Unit 7: Run for Your Life

Question 1

What is the skeletal muscle?

Answer 1

It is the type of muscle you use to move like the biceps and triceps to move the lower arm. They are attached to bones by tendons. They contract and relax to move bones at a joint.

Question 2

What are ligaments?

Answer 2

Attach bones to other bones, to hold them together.

Question 3

What is an example of the muscles and tendon working in the lower arm?

Answer 3

When your biceps contract your triceps relax. This pulls the bone so your arm bends (flexes) at the elbow. A muscle that bends a joint when it contracts is called a flexor.
But when your triceps contracts your bicep relaxes. This pulls bone so your arm extends (straightens) at the elbow. A muscle that straightens a joint when it contracts is called an extensor.

Question 4

What is it called when muscles work together to move a bone?

Answer 4

Antagonistic pairs

Question 5

What is the skeletal muscle made up of?

Answer 5

It is made up of large bundles of long cells, called muscle fibres.

Question 6

What is the cell membrane called on the muscle fibres called and the structure of the muscle fibres?

Answer 6

Sarcolemma. Bits of this are folded inwards across the muscle fibres and stick into the sarcoplasm (muscle cells cytoplasm). These folds are called transverse (T) tubules and they help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre.

Question 7

What are the internal membranes?

Answer 7

Called sarcoplasmic reticulum runs through the sarcoplasm. The sarcoplasmic reticulum stores and releases calcium ions that are needed for muscle contraction.

Question 8

Why do muscle cells have lots of mitochondria?

Answer 8

To provide ATP that is needed for muscle contraction.

Question 9

Muscle cells contain many nuclei, what is this called?

Answer 9

Multinucleate

Question 10

What are myofibrils?

Answer 10

Long, cylindrical organelles. They are made up of proteins and are highly specialised for contraction.

Question 11

What are the thick myofilaments called?

Answer 11

Made up of protein called myosin.

Question 12

What are the thin myofilaments called?

Answer 12

Made up of a protein called actin.

Question 13

What do the dark bands show you under a microscope of a myofibril?

Answer 13

Dark bands contain the think myosin filaments and some overlapping thin actin filaments are called A-bands

Question 14

What do the light bands show under a microscope

Answer 14

Light bands contain thin actin filament only- these are called I-bands

Question 15

What are myofibrils made up of?

Answer 15

Made up of many short units called sarcomeres. The ends of the sarcomeres are marked with a Z-line and are joined together here at the Z-line lengthways. In the middle of each sarcomere is an M-line in the middle of the myosin filament. Around the M-line is the H-zone. The H-zone only contains myosin filaments.

Question 16

What is the sliding filament theory?

Answer 16

1) Myosin and actin filaments slide over one another to make sarcomere contract- the myofilaments themselves don’t contract and the myosin and the actin molecules stay the same length.
2) The simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract.
3) Sarcomeres return to their original length as the muscle relaxes.

Question 17

How does muscle contraction occur (stage 1)?

Answer 17

Myosin filaments have globular heads that are hinged, so they can move back and forth. Each myosin head has a binding site for actin and a binding site for ATP. Actin filaments have a binding site for myosin heads, called actin-myosin binding sites. Two other proteins called tropomyosin and troponin are found between actin filaments. These proteins are attached to each other and help the myofilaments move past each other.

Question 18

How does muscle contraction occur (stage 2)?

Answer 18

In a resting (unstimulated) muscle, the actin-myosin binding site is blocked by tropomyosin, which is held in place by troponin. So myofilaments can’t slide past each other because the myosin heads can’t bind to the myosin-actin binding site on the actin filaments

Question 19

How does action potential trigger an influx of calcium ions?

Answer 19

Action potential from a motor neurone stimulates a muscle cell, it depolarises the sarcolemma. Depolarisation spreads down the T-tubules to the sarcoplasmic reticulum, which causes the release of calcium ions to be released into the sarcoplasm. Calcium ions bind to troponin, causing it to change shape. This pulls the attached tropomyosin out of the action-myosin binding site on the actin filament. Exposes the binding site, which allows the myosin head to bind. The bond is formed when a myosin head binds to an actin filament called the actin-myosin cross-bridge.

