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AQA A-level Biology > Topic 6: Learn And Churns > Flashcards

Topic 6: Learn And Churns Flashcards

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1
Q

Explain the importance of reflex actions (3 marks)

A
  1. Automatic/ involuntary adjustments to changes in the environment
  2. Reducing damage to tissues/ prevents injury/ e.g burning
  3. Role in homeostasis/ example;
    4.posture/balance
    5.finding food/ mate
  4. Escape from predators
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2
Q

Describe te sequence of events which allows information to pass from one neurone to the next neurone across the cholinergic synapses (6 marks)

A
  1. Impulses cause calcium ions to enter axons
    2.vesicles fuse with presynaptic membrane
  2. Acetylcholine released
    4.acetylcholine diffuses across synaptic cleft
    5.binds with receptors on postsynaptic membrane
  3. Sodium ions enter post synaptic neurone
  4. Depolarisation of postsynaptic membrane
  5. If above threshold, action potential produced
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3
Q

Explain how a resting potential is maintained in a neurone (4 marks)

A
  1. Membrane is relatively impermeable to sodium ions/gated channels are closed/fewer channels
  2. Sodium ions pumped/actively transported out
  3. By sodium ion carriers
  4. Inside is negative compared to outside/ 3 sodium ions out for 2 potassium ions in
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4
Q

Describe how the release of acetylcholine into a neuromuscular junction causes the cell membrane of a muscle fibre to depolarise (3 marks)

A
  1. Movement by diffusion
  2. Binding to receptors on the postsynaptic membrane
  3. Causing sodium channels to open/ sodium ions move into muscle cell
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5
Q

Describe how a pacinian corpuscle produces a generator potential when stimulated (3 marks)

A
  1. Increase pressure deforms/ changes stretch mediated sodium ion channels
    2 sodium channels open & sodium ions flow in
  2. Depolarisation- eating to generator potential
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6
Q

What does the data suggest about the control of heart rate by the sympathetic and parasympathetic nervous system in response to changes in arterial blood pressure (3 marks)

A
  1. Parasympathetic greater effect than sympathetic
  2. Parasympathetic keeps heart rate down/ decreases heart rate (as blood pressure increases)
  3. Sympathetic keeps heart rate up/increase heart rate
  4. Parasympathetic greatest/ greater effect at high blood pressure/ sympathetic greatest effect at low blood pressure
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7
Q

Describe the sequence of events leading to the release of acetylcholine and its binding to the postsynaptic membrane (4 marks)

A
  1. Action potential arrives/ depolarisation occurs
  2. Calcium ions enter synaptic knob
  3. Vesicles fuse with the membrane
  4. Acetylcholine diffuses across the synaptic cleft
  5. Binds to receptors
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8
Q

the binding of GABA to receptors on the postsynaptic membranes causes negatively charged chloride ions to enter the postsynaptic neurones.
explain how this will inhibit transmission of the nerve impulses by postsynaptic neurones (3 marks)

A
  1. inside becomes more negatively charged/ hyperpolarised
  2. stimulation doesn’t reach threshold level/ action potential not produced
  3. depolarisation does not occur/ reduces effect of sodium ions entering
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9
Q

Cannabinoid receptors are found in the pre-synaptic membrane of neuromuscular junctions. When a cannabinoid binds to its receptors, it closes calcium ion channels
suggest how cannabinoids could prevent muscle contraction
(4 marks)

A
  1. prevents influx of calcium ions into the pre-synaptic membrane
    2.synaptic vesicles don’t fuse with membrane/release neurotransmitter
  2. neurotransmitter doesn’t diffuse across synapse/doesnt bind to receptors on post synaptic membrane
  3. no action potential/depolarisation of post-synaptic membrane/ sodium ion channels do not open
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10
Q

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

A
  1. non-myelinated- whole membrane is depolarised
  2. myelinated-depolarisation/ion movement only at the nodes
  3. impulses jump from node to node/salatory conduction
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11
Q

describe how calcium ions are involved in synaptic transmission
(2 marks)

A
  1. nerve impulses causes calcium ions to enter presynaptic neurone
  2. calcium ion entry causes fusion of vesicles with presynaptic membrane/ release of transmitter
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12
Q

when a person looks directly at an object, it’s image is focused on the fovea. When the image is focused on the fovea, the person sees the object in colour. Explain why. (3 marks)

