH) in theblood. Which of the following stimulatesthe pituitary to release hGH?A. liver C. hypothalamusB. pituitary gland D. hGH

23. When the pituitary gland releases humangrowth hormone (hGH), what is the effecton the liver? A. stimulates the pituitary gland to release hGHB. stimulates the liver to convert glycogen

into glucoseC. stimulates the liver to store glucoseD. decreases sugar level in blood

24. What stimulates the hypothalamus to initi-ate the entire sequence involving humangrowth hormone (hGH)? A. low blood glucose levelsB. high blood glucose levelsC. low levels of hGHD. high levels of hGH

Use the table to answer questions 25–27.

25. Using the table, calculate how many Calories of carbo-hydrates a person should be getting if he or she were con-suming 2800 Caloriesof food energy per day.A. 1000 Cal C. 1680 CalB. 1550 Cal D. 2000 Cal

26. If a person were using the table as a guide-line to consume 50 g of protein per day(10% of the DV), calculate how manyCalories of food energy that person is takingin each day. (1 g of protein � 4 Calories)A. 1000 Cal C. 1600 CalB. 1200 Cal D. 2000 Cal

Hypothalamus Hypothalamus

Pituitary

LiverPercentage of Daily Value (DV)

Carbohydrates 60%

Fat 30%Saturated fats 10%

Protein 10%

Total Calories 2000

ca.bdol.glencoe.com/standardized_test

9c

9c

9f

9c

The assessed California standard appears next to the question.

929-941 C35S3 BDOL-829900 8/5/04 3:38 AM Page 941

http://ca.bdol.glencoe.com/standardized_test

chapter 35: the digestive and endocrine systems · the digestive and endocrine systems • review...

Documents