Action potential

Question 1

gmailWhen is an active potential happens?

Answer 1

= when the nuerons voltage increaes beyond a set point, from the resting potential, this generates a nerve impulse
= an increase un voltagem depolorisation, is due to the nuerone membrane becoming more permeableto Na+ ions
=

Question 2

What does a stimulus do?

Answer 2

= provides energy so that sodium voltage gated ion channels open
= sodium ions diffuse into the axon, as pottasium ions diffuse out the axon
= there is an increase in voltage, if you get above threshold, (action potential) this provides more energy for more votage gated ion channels to open, so more sodium ions diffuse in and same K+ ions diffusiong out, depolorisation
=

Question 3

What does depolorisatio happen?

Answer 3

= +40 mv
= the sodium voltage gated ion channels close,
=

Question 4

What happens in repolorisation?

Answer 4

= pottasium channels are opened, so pottasium ions diffuse out, so there is a decrease in voltage
= as it becomes more permeabnle to K+ ions

Question 5

What happens if the voltage becomes less than the resting potential (-70mv)?

Answer 5

= hyperpolorisation
= refractory period
= below resting potential, reach 80mv
=

Question 6

What do action potentials do?

Answer 6

= when an action potential is released, it is contonious, and causes the next action potential in the adacent cell

Question 7

What is the all or nothing principle?

Answer 7

= if the depolorisatio n does not excess threshold, there are no action potential, and an umpilse is nor produced
= any stimulus that triggers, to -55mv will always peak at the same maximum
= bigger stumulis, increase drequency of action potentials
= important animals only react to large enrough stimulus, rather than responding to every slugt change

Question 8

What is refractory period?

Answer 8

= after an action potential has ben generated- can’t be stimulated
= sodium ion channels are recovering and cannot be opened
=

Question 9

What 3 reasons are refractory period important for?

Answer 9

= ensures desecrete inpulses are produced, an action potential cannot be generated immediatley, after another one, to make sure that each is seperate from another
= ensures action potentials travel in one direction, this stops the action potentisl from spreading out in two directions which would prevent a response
= limits the number of impulse transmissions, prevents over reaction to a stimulus and therefore ovweherlming senses