How Nerves Work 4 Flashcards Preview

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Flashcards in How Nerves Work 4 Deck (9)
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1
Q

What are the values for resting membrane potential, threshold and overshoot?

A

-70mV
-55mV
40mV

2
Q

Why is there an depolarisation when sodium and potassium channels open at the same membrane potentials?

A

Sodium channels are opened for a much shorter time.

3
Q

Why is the excitability of a cell at zero when channels are open?

A

As another firing action potential cannot be made.

4
Q

Define self-propagation.

A

Depolarisation can spread isotonically which can fire action potentials across the membrane due to the spreading of a positive charge.

5
Q

Why can’t self-propagation go backwards?

A

Due to the former voltage gated channel going through a refractory period.

6
Q

The positive charge can passively spread better through ______ axons and ______ axon resistance.

A

Larger, removes.

7
Q

What type of cells form myelin sheaths?

A

Schwann cells in the peripheral nervous system and oligodendrocytes in the CNS.

8
Q

Myelination ______ membrane resistance and ______ the capacitance of the membrane which allows passive current to spread better.

A

Increases, decreases.

9
Q

Define demyelination.

A

Decay of depolarisation is a lot quicker so the action potential cannot always reach the next voltage gated channel.