Question 20

How is ATP provided?

Answer 20

Calcium ions activate ATPase and break down ATP, to provide the energy needed for muscle contraction. The energy released from ATP moves the myosin head, which pulls the actin filament along in a rowing action.

Question 21

How is the cross bridge broken?

Answer 21

ATP provides energy to break down the actin-myosin cross-bridge so the myosin head detaches from the actin filament after it’s moved. The myosin head reattaches to a different binding site further along the actin filament. A new actin-myosin cross-bridge is formed and the cycle repeats as it attaches, moves, detaches, and reattaches. Many cross-bridges are formed and break very rapidly, pulling the actin filament along - which shortens the sarcomere, causing muscle contraction. The cycle continues as long as calcium ions are present and bound to troponin.

Question 22

What happens when the excitation stops and the calcium ions leave the troponin molecules?

Answer 22

When the muscle stops being stimulated, calcium ions leave their binding sites on the troponin and are moved by active transport back into the sarcoplasmic reticulum (ATP needed). The troponin muscles return to their original shape, pulling the attached tropomyosin molecules back with them. This means the tropomyosin blocks the actin-myosin binding sites again. Muscles aren’t contracted because no myosin heads are attached to actin filaments (no actin-myosin cross bridge). Actin filaments slide back to their relaxed position, which lengthens the sarcomere.

Question 23

What are the properties of slow-twitch muscle fibres?

Answer 23

Muscle fibres contract slowly. Muscles you use for posture, e.g. those in the back, have a high proportion of them. Good for endurance activities, e.g. maintaining posture, and long-distance running. Can work for a long time without getting tired. Energy is released slowly through aerobic respiration. Lots of mitochondria and blood vessels supply the muscles with oxygen. Reddish in colour because they are rich in myoglobin- a red-coloured protein that stores oxygen.

Question 24

What are the properties of fast-twitch muscle fibres?

Answer 24

Muscle fibres contract very quickly. Muscles you use for fast movement, e.g. those in the eyes and legs, have a high proportion of them. Good for short bursts of speed and power, e.g. eye movement and sprinting. Get tired easily and very quickly. The energy is released quickly through anaerobic respiration using glycogen (stored glucose). There are few mitochondria or blood vessels. Whitish in colour because they don’t have much myoglobin (so they can’t store much oxygen).

Question 25

What is the balanced symbol equation for aerobic respiration?

Answer 25

C6H12O6 + 6O2 –> 6CO2 + 6H2O + Energy

Question 26

How is the energy released used in aerobic respiration?

Answer 26

Used to phosphorylate ADP to ATP, which is then used to provide energy for all biological processes inside the cell.

Question 27

What are the four stages of aerobic respiration?

Answer 27

Glycolysis, the link reaction, Krebs cycle and oxidative phosphorylation. The products from the first three stages are used in the final stage to produce loads of ATP.

Question 28

Where does each of the reactions take place?

Answer 28

The first stage happens in the cytoplasm of the cells and the others occur in the mitochondria.

Question 29

What is each reaction controlled by?

Answer 29

They are controlled and catalysed by a specific intracellular enzyme. The enzyme with the slowest activity is rate limiting - it determines the overall rate of respiration.

Question 30

What are the coenzymes used in aerobic respiration?

Answer 30

NAD and FAD transfer hydrogen from one molecule to another- this means they can reduce (give hydrogen to) or oxidise (take hydrogen from) a molecule. Coenzyme A transfers acetate between molecules.

Question 31

What do organisms use to respire?

Answer 31

Glucose and break down other complex organic molecules.

Question 32

What is the first stage of aerobic respiration (overview)?

Answer 32

Glycolysis makes pyruvate from glucose.
Glycolysis involves splitting one molecule of glucose (a hexose sugar, 6 carbons- 6C) into two smaller molecules of pyruvate (3C). This happens in the cytoplasm. This can also occur in anaerobic respiration and doesn’t require oxygen. ATP is used to phosphorylate glucose to triose phosphate. Then triose phosphate is oxidised, releasing ATP. Net gain of 2 ATP.

