Nerve Physiology

Question 1

When N gates open, K+ moves _____

Answer 1

out of the cell

Question 2

All or None Law

Answer 2

-once an action potential is created, the nerve signal can’t be stopped

Question 3

Ca++ causes Ach to_____

Answer 3

move down terminal bouton to release Ach from synaptic vesicles to synaptic cleft via exocytosis

Question 4

Ca++ is usually higher _____

Answer 4

extracellularly

Question 5

If pt has low K+ levels

Answer 5

the resting membrane potential is more negative and farther from action potential threshold, so it will take a stronger stimulus to elicit an action potential

Question 6

Acetylcholinesterase

Answer 6

enzyme that breaks down Ach into an acetate ion and choline

Question 7

If pt has high K+ levels

Answer 7

resting membrane potential would be closer to threshold for an action potential so a weaker stimulus would cause depolarization

Question 8

Depolarization

Answer 8

• inside cell becomes less negative

- voltage dependent gaits (m & h) begin to open and close

Question 9

Optimal Sarcomere Length

Answer 9

-2.0-2.2 microns

Question 10

Nerve Impulse

Answer 10

cascade of ionic exchanges along the nerve until it reaches terminal end

Question 11

Na+–K+ pump

Answer 11

pump in plasma membrane that pumps out 3 Na+ per every 2 K+ ions it brings in, creating a net efflux of positive charges

(20% of membrane potential)

Question 12

n gates

Answer 12

• face intracellularly
• most closed at -100mv
• most open at -0mv
• open and close slowly

Question 13

Depolarization is due to:

Answer 13

movement of Na+ into cell through open Na+ gates (m & h gates)

Question 14

m Gates

Answer 14

• face extracellarly
• most closed at -100mv
• most open at -0mv
• open/close rapidly

Question 15

Na+ channel inactive state

Answer 15

-m gate open and h gate closed
OR
-m gate closed and h gate closed

Question 16

When the cell is at rest, it is ______

Answer 16

polarized

negative inside and positive outside

Question 17

Local Potential

Answer 17

• (graded/generator potential)

- create small changes in membrane potential that can be summed

Question 18

At rest, ____ ions line up along inside of cell and ___ ions on outside

Answer 18

• negative

- positive

Question 19

K+ moves ____ cell during repolarization

Answer 19

-out of the cell

Question 20

Repolarization

Answer 20

-making the inside of cell more negative again by taking K+ out of cell

Question 21

h gates

Answer 21

• face intracellularly
• most open at -100mv
• most closed at -0mv
• open/close slowly

Question 22

Postsynaptic receptors are

Answer 22

nicotinic (Ach binds here)

Question 23

Choline

Answer 23

• byproduct of Ach breakdown

- taken back up by presynaptic membrane to make new Ach

Question 24

Why is the inside of the cell negative?

Answer 24

• Na-K pump: net leaving of positive
• membrane more permeable to K+
• large negatively charged intracellular proteins (can’t diffuse)

Question 25

Membrane Potential

Answer 25

-difference in electrical changes between 2 sides of a cell membrane

Question 26

Hyperpolarization

Answer 26

Inside of cell becomes more negative

Question 27

Potential

Answer 27

potential energy in the charge separation

Question 28

What happens around -60mv?

Answer 28

-enough h gates are closing slowly and m gates opening rapidly to result in an influx of enough Na+ to reach threshold to create an action potential

Question 29

2 Types of Local Potentials

Answer 29

• depolarization

- hyperpolarization

Question 30

Resting Potential of:

• Small neurons
• Large Neurons/Skeletal Mm
• Smooth Muscle

Answer 30

• Small: -70mv
• Large/Skel: -90mv
• Smooth Mm: -50mv

Question 31

m gates begin to open when voltage gets:

Answer 31

less negative

Question 32

At rest m gates are ____

Answer 32

closed

Question 33

At rest h gates are ____

Answer 33

Open

Question 34

h gate begins to close when voltage gets ___

Answer 34

less negative

Question 35

When m & h gates are open, Na+ moves ____

Answer 35

into cell

Question 36

n gates open when ____

Answer 36

inside becomes less negative

Question 37

Repolarization is due to:

Answer 37

movement of K+ out of cell through n gates

Question 38

Na+ channel resting state=

Answer 38

m gate closed & h gate open

Question 39

Na+ channel Active state

Answer 39

-m gate open, h gate open

Question 40

Sodium goes ____ cell during depolarization

Answer 40

into

Question 41

It is easier for K+ to pass through the membrane than Na+ because:

Answer 41

there are usually more K