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Unit 5 Biology Notes

Topic 7: Run for Your Life 2. Describe the structure of a muscle fibre and explain the structural and physiological differences between fast and slow twitch muscle fibres. Muscle is made up of myofibrils lying parallel to each other. Each myofibril is made up of sarcomeres. Actin and myosin are proteins that make up a large part of the sarcomeres. The cytoplasm of myofibrils is called the sarcoplasm. There are a lot of mitochondria to provide energy. The sarcoplasmic reticulum is a network of membranes that stores and releases calcium ions. Properties of slow twitch muscle fibres

Have steady action over a long period of time

Contract slowly and stay in tetanus long

Used to maintain body posture

Rely on glucose for fuel

Known as oxidative/red muscle due to rich blood supply and high levels of myoglobin

Rich blood supply, a lot of mitochondria and plenty of myoglobin means they can continue their activity without the need to respire anaerobically

Properties of fast twitch muscle fibres

Contract rapidly so suited for rapid bursts of activity

Functions anaerobically so pale in colour; lack of blood supply. This is why it is known as white muscle fibre

Relatively few blood vessels and low levels of myoglobin

Fatigues quickly

Small number of mitochondria

Rich glycogen stores

High levels of creatine phosphate. Also known as phosphocreatine

3. Explain the contraction of skeletal muscle in terms of the sliding filament theory, including the role of actin, myosin, troponin, tropomyosin, calcium ions, ATP and ATPase Sliding filament theory – Theory developed by Hugh Huxley and Jean Hanson in the 1950s to explain the patterns seen when muscle contracts Actin – One of the contractile proteins that make up the structure of the muscle cells. It is made up of two chains of actin monomers joined together like beads on a necklace. Actin’s shape produces myosin binding sites where myosin’s globular heads can fit. Myosin – Contractile protein that interacts with actin to bring about the contraction of a muscle. It is made up of two long polypeptide chains twisted together, each ending in a large globular head which has ADP and inorganic phosphate molecules bound to it. The head can act as an ATPase enzyme Troponin – A protein associated with tropomyosin in the muscle structure. It is attached regularly along the chain of tropomyosin. It has 3 sub units, one binds to actin, one binds tropomyosin and the final one binds calcium ions. Tropomyosin – Long chain protein which wraps around actin chains in the structure of a muscle and, in a relaxed muscle, it covers up the myosin binding sites on actin filaments. Calcium ions – Released from the sarcoplasmic reticulum as a result of a stimulus. Ca2+ binds to troponin molecules causing it to change shape. It is also required in the activation of ATPase in the myosin globular head.

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The Process

Calcium ions bind to troponin, changing their shape. Troponin molecules pull on the tropomyosin molecules they are attached to, moving tropomyosin away from the myosin binding site, exposing them, ready for action

Myosin’s globular head bind to actin forming an actomysosin bridge

ADP and an inorganic phosphate group are released from the myosin head. Myosin changes shape – the head bends forward moving the actin along the myosin filament, shortening the sarcomere.

Free ATP binds to myosin’s head causing myosin to change shape again. This breaks the actomysosin bridge. ATPase is activated in the myosin head; this requires calcium ions as well. ATP is hydrolysed to provide energy to return the myosin head to its original position.

Calcium ions remain in the sarcoplasm and the cycle is repeated if there is continuous stimulation. If not, ATP is used to pump calcium ions back into the sarcoplasmic reticulum. Troponin and tropomyosin return to their original positions.

4. Recall the way in which muscles, tendons, the skeleton and ligaments interact to enable movement, including antagonistic muscle pairs, extensors and flexors. Muscle - Largely made up of protein. They can shorten to do work Tendons – Made up of white fibrous tissue and has bundles of collagen fibres. The tissue is strong but relatively inelastic. It attaches muscle to bone Skeleton – It is made up of bone. It is strong and hard. Made up of bone cells embedded in a matrix of collagen and calcium salts. It is strong under compression but not dense. This is to reduce the weight moved about Ligament – Holds bones together in the correct alignment. Elastic to allow the bones of the joint to move Cartilage – Hard, flexible and elastic. Made up of cells called chondrocytes in a matrix of collagen. It is a good shock absorber. There are two types of cartilage; hyaline is found at the ends of bones. White fibrous cartilage has densely packed collage in the matric and has great tensile strength but it however less flexible. Muscles work in antagonistic pairs. This means that when one muscle contracts, the other relaxes. 5. Describe the overall reaction of aerobic respiration as splitting of the respiratory substrate (eg glucose) to release carbon dioxide as a waste product and reuniting of hydrogen with atmospheric oxygen with the release of a large amount of energy. C6H12O6 + 6O2 → 6CO2 +6H2O + ATP Glucose + oxygen → carbon dioxide + water + energy 6. Describe how to investigate rate of respiration practically.

