Unit 5 Questions Taxes to Homeostatis and Hormones

Question 1

Name 2 things needed for cross bridge formation and where they come from

Answer 1

Calcium ions and ATP. Calcium from sarcoplasmic rteticulum and ATP produce from CP hydrolyses the glycolytic or the oxidative process

Question 1

Explain how the body of a mammal may respond to a rise in the environmental temperature

Answer 1

Hot receptors in skin; nervous impulse; to hypothalamus; blood temperature monitored; heat loss centre involved; vasodilation / dilation of arterioles; more blood to surface / heat lost by radiation; piloerector muscles relax; hairs flatten on skin surface; less insulation; sweating initiated / increased; panting / licking; evaporation removes latent heat; drop in metabolic rate / use less brown fat; accept long term changes such as less fat deposition; thinner fur; migration; accept one behavioural process

Question 2

The rate of oxygen consumption of a neurone increases when it conducts a high frequency of impulses. Explain why.(4)

Answer 2

Oxygen used in respiration; [Reject: Anaerobic reference] Valid reference to ATP/energy; [Reject: Production of energy] (For) sodium-potassium pump/ active transport of ions/ uptake/ synthesis of transmitter/ vesicle movement; (Higher rate of impulses means) more high / amount of sodium ion entry/ potassium ion loss / transmitter uptake / release / vesicle movement;

Question 3

Explain the advantage of having large amounts of glycogen in fast muscle fibres

Answer 3

Anaerobic respiration / glycolysis inefficient / produces little ATP; requires large amount of glucose to produce enough ATP; glycogen acting as glucose store / glycogen converted to glucose; energy store

Question 4

Slow muscle fibres have capillaries in close contact. Explain the advantage of this arrangement

Answer 4

Requires oxygen / glucose; short diffusion pathway / rapid passage of oxygen; Removal of heat/CO2

Question 5

Explain why increased cardiac output is an advantage during exercise

Answer 5

In exercise ? More energy release / more respiration / actively respiring muscles / for aerobic respiration; Higher cardiac output ? Increases O2 supply (to muscles); Increases glucose supply (to muscles); Increases CO2 removal (from muscles) /lactate removal; Increases heat removal (from muscles) /for cooling

Question 5

Describe the role of the nervous system in modifying the heart rate in response to an increase in blood pressure

Answer 5

Pressure receptors; in aorta/carotid artery/sinus; send impulses (award once only); to medulla; send impulses; along parasympathetic / vagus pathway; slows heart rate

Question 6

Suggest how diet and exercise can maintain low glucose concentrations in the blood of type II diabetics

Answer 6

feed on polysaccharides / named example (not cellulose); slower digestion therefore no surge in blood sugar level; exercise - increased respiration / BMR

Question 7

Neurones can respond to both strong and weak stimuli. Describe how a neurone conveys information about the strength of a stimulus

Answer 7

Frequency of action potentials

Question 8

What is meant by the ?all or nothing? nature of a nerve impulse?

Answer 8

All action potentials are the same size; threshold value for action potential to occur

Question 9

Explain the importance of reflex actions

Answer 9

1. Automatic (adjustments to changes in environment)/ involuntary; 2. Reducing/avoiding damage to tissues / prevents injury/named injury e.g. burning; 3. Role in homeostasis/example; 4. Posture/balance; 5. Finding/obtaining food/mate/suitable conditions; 6. Escape from predators

Question 10

When pressure is applied to a Pacinian corpuscle, an impulse is produced in its sensory neurone. Explain how

Answer 10

(Pressure) deforms and opens (sodium) channels; Entry of sodium ions; Causes depolarisation (generator potential); Ions diffuse downstream and when threshold of nearby voltage gated channels is reached they; open and sodium diffuses in causing depolarisation

Question 11

Describe the role of the mitochondria in the synaptic bulb

Answer 11

Active transport of ions/ ionic pump; (reject active transport of Ach) Synthesis of acetylcholine / neurotransmitter/ reform vacuole; Reabsorption of acetylcholine, or acetyl + choline (from cleft); Movement of vesicles (to membrane); Synthesis of relevant enzyme, e.g. acetylcholinesterase. (Reject - general uses of energy, or use in muscle fibril

Question 12

Explain what causes the conduction of impulses along a non-myelinated axon to be slower than along a myelinated axon.(3)

Answer 12

non-myelinated ? next section of membrane depolarised / whole membrane; myelinated ? depolarisation / ion movement only at nodes; impulse jumps from node to node /saltatory conduction

Question 12

The relationship between oestrogen and LH is an example of positive feedback. Explain how

Answer 12

Answer showing understanding of positive feedback i.e. more produces more / differs further; Answer showing understanding of positive feedback correctly linked to oestrogen and LH i.e. more oestrogen produces more LH

Question 13

The hormones which control the concentration of glucose in the blood affect some cells in the body but not others. Use your knowledge of the structure of cell surface membranes to explain why

Answer 13

Only target cells have appropriate receptors; These are the proteins in cell surface membrane; Receptor sites/hormones with a particular shape; Concept of fitting/binding between receptor and hormone

