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Left RSFC Year 13 2022-24 > Year 13.6 Organisms respond to changes in their internal and external environments > Flashcards

Year 13.6 Organisms respond to changes in their internal and external environments Flashcards

1
Q

Describe the effect of IAA on root and shoot growth. [6]

A
  • IAA synthesised in shoots tips.
  • IAA diffuses into growing (cell elongating) region.
  • Light causes movement of IAA from light side to shaded side.
  • Proportionally more IAA on shaded side.
  • Causes directional growth as there is greater cell elongation on shaded side.
  • Shaded side grows faster and causes shoot to bend towards the light.
  • IAA synthesised in root tips.
  • IAA diffuses into growing (cell elongating) region.
  • IAA moves towards underside/shaded side.
  • Inhibits cell elongation.
  • Uneven growth (more elongation on side with less IAA).
  • Causes directional growth away from light and downwards towards gravity.
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2
Q

Describe what is meant by the term taxis

A
  • Moves towards or away from directional stimulus
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3
Q

Describe what is meant by the term kinesis

A
  • Movement is random/non-directional response
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4
Q

Compare & Contrast taxis and tropism [2]

A
  • Both are directional responses to stimuli
  • Taxis involves the movement of the entire organism whereas tropism is the movement of part of an organism
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5
Q

Explain the advantages of simple reflex arcs [3]

A
  • Rapid;
  • Protect against damage to body tissues;
  • Do not have to be learnt;
  • Help escape from predators;
  • Enable homeostatic control;
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6
Q

As a neurone transmits an impulse, its rate of oxygen consumption increases.
Explain why.
[2]

A
  • ATP required for active transport;
  • Na+ (actively) moved out only at nodes in myelinated / Na+ (actively) moved out along whole length of axon in non-myelinated;
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7
Q

Describe how a resting potential is maintained in a neurone. [4]

A
  • active transport/pumping of sodium (ions across membrane);
  • out of neurone/higher concentration outside;
  • differential permeability to K+ and Na+;
  • Membrane more permeable to K+ ions;
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8
Q

The potential across the membrane is reversed when an action potential is produced.

Describe how.
[2]

A
  • Sodium ion gates / channel (proteins) open;
  • Na+ (rapidly) diffuse in;
    REJECT INFLUX
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9
Q

SYNAPSE:

Describe the sequence of events leading to the release of acetylcholine and its binding to the postsynaptic membrane. [5]

A
  • Depolarisation of presynaptic membrane;
  • Ca2+ channels open and calcium ions enter synaptic knob (by facilitated diffusion);
  • (Calcium ions cause) synaptic vesicles move AND fuse with presynaptic membrane and release acetylcholine / neurotransmitter;
  • Acetylcholine/neurotransmitter diffuses across (synaptic cleft);
  • (Acetylcholine attaches) binds to receptors on the postsynaptic membrane;
  • Sodium ions enter (postsynaptic neurone) leading to depolarisation;
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10
Q

When a nerve impulse arrives at a s[3]ynapse, it causes the release of neurotransmitter from vesicles in the presynaptic knob.

Describe how.
[3]

A
  • (Nerve impulse/depolarisation of membrane) causes Ca2+ channel (proteins) to open;
  • Ca2+ enter by (facilitated) diffusion;
  • Causes (synaptic) vesicles to fuse with (presynaptic) membrane;
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11
Q

Give two reasons why transmission across a cholinergic synapse is unidirectional. [2]

A
  1. (Only) the presynaptic neurone/knob/membrane releases/has neurotransmitter/acetylcholine;

2.(Only) the postsynaptic neurone/membrane has receptors OR No receptors in the presynaptic neurone/membrane;

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12
Q

The binding of GABA to receptors on postsynaptic membranes causes negatively charged chloride ions to enter postsynaptic neurones.

Explain how this will inhibit transmission of nerve impulses by postsynaptic neurones. [3]

A
  • (Inside of postsynaptic) neurone becomes more negative/hyperpolarised;
  • More sodium ions required (to reach threshold) OR Not enough sodium ions enter (to reach threshold);
  • For depolarisation/action potential;
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13
Q

Describe how the speed of the conduction could be increased in a neurone. [2]

A
  • Axon is myelinated which provides (electrical) insulation;
  • So shows saltatory conduction/ Action potentials jump from node of Ranvier to node of Ranvier;
    OR
  • Axon has a larger diameter;
  • So less resistance to flow of ions; / more surface area for more channel proteins which meeans faster rate of diffusion of ions.
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14
Q