Question 33

What is the first stage of glycolysis?

Answer 33

Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP. This creates 2 molecules of triose phosphate and 2 molecules of ADP.

Question 34

What is the second stage of glycolysis?

Answer 34

Triose phosphate is oxidised (loses hydrogen), forming 2 molecules of pyruvate. NAD collects the hydrogen ions, forming 2 reduced NAD. 4 ATP are produced, but 2 are used again in stage 1, so there is a net gain of 2.

Question 35

What happens to the products of glycolysis?

Answer 35

The two molecules of reduced NAD are used in the last stage (oxidative phosphorylation). The two pyruvate molecules go into the matrix of the mitochondria for the link reaction.

Question 36

Where does the link reaction take place?

Answer 36

The enzymes and coenzymes needed for the link reaction are located in the mitochondrial matrix, so that’s where the link reaction takes place. This means that the reduced NAD produced by the link reaction is made in the right place to be used in oxidative phosphorylation, which occurs across the inner mitochondrial membrane.

Question 37

What are the steps for the link reaction?

Answer 37

Pyruvate is decarboxylated (carbon is removed) - one carbon atom is removed from pyruvate in the form of CO2. NAD is reduced - it collects hydrogen from pyruvate, changing pyruvate to acetate. Acetate is combined with coenzyme A (CoA) to form acetyl coenzyme A (acetyl CoA). No ATP is produced in this reaction.
Pyruvate (3C) –> Acetate (2C) –> Acetyl CoA (2C)

Question 38

Why does the link reaction occur twice?

Answer 38

For every glucose molecule. Two pyruvate molecules are made for every glucose molecule that enters glycolysis. This means the link reaction and the third stage (the Krebs cycle) happen twice for every glucose molecule.

Question 39

As the Link reaction happens twice, what does this mean for the products produced?

Answer 39

Two molecules of acetyl coenzyme A go into the Krebs cycle. 2 CO2 molecules are released as waste products of respiration. Two molecules of reduced NAD are formed and are used in the last stage (oxidative phosphorylation)

Question 40

What are the stages of the Krebs cycle?

Answer 40

1) Acetyl CoA from the link reaction combines with oxaloacetate to form citrate.
2) Coenzyme A goes back to the link reaction to be used again.
3) The 6C citrate molecule is converted to a 5C molecule.
4) Decarboxylation occurs, where CO2 is removed
5) Dehydrogenation also occurs- this is where hydrogen is removed
6) The hydrogen is used to produce reduced NAD from NAD
7) The 5C molecule is then converted to a 4C molecule
8) Decarboxylation and dehydrogenation occur, producing one molecule of reduced FAD and two reduced NAD.
9) ATP is produced by the direct transfer of a phosphate group from an intermediate compound to ATP. When a phosphate group is directly transferred from one molecule to another its called substrate-level phosphorylation. Citrate has been converted into oxaloacetate.

Question 41

What are the products of the Krebs cycle and what are they used for?

Answer 41

1) 1 coenzyme A - reused in the link reaction
2) Oxaloacetate- regenerate for use in the next Krebs cycle
3) 2 CO2- released as a waste product
4) 1 ATP- used for energy
5) 3 reduced NAD- To oxidative phosphorylation
6) 1 reduced FAD- To oxidative phosphorylation

Question 42

What is oxidative phosphorylation?

Answer 42

It is the process where the energy carried by electrons, from reduced coenzymes (FAD and NAD), is used to make ATP. (previous stages were to make reduced NAD and reduced FAD for the final stage). Involves two processes- the electron transport chain and chemiosmosis.

Question 43

What are the stages of oxidative phosphorylation?

Answer 43

1) Hydrogen ions are released from reduced NAD and reduced FAD as they oxidise to NAD and FAD. H atoms split into protons (H+) and electrons (e-).
2) Electrons move down the electron transport chain (made up of electron carriers) losing energy at each carrier.
3) Energy is used by the electron carriers to pump protons from the mitochondrial matrix into the intermembrane space.
4) The concentration of protons is now higher in the intermembrane space than in the mitochondrial matrix- this forms an electrochemical gradient
5) Protons move down the electrochemical gradient, back into the mitochondrial matrix, via the enzyme ATP synthase. This movement drives the synthesis of ATP from ADP and inorganic phosphate.
6) The movement of H+ ions across the membrane, which generates ATP is called chemiosmosis
7) In the mitochondrial matrix, at the end of the transport chain, the protons, electrons and O2 combine to form water. Oxygen is said to be the final electron acceptor.

