the nervous system - nerve impulses

Question 1

function of dendrites

Answer 1

• carry nerve impulses towards cell body

Question 2

function of axon

Answer 2

• carry nerve impulses away from cell body

Question 3

function of schwann cells

Answer 3

• produce myelin

Question 4

function of myelin sheath

Answer 4

• insulates axon increasing speed of transmission of nerve impulses

Question 5

function of node of ranvier

Answer 5

• gap between schwaann cells where myelin sheath absent

Question 6

describe resting potential

Answer 6

• at rest potential difference of -70mV across the membrane
• membrane polarised maintaining PD between 2 sides
• axon at rest = resting potential

Question 7

describe how resting potential is established
(NOT KEYPOINTS)

Answer 7

• higher conc of Na outside of neuron
• higher conc of K inside of neuron
• 3x Na+ OUT, 2x K+ IN
• in resting potential Na+ volted gated channels are closed,
• Na pumped out cant diffuse back in
• some K+ channels open (membrane more permeable to K+)
• some K+ can diffuse
• more (+) outside than in so slightly (-) in

Question 8

How is a nerve impulse transmitted

Answer 8

• resting pot maintained until disturbed or stimulated
• once threshold reached action potential generated
• AP happens when membrane becomes depolarised
• resting goes from -70mV -> +40mV

Question 9

Describe the sequence of events leaving to release of acetlycholine + its binding to PSN

Answer 9

• Depolarisation of presynaptic membrane
• Ca2+ channels open + ca2+ ions enter
• Synaptic vesicles fuse with presynaptic membrane + release Acetylcholine which diffuses across
• Acetylcholine binds to receptors on post synaptic membrane
• Na+ ions enter leading to depolarisation