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Rate of respiration can be determined by measuring the uptake of oxygen or output of carbon dioxide by organisms

A basic respirometer has a sealed chamber containing living organisms such as mice or germinating seeds

The volume of carbon dioxide given off is equivalent to the volume of oxygen taken in. Therefore a chemical such as potassium hydroxide is used absorb carbon dioxide produced during respiration

The loss of carbon dioxide is measured by observing the moment of fluid in a capillary tube. The amount of oxygen used is calculated from this.

The effect on the rate of respiration can be measured by recording changes in oxygen uptake in different conditions.

7. Recall how phosphorylation of ADP requires energy and how hydrolysis of ATP provides an accessible supply of energy for biological processes. 8 Describe the roles of glycolysis in aerobic and anaerobic respiration, including the phosphorylation of hexoses, the production of ATP, reduced coenzyme and pyruvate acid (details of intermediate stages and compounds are not required).

Occurs in the cytoplasm

4ATPs & 2NADHs are made, 2 ATPs are used.

ATP is sued to phosphorylate glucose to a 6 carbon sugar with a phosphate group.

The phosphorylated sugar splits into two molecules of GALP

GALP is converted to pyruvate.

2 hydrogens from GALP are taken up by NAD to form reduced NAD.

Reduced NAD goes into the electron transport system and provides energy to phosphorylate ADP to ATP

In the presence of oxygen, pyruvate goes into the Krebs cycle via the link reaction. In anaerobic conditions, pyruvate is converted to lactic acid

9 Describe the role of the Krebs cycle in the complete oxidation of glucose and formation of carbon dioxide (CO2), ATP, reduced NAD and reduced FAD (names of other compounds are not required) and that respiration is a many-stepped process with each step controlled and catalysed by a specific intracellular enzyme.

Pyruvate splits into a 2C molecule and CO2

2C molecule attaches to coenzyme A to form acetyl coenzyme A

NAD accepts hydrogen from pyruvate to form reduced NAD

Acetyl coenzyme A combines with a 4C compound to for 6C citric acid.

Citric acid is broken down in a series of reactions to form the original 4C compound

2 molecules of CO2 are liberated

For each pyruvate, 2 molecules of reduced NAD, 1 reduced FAD, 2 CO2 and 1 ATP are made 10 Describe the synthesis of ATP by oxidative phosphorylation associated with the electron transport chain in mitochondria, including the role of chemiosmosis and ATPase. Electron Transport Chain

Occurs in the cristae of mitochondria

Electrons are passed down energy levels releasing energy to power the phosphorylation of ADP

Oxygen is the terminal acceptor, forming H2O

Without oxygen, the electron transport chain cannot occur as all the electron acceptors are saturated with electrons

It is called oxidative phosphorylation as it is a process dependent on oxygen to phosphorylate ADP

Chemiosmosis

NADH and FADH2 contain stored chemical energy

Energy is used to pump H+ ions into the mitochondrial membrane, against a concentration gradient

The inner membrane is impermeable to protons creating a concentration, electrochemical and pH gradient

H+ leaves the envelope through ATPase proteins. The energy generated is used to phosphorylate ATP

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11 Explain the fate of lactate after a period of anaerobic respiration in animals.

Oxidative phosphorylation stops as oxygen is not available to accept electrons; electron carriers are saturated meaning NAD and FAD cannot be regenerated

Krebs cycle stops as coenzyme A is not regenerated and pyruvate builds up in cell

Cells convert pyruvate to lactic acid which generates less ATP than in aerobic conditions

When oxygen is available, lactic acid is converted back to pyruvate in the liver using oxygen. This is known as repaying the oxygen debt. It is important that this happens as lactic acid is poisonous.

