Action Potentials Part 2

Question 1

voltmeter

Answer 1

measures potential difference in charge between electrode placed inside cell vs electrode outside cell

Question 2

where does inside negative come from

Answer 2

ions like cl- can’t leave cell, make inside more negative

more k+ leaks out so outside positive

Question 3

action potential graph

Answer 3

resting phase (straight line)
rising phase (upward line)
overshoot (top part, top curve, above 0 mV)
falling phase (line going down)
undershoot (line dips below -70 mV)
restoration of resting potential

Question 4

resting potential

Answer 4

-65 to -70 mV

Question 5

threshold

Answer 5

-55 mV
excitatory neurotransmitters cause depolarizations to reach axon hillock
once threshold reached, action potential triggered and na+ channels open

Question 6

rising phase

Answer 6

na+ ion channels open, k+ channels closed
na+ rushes in, inside of cell positive (depolarization)
voltage rises

Question 7

overshoot

Answer 7

inside so depolarized that passes 0 mV and is positive

end of depolarization, na+ channels close and k+ channels open

Question 8

falling phase

Answer 8

k+ channels open as na+ channels close
k+ concentration higher inside cell, k+ rushes out, reduces positive charge ins, depolarization
voltage goes from positive to below resting potential (hyperpolarization)

Question 9

hyperpolarization

Answer 9

falling phase

voltage goes from positive to below resting potential

Question 10

undershoot

Answer 10

k+ pumped out so inside potential even lower than resting potential (hyper polarization)
k+ channels close (na+ also closed already)
na+/k+ pump works to reestablish concentration gradient and potential difference back to -65 mV

Question 11

absolute refractory period

Answer 11

time when no action potential can be generated
na+ channels open (depolarization, rising phase) until na+ inactivation gates close and stay closed
through first half of depolarization and falling phase

Question 12

relative refractory period

Answer 12

another action potential can be produced but only if stimulus is much greater than threshold
k+ channels open (depolarization, falling phase, hyper polarization)
slowly gets more and more easy to stimulate over period
ends with k+ channels closing and sodium potassium pump returning concentration gradient

Question 13

how do ion channels work

Answer 13

voltage gated channels: change shape based on voltage inside cell
changing shape allows different ions to come in/out
protein in channel twists in response to changes in potential

Question 14

how do ion channels work etc

Answer 14

channel monitors what goes through based on charge, size, water (molecular chaperone)
when membrane depolarized to threshold, voltage sensor twists and changes shape, opening the pore

Question 15

water

Answer 15

molecular chaperone

oxygen slightly negative, allows ion to go through

Question 16

functional properties of sodium channel

Answer 16

opens with little delay
stays open for ~1 msec
can’t be opened again by depolarization until resting potential is reestablished

Question 17

absolute refractory period 2

Answer 17

na+ channels are inactivated