A
  1. colour detected by cone cells
  2. fovea contains only/mainly cone cells
  3. 3 types of cone cells(described) each sensitive to different wavelengths/red green or blue
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13
Q

explain why vision using other parts of the retina has high sensitivity to light (3 marks)

A
  1. many rods in other parts of the retina
  2. rhodopsin/ rod cells very sensitive to light/ work in low light
  3. rods connect in groups to ganglion cell/neurone
  4. summation
  5. if enough light above threshold, nerve impulses are sent to the brain along the optic nerve
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14
Q

describe the role of calcium ions and ATP In the contraction of a microfibril
(5 marks)

A
  1. calcium Ions diffuse into myofibrils from sarcoplasmic reticulum
  2. calcium ions cause movement of tropomyosin
    3.causes exposure of the binding sites on actin
  3. myosin heads attach to binding sites on actin
    5.hydrolysis of ATP causes myosin heads to bend
  4. bending pulls actin molecule
  5. attachment of a new ATP molecule to each myosin head causes myosin head to detach from actin sites
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15
Q

describe the role of each of the following in muscle contraction; tropomyosin and ATP (4 marks)

A
  1. blocks myosin binding site on actin
  2. moves from binding site on actin due to calcium ions, allowing cross bridge formation
  3. releases myosin from actin
  4. causes myosin head to tilt
  5. used in the active transport of calcium ions
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16
Q

explain how muscles maintain posture (3 marks)

A
  1. antagonistic muscles
  2. working across joints
  3. both contract to keep joint/ body at a certain angle/upright
  4. isometric contraction
  5. only a few fibres contract to avoid fatigue/ slow muscle fibres used
17
Q

describe the role of calcium ions in the contraction of a sarcomere
(4 marks)

A
  1. moves tropomyosin
  2. to reveal binding sites on actin
    3.allowing myosin heads to bind to actin/actinomyosin cross bridges formed/ activates ATPasa
18
Q

Dopamine is a neurotransmitter, the transmission of which is similar to acetylcholine. Dopamine stimulates the production of nervous impulses in the postsynaptic neurone. Describe how.
(3 marks)

A
  1. dopamine diffuses across the synapse
  2. attaches to receptors on the postsynaptic membrane
  3. stimulates entry of sodium ions/depolarisation/action potential
19
Q

describe how a heartbeat is initiated/ coordinated
(5 marks)

A

1.SAN sends a wave of electrical activity/ impulses causing atrial contraction
2. non- conducting tissue prevents immediate contraction of the ventricles
3. AVN delays the impulse whilst the blood leaves the atria/ventricles fill
4. AVN sends wave of electrical activity/ impulses down the bundle of His
5. causing ventricles to contract from the base up

20
Q

explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta (5 marks)

A
  1. atria has higher pressure than ventricle causing AV valves to open
  2. ventricle has higher pressure than atrium due to filling causing AV valve to close
  3. ventricle has higher pressure than the aorta causing semi lunar valve to open
  4. higher pressure in aorta than ventricle causes semilunar valve to close
  5. muscle/atrial/ventricular contraction causes increase in pressure
21
Q

a woman takes moderate exercise. explain what causes her heart rate to increase while she exercises ( 6 marks)

A
  1. rate of respiration increases in muscle cells
  2. carbon dioxide concentration increases/ph falls/ acidity increases
  3. chemo receptors in aortic/carotid arteries
  4. impulses to medulla/cardioacceleratory centre
  5. increases the frequency of impulses
  6. along the sympathetic pathway to the SAN
22
Q

the heart controls and coordinates the regular contraction of the atria and ventricles. Describe How (5 marks)

A
  1. SAN- AVN- bundle of his/purkyne fibres
    2.impulses/electrical activity over atria
  2. atria contract
    4.non conducting tissue (between atria and ventricles)
  3. delay at AVN ensures atria are empty/ventricles fill before contract
  4. Ventricles contract from Apex upwards
23
Q

explain how a rise in blood pressure results in a decrease in the rate of heartbeat (6 marks)

A
  1. pressure receptors/baroreceptors in carotid arteries
  2. send impulses to cardio-inhibitory centre in medulla
    3.impulses via parasympathetic nerves
  3. to SAN
  4. release of ACh/decreases impulse from SAN
  5. decreases impulses to AVN/decreases impulses from AVN
24
Q

describe the role of the hormone glucagon in the control of blood sugar concentration (4 marks)