12 Understand that cardiac muscle is myogenic and describe the normal electrical activity of the heart, including the roles of the sinoatrial node (SAN), the atrioventricular node (AVN) and the bundle of His, and how the use of electrocardiograms (ECGs) can aid the diagnosis of cardiovascular disease (CVD) and other heart conditions. Myogenic – The heart is said to be myogenic as it beats without external stimulation from the central nervous system. It sets up its own wave of depolarisation Sequence of heart beat – The sinoatrial node initiates the depolarisation. The depolarisation passes through the wall of the atria causing an atrial systole. The depolarisation passes to the atrioventricular node. It is held here as the right and left atria are emptying blood into the ventricles. The impulse is then taken to the bundle of His, bundle of his carries the excitation from the AVN to the Purkyne tissue. The ventricles contract from the apex up. This is known as ventricular systole. The atrioventricular valves close to prevent the backflow of blood to the atria. The semilunar valves are forced open by the build-up of pressure. Blood is then forced into the arteries. Change of pressure during diastole closes the semilunar valves. Normal electrical activity of the heart

The peak at p represents an atrial systole. A wave of depolarisation has been sent from the SAN causing the atria to contract. The time between P and the QRS complex is known as the PR interval. During this time, the impulse is at the atrioventricular node. This delay allows for atria to completely empty blood into the ventricles The electrical impulse travels from the bundle of his to the Purkyne tissue. The Purkyne tissue passes the impulse to ventricles, and the ventricles contract base up. This is known as the ventricular systole. The QRS complex represents the ventricular systole. The T wave represents the rapid repolarisation of the Purkyne tissue in the ventricles. This is also known as diastole. How ECGs can aid the diagnosis of CVDs and other heart conditions An ECG is used to investigate the rhythms of the heart by producing a record of the electrical activity of the heart. The depolarisation in the heart causes tiny little electrical changes on the surface of the skin. Electrodes attached to the skin measure these changes. Usually, when an ECG is taken, the patient is lying down. However, some heart conditions are only shown when the patient is exercising. Therefore, during a stress test, the patient is exercising.

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Arrhythmias are when the heart has different rhythms to what is expected. Atrial fibrillation is when the atria are contracting too fast and ineffectively; blood is not pumped under a high enough pressure. Tachycardia is when the heart beats too quickly. 13 Explain how variations in ventilation and cardiac output enable rapid delivery of oxygen to tissues and the removal of carbon dioxide from them, including how the heart rate and ventilation rate are controlled and the roles of the cardiovascular control centre and the ventilation centre. During exercise, extra oxygen is needed in rapidly respiring tissue. Also CO2 and lactate need to be removed quickly. In order to cope with this, the hear uses negative feedback systems. To increase the amount of oxygen, the heart increases the number of beats per minute and the volume of blood pumped per heartbeat. These are known as heart rate and cardiac volume respectively. The combination of these gives the cardiac output During exercise, blood is redirected from other parts of the body to the areas of the body where it is needed. Tidal Volume – The volume of air that enters and leaves the lings at each natural resting breath Ventilation Rate – Tidal volume X frequency of inspiration – It is a measure of the volume of air breathed in per minute. How the heart rate is controlled Nervous control of the heart

The cardiovascular centre in the medulla controls the heart rate.

Chemical and stretch receptors in the lining of blood vessels and chambers of the heart send impulses to the

cardiovascular centre

Nervous control of the heart is autonomic and is divided into the sympathetic and parasympathetic nervous

systems. Sympathetic is excitatory and parasympathetic is inhibitory.

Impulses travelling down the sympathetic nerve increase the frequency of impulses from the SAN. The

parasympathetic does the opposite.

Hormonal control

The heart rate increases when you are nervous. The hormone adrenaline is produced. This speeds up the

frequency of impulses from the SAN, thereby increasing the heart rate.

How is the ventilation rate controlled?

The ventilation centre in the medulla provides the basic stimulus to inhale and exhale. It involves a feedback

system based on the stretching of the bronchi during exercise.

We inhale as a result of impulses travelling along the sympathetic nerves. This causes the intercostal muscles

and the diaphragm to contract

As the lungs get larger, stretch receptors in the walls of the bronchi send impulses to the respiratory centre.

The impulses from the stretch receptors inhibit impulses from the respiratory centre thereby stopping the

muscles from being stimulated

Conscious areas of the brain can override the respiration centre. This is why we can hold our breath

The level of carbon dioxide is the main stimulus that affects breathing rate.

