the action potential and its properties

Question 1

when is an action potential generated

Answer 1

if the threshold Is reached

Question 2

what is the conductance of an action potential dependant upon

Answer 2

the greater the conductance means the more ions moving in and the closer they are coming to their equilibrium potentials

Question 3

where do K+ and Na+ move during an action potential

Answer 3

Na+ movie moving closer to ENa and k+ moves out moving closer to Ek

Question 4

how do we know Na+ is responsible for depolarisation

Answer 4

as [na+] is decreased action potentials are reduced because the threshold is not reached

Question 5

what do the movements of Na+ and k+ cause

Answer 5

Na+ moves in v quickly and depolarises the cell but is quickly inactivated by inactivation molecule. once membrane is depolarised K+ channels open except it is inactivated much later than Na+ resulting in the hyperpolarisation and then once they are shut repolarisation. draw this

Question 6

what is the ARP

Answer 6

absolute refractory period where no more action potentials are possible because Na+ channels are either inactivated or open

Question 7

what is the RRP

Answer 7

relative refractory period where the excitability is returning as K+ channels close. large stimulus need for AP

Question 8

Na+ voltage-gated channel structure- how it opes

Answer 8

many positively charged amino acids so when membrane potential changes shape so will the protein causing the channel to open. Can be 1-6 subunits large

Question 9

Na+ voltage-gated channel-how it closes

Answer 9

when pore is open inactivation particle forces its way into the channel closing it and preventing Na+ flow

Question 10

structure of K+ voltage gated channels

Answer 10

exactly the same as Na+ except that it has minimum 4 subunits and inactivation happens much later

Question 11

how anaesthetics work

Answer 11

local aesthetics block Na+ channels. LIDOCAINE enters cell because its uncharged and lipopillic and then becomes protonated (+charge) and blocks the Na+ pore

Question 12

action potential conduction currents

Answer 12

positive charges (na+) diffuse down axon towards negative and the influx in Na+ there causes the Na+ channels to open.

Question 13

what is the length constant

Answer 13

This is the distance along the axon for the action potential to fall to 37% of its original value

Question 14

what is conduction velocity - how it affects currents

Answer 14

conduction velocity- further distance means it takes a longer time

Question 15

what s resistance - how it affects currents

Answer 15

resistance- higher means it spreads further along the axon

Question 16

whats capacitance and how does is affect currents

Answer 16

capacitance is the ability to store charges and if its higher voltage changes more slowly in response to current injection

Question 17

what is saltatory conduction

Answer 17

depolarisation only allowed at nodes of ranvier- much faster than normal conduction because can travel much further distances

Question 18

disease affecting action potential conduction

Answer 18

multiple sclerosis - myelin is attacked resulting in much slower conduction of AP in some areas