Question 44

What do some metabolic poisons do to oxidative phosphorylation?

Answer 44

Target electron carriers, preventing them from passing on electrons. This stops electrons from moving down the electron transport chain, which stops chemiosmosis. Reduced NAD and reduced FAD are no longer oxidised, so FAD and NAD aren’t regenerated for the Krebs cycle- stopping that too. ATP synthesis in the cell ends up hugely reduced, so there’s not enough ATP to fuel ATP-requiring cellular processes (e.g. the concentration of heart muscles). This can be fatal for the organism.

Question 45

How much ATP can be made with one glucose molecule?

Answer 45

38 ATP

Question 46

What is the investigation for measuring the rate of respiration?

Answer 46

1) Place 5 g of maggots, woodlice, or germinating peas or seeds into the boiling tube and replace the bung. Handle live animals with care to avoid harming them.
2) Introduce a drop of marker fluid into the pipette using a dropping pipette. Open the connection (three-way tap) to the syringe and move the fluid to a convenient place on the pipette if needed (i.e. towards the end of the scale that is furthest from the test tube).
3) Mark the starting position of the fluid on the pipette with a fine permanent pen.
4) Isolate the respirometer by closing the connection to the syringe and the atmosphere, and immediately start the stop clock. Mark the position of the fluid on the pipette at 1-minute intervals for 5 minutes.
5) At the end of 5 minutes open the connection to the outside air.
6) Measure the distance travelled by the liquid during each minute (the distance from one mark to the next on your pipette).
7) If your tube does not have volumes marked onto it you will need to convert the distance moved into the volume of oxygen used. (Remember the volume used = πr 2 × distance moved, where r = the radius of the hole in the pipette.)
8) Record your results in a suitable table.
9) Calculate the mean rate of oxygen uptake during the 5 minutes.
10) Collect the mean rate of oxygen uptake results from other groups in the class. Note the range of data recorded for mean oxygen uptake.

Question 47

What is anaerobic respiration?

Answer 47

Doesn’t use oxygen. Doesn’t involve the link reaction, Krebs cycle, or oxidative phosphorylation. Lactate fermentation occurs in animals and produces lactate.

Question 48

How does anaerobic respiration occur?

Answer 48

Glucose is converted to pyruvate via glycolysis
Reduced NAD (from glycolysis) transfers hydrogen to pyruvate to form lactate and NAD.
NAD can then be reused in glycolysis

Question 49

What does it mean if lactate regenerates NAD?

Answer 49

The production of lactate regenerates NAD. This means glycolysis can continue even when there isn’t much oxygen around, so small amounts of ATP can still be produced to keep some biological processes going.

Question 50

How is lactic acid broken down?

Answer 50

• cells can convert the lactic acid back to pyruvate (which re-enters aerobic respiration at the Krebs cycle)
• liver cells can convert the lactic acid back to glucose (which can then be respired and stored)

Question 51

What does the term ‘myogenic’ mean?

Answer 51

It can contract and relax without receiving signals form neurones.

Question 52

What does the electrical activity in the heart create?

Answer 52

pattern of contractions, which coordinates the regular heartbeat

Question 53

What is the process of myogenic (electrical activity) in the heart?

Answer 53

1) Starts in the Sino-atrial node (SAN)- in the wall of the right atrium
2) SAN is like a pacemaker- it sets the rhythm of the heartbeat by sending our regular waves of electrical activity to the atrial walls.
3) This causes the right and left atria to contract at the same time.
4) A band of non-conducting collagen tissue prevents the waves of electrical activity from being passed directly from the atria to the ventricles.
5) Instead, these waves of electrical activity are transferred from the SAN to the atrioventricular node (AVN)
6) The AVN is responsible for passing the waves of electrical activity onto the bundles of His. But, there is a slight delay before the AVN reacts, to make sure the ventricles contract after the atria have emptied.
7) Bundles of His is a group of muscle fibres responsible for conducting the waves of electrical activity to the finer muscle fibres in the right and left ventricle walls, called the Purkyne fibres.
8) Purkyne fibres carry the waves of electrical activity into the muscular walls of the right and left ventricles, causing them to contract simultaneously, from the bottom up.