Question 14

Describe the role of calcium in the contraction of a muscle

Answer 14

Moves / detaches / changes position of / shape of / switch protein / blocking molecule / tropomyosin / troponin; (Not just ?switches on?) uncovering binding site (on actin) / allows cross bridges to form / eq; activates myosin ATP?ase / enables myosin head to split ATP

Question 15

Describe how insulin reduces the concentration of glucose in the blood

Answer 15

Insulin binds to specific receptors (on membranes); insulin activates carrier proteins / opens channels / causes more channels to form; insulin increases the permeability of liver/muscle cells/tissues to glucose; insulin action results in glucose conversion to glycogen / glycogenesis

Question 16

Describe what happens to the sodium ions immediately after the passage of an action potential along the neurone

Answer 16

Sodium ions move out; By active transport/pump;

Question 17

Describe how the regular contraction of the atria and ventricles is initiated and coordinated by the heart itself

Answer 17

(cardiac) muscle is myogenic; sinoatrial node/SAN; wave of depolarisation/impulses/electrical activity (across atria); initiates contraction of atria atrioventricular node/AVN; bundle of His/purkyne tissue spreads impulse across ventricles; ventricles contract after atria/time delay enables ventricles to fill

Question 19

What is meant by the refractory period

Answer 19

No (new) action potential/nerve impulse be produced in this time

Question 20

Describe the events that take place in a neurone which produce an action potential (6)

Answer 20

1 Stimulus to threshold / critical firing level; 2 Sodium channels/gates open; 3 Sodium ions enter; 4 Down electrical/chemical gradient; 5 Positive feedback; 6 Depolarisation; 7 Inside becomes positive / membrane potential reverses; 8 Potassium channels/gates open; 9 Potassium ions leave; 10 Down electrical/chemical gradient [Note: only credit if not awarded earlier in point 4]11 Repolarisation; 12 Sodium channels/gates close; 13 Undershoot / hyperpolarisation; 14 Sodium-potassium pump restores resting potential

Question 21

Explain the role of negative feedback in the control of plasma glucose concentration

Answer 21

1. Deviation of a value from norm initiates corrective mechanisms; 2. fluctuations in plasma glucose concentration detected by hypothalamus/islet cells in pancreas; 3. initial decrease, no food given (in plasma glucose) stimulates (increased) secretion of glucagon; 4. increases (in plasma glucose) stimulate (increased) secretion of insulin; 5. correct ref. to role of cells as secretors; 6. correct ref. to inter conversion of glycogen / glucose; 7. increased/decreased uptake of glucose by cells (as appropriate)/correct ref to change in membrane permeability;

Question 22

Describe how the rate of heartbeat is increased as muscle activity increases during exercise

Answer 22

Increase in carbon dioxide / hydrogen ions; detection by / stimulation of chemoreceptors; pressure receptors detect changes in blood pressure; (receptors) in aorta / carotid arteries / medulla; (cardio) acceleratory centre (in medulla) / cardiovascular centre; impulses via sympathetic nerves/system; to SAN; change in rate of impulse production by SAN

Question 23

Explain why runners are more likely to overheat in humid conditions

Answer 23

Humidity reduces diffusion gradient / less difference in water potential; less evaporation of sweat; less cooling due to use of heat energy for evaporation of sweat

Question 25

Explain how the structure of the retina and its neuronal connections enable a person to have a high degree of visual sensitivity in low light levels

Answer 25

Rod cells (responsible for sensitivity); Several rods connected to each bipolar cell; Additive effect of small amount of light striking several rod cells; creating a large enough depolarisation to generate a action potential; Several rod cells to each neurone/bipolar cell; additive effect of light striking several rod cells

Question 26

Sodium and potassium ions can only cross the axon membrane through proteins. Explain Why

Answer 26

cannot pass through phospholipid bilayer; because water soluble / not lipid soluble / charged / hydrophilic / hydrated

Question 26

Explain what causes transmission at a synapse to occur in only one direction

Answer 26

(Vesicles containing) neurotransmitter only in presynaptic membrane/ neurone; receptor/proteins only in postsynaptic membrane/neurone; so neurotransmitter diffuses down concentration gradient

Question 26

What is the role of phosphocreatine in muscle contraction

Answer 26

Allows the regeneration of ATP without respiration. Produces ATP; release Pi to join with ADP

Question 27

How does maintaining a constant body temperature allow metabolic reactions in cells to proceed with maximum efficiency? (5)

Answer 27

1. Body temp./37?C is optimum temp for enzymes; 2. excess heat denatures enzymes/alters tertiary structure/alters shape of active site/enzyme; 3. substrate cannot bind/e.q,; 4. reactions cease/slowed; 5. too little reduces kinetic energy of molecules / molecules move more slowly; 6. fewer collisions/fewer ES complexes formed?

