ACTION POTENTIALS

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Describe a neurone's membrane at rest
-60mV// impermeable to Na+/Na+ actively pumped out/ freely permeable to K+// K+ attracted to mem/ influx never matches outflow
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Outline the stages of the generation of an action potential
mem at rest/ some Na+ channels open/ depolarisation/repolarisation/ refractory period with hyper polarisation
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Outline depolarisation
as charge increases voltage gated Na+ ions open/ further increasing permeability/ charge increase to +40mV
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Outline repolarisation
at +40 Na+ channels close / K+ channels open and they flow into cell
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Outline the refractory period
outflow over shoots pd to -80mV/ K+ channels close and cell returns to resting state
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What is the purpose of the refractory period?
neurone cell can't be excited again straight away/ ion channels need to recover/ so APs don't overlap / so AP travels in right direction
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What happens when an action potential arrives at a synapse?
causes depolarisation at presynaptic / voltage gated Ca2+ channels open/ Ca2+ diffuses in/ synaptic vesicles move to presynaptic mem/ fuse/ ACh released into cleft by exocytosis
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What happens when a neurotransmitter reaches the post synaptic membrane?
ACh binds to receptors on the mem/ causes Na+ channels to open and diffuse down conc gradient/ depolarisation/ if enough Ach transmitted to produce enough generator potentials pd will reach threshold
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How and why must a neurotransmitter be removed from the post synaptic receptors?
so ready for another AP transmission/ AChE (acetylcholinesterase) enzyme removes ACh from receptors and breaks them down. products then absorbed at pre synaptic mem
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How can the transmission of action potentials be disrupted? Why is this sometimes done purposely?
drugs/toxins/poisons - bind to receptors and mimic their action/ block receptors/ inhibit AChE so all receptors bind/ inhibits release of ACh/ pain relief/ paralyses
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Describe an action potential graph, what happens at the different points?
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Other cards in this set

Card 2

Front

Outline the stages of the generation of an action potential

Back

mem at rest/ some Na+ channels open/ depolarisation/repolarisation/ refractory period with hyper polarisation

Card 3

Front

Outline depolarisation

Back

Preview of the front of card 3

Card 4

Front

Outline repolarisation

Back

Preview of the front of card 4

Card 5

Front

Outline the refractory period

Back

Preview of the front of card 5
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