Question 54

What is an electrocardiograph?

Answer 54

Checking someone’s heart function. A machine that records the electrical activity of the heart, The heart muscles depolarise (loses electrical charge) when it contracts and repolarises (gains charge) when it relaxes. Records these changes in electrical charge using electrodes placed on the chest. The trace produced is called an electrocardiogram (ECG)

Question 55

What does a normal ECG look like?

Answer 55

The p wave is caused by a contraction (depolarisation) of the atria. The main peak of the heartbeat, together with the dips at either side, is called the QRS complex- it’s caused by contraction (depolarisation) of the ventricles. The T-waves are due to the relaxation (repolarisation) of the ventricles. The height of the waves indicates how much electrical charge is passing through the heart- a bigger wave means more electrical charge, so (for the P and R waves) a bigger wave means a stronger contraction.

Question 56

How do doctors use ECGs to diagnose people with heart problems?

Answer 56

Compare patients’ ECG with a normal trace. This helps them to diagnose any problems with the heart’s rhythm, which may indicate cardiovascular disease or other heart conditions.

Question 57

What is an example of abnormal traces?

Answer 57

The heartbeat is too fast- around 120 beats per minute. Tachycardia is OK during exercise, but at rest, it shows that the heart isn’t pumping blood efficiently. Heartbeat can be too slow- below 60 beats per minute at rest (bradycardia)

Question 58

What is an ectopic heartbeat?

Answer 58

It is an extra heartbeat and caused by an earlier contraction of the atria than in the previous heartbeats but can also be caused by early contraction of the ventricles.

Question 59

What is fibrillation?

Answer 59

Irregular heartbeat. The atria or ventricles completely lose their rhythm and stop contracting properly. It can result in anything from, chest pain and fainting to lack of pulse and death.

Question 60

Why does breathing rate and depth?

Answer 60

To obtain more oxygen and to get rid of more carbon dioxide

Question 61

Why does the heart rate increase?

Answer 61

to deliver more oxygen (and glucose) to the muscles faster and remove extra carbon dioxide produced by the increased rate of respiration in muscle cells.

Question 62

How does the medulla oblongata control breathing rate?

Answer 62

1) The inspiratory centre in the medulla oblongata sends nerve impulses to the intercoastal and diaphragm muscles to make them contract.
2) This increases the volume of the lungs, which lowers the pressure. The inspiratory centre also sends nerve impulses to the expiratory centre. These impulses inhibit the action of the expiratory centre.
3) Air enters the lungs due to the pressure difference between the lungs and the air outside
4) As the lungs infiltrate, stretch receptors in the lungs are stimulated. The stretch receptors send nerve impulses back to the medulla oblongata. These impulses inhibit the action of the inspiratory centre.

Question 63

How does breathing rate decrease blood pH during exercise?

Answer 63

1) During exercise, the level of CO2 in the blood increase. This decreases the pH in the blood.
2) There are chemoreceptors (receptors that sense chemicals) in the medulla oblongata, aortic bodies (cluster of cells in the aorta) and carotid bodies (clusters of cells in the carotid arteries) that are sensitive to changes in the blood pH.
3) If the chemoreceptors detect a decrease in blood pH, they send nerve impulses to the medulla oblongata, which sends more frequent nerve impulses to the intercostal muscles and diaphragm. This increases the rate and depth of breathing.
4) This causes gaseous exchange to speed up. The CO2 level drops and extra O2 is supplied to the muscles- the pH returns to normal and the breathing rate decreases.

Question 64

What is the ventilation rate?

Answer 64

It is the volume of air breathed in or out over some time. It increases during exercise because breathing rate and depth increase

Question 65

How does the medulla oblongata control heart rate?