Question 28

When a muscle contracts what happens to the A band, I band and H zone respectively

Answer 28

A-band: no change AND I-band: shorter; H-zone: shorter / disappears

Question 28

Describe how the body responds to a rise in core body temperature

Answer 28

Temperature receptors stimulated in; (in skin disqualifies) hypothalamus; heat loss centre stimulated; nerve impulses to sweat glands; increase rate of / start sweat production; nerve impulses to skin arterioles; vasodilation (ref to vessels moving disqualifies)

Question 30

Explain the advantage of having both fast and slow twitch fibres

Answer 30

Fast fibres make immediate/fast contraction possible before the circulation/blood supply adjusts/ most energy anaerobically generated; fast fibres used in explosive/sprints locomotion; slow fibres allow sustained contraction/anaerobic energy generation; slow fibres used in maintaining posture/endurance events

Question 32

Describe 2 ways in which the muscle as a whole can produce contractions of varying force

Answer 32

By changing the frequency of stimulation so that the fibre receives impulses at a greater rate. Changing the number and sizes of the motor units (a motor unit is all the muscle fibres supplied by a single motor neurone). Large number of units gives a more intense contraction

Question 33

Describe the role of ATP in muscle contraction

Answer 33

ATP provides energy for release / attachment / movement of myosin (head) (from binding site) / removal of calcium ions

Question 35

Describe how transmission occurs across a synapse

Answer 35

1 Presynaptic membrane depolarises; 2 Calcium channels/gates open; 3 Calcium ions enter; 4 Vesicles move to/fuse with presynaptic membrane; 5 Release of transmitter / exocytosis; 6 Diffusion across gap/cleft; 7 Binds to receptors in postsynaptic membrane; [Reject: references to active site] 8 Sodium channels open / sodium ions enter

Question 36

Explain how changing concentrations of oestrogen and progesterone regulate the oestrous cycle

Answer 36

1 Progesterone inhibits (release of) FSH/LH; 2 Once progesterone falls (on day 16) FSH increases; 3 FSH increase causes follicles to develop; 4 Developing follicles produce oestrogen; 5 Oestrogen inhibits FSH (release); 6 High oestrogen/approx. day 18 stimulates FSH (release); 7 High oestrogen stimulates LH (release); 8 LH causes ovulation/causes progesterone (release)/formation of corpus luteum

Question 37

What are Taxes

Answer 37

A taxis (plural taxes) is a directional response to a directional stimulus. Taxes are common in invertebrates, and even motile bacteria and protoctists show taxes. The taxis response can be positive (towards the stimulus) or negative (away from the stimulus)

Question 38

Explain how nervous control in a human can cause increased cardiac output during exercise

Answer 38

1. Coordination via medulla (of brain) / cardiac centre; 2. (Increased) impulses along sympathetic (/ cardiac accelerator) nerve; 3. To S.A. node / pacemaker; 4. Release of noradrenalin; 5. More impulses sent from / increased rate of discharge of S.A. node /pacemaker; Not ?beats?; not ?speeds up? 6. Increased heart rate / increased stroke volume

Question 39

What are Kineses

Answer 39

A kinesis (plural kineses) is a response to a changing stimulus by changing the amount of activity. Sometimes the speed of movement varies with the intensity of the stimulus (orthokinesis) and sometimes the rate of turning depends on the intensity of the stimulus (klinokinesis). The response is not directional, so kinesis is a suitable response when the stimulus isn?t particularly localised. The end result is to keep the animal in a favourable environment.

Question 41

Explain how normal core body temperature is maintained when a person moves into a cold room

Answer 41

1.???? Sensors in skin/hypothalamus detect reduced temperature; 2. heat gain centre activated/inhibition of heat loss centre; 3. vasoconstriction/constriction of arterioles in skin surface; 4. dilation of shunt vessels/constriction of ? capillary sphincter; 5. less blood to skin surface/capillaries 6. reduced heat loss by radiation; 7. increased heat gain by increased metabolic rate/respiration/ movement/shivering; 8. decreased heat loss by putting on clothes/huddling/reduced sweating;

Question 42

At a neuromuscular junction there is a 0.6ms delay between maximum depolarisation in the presynaptic neurone and maximum depolarisation in the post synaptic neurone, explain why

Answer 42

Calcium ion/Ca2+ entry; vesicles fuse with preSM ( and rupture); exocytosis of/release (neuro)transmitter substance / named e.g.; diffuse across gap; attach to receptors on post SM; (not ?fuse with….?) increase permeability to sodium (ions) open Na channels

Question 43

Explain what is meant by depolarisation

Answer 43

Inflow of sodium ions; So inside (more) positive (or outside more negative)/ change in membrane potential

Question 44

Describe how the resting potential is established in an axon by the movement of ions across the membrane.

Answer 44

active transport / pump of Na+ out of axon; diffusion of K+ out of axon / little diffusion of Na+ into the axon; membrane more permeable to loss of potassium ions; limits entry of sodium ions; negatively charged proteins inside; sodium pump membrane relatively impermeable / less permeable to sodium ions / gated channels are closed / fewer channels; sodium ions pumped / actively transported out; by sodium ion carrier / intrinsic proteins; higher concentration of sodium ions outside the neurone; inside negative compared to outside / 3 sodium ions out for two potassium ions in