Myelination affects the rate of conduction of a nerve impulse. Explain how. [3]

A
  • Myelination provides (electrical) insulation;
  • Action potentials jumps from node of Ranvier to node of Ranvier / depolarisation only at node of Ranvier;
  • Fewer jumps / depolarisations to travel length of axon;
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15
Q

Describe how the inhibition of acetylcholinesterase affects the action of synapses. [2]

A
  • Acetylcholine not broken down / stays bound to receptor;
  • Na+ ions (continue to) enter / (continued) depolarisation / Na+ channels (kept) open / action potentials;
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16
Q

Describe what is meant by the term refractory period [2]

A
  • (Refractory period) limits number of impulses per second/frequency of nerve impulses;
  • Maximum frequency of impulse transmission
  • Period of time between threshold and resting membrane potential.
  • When maximum frequency reached/exceeded, no further increase in information/ all (higher) stimuli seem the same;
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17
Q

What is meant by the All or Nothing rule.

A
  • Action potential ALWAYS occurs if THRESHOLD is reached.
  • No action potential if stimulus is SUB THRESHOLD
  • Size of stimulus (above threshold) does not increase the membrane potential above +40mV.
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18
Q

Explain how pressure on the Pacinian corpuscle produces the changes in membrane potential recorded by microelectrode A. [6]

A
  • (Pressure) deforms lamellae.
  • Opens stretch-mediated Na+ (sodium ion) channel proteins;
  • Na+ diffuse into neurone / across membrane;
  • Causing depolarisation;
  • Increased pressure opens more channels / greater sodium entry;
  • Size of generator potential determines frequency of action potentials
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19
Q

The rate of ATP consumption of a de-myelinated neurone is greater than that of a myelinated neurone when conducting impulses at the same frequency.

Explain why.
[3]

A
  • Greater entry of sodium ions / greater exit of K+
  • in de-myelinated neurone;
  • Ref. to active transport / ref. to ion pumps;
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20
Q

Explain how the fovea increases the detail of an image [3]

A
  • High (visual) acuity
  • Each / every single cone is connected to a single bipolar/neurone
  • Each cone sends separate impulse / action potential to the brain
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21
Q

Explain how the connection of several rods to a single bipolar cell (Retinal convergence) influences visual acuity [2]

A
  • (Spatial) Summation means cannot distinguish between stimuli from different rod cells linked to same bipolar cell;
  • Decreased acuity;
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22
Q

Explain how the connection of several rods to a single bipolar cell (Retinal convergence) influences sensitivity [2]

A
  • (Summation of) sub-threshold stimuli produces threshold stimulation;
  • Increases sensitivity;
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23
Q

People with red-green colour blindness are unable to distinguish between red and green, and also between other colours

Explain why. [3]

A
  • Green sensitive pigment/cones non-functional
    OR
    Cones that detect green light non-functional;
  • Three different types of pigment/cone;
  • Other/different colours (‘seen’) due to stimulation of more than one cone/pigment;
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24
Q

Exercise causes an increase in heart rate.

Describe the role of receptors and of the nervous system in this process.
[4]

A
  1. Chemoreceptors detect rise in CO2 / H+ / acidity / carbonic acid /fall in pH
    OR
    Baro / pressure receptors detect rise in blood pressure;
  2. Send more frequent actionn potentials / impulses to cardiac centre/medulla;
  3. More impulses to SAN;
  4. By sympathetic (nervous system for chemoreceptors / CO2)
    OR
    By parasympathetic (nervous system for baro / pressure receptors / blood pressure);
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25
Q

Explain how nervous control in a human can cause increased cardiac output during exercise. [5]

A
  • Coordination via medulla (of brain) / cardiac centre;
  • (Increased) impulses along sympathetic nerve;
  • To S.A. node;
  • Release of noradrenalin;
  • More impulses sent from S.A.N (across atria);
  • Increased heart rate / increased stroke volume;
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26
Q

Explain why increased cardiac output is an advantage during exercise. [5]

A
  • Higher cardiac output - Increases O2 supply (to muscles);
  • Increases glucose supply (to muscles);
  • More ATP produced by oxidative phosphorylation / more energy release / more aerobic respiration / actively respiring muscles
  • Increases CO2 removal (from muscles) / lactate removal;
  • Increases heat removal (from muscles) / for cooling;
  • Delays the formation of lactate
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27
Q

Describe how the Pacinian corpuscle propagates an action potential. [4]

A
  • (Pressure causes) membrane/lamellae to become deformed/stretched;
  • Stretcg=h mediated Sodium ion channels in membrane open and sodium ions (f) diffuse / move in;
  • Depolarisation leading to generator potential;
  • Greater pressure more channels open/sodium ions enter (greater generator potential);
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28
Q

Describe what is meant by the term threshold [2]

A
  • When threshold has been reached;
  • (Threshold or above) causes maximal response / all or nothing principle;
29
Q

How do you calculate Cardiac output?

