How nerves work 2 Flashcards
what is the resting potential mv?
-70mv
what happens at resting potential?
Na+/K+ pump, Na+ out and K+ in
membrane more permeable to K+ so K+ out
so outside is more +ve
requires ATP
what is mv for threshold potential?
-55mv
explain the steps in an action potential
Na+ gates open, Na+ in -> depolarisation
voltage becomes +ve
K+ gates open K+out, Na+ gates close -> repolarisation
hyperpolarisation due to delay in K+ gate closure
Na/K pump restores resting potential
how does local anaesthetic work?
keeps Na+ gates closed by binding to inactivation site
how is the action potential propagated along an axon?
depolarisation opens next sodium channel along membrane etc.
why is the refractory period necessary?
means that action potential travels in one direction
can an action potential occur in the absolute refractory period? why?
no because Na+ not in resting configuration
can an action potential occur in the relative refractory period? why?
yes because K+ channels are open, membrane is hyperpolarised but it requires a bigger stimulus.
the conducting velocity of a nerve depends on what?
width
myelination
how does the width affect the conducting velocity of a nerve?
wide = faster as lower resistance
how does the myelination affect the conducting velocity of a nerve?
sheaths in zones, depolarisation jumps between sheaths to nodes of Ranvier so faster
what are the 4 types of nerves from slow to fast?
C
Aδ
Aβ
Aα
what do C nerves do?
transmit nociceptors -> Ap in response to a stimuli that is damaging and usually cause pain
what do Aδ nerves do?
pain nociceptors -> Ap in response to a stimuli that is damaging and usually cause pain