Answer 65

It is controlled unconsciously by the cardiovascular centre in the medulla oblongata. Controls the rate at which the SAN fires and generates electrical impulses that cause the atria to contract, which sets the rhythm of the heartbeat. Animals need to alter their heartbeat to respond to internal stimuli. There are pressure receptors called baroreceptors in the aortic and carotid bodies. They’re stimulated by high and low blood pressure. There are chemoreceptors in the aortic and carotid bodies and the medulla oblongata. They monitor the oxygen level in the blood and also carbon dioxide and pH. Electrical impulses from receptors to the medulla oblongata along the sensory neurone. The cardiovascular control centre processes the information and sends impulses to the SAN along sympathetic (action- ‘flight or fight’- increase the heart rate during exercise) or parasympathetic (rest and digest- decrease the heart rate) neurones- these release different chemicals (neurotransmitters)onto the SAN, which determines whether it speeds up or slows down the heart rate.

Question 66

What are the receptor, neurone, transmitter and response to high blood pressure?

Answer 66

Receptor- baroreceptors
Neurone and transmitter- impulse sent to the cardiovascular control centre, sends impulse along parasympathetic neurones and secrete acetylcholine (neurotransmitter), which binds to receptors on the SAN.
Response- SAN fires less frequently to slow heart rate and reduce blood pressure back to normal.

Question 67

What are the receptor, neurone, transmitter, and response to low blood pressure?

Answer 67

Receptor- baroreceptors
Neurone and transmitter- impulse sent to the cardiovascular control centre, sends impulse along sympathetic neurones, secrete noradrenaline (neurotransmitter), binds to receptors on the SAN.
Response- SAN fires more frequently to increase the heart rate and increase blood pressure back to normal.

Question 68

What are the receptor, neurone, transmitter and response to high blood O2 and low CO2 (/ high pH levels)?

Answer 68

Receptor- chemoreceptors
Neurone and transmitter- impulses are sent to the cardiovascular control centre, send an impulse along the parasympathetic neurones, secrete acetylcholine, and bind to the receptor on SAN.
Response- SAN fires impulses less frequently to decrease heart rate and return O2, CO2, and pH levels to normal.

Question 69

What are the receptor, neurone, transmitter and response to low blood O2 and high CO2 (/ low pH levels)?

Answer 69

Receptor- chemoreceptors
Neurone and transmitter- impulses are sent to the cardiovascular control centre, sent impulses along sympathetic neurones, secrete noradrenaline, which binds to receptors on the SAN.
Response- SAN fires impulses more frequently to increase heart rate and return O2, CO2 and pH levels back to normal

Question 70

What is the cardiac output?

Answer 70

It is the total volume of blood pumped by a ventricle every minute.
Equation:
Cardiac output= heart rate x stroke volume

Question 71

What is stroke volume?

Answer 71

It is the volume of blood pumped by one ventricle each time it contracts.
Equation:
stroke volume= cardiac output/ heart rate

Question 72

What happens to the cardiac output during exercise?

Answer 72

cardiac output increases during exercise because heart rate and stroke volume increase

Question 73

What is the tidal volume?

Answer 73

The volume of air in each breath

Question 74

What is the breathing rate?

Answer 74

It is how many breaths are taken, usually in a minute

Question 75

What is oxygen consumption?

Answer 75

The volume of oxygen used by the body, often expressed as a rate

Question 76

What are respiratory minute ventilation and the equation?

Answer 76

The volume of gas breathed in or out in a minute
Respiratory minute ventilation= tidal volume x breathing rate

Question 77

What is a spirometer and how does it measure ventilation?

Answer 77

It is an oxygen-filled chamber with a moveable lid. A person breathes through a tube connected to an oxygen chamber. As the person breathes in the lid of the chamber moves down. When they breathe out it moves up. These movements are recorded by a pen attached to the lid of the chamber- this writes on a rotating drum, creating a spirometer trace. The total volume of gas in the chamber decreases over time. This is because the air that’s breathed out is a mixture of oxygen and carbon dioxide, but the CO2 is absorbed by the soda lime in the tube. This means there’s only oxygen in the chamber which the person inhales from- as this oxygen gets used up by respiration, the total volume decreases.

