How Nerves Work 4

Question 1

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

Answer 1

-70mV
-55mV
40mV

Question 2

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

Answer 2

Sodium channels are opened for a much shorter time.

Question 3

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

Answer 3

As another firing action potential cannot be made.

Question 4

Define self-propagation.

Answer 4

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

Question 5

Why can’t self-propagation go backwards?

Answer 5

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

Question 6

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

Answer 6

Larger, removes.

Question 7

What type of cells form myelin sheaths?

Answer 7

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

Question 8

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

Answer 8

Increases, decreases.

Question 9

Define demyelination.

Answer 9

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