A

Cardiac Output = Heart Rate X Stroke Volume
units = dm3 min-1

30
Q

Contrast Cholinergic & NMJ synapses. [2]

A

NMJ:
* ACh is always excitatory
* Post synaptic membrane (sarcolemma) highly folded to increase surface area for more ACh protein receptors
* Neurone to effector (not neurone to neurone)

31
Q

Describe the banding pattern in striated muscle [3]

A
  • Lightest band is I band, Actin only
  • Darkest band is overlapping region, Actin and Myosin
  • Medium shading is H zone/band is Myosin only.
32
Q

Describe the sliding filament theory [4]

A
  • Attachment / cross bridges between actin and myosin heads;
  • ‘Power stroke’ / movement of myosin heads / pulling of actin (over myosin);
  • Detachment of myosin heads (requires ATP binding);
  • (Energy from ATP) Myosin heads move back/to original position / ‘recovery stroke’;
33
Q

Describe the function of calcium ions in muscle contraction [4]

A
  • Ca2+ Binding/changing shape/removing tropomyosin;
  • Exposes actin binding sites;
  • Myosin head attaches/cross-bridge formation;
  • Activates ATP hydrolase;
34
Q

Nerve impulses arriving at the presynaptic membrane at the neuromuscular junction
result in shortening of sarcomeres. Describe how [6]

A
  • Entry of calcium ions (presynaptic membrane);
  • Vesicles fuse with membrane / exocytosis /release Ach (Acetylcholine);
  • Neurotransmitter diffuses;
  • Binds to receptors, postsynaptic / membrane / muscle membrane;
  • Depolarisation / sodium ions enter;
  • Release of calcium ions (from sarcoplasmic reticulum);
  • Removes tropomyosin / bind to troponin;
  • Exposing binding sites on the actin;
  • Actinomyosin cross bridge formation / myosin binds;
  • Myosin head moves / pulls the actin along;
  • Rachet mechanism / description /detach and reattach;
  • ATP hydrolase activated;
35
Q

Explain the importance of ATP hydrolase during muscle contraction. [2]

A
  • Hydrolysis of ATP releasing energy;
  • used to form / break actinomyosin cross-bridges;
36
Q

State 3 uses of ATP in muscle contraction [3]

A
  • Breaks Actinomyosin cross bridges
  • Hydrolysis to release energy for power/recovery stroke
  • Active reuptake / removal / transport of Ca”+ from sarcoplasm into sarcoplasmic reticulum.
37
Q

Muscle contraction requires ATP. What are the advantages of using aerobic rather than anaerobic respiration to provide ATP in a long-distance race? [4]

A
  • Aerobic respiration releases more energy /produces more ATP;
  • Little/no lactate produced / does not accumulate;
  • Avoids cramp / muscle fatigue;
  • CO2 easily removed from the body / CO2 removed by breathing;
38
Q

A muscle fibre contracts when it is stimulated by a motor neurone. Describe how transmission occurs across the synapse between a motor neurone and a muscle fibre.

[6]

A
  • Ca2+ channels / gates open;
  • Ca2+ ions enter (pre-synaptic neurone);
  • Vesicles move towards / fuse with presynaptic membrane;
  • Release / exocytosis of transmitter substance / of acetylcholine;
  • Diffusion (of transmitter) across gap / cleft;
  • (Transmitter) binds to receptors in postsynaptic membrane;
  • Na+ channels open / Na+ ions enter (postsynaptic side);
39
Q

After death, cross bridges between actin and myosin remain firmly bound resulting in rigor mortis. Explain what causes the cross bridges to remain firmly bound. [3]

A
  • respiration stops;
  • no ATP produced;
  • ATP required for separation of actin and myosin/cross bridges;
40
Q

Describe the role of calcium ions in the contraction of a sarcomere. [4]

A
  • interact with/move/touch tropomyosin; (allow troponin as alternative)
  • to reveal binding sites on actin; (not active sites)
  • allowing myosin (heads) to bind/touch actin / actinomyosin formed;
  • activate ATP hydrolase / energy released from ATP;
41
Q

Describe slow twitch muscle fibres [2]

