action potentials

Question 1

what is paracrine signalling?

Answer 1

cell to cell communication where a cell produces a signal to induce changes in nearby cells

local

Question 2

what is endocrine signalling?

Answer 2

when cells release hormones to act on distant targets

Question 3

is sodium higher intracellularly or extracellulary?

Answer 3

extracellularly

Question 4

is potassium higher intracellularly or extracellularly?

Answer 4

intracellularly

Question 5

what three mechanisms contribute to the resting membrane potential?

Answer 5

passive ionic diffusion
active transport
gibbs donnan equilibrium

Question 6

how does passive ionic diffusion contribute to the resting membrane?

Answer 6

leaky ion channels which are always open

Question 7

how does active transport contribute to the resting membrane?

Answer 7

works against the conc gradient using the Na+/K+ ATPase

Question 8

what ions does the Na+/K+ ATPase pump move across the membrane?

Answer 8

pumps 3 Na+ out

2 K+ in

Question 9

what is the voltage of the ECF with respect to the ICF?

Answer 9

positive

Question 10

what is the resting potential?

Answer 10

-70mV

Question 11

what is the nernst equation?

Answer 11

relates membrane potential to the concentration gradient

Em = 61.5 x log [conc outside]/[conc inside]

Question 12

what are action potentials?

Answer 12

rapid changes in voltages

Question 13

what is the axon hillock?

Answer 13

the trigger region

generates the action potential

Question 14

what are the two gates of the voltage gated sodium channels?

Answer 14

activation gate

inactivation gate

Question 15

when does the sodium channel activation gate open and how fast is it?

Answer 15

in response to depolarisation

v fast

Question 16

when does the inactivation gate of the sodium channel close?

Answer 16

in response to depolarisation

Question 17

how do K+ channels cause hyperpolarisation?

Answer 17

stay open for longer

Question 18

explain the stages of an action potential

Answer 18

resting potential - -70mV
depolarisation - sodium channels open
repolarisation - potassium channels open
hyperpolarisation - potassium takes ages to shut
refractory period

Question 19

what is the absolute refractory period?

Answer 19

when the sodium channels cannot open regardless of the size of the stimulus

Question 20

what is the relative refractory period?

Answer 20

when a suprathreshold stimulus can stimulate the opening of sodium channels
threshold is increased

Question 21

how do local anaesthetics work?

Answer 21

bind to sodium channels in their active state
inactivates them
prevent it from returning to resting state and stimulating APs