action potential

Question 1

what does a stimulus trigger

Answer 1

sodium ion channels to open

Question 2

what is the first stage of generating an action potential

Answer 2

a stimulus excites the neuron causing sodium ion channels to open causing the membrane to become more permeable to Na+ ions

Question 3

once sodium ion channels have been opened, what begins to happen

Answer 3

sodium ions diffuse into the neuron down their electrochemical gradient making the inside of the neuron less negative

Question 4

what is the second stage of generating an action potential

Answer 4

depolarisation, when the potential difference reaches a threshold point (-55mv) voltage gated sodium ion channels open

Question 5

what does the opening of voltage gated sodium channels cause

Answer 5

more sodium ions to diffuse into the neuron

Question 6

what is the opening of voltage gated sodium channels an example of

Answer 6

positive feedback

Question 7

what is the third stage of generating an action potential

Answer 7

repolarisation, at a potential difference of around +30mv, sodium ion channels close and voltage gated potassium channels open

Question 8

what happen when potassium channels open

Answer 8

the membrane is more permeable to potassium ions causing them to diffuse out of the neuron down their concentration gradient

Question 9

what is the purpose of the potassium channels opening

Answer 9

starts to restore a resting potential

Question 10

what is the potassium channels opening an example of

Answer 10

negative feedback

Question 11

what is hyperpolarisation

Answer 11

potassium ion channels have a delay in closing, this causes an overshoot of potassium out of the neuron causing the potential difference to be more negative than the resting potential

Question 12

what happens after hyperpolarisation

Answer 12

the ion channels are reset and the sodium potassium pumps return the membrane to resting potential

Question 13

what is the refractory period

Answer 13

after an action potential, ions cannot be stimulated as the ion channels are recovering and cannot open

Question 14

what does a bigger stimulus cause

Answer 14

causes action potentials to fire more frequently

Question 15

what is local currents

Answer 15

the influx of sodium ions into the neuron results in them diffusing and spreading out causing voltage gated sodium ion channels to open