An increase in CO2 levels leads to a fall in pH which then leads to an increase in the rate and depth of

breathing. This is because the diaphragm and intercostal muscles are contracting harder and more frequently

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14 Describe how to investigate the effects of exercise on tidal volume and breathing rate using data from

spirometer traces.

A Spirometer trace

15 Explain the principle of negative feedback in maintaining systems within narrow limits.

A negative feedback system is a system enabling the body to maintain a condition within a narrow range. For

example if one factor goes up, system instigates change to bring it back down again.

Change in normal level of a factor

Receptor detects change

Receptor sends a communication hormonally or via the nervous syste,

The effector carries out a response to bring about corrective change

Return to normal level of factor

Negative Feedback system in the heart -1

Baroreceptors are sensitive to pressure. They detect changes in pressure in the carotid arteries.

An increase in blood pressure in the arteries stretches the baroreceptors

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Baroreceptors send impulse to the cardiovascular centre

Cardiovascular centre sends impulses through the parasympathetic nerves to slow down the heart rate and

widens the blood vessels, thereby lowering the blood pressure

Negative feedback system in the heart -2

During exercise, adrenaline dilates the blood vessels causing the blood pressure to fall

The baroreceptors stop sending impulses

The cardiovascular centre detects this and sends impulses down the sympathetic nerve to stimulate the heart

and increase blood pressure.

Negative feedback system in the lungs

Chemoreceptors detect fall in pH of the blood

Impulse sent to respiratory centre

Respiratory centre sends impulse sent to diaphragm and intercostal muscles to contract harder and more

rapidly to increase breathing rate

16 Discuss the concept of homeostasis and its importance in maintaining the body in a state of dynamic

equilibrium during exercise, including the role of the hypothalamus and the mechanisms of thermoregulation.

Homeostasis is controlling the internal conditions within very narrow limits. Thanks to many feedback systems,

we are able to maintain a fairly constant internal temperature even if there are fluctuations in the external

conditions. The low critical temperature is the temperature at which the normal thermoregulatory measures to

conserve heat and the metabolic rate increases to produce extra heat. The low lethal temperature is the

temperature below which chemical reactions of the body can no longer take place at a quick enough rate to meet

the demand. If the temperature gets too high, enzymes are denatured. This means that biological reactions can

no longer take place.

The Role of the hypothalamus

Receptors in the brain detect changes in blood temperature. Receptors in skin detect changes in external

temperature. The temperature receptors are found in the hypothalamus.

Increase in blood temperature

Heat loss centre activated

Impulse sent to effectors to increase blood flow close to skin and increase sweating

Erector pilli muscles are relaxed so hairs lie flat

Any shivering stops

Decrease in blood temperature

Heat gain centre activated

Impulse sent to effectors to decrease blood flow close to skin and decrease sweating

Erector pilli muscles contract so hairs stand trapping an insulating layer of air

Involuntary muscle contraction stimulate (shivering)

Mechanisms of thermoregulation

Our body’s main source of heat is from our metabolism. The main organ involved in temperature regulation is the

skin.

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Adaptation Keeping warm Keeping cool

Capillaries close to the skin Vasoconstriction occurs

Sphincter muscles contract so less blood flows into superficial capillaries close to the skin’s surface

More blood flows through deeper shunt vessels

Less blood flows close to the body’s surface

Temperature gradient between body surface and environment decreases

Therefore, less heat is lost by conduction and radiation

Vasodilation occurs

Sphincter muscles relax so more blood flows into superficial capillaries

Less blood flows through deeper shunt vessels

More blood is flowing closer to the body surface

Temperature gradient between body surface and environment increases

Therefore, more heat is lost by conduction and radiation.

Hairs Hairs stand erect as erector pilli muscles contract. This increases an insulation air layer that is trapped next to the skin

Hairs lie flat because erector pilli muscles are relaxed. This minimises any insulation air layer that is trapped next to the skin

Sweat No sweat produced More sweat is produced as temperature increases. Heat is lost as the water evaporates from the surface of the skin

Subcutaneous fat More subcutaneous fat to provide insulation and reduce heat loss by conduction and radiation

Physically active people have little subcutaneous fat to reduce insulation. Thus increasing the amount of heat loss by conduction

Metabolism Metabolic rate decrease Metabolic rate increases

Muscles Shivering – skeletal muscles contract involuntarily. When muscles contract, they produce heat

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17 Explain how genes can be switched on and off by DNA transcription factors including hormones.

