paper 3

Question 1

factors affecting conducting speed in axon

Answer 1

1) temperature - Kinetic energy, rate of diffusion increases etc…]
2) axon diameter-less resistance
3) myelin sheath- increase speed of saltatory propagation- insulator

Question 2

what occurs during resting potential on axon membrane

Answer 2

both K and Na voltage gated channels are closed and the sodium potassium ion pump is active - 3Na+ out of axon and 2K+ into axon

Question 3

key voltages in a nerve impulse

Answer 3

resting potential = -70mV
threshold potential = -55mV
action potential = +40mV

Question 4

how is an action potential initiated

Answer 4

stimulus above threshold potential is reached (-55mV)
sodium-potassium ion pump closes
sodium ion voltage gated channel opens pumping Na+ into the axon
AXON DEPOLARISES

Question 5

how does repolarisation occur

Answer 5

at 40mV sodium ion voltage gated channels shut
K+ v.g.c open and k+ leaves the axon
overshoot occurs causing HYPERPOLARISATION
so Na+/K+ pump opens to re-establlish resting potential