A 9 Action Potential

Question 0

Tetrodotoxin and saxitoxin does what?

Answer 0

Blocks Na+ channels

Question 1

tetraethylammonium (TEA) do what?

Answer 1

Blocks potassium channels

Question 3

Veratridine does what?

Answer 3

Activates Na channel

Question 4

what is passive conduction?

Answer 4

the result of a change in membrane potential where the change change moves away from the point of origin in both directions and decays exponentially.

Question 5

what is active conduction?

Answer 5

the movement of conduction such as in a nerve cell where the intensity of the signal does not decrease as it moves more distantly.

Question 6

what is the space constant (AKA length constant)?

Answer 6

the distance that a passively conducted local response will travel before decaying to 37% of its original size.

Question 7

T/F actions potentials are the same size and shape along the entire length of a nerve cell.

Answer 7

True

Question 8

What is the resting membrane potential for muscle cells?

Answer 8

about -85 mV

Question 9

The resting membrane potential is mainly due from which ions?

Answer 9

K+ efflux

Cl- influx

Question 10

what factors cause a better action potential?

Answer 10

increased membrane resistance (not leaky)

decreased cytoplasm resistance (large diameter)

Question 11

smaller diameter neurons have _________ time constants, and larger diameter neurons have _______ time constants.

Answer 11

1) smaller

2) larger

Question 12

what is a normal length for lambda? (AKA length constant)

Answer 12

1-3 mm

Question 13

what is the general range for threshold?

Answer 13

-50 to -40 mV

Question 14

what causes hyperpolarization?

Answer 14

Hyperpolarization is caused by the K+ channels remaining open longer therefore letting more K+ to escape from the cytoplasm. The Na+/K+ atpase also has a small effect because of its 2/3 ratio.

Question 15

what causes the absolute refractory period?

Answer 15

once the Na+ channels have been stimulated, the activation gates open quickly but the deactivation gates are also activated to close at the same time. Therefore, if already stimulated the deactivation gates are already closed to an action potential will just cause them to close more.

Question 16

which parts make up the Na+ channel?

Answer 16

one large alpha, and two small beta units.

Question 17

What makes up the Alpha subunit of the Na+ Chanel?

Answer 17

It consists of four repeating motifs with six membrane spanning domains.

Question 18

What region of the alpha unit is considered to be the pore?

Answer 18

The pore is made between units S5 and S6

Question 19

what region of the alpha unit is considered to be the voltage sensor?

Answer 19

the S4 region

Question 20

what causes repolarizaton?

Answer 20

The efflux of K+ out of the cell.

Question 21

Is the activation gate of the K+ channel fast or slow?

Answer 21

it is slow unlike the Na+ channel. This is why it takes so long for the outward current to rise.

Question 22

What makes up the K+ channel?

Answer 22

4 alpha subinits with 6 transmembrane domains. This is exactly the sodium channel without the 2 beta units on the sides.

Question 23

How does myelin increase the velocity of an action potential?

Answer 23

1) it increases membranes resistance resulting in a longer length constant.
2) decreasing the capacitance of the axon.
3) restricting the action potential to the nodes of ranvier.

Question 24

what is the capacitance of a neuron?

Answer 24

the current needed to change the membrane potential.

Question 25

what is periodic paralysis?

Answer 25

paralysis due to electrical inexcitability of muscle surface membranes.

Question 26

what are some characteristics of Hyperkalemic periodic paralysis?

Answer 26

1) caused by a Na+ channel defect (alpha subunit)
where the channel just stays open
2) spontaneous muscle contractions initially because Na+ open = close to threshold.
3) followed by muscle inexcitability because of Na+ channel becomes too polarized = inactivation.
4) .High serum K+