A
  • have lots of mitochondria/ (slow fibres) respire aerobically;
  • More myoglobin
  • Less / no glycogen stores
42
Q

Describe fast twitch muscle fibres [5]

A
  • used for rapid/brief/powerful/strong contractions;
  • Phosphocreatine used up rapidly during contraction/to make ATP;
  • Anaerobic respiration involved;
  • ATP used to reform phosphocreatine;
  • Lots of phosphocreatine in fast twitch fibres;
  • No myoglobin
43
Q

Describe the role of phosphocreatine [2]

A
  • Provides (energy and) phosphate / phosphorylates;
  • To make ATP from ADP & Pi;
44
Q

Explain how insulin reduces the blood glucose concentration. [3]

A
  • (More) insulin binds to receptors of target cells (All body cells);
  • (Stimulates) uptake of glucose by GLUT channel/transport proteins;
  • Activates (liver & muscle) enzymes which convert glucose to glycogen;
45
Q

Explain the action of Glucagon [3]

A
  • Attaches to receptors on target cells and activates/stimulates enzymes;
  • Glycogen to glucose / glycogenolysis;
  • Gluconeogenesis;
46
Q

Describe how a change in blood pH or blood pressure can cause a change in heart rate. [6]

A
  • (Carbon dioxide) detected by chemoreceptors / (pressure) detected by baroreceptors;
  • Medulla/cardiac centre involved;
  • More impulses to SAN/along sympathetic nerve;
  • (Decrease) pH detected by chemoreceptors in carotid artery /aorta;
  • Sends (more) impulses to medulla (oblongata);
  • More Nerve impulses sent by sympathetic nervous system to SAN;
47
Q

Less CO2 in the blood leads to a reduction in heart rate.

Describe how.
[5]

A
  • (less CO2 in blood) Detected by chemoreceptors;
  • (Chemoreceptors) located in aorta / carotid artery;
  • Fewer impulses to cardiac centre / medulla (oblongata);
  • (More) impulses along parasympathetic nerve OR less impulses along sympathetic nerve;
  • (To) SAN;
48
Q

Describe the secondary messenger model [3]

A
  • Adenylate cyclase activated / cAMP produced / second messenger produced;
  • Activates protein kinase enzyme(s) (in cell);
  • (So) glycogenolysis/ gluconeogenesis occurs / glycogenesis inhibited;
49
Q

Describe the role of glycogen formation and its role in lowering blood glucose levels. [4]

A
  • Glucose concentration in cell/liver falls;
  • Below that in blood (plasma)/ higher in blood;
  • Creates/maintains glucose concentration/diffusion gradient;
  • Glucose enters cell/leaves blood by facilitated diffusion/via carrier(protein)/channel (protein);
50
Q

Describe how ultrafiltration occurs in a glomerulus. [4]

A
  • High (higher than normal) blood/hydrostatic pressure;
  • Two named small substances pass out eg water, glucose, ions, urea;
  • (Through small) gaps/pores/fenestrations in (capillary) endothelium;
  • (And) through (capillary) basement membrane;
51
Q

Describe and explain how three features of the cells in the proximal convoluted tubule allow the rapid reabsorption of glucose into the blood. [6 ]

A
  1. Microvilli provide a large surface area OR Folded (cell-surface) membrane provides a large surface area;
  2. Many channel/carrier proteins for facilitated diffusion;
  3. Many carrier proteins for active transport;
  4. Many channel/carrier proteins for co-transport;
  5. Many mitochondria produce ATP OR Many mitochondria for active transport/co-transport;
  6. Many ribosomes to produce carrier/channel proteins;
52
Q

Explain why a thicker medulla leads to more concentrated urine. [3]

A
  • Thicker medulla means a longer loop of Henle;
  • (The longer the loop of Henle means) increase in sodium ion concentration (in medulla) so sodium ion gradient maintained for longer (in medulla);
  • (Therefore) water potential gradient maintained (for longer), so more water (re)absorbed (from loop and collecting duct) by osmosis;
53
Q

Describe the action of ADH in the kidney [6]

A
  • ADH bind to (target cell) membrane receptor proteins on cells lining DCT and CD
  • Permeability of membrane/cells (to water) is increased;
  • More water absorbed from/leaves distal convoluted tubule/collecting duct;
  • by osmosis;
  • Smaller volume of urine produced;
  • Urine becomes more concentrated;
54
Q

Explain why glucose is found in the urine of a person with untreated diabetes. [3]

A
  • High concentration of glucose in blood/filtrate;
  • Not all the glucose is (re)absorbed at the proximal convoluted tubule;
  • Carrier/co-transport proteins are working at maximum rate OR Carrier/co-transport proteins/ are saturated;
55
Q

Define homeostasis

A

The maintainance of a constant internal environment, within restricted limits / set point.

