Action Potentials-L4

Dendrites

All Action Potential begain as what?

Graded Potentials

What is the threshold value for an action potential to be initiated?

15-20 mV

What is the membrane voltage at which a graded potential becomes an action potential?

Depolarization threshold

What is the All or none principle

once the threshold is met or exceeded an action piotential must go and it cannot be stopped

Can an Action potential start to go and then be stopped?

No

Events in order during an action potential

1. Resting State

2. Depolarization

3. Propagation of an action potential

4. Repolarization

5. Return to the resting state with the help of the sodium potassium pump

What is the area under the curve called and represent

Absolute refractory period

What happeneds on the upsload of the graph??

Sodium floods into the cell

What happens on the downslope of the graph

Potassium flows out of the cell

How can you increase a signal stimulus

Increase action potential frequency

Mylentated fibers

Action potential is faster in myelinated fibers than in unmylenated fibers

Saltatory Conduction

Action potentials travel quickly from one node of Ranvier to the next

What sourounds the nerve axon forming the mylen sheath

Schwann cells

How fequent are the nodes of ranvier

Every 1-3 mm

How much does myelination increase conduction velocity

5-50 fold

Where do Action potentials only occur at?

The nodes of ranvier

Why do action potentials only occur at the nodes of ranvier?

• Sodium channels are concentrated in this area

• Increased Velocity

• Energy conservation

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is an immune mediated inflammatory demyelinating disease of the central nervous system