Action Potential

Question 1

Charge of axon at Resting potential

Answer 1

-70mv

Question 2

First step of action potential

Answer 2

Neurone is stimulated by an impulse changing permeability of cell membrane to Na+
Change occurs due to stimulus or arrival of a neurotransmitter to a motor neurone
voltage gated Na+ channels open
Na+ enters axon by facilitated diffusion
Depolarisation

Question 3

How the depolarisation is transmitted down an axon

Answer 3

As one section becomes depolarised the VG Na+ channels Infront are opened

Question 4

How repolarisation occurs

Answer 4

Voltage gated Na+ channels close again
Excess Na+ pumped out by Na+/K+ (active transport)

Question 5

What happens as a result of repolarisation

Answer 5

VG K+ channels open and K+ diffuses out of the axon
(down the electrochemical gradient, they are attracted to the -ve charge outside the axon)

Question 6

Refractory period

Answer 6

VG K+ channels close
Refractory period occurs
So impulse cannot travel backwards

Question 7

Hyperpolarisation

Answer 7

Too negative
So K+ channels close
K+ diffuses back into the axon to recreate resting potential

Question 8

How nerve toxins can affect potential difference to cause paralysis

Answer 8

Change in PD is smaller with toxin
No axon potential/ less depolarisation
VG Na+ channels stay closed
Na+ cannot pass through membrane and enter neurone
Muscles not stimulated