56
Q

Define a negative feedback loop

A

Any change / deviation away from a set point leads to a response that returns back to the the set point.

57
Q

Define positive feedback.

A

Any deviation away from the set point, leads to even further deviation from the set point.

More leads to even more.
Less leads to even less.

58
Q

What is a stimuls?

A

A detectable change to the internal or external environment

59
Q

What is a response?

A

A change that occurs by the action of an effector (Muscle or gland)

60
Q

Define Cardiac output

A

= Stroke Volume X Heart Rate

SV= Volume of blood exiting the Left ventricle
CO= Volume of blood circulated around the body per minute

61
Q

Calculate the speed of nerve impulse transmission, when:

  • The length of one nerve pathway involved is 175 cm.
  • A reaction time took 136 ms

Answer Units are m per second

A

12.9 m per second

62
Q

In response to touch, nerve impulses can be transmitted at speeds of 76.2 m s–1

Suggest THREE reasons why in reality this could be slower. [3]

A
  1. Synaptic transmission OR Transmission at neuromuscular junction;
  2. Time for muscle contraction;
  3. Time taken for (stretch-mediated) sodium ion channels to open (in the Pacinian corpuscle);
  4. Time taken for coordination/comprehension (by the brain);
63
Q

Explain how a resting potential is maintained across the axon membrane in a neurone. [3]

A
  1. Higher concentration of potassium ions inside and higher concentration of sodium ions outside (the neurone) OR potassium ions diffuse out OR sodium ions diffuse in;
  2. (Membrane) more permeable to potassium ions (leaving than sodium ions entering) OR (Membrane) less permeable to sodium ions (entering than potassium ions leaving);
  3. 3 Sodium ions (actively) transported out and 2 potassium ions in;
64
Q

A scientist investigated the effect of inhibitors on neurones. She added a respiratory inhibitor to a neurone. The resting potential of the neurone changed from –70 mV to 0 mV.

Explain why. [3]

A
  1. No/less ATP produced;
  2. No/less active transport OR Sodium/potassium pump inhibited;

Accept Na+ not/fewer moved out and K+ not/fewer moved in.

  1. Electrochemical gradient not maintained OR (Facilitated) diffusion of ions causes change to 0 mV OR (Results in) same concentration of (sodium and potassium) ions (either side of membrane) OR No net movement of (sodium and potassium) ions;

Accept reaches electrical equilibrium/balance.

65
Q

Damage to the myelin sheath of neurones can cause muscular paralysis.

Explain how. [3]

A

1.   (Refers to) saltatory conduction OR (Nerve) impulses/depolarisation/ions pass to other neurones

OR Depolarisation occurs along whole length (of axon);

Accept suitable description that refers to (transmission) from node to node (of Ranvier).

Accept action potential for depolarisation.

1 and 2. Accept action potentials for impulses.

2.   (Nerve) impulses slowed/stopped;

3.   (Refers to) neuromuscular junction OR (Refers to) sarcolemma;

66
Q

Suggest two advantages of simple reflexes.

A
  1. Rapid;
  2. Protect against damage to body tissues;
  3. Do not have to be learnt;
  4. Help escape from predators;
  5. Enable homeostatic control.
67
Q

In the nerve pathway in the diagram, synapses ensure that nerve impulses only travel towards the muscle fibre.

Explain how. [2]

A
  1. Neurotransmitter only made in / stored in / released from pre-synaptic neurone;
  2. (Neuro)receptors only on the post-synaptic membrane;
68
Q

Cannabinoid receptors are found in the pre-synaptic membrane of neuromuscular junctions. When a cannabinoid binds to its receptor, it closes calcium ion channels.

Suggest how cannabinoids could prevent muscle contraction. [4]

A
  1. Prevents f.diffusion of calcium ions (into pre-synaptic membrane);
  2. (Synaptic) vesicles don’t fuse with membrane / vesicles don’t release neurotransmitter; Accept vesicles don’t release acetylcholine
  3. Neurotransmitter does not diffuse across synapse / does not bind to receptors (on post-synaptic membrane); Accept: sarcolemma / muscle membrane for post-synaptic membrane
  4. No action potential / depolarisation (of post-synaptic membrane) / sodium (ion) channels do not open / prevents f.diffusion of sodium ions.
69
Q
A

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