Question 78

How can a spirometer be used to investigate the effects of exercise?

Answer 78

1) As a person breathes in for 1 minute at rest and recordings are taken
2) The person exercises for 2 minutes and while the person is exercising, the spirometer chamber is refilled with oxygen
3) Immediately after the person stop exercising, they breathe out the spirometer again and recordings are taken for another minute
4) The recordings taken before and after exercise are then compared

Question 79

What is the effect of a fitness training programme on breathing rate and tidal volume?

Answer 79

1) Training decreased breathing rate both at rest and during recovery because the lung muscles are strengthened, so more air is taken in with each breath, meaning fewer breaths are needed.
2) Training also increased tidal volume, again because muscles are strengthened, so more air is taken in with each breath.
3) During recovery, breathing rate and tidal volume decrease faster due to training because the muscles are strengthened, so the lungs can get oxygen and carbon dioxide supplies back to normal quicker.

Question 80

What is homeostasis?

Answer 80

It is the maintenance of a stable internal environment like body temperature, energy, and water supply

Question 81

How does homeostasis use a negative feedback loop to reverse change?

Answer 81

Involves receptors, a communication system and effectors. Receptors detect when a level is too high or too low, and the information’s communicated via the nervous system or the hormonal system to the effectors. The effectors respond to counteract the change and bring it back to normal. The mechanism that restores the level to normal is called a negative feedback mechanism.

Question 82

Can negative feedback work all the time?

Answer 82

Negative feedback only works within a certain limit- if the change is too big then the effectors may not be able to counteract it.

Question 83

How can positive feedback mechanisms amplify a change from the normal level?

Answer 83

1) effectors respond to further increase the level away from the normal level
2) positive feedback is useful to rapidly activate something
3) It can also happen when a homeostatic system breaks down
4) It isn’t involved in homeostasis because it doesn’t keep your internal environment stable

Question 84

What are some of the mechanisms to reduce body temperature?

Answer 84

• sweating- more sweat is secreted from the sweat glands when the body temp is too high. The water is evaporated from the surface of the skin and takes heat from the body, making to skin cool.
• Hair lies flat- mammals have a layer of hair that provides insulation by trapping air. When it’s hot, erector pili muscles relax so that the hairs lie flat. Less air is trapped, so the skin is less insulated and heat can be lost easily.
• Vasodilation- when it’s hot, arterioles near the surface of the skin dilate (vasodilation). More blood flows through the capillaries in the surface layer of the dermis. This means more heat is lost from the skin by radiation and the temp is lowered.

Question 85

What are some of the mechanisms to increase body temperature?

Answer 85

• shivering- muscles contract causing a and more heat to be produced from increased respiration.
• much less sweat- less sweat is secreted from sweat glands when its cold, reducing the amount of heat loss
• hair stands up- erector pili muscles contract when it’s cold, hairs stand up. This traps more air and so prevents heat loss
• vasoconstriction- when it’s cold, arterioles near the surface of the skin constrict so less blood flows through the capillaries in the surface layers of the dermis. This reduces heat loss
• hormones- the body releases adrenaline and thyroxine. These increase metabolism and so more heat is produced.

Question 86

How does the hypothalamus control body temp?

Answer 86

• receives information about temperature from thermoreceptors (temp receptors).
• thermoreceptors send impulses along sensory neurones to the hypothalamus, which sends impulses along motor neurones to effectors
• the effectors respond to restore the body temperature to normal.
• the control of body temp is called thermoregulation

Question 87

How can hormones affect transcription factors?

Answer 87

• transcription factors bind to DNA sites near the start of genes and increase or decrease the rate of transcription. Factors that increase the rate are called activators and those that decrease the rate are repressors
• Hormones can affect the activity of transcription factors.
• some hormones can cross the cell membrane, enter the nucleus, and bind to transcription factors to alter gene transcription

Question 88

What is an example of hormonal regulation of body temp?