Anabolic steroids

Steroid hormone enters the cell and binds to receptor

Hormone receptor complex enters nucleus and acts as a transcription factor, switching a gene linked to

enzyme synthesis on or off

Synthetic forms of testosterone stimulate more protein synthesis, this leads to more muscle being made

Erythropoietin

Peptide hormone binds to receptor in the cell surface membrane

Membrane bound complex triggers protein kinase cascade

Transcription factor moves into the nucleus of the cell and switches on a specific gene resulting in the

production of new proteins

18 Analyse and interpret data on possible disadvantages of exercising too much (wear and tear on joints,

suppression of the immune system) and exercising too little (increased risk of obesity, coronary heart disease

(CHD) and diabetes), recognising correlation and causal relationships.

Correlation – As one variable changes, another changes

Causal relationship – One variable effects a change in another variable

19 Explain how medical technology, including the use of keyhole surgery and prostheses, is enabling those with

injuries and disabilities to participate in sports, eg cruciate ligaments repair using keyhole surgery and knee

joint replacement using prosthetics.

Modern imaging techniques such as MRI and CT scans are able to diagnoses injuries accurately and quickly

Keyhole surgery

A fibre optic tube with a small camera and light attached is used to look inside the joint

Small incisions are made around the joint to fit in small surgical instruments

Prosthetics

Damaged joints can be completely replaced

This frees patients from pain and restores mobility

Replacement joints wear out more quickly if you exercise a lot

For athletes, prosthetics are designed so they are able to give good performance. For example, the dynamic

prosthetic foot changes shape as the body weight presses down on it, returning back to shape as it lifts off the

ground.

20 Outline two ethical positions relating to whether the use of performance-enhancing substances by athletes

is acceptable.

There are two major ethical points of view, relativists and absolutists. Relativists believe that it can be justified for

atheletes to use performance enhancing drugs in some circumstances. Absolutists on the other hand believe

performance enhancing drugs can never be justified

Problems with using anabolic steroids

They disrupt normal production of hormones so are linked to:

Infertility

Problems in menstrual cycle for women

Drop in sperm production and impotence in men

Liver damage

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High blood pressure

Heart attacks

Increased aggression particularly in young men

Advantages of using erythropoietin

Can be used to treat anaemia

Improves performance of athletes as they are able to carry more oxygen

Disadvantages of using erythropoietin

Provides competitive edge for athletes – more red blood cells means more oxygen can be carried to muscles

Leads to serious health problems and death

Excess red blood cells thicken the blood and can lead to stroke and heart attacks.

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Keywords Respiratory substrate – The food, usually glucose used as fuel for cellular respiration

Nicotinamide adenine dinucleotide (NAD) – An electron acceptor

Reduced NAD – The coenzyme NAD when it has accepted a hydrogen atom

Flavine adenine dinucleotide (FAD) – A hydrogen carrier and coenzyme which plays a role in cellular respiration

Aerobic respiration – Cellular respiration which takes place in the presence of oxygen

Krebs’s cycle – The reactions of cellular respiration which take place in the mitochondria

Anaerobic respiration – Cellular respiration which takes place without oxygen. (includes glycolysis)

Mitochondria – Cell organelles where aerobic respiration takes place. Main site of ATP production for the cell

Pyruvate – 3 carbon compound produced from the splitting of glucose in glycolysis

Pyruvic acid – 3 carbon compound produced from the splitting of glucose in glycolysis – produces pyruvate ions in

solution

Creatine phosphate – energy store in skeletal muscle

Lactate – 3 carbon compound formed in the absence of oxygen cannot be fed on into aerobic respiration. Also

known as lactic acid

Gluconeogenesis – Conversion of lactate from exercising muscles to pyruvate and then back to glucose to

circulate in the blood and replenish the glycogen stores

Phosphofructokinase – Enzyme which plays an important role in controlling the rate of glycolysis

