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What happens once the action potential is generated? (2)
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Why does propogation/conduction occur?
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PhysioEx Ex3Actvy7
Action Potential: Conducting Velocity
| Question | Answer |
|---|---|
| What happens once the action potential is generated? (2) | It is propagated or conducted down the axon. This propagation ensures that the amplitude of the axon does not diminish as it is conducted along the axon. |
| Why does propogation/conduction occur? | B/c there are voltage gated sodium and potassium channels located along the axon & b/c the large depolarisation that constitutes the action potential easily brings the next region of the axon to threshold. |
| How can conduction velocity be calculated? | By knowing the distance the action potential travels and the amount of time it takes |
| What influences the conduction velocity of an axon? | axon diameter & amount of myelination |
| What is myelination? | special wrapping of the membrane from glial cells around the axon |
| What are the names of the glia that wrap around the axons in the CNS and PNS? | CNS: Oligondendrocytes PNS: Schwann Cells |
| How are myelin sheaths separated? | by gaps called nodes of Ranvier |
| Action potential conduction velocity is fastest in which of the following fibers? | A fibers (large diameter, heavily myelinated) |
| Action potential conduction velocity is slowest in which of the following fibers? | C fibers |
| Why did the timescale have to be changed to measure the conduction velocity of the C fibers? | The total time shown on the oscilloscope would have been too short to see the action potential at R2. |
| The axons from touch fibers are A fibers, and the axons from pain fibers are C fibers. When you stub your toe, which would you expect to perceive first? | your toe touching something |
| How did the conduction velocity in the B fiber compare with that in the A Fiber? How well did the results compare with your prediction? | B fiber conduction was much slower than A fiber |
| How did the conduction velocity in the C fiber compare with that in the B Fiber? | C fiber conduction was slower than B fiber. |
| What is the effect of axon diameter on conduction velocity? | The larger the axon diameter, the greater the conduction velocity. |
| What is the effect of the amount of myelination on conduction velocity? | The greater the amount of myelination, the greater the conduction velocity. |
| Why did the time between the stimulation and the action potential at R1 differ for each axon? | The time between the stimulation and the action potential at R1 differed for each axon because the axon diameter and amount of myelination varied for each axon. |
| Why did you need to change the timescale on the oscilloscope for each axon? | This is necessary in order to see the action potentials. The velocity changes so when it gets very slow you need a longer time scale. |
Created by:
meunid