Lecture 4

Question 1

Forces contributing to action potentials

Answer 1

The Na+/K+ pump (3 Na+ out, 2 K+ in)(K+ can go back out passively)
concentration gradient
charge gradient

Question 2

leading up to action potential

Answer 2

cell has negatively charged molecules inside
Na+/K+ pump (3 Na+ out, 2 K+ in)(K+ can go back out)
K+ equilibrium (electrical attraction pulling K+ in balances with concentration gradient pushing K+ out, cells resting potential)
inside anions push against the membrane attracted to the cations on the outside, vice versa

Question 3

depolarization

Answer 3

moving from -65mV toward 0

Question 4

hyperpolarization

Answer 4

moving from -65mV to more negative

Question 5

the action potential steps on graph

Answer 5

1- open K+ channels create resting potential (Na+ closed)
2- any depolarization brings the membrane potential closer to threshold
3- at threshold, voltage gated Na+ channels open, rapid change of polarity (action potential)
4- Na+ channels close, gated K+ channels open (at top), repolarizing and even hyperpolarizing the cell (after potential)
5- all gated channels close, cell returns to resting potential

Question 6

the action potential moving down an axon

Answer 6

1- all channels closed (except passive K+)
2- with depolarization at a spot on axon, Na+ channels open, Na+ flows in, K+ flows out
3- the depolarization they bring causes the Na+ channels to open nearby
4- the axon potential moves along the axon

Question 7

active propagation

Answer 7

the action potential progresses down the axon without decreasing with distance

Question 8

saltatory conduction

Answer 8

leap from gap to gap (nodes of ranvier) to make it go faster (myelinated axon)

Question 9

puffer fish toxin

Answer 9

blocks Na+ channels, cause paralysis

Question 10

demyelinated disease

Answer 10

autoimmune, genetic, MS is an example: results in weakness and slowed movement