Regulatory enzymes – Enzymes which control the rate of biochemical pathways

Acetyl coenzyme A – Two carbon compound derived from glucose which combines with a four carbon compound

to form citric acid at the start of the krebs cycle in aerobic respiration

Decarboxylases – Enzymes involved in the removal of carbon dioxide from molecules. For example during cellular

respiration

Dehydrogenases – enzymes involved in the removal of hydrogen from molecules. For example during cellular

respiration

Citric acid cycle – Alternative name for the krebs cycle in aerobic respiration

Oxidative phosphorylation – The phosphorylation of ADP which is dependent on the presence of oxygen

Cytochromes – Pigment proteins in the electron transport chain associated with the production of ATP

Cytochrome oxidase – Enzyme in the electron transport chain which receives electrons from the cytochromes and

is reduced as the cytochromes are oxidised, resulting in the production of a molecule of ATP

Oxygen – Final acceptor in the electron transport chain. Combines with H+ and electrons to form water

Skeletal muscle, striated muscle or voluntary muscle – The muscle attached to the skeleton and is involved in

locomotion which is under voluntary control and has a striated (stripy) microscopic appearance

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Myofibrils – Very thin fibres which make up the muscle structure

Sarcomere – single contractile unit of a muscle microfibril

Actin – One of the contractile proteins which make up the structure of muscle cells

Myosin – contractile protein which interacts with actin to bring about the contraction of muscle

Smooth muscle (Involuntary muscle) – Muscle which is not striped and is controlled by the involuntary nervous

system

Cardiac muscle – The muscle which makes up the heart

Summation – The effect of more than one impulse arriving at a synapse at the same time, either in different nerve

fibres or in rapid succession in the same nerve fibre

Myoglobin – protein similar to haemoglobin with a high affinity for oxygen which acts as an oxygen store in the

muscles

Slow twitch muscle fibres – Muscle fibres which contract relatively slowly and stay in tetanus for a long time. Also

known as oxidative or red muscle fibre

Fast twitch muscle fibres – Muscle fibres which contract very rapidly and often function anaerobically so they

fatigue relatively fast

ACTN3 – A protein which is found in fast twitch muscle fibres

Sliding filament theory – Theory developed by Hugh Huxley and Jean Hanson in the 1950s to explain patterns

seen during muscle contraction

Tropomyosin – Long chain protein which wraps around the actin chains in the structure of muscle. In a relaxed

muscle, it covers up the myosin binding sites in actin

Troponin – A protein associated with tropomyosin in the muscle structure

Bone – Strong hard tissue which is the basis of the skeleton

Cartilage – Hard but elastic tissue found between the bones in joints and covering the articulating surfaces of

bones

Chrondocytes – Cells which make up cartilage

Tendons – Tissue which joins muscle to bone , made up almost entirely of white fibrous tissue

White fibrous tissue – Tissue made up mainly of collagen fibres

Ligaments – Form capsules around joint holding the bones together. They are made of yellow elastic tissue which

provides a combination of strength with elasticity

Synovial fluid – Liquid lubricant secreted into the most mobile joints by the synovial membrane.

Intrinsic rhythmicity – The basic rhythm of the heart beat which is present in the individual cells

Sinoatrial node (SAN) – The natural pacemaker region of the heart which sets up the heart’s own intrinsic rhythm

Bundle of His – Conducting tissue in the heart

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Purkyne tissue – Tissue which spreads through the septum and ventricles of the heart carrying a wave of

depolarisation which started at the SAN and triggering contraction of the ventricles

Electrocardiogram – A recording of the electrical activity of the heart. Often used to help diagnose heart problems

Homeostasis – Maintenance of a steady internal state in the body almost regardless of changes in the internal or

external conditions

Sensor or receptor – Specialised cell, tissue or organ which detects changes in the body or in the external

environment

Effector – Cell, tissue or organ which responds to stimulation by the motor nerves and works to reverse a change

or increase it

Negative feedback system – A system enabling the body to maintain a condition within a narrow range. If one

factor goes up, the system instigates change to bring it down again

Positive feedback system – A system enabling the body to change conditions. For example if one factor increases,

the system instigates change to increase the effect

Cardiac volume – the volume of blood pumped out in each heart beat

Cardiac output – The volume of blood pumped out of the heart per minute

Cardiovascular control centre – Centre involved in the control of the heart rate. Found in the medulla of the brain

Autonomic (involuntary) – The part of the nervous system that acts without conscious control

Sympathetic nervous system – Part of the autonomic nervous system – usually has excitatory effects

Excitatory – Increases the likelihood of an action potential

Parasympathetic nervous system – Part of the autonomic nervous system – usually has inhibitory effects

Inhibitory – Decreases the likelihood of an action potential

Stretch receptors – Receptors in the wall of the heart which respond to the stretching of the walls as the heart fills

with blood and send impulses to the cardiovascular control centre

Baroreceptors – Sensors which are receptive to changes in pressure

Tidal volume – The volume of air that enters and leaves the lungs at each natural resting breath

Inspiratory reserve volume – The volume of air that can be taken in over and above the normal inspired tidal air.

