lecture_8 - Fig. 5.11/ 4.11 Voltage-gated potassium...

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Neuron Structure and Function Action potentials Signal conduction Signal transmission Photo from Dr. Michael Silverman’s website http://www.sfu.ca/biology/faculty/silverman/index.html
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Graded vs. action potentials Graded potential Action Potential Distance travelled Short Potentially long Magnitude Varies Does not vary Duration Varies Does not vary Caused by Various ion channels Voltage-gated ion channels
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Action potentials Cycle of depolarization/ repolarization due to opening of sodium and potassium channels Absolute refractory period – new action potential cannot occur Relative refractory period – a greater stimulus is required for a new action potential see also Fig 5.10/ 4.10
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Voltage-gated ion channels Fig. 3.26/ 2.49
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Voltage-gated sodium channels Rapid opening of sodium channels involves positive feedback Positive feedback involves high density of sodium channels Sodium channel has 3 states: deactivated, activated and inactivated
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Unformatted text preview: Fig. 5.11/ 4.11 Voltage-gated potassium channels • Voltage-gated K + channels open and close more slowly than Na + channels Maintenance of ion gradients • Action potentials reduce ion gradients slightly • Na+/K+ ATPase (sodium pump) restores ion gradients Signal conduction: Travel of action potentials along axon • Action potentials can travel long distances without decay • Axons conduct signals unidirectionally • Action potential frequency carries information • See also Fig. 5.13/ 4.13, Fig. 5.15/ 4.15 Signal transmission Signal is transmitted • across the synapse • from the presynaptic cell to the post synaptic cell • Often via a chemical messenger (neurotransmitter) • See also Fig. 5.16/ 4.16 Fig. 5.1/ Signal transmission Neurotransmitter release • is regulated by calcium • Is regulated by action potential frequency • See Fig. 5.16/ 4.16 Fig. 5.1/...
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This note was uploaded on 11/05/2011 for the course BISC 305 taught by Professor Christians during the Fall '11 term at Simon Fraser.

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lecture_8 - Fig. 5.11/ 4.11 Voltage-gated potassium...

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