Answer 88

1) At normal body temp, the thyroid hormone receptor binds to DNA at the start of a gene
2) This decreases the transcription of a gene coding for a protein that increases metabolic rate.
3) At cold temperatures thyroxine is released, which binds to the thyroid hormone receptor, causing it to act as an activator.
4) The transcription rate increases, producing more protein. The protein increases the metabolic rate, causing the body temp to increase.

Question 89

How do hormones work from the cell membrane?

Answer 89

1) Some hormones can’t cross the cell membrane, but they can still affect the activity of transcription factors.
2) They bind to receptors in the cell membrane, which activate messenger molecules in the cytoplasm of the cell
3) These messenger molecules activate enzymes called protein kinases, which trigger a cascade (a chain reaction) inside the cell
4) During the cascade, transcription factors can be activated- these then affect the transcription of genes in the cell nucleus

Question 90

What can too much exercise cause?

Answer 90

• Immune suppression
• Damage to the joints and bones.

Question 91

What can too little exercise cause?

Answer 91

Becoming overweight with associated problems of heart disease and diabetes.

Question 92

How does moderate exercise effect immunity?

Answer 92

• Increases the number and activity of Natural Killer cells.
• These target cells do not display “self” markers. (these can be cells invaded by viruses, bacteria and cancer cells)
• They attack the cell membrane by making pores in it (making protein perforin).
• Proteases can invade cells and cause apoptosis.
• Give non-specific protection.

Question 93

How does too much exercise effect immunity?

Answer 93

-After exercise, the number of these immune system cells falls
-Natural killer
-Phagocytes
-B cells
-Helper T cells.

The specific immune system is depressed. The debate about whether physical or psychological. The stress of training could release adrenalin and cortisol both known to suppress the immune system.

Question 94

How do joints get damaged by exercise like knees?

Answer 94

-Cartilage is worn away
-Patellar tendonitis – kneecap does not move easily over the femur
-Bursitis – fluid-filled sacs around joints swell up with extra fluid. Inflammation and tenderness.
-Ligament damage.

Question 95

What is keyhole surgery?

Answer 95

• doing surgery without making large incisions
• surgeons make a much smaller incision in the patient, and they insert a tiny video camera and specialised medical instruments through the incision into the body.

Question 96

What are the advantages of keyhole surgery?

Answer 96

• loss less blood
• less scarring
• less pain
• recover quicker
• shorter hospital stay

Question 97

What is an example of a ligament being fixed by keyhole surgery?

Answer 97

• cruciate ligament
• common sports injury and connects the high thigh bone to the lower leg bone
• damaged–> can be removed and replaced with a graft and likely to be from a tendon from the patient or a donor.

Question 98

What is a prostheses and how does it operate?

Answer 98

It can be used to replace whole limbs or parts of limbs. Some include electronic devices that operate the prosthesis by picking up information sent by the nervous system

Question 99

What is an example of a damaged knee joint being replaced by prosthetic joints?

Answer 99

• the metal device is inserted into the knee to replace damaged cartilage and bone
• providing a smooth knee joint, cushioning on new joints helps to reduce the impact on the knee.
• This allows people with serious knee problems to move around and participate in low-impact sports, like walking and swimming

Question 100

What are anabolic steroids?

Answer 100

drugs to increase strength, speed and stamina by increasing muscle size and allowing athletes to train harder. They also increase aggression

Question 101

What are stimulants?

Answer 101

drugs to speed up reactions, reduce fatigue and increase aggression

Question 102

What are narcotic analgesics?

Answer 102

drugs to reduce pain, so injuries don’t affect performance

Question 103

What are the arguments against performance-enhancing drugs?

Answer 103

• illegal
• competition becomes unfair as people will have a gained advantage
• some have serious health risks associated with these drugs and some side effects include high blood pressure and heart problems
• athletes may not be fully informed of the health risks

Question 104

What are the arguments for using performance-enhancing drugs?

Answer 104

• athletes have the right to make their own decision and whether they are worth the risk or not
• drug-free sport isn’t fair anyway- different athletes have different access to training and coaches- overcome the inequalities
• athletes that want to compete at a higher level may only be able to by using performance-enhancing drugs.