A
  1. binds to specific receptor
  2. on muscle/liver cell
  3. activation of enzymes in liver
    4.hydrolysis of glycogen
  4. facilitated diffusion of glucose out of liver cells
  5. increases blood glucose levels
25
Q

explain the role of negative feedback in the control of the plasma glucose concentration (5 marks)

A
  1. deviation of a value from the norm intitiates corrective mechanisms
  2. fluctuations in plasma glucose concentration detected by hypothalamus/islets cells in pancreas
  3. initial decrease, no food stimulates secretion of glucagon
    4.increase in plasma glucose stimulates secretion of insulin from b cells
    5.change in membrane permeability to glucose
26
Q

how does maintaining a constant body temp allow metabolic reactions in cells to proceed with maximum efficiency? (5 marks)

A
  1. body temp/37 is optimum for enzymes
  2. excess heat denatures enzymes/alters shape of active site/substracte cant bind
    3.reactions slowed
  3. reduces kinetic energy of molecules
  4. fewer collisions/ es complexes formed
27
Q

describe how insulin reduces the concentration of glucose in the blood (3 marks)

A
  1. insulin binds to specific receptors
  2. insulin activates carrier proteins/more channels to form
  3. insulin increases permeability of liver/muscle cells to glucose
  4. insulin action results in glucose conversion to glycogen/glycogenesis
28
Q

stimulation of osmoreceptors can lead to the secretion of ADH. describe and explain how this affects urine produced by kidneys.
(4 marks)

A

1.permeability of membrane to water increased
2. more water absorbed from distal tube/collecting duct
3. smaller volume of urine
4. urine becomes more concentrated

29
Q

explain how the loop of hence maintains the gradient of ions which allows water to be reabsorbed from the filtrate in the collecting duct.
(5 marks)

A
  1. active transport of chloride/sodium ions out of filtrate
  2. from the ascending limb
    3.into surrounding tissue fluid
  3. ascending limb impermeable to water
  4. lower WP in interstitial fluid compared to filtrate
  5. water leaves the descending limb via osmosis
  6. lower WP down the medulla
  7. water is absorbed from the collecting duct via osmosis
30
Q

explain how ADH is involved in the control of the volume of urine produced (4 marks)

A
  1. if WP of blood falls, detected by receptors in hypothalamus
  2. leads to ADH released from pituitary gland
  3. ADH makes cells of collecting duct/DCT more permeable to water
  4. water leaves filtrate by osmosis
  5. smaller volume of urine produced
31
Q

describe how ultrafiltration produces glomerular filtrate
(5 marks)

A
  1. blood pressure/hydrostatic pressure
    2.small molecules/named example
  2. pass through basement membrane (it acts as a filter)
  3. proteins too large so stay behind
  4. presence of pores in capillaries/podocytes
32
Q

explain how a lack of insulin affects the reabsorption of glucose in the kidneys of a person who doesn’t secrete insulin (4 marks)

A
  1. high concentration of glucose in the blood
  2. high concentration in filtrate
  3. reabsorbed by facilitated diffusion/active transport
  4. requires proteins/carriers
  5. these are working at maximum rate/saturated
  6. not all glucose reabsorbed/some lost in urine
33
Q

some desert mammals have long loops of Henle and secrete large amounts of ADH
explain how these 2 features are adaptations to living in desert conditions (6 marks)

A
  1. more water reabsorbed/less lost in urine
    2.by osmosis
  2. from collecting duct
    4.due to longer loop of hence
  3. sodium/chloride ions absorbed from filtrate in ascending limb
    6.gradient established in medulla/concentrations of ions increases down the medulla
  4. (adh) acts on collecting duct/DCT
  5. makes cells more permeable/ inserts aquaporins in plasma membrane
34
Q

in a mammal, urea is removed from the blood by the kidneys and concentrated in the filtrate. Describe how urea is removed from the blood. Explain how urea is concentrated in the filtrate (5 marks)

A
  1. hydrostatic pressure is generated
  2. causes ultrafiltration at glomeruli/renal capsule
  3. through basement membrane
  4. enabled by small size urea molecule
  5. reabsorption of water by osmosis
  6. at PCT/descending loop of hence
    7.at DCT/collecting duct
    8.active transport of ions/glucose creates a gradient
35
Q
A

AQA A-level Biology (32 decks)

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