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22 Cards in this Set
- Front
- Back
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What evidence usually indicates a kinetic response? |
Random movements, more turning/change in rate of movement and non-directional stimulus |
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Suggest and explain one advantage of the human body-louse having a positive thermokinetic response |
Stays in a favourable environment and in warmer temperautres - close to food/on host |
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What is a reflex? |
A rapid, automatic response to a stimulus |
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Explain the importance of reflex actions |
Prevents damage to tissues role in homeostasis escape from predators find a mate |
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Explain how a Pacinian corpuscle produces a generator potential in response to a specific stimulus. (3) |
Pressure changes shape of stretch mediates sodium channels Sodium channels open Results in depolarisation |
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Explain how stimulation of chemoreceptors during exercise results in a change in heart rate. (5) |
increase CO2 from resp decrease in blood pH Chemoreceptors in carotid artery detect lower pH Send more impulses to medulla oblongata in brain Medulla sends more impulses to the SAN via the sympathetic nervous system to increase rate |
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Why is most detail perceived when light strikes the fovea? |
Max. number of cone cells Each cone cell connected to a single bipolar cell (neurone) |
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Rod cells allow us to see objects in dim light. Explain how the connections of rod cells to neurones make this possible. |
High retinal convergence/many rod cells connected to a single bipolar cell Each generator potential produced by receptor cell is < threshold But due to summation Exceeds threshold |
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Describe the events that produce an action potential |
Polarised membrane(negative inside the cell) Voltage gated sodium channels open, causing sodium ions to diffuse in Depolarisation occurs, wich through positive feedback, causes depolarisation further along the axon If stimulus > TSI, then max.depolarisation occurs, as all sodium channels open BUt if < then threshold, no action potential |
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Describe how transmission occurs across a synapse. |
action potential causes influx of calcium ions vesicles in synaptic knob fuse with pre-synaptic membrane neurotransmitter released diffuses across synapse Binds with receptors |
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Describe how the resting potential is established. |
polarisation Sodium-potassium pump in axon membrane pumps out 3 sodium ions for every two potassium in Potassium ions also diffuse out 50* faster than Na* |
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Why are carrier proteins necessary for Na+ ions? |
Charged particles can't pass through phospholipid bilayer |
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How does myelination affect the rate of conduction of a nerve impulse |
Nodes of Ranvier are permeable/allow movement of ions/unmyelinated Larger local circuits and saltatory conduction (jumping of impulses) increasesrate |
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Explain why anotehr action potential cannot be generated during repolarisation |
Open potassium channels produces hyperpolarisation |
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GABA binds to postsynaptic membranes causes chloride ions to enter postsynaptic neirones. Explain how this inhibits transmission of nerve impulses. |
Causes hyperpolarisation Action potential can't be produced as threshold greater depolarisation doesnt occur
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Explain what causes the conduction of impulses along a non-myelinated axon to be slower. |
Depolarisation occurs acroos whole of memnbrane In myelinated, saltatory conduction occurs, and depolarisation only occurs at nodes of Ranvier. |
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How does hormonal control differ from nervous control |
Hormonal = chemical Hormones - blood as a medium hormones - widespread effect (not localised) hormones - long lasting hormones - slow acting |
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Explain the change in resting potential after a metabolic poison is applied |
(Resting potential rises) No respiration, no ATP prodcued Sodium-potassium pump no longer functions Sodium ions no longer pumped out but still diffuse in + accumulate = more positive potassium ions no longer pumped in |
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Why is nervous transmission delayed at synapses? |
Time taken for neurotransmitters to diffuse across synapse Movement of chemicals slower than electrical impulse |
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Why does an axon with a larger diameter have a higher rate of conduction? |
Less leakage of ions so membrane potentials harder to maintain |
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Why is the refractory period important? |
Unidirectional impulses, from active region to resting, can't be propagated to refractory area discrete impulses Limited impulses |
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What is the advantage of synapses? |
A simple impulse transmitted to different neurones Number of impulses can be combined at a synapse |
