membrane and action potentials (midterm 1)

Question 1

what is a membrane potential

Answer 1

concentration gradient establishes potential gradient/potential difference

Question 2

since K+ is high inside the nerve fiber membrane and low outside the membrane, what occurs

Answer 2

K+ carry positive electrical charges to the outside, creating electropositivity outside the membrane and electronegativity inside

Question 3

when does K+ transport stop

Answer 3

when the potential difference is ultimately balanced with the concentration difference

Question 4

since Na+ is high outside the membrane and low inside the membrane, what occurs

Answer 4

Na+ diffuses inside and creates electropositivity inside the membrane and electronegativity outside

Question 5

when does Na+ transport stop

Answer 5

when the potential difference is ultimately balanced with the concentration difference

Question 6

what is the Nernst potential of an ion

Answer 6

the diffusion potential level across a membrane that is opposite of the net diffusion of an ion through the membrane

Question 7

what happens through a greater ratio of concentration of specific ions on two sides of the membrane

Answer 7

the tendency for the ion to diffuse in one direction is greater and so is the Nernst potential required to prevent additional net diffusion

Question 8

what is the resting membrane potential of mammalian cells? large nerve fibers?

Answer 8

-60 to -90 mV
- 90 mV

Question 9

what are nerve signals transmitted by

Answer 9

action potentials

Question 10

what do v-gated Na+ channels and K+ channels do

Answer 10

v-gated Na+ channels drives the action potential and K+ channel speeds the repolarization of the membrane

Question 11

how does a membrane depolarize

Answer 11

the action potential travels in all directions away from the stimulus

Question 12

what is the all-or-nothing principle

Answer 12

once an action potential has been elicited on a membrane of a normal fiber, the depolarization process either propagates or does not propagate

Question 13

how are Na+ and K+ concentrations re-established after action potential transmission reduces them

Answer 13

Na+-K+ pump, which requires ATP

Question 14

what is an example of a fast channel

Answer 14

v-activated Na+ channels - opening of fast channels causes the spike portion of the action potential

Question 15

what is an example of a slow channel

Answer 15

v-activated Ca++-Na+ channels

Question 16

what are the periods of an action potential

Answer 16

propagation, stimulus, threshold, refractory

Question 17

what occurs in each period of an action potential

Answer 17

propagation: depolarization process either does or does not propagate
stimulus: ??????
threshold: the level required to elicit an action potential
refractory: the period during which a second action potential cannot be elicited

Question 18

what are acute local potentials and acute subthreshold potentials

Answer 18

• local potential changes
• failure to elicit an action potential

Question 19

why does the refractory period occur

Answer 19

a new action potential cannot occur in an excitable fiber as long as the membrane is still depolarized from the preceding action potential