In other words, the extra air that you can take in when you breathe in as deeply as possible after a normal

exhalation

Expiratory reserve volume – The extra air breathed out when you force the air out of your lungs as had as possible

after a normal inspiration

Vital capacity – the total of the tidal air and the inspiratory and expiratory reserves. It is the volume of air which

can be breathed out by the most vigorous possible expiratory effort following the deepest possible inspiration

Residual volume – The volume of air left in the lungs after the strongest possible exhalation

Total lung capacity – The sum of the vital capacity and the residual volume

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Inspiratory capacity – The volume that can be inspired from the end of a normal exhalation

Ventilation rate – A measure of the volume of air breathed in a minute – the tidal volume multiplied by the

inspiration rate

Medulla – Area of the hindbrain, the most primitive part of the brain which controls basic functions such as

breathing rate and blood pressure

Respiration centre (ventilation centre) – Region of the medulla which controls the rate of breathing based on a

number of feedback mechanisms

Chemoreceptors – Receptors which respond to the presence of particular chemicals

Carotid bodies – Chemoreceptors sensitive to carbon dioxide levels in the blood. Found in the carotid artery

Aortic bodies – Receptors in the all of the aortic arch

Acclimatise – Get used to

Thermoregulation – Homeostatic control of the core body temperature

Low critical temperature – The temperature at which the normal thermoregulatory measures to conserve heat

are no longer enough and the metabolic rate increase to produce extra heat

Low lethal temperature – the temperature below which the chemical reactions of the body can no longer take

place fast enough to maintain life; death results

High critical temperature – Degree rise in temperature. Positive feedback occurs and the high lethal temperature

is soon reached

Ateriovenous shunt – System controlling the blood supply to the skin

Vasodilation – Dilation of the lumen of the blood vessels due to the relaxation of the smooth muscles lining them.

In context, the dilation of the capillaries near the skin as more blood is allowed to flow through them

Hypothalamus – Small area of the brain which regulates many biological processes and also controls hormone

production in the pituitary gland

Heat loss centre – Region of the hypothalamus sensitive to temperature of the blood flowing though the region.

Send out impulses to effectors to reduces the core temperature to lose heat

Heat gain centre – Region of the hypothalamus sensitive to temperature of the blood flowing through rhe region.

Sends out impulses to effectors to raise the core temperature to gain heat

Arrhythmias – Irregular patterns in the heart beat

Ischaemic – Starved of oxygen

Atrial fibrillation – The atria of the heart beating too fast and arrhytmically

Defibrillator – Equipment used to restore the normal rhythm to a heart which is in ventricular fibrillation

Tachycardia – An unusually fast heart rate

RICE (rest, ice, compression, elevation) – The initial treatment for sprains and other sports injuries, at least until

more detailed diagnosis can be carried out

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Anabolic steroids – Steroid hormones often closely related to the male sex hormone testosterone

Hormones – A chemical produced in one part of the body which has an effect in another part of the body. In

humans, hormones are made in the endocrine glands and carried around the body in the blood stream

Beta-2-agonists – chemicals that dilate the airways allowing more air into the lungs

Hormone agonists – Chemicals which mask or change the action of another hormone

Diuretics – Increases the volume of urine produced

Blood doping – Athletes have blood transfusions either of their own blood, removed months earlier, or donated

blood, or even artificial oxygen carrying compounds. All these techniques raise the amount of oxygen carried in

the blood, enhancing performance

Gene doping – Any attempt to change the genetic makeup of the cells to enhance athletic performance is banned

Stimulants – Drugs that increase the heart rate and make you more alert. E.g. caffeine, amphetamines and

cocaine

Narcotics – Powerful painkillers

Beta blockers – drugs that block the response of the heart to adrenaline, slowing down the heart rate and

lowering blood pressure