Topic 19: Action Potentials Flashcards Preview

Biology 116 > Topic 19: Action Potentials > Flashcards

Flashcards in Topic 19: Action Potentials Deck (25):
1

What is membrane potential?

the potential to do work

2

What is voltage?

a measurement of membrane potential

3

What are excitable cells?

cells that can rapidly change membrane potential

4

What is the resting potential?

MP of a cell at rest
-70mV

5

Why is the inside more negative than the outside?

because of the Na/K pump
and ion channels

6

What is the sodium-potassium pump? Where is it found? What does it do in relation to action potentials? Active or passive?

transmembrane transport protein
found of PM throughout neuron
3 Na+ out and 2 K+ in
Active transport (charged ions cannot diffuse)

7

What does hyperpolarization do?

becomes more negative inside the cell
MP decreases below RP
it is inhibitory

8

What does depolarization do?

becomes less negative inside cell
MP increases above RP
it is excitatory

9

What is action potentials?

electrical signal within neuron

10

How are voltage gated ion channels opened?

by a stimulus
-> facilitated diffusion of that ion down concentration gradient

11

What forms the concentration gradient?

Na/K pump

12

What happens when the VG sodium channels open?

Na+ rushes into the cell
-> inside becomes more positive (depolarization)

13

What happens when the VG potassium channels open?

K+ rushes out of cell
-> inside becomes less positive (hyperpolarization)

14

What is the membrane potential when the neuron is at rest?

-70 mV

15

What happens when there is a small stimulus?

FEW Na+ gates opne
weak depolarization
MP does not reach -55 mV
No AP

16

What happens when there is a strong stimulus?

MANY VG Na+ channels open
Strong depolarization
if MP reaches -55 mV -> AP

17

During the rising phase, what voltage does the depolarization reach?

+35 mV

18

What happens after the rising phase, when the voltage reaches +35 mV?

Na+ gates close
K+ gates begin to open
by +35 mV, K+ gates now fully open
K+ diffuses out
repolarization

19

What happens during the undershoot phase?

Na+ gates closed
K+ gates start to close slowly
hyperpolarization occurs
when the K+ gates fully close, it then returns to RP

20

Where does continuous conduction occur in?

unmyelinated axons

21

What happens during continuous conduction?

every spot on axon depolarizes, repolarizes

22

Where does saltatory conduction occur in?

myelinated axons with myelin sheath

23

What are internodes?

regions covered in myelin - no depolarization

24

What are nodes of ranvier?

no myelin - lots of Na+, K+, VG channels
depolarization only occurs at nodes

25

What happens in multiple sclerosis? What are symptoms?

immune system attacks myelin sheath and oligodendrocytes in CNS
-> slows AP conduction, exposes nerve fibers to damage
-> weakness, impaired vision, numbness... depends on sites of damage