5.3.4 nerve impulses: transmission Flashcards
1
Q
what creates local currents
A
when sodium ions are allowed to flood into neurone causing depolarisation
2
Q
describe local currents
A
- cytoplasm of neurone
- sodium ions begin to move along neurone towards regions of lower conc
- cause slight depolarisation of membrane
- cause sodium ion channels further along membrane to open (positive feedback)
3
Q
steps in formation of local currents & transmission of nerve impulse
A
- when action potential occurs, sodium ion channels open at point in neurone
- open sodium channels allow sodium ions to diffuse into cell = less negative inside
- sodium ions continue to diffuse sideways along neurone, away from region of increased concentration = local current
- local current causes slight depolarisation further along neurone, affecting voltage-gated sodium ion channels causing them to open
–> open channels allow influx of sodium ions into neurone causing full depolarisation further along neurone & action potential moves along
4
Q
direction of action potential
A
one way - concentration of sodium ions behind it is still high
5
Q
myelin sheath
A
insulating layer of fatty material, composed of schwann cells wrapped tightly around neurone
6
Q
local currents in myelinated neurones
A
- elongated
- sodium ions diffuse along neurone from one node of ranvier to the next
7
Q
saltatory conduction
A
when a neurone ‘jump’ along the neurone - from 1 node of ranvier to the next
8
Q
advantages of saltatory conduction
A
- speeds up transmission of action potential along neurone
- quicker than myelinated neurones
9
Q
intensity of action potentials
A
‘all-or-nothing’ rule
- all the same intensity
- frequency of action potentials = intensity of stimulus
10
Q
action potentials when stimulus is at higher intensity
A
- more sodium channels opened in sensory receptor
- produces more generator potentials
- more frequent action potentials in sensory neurone
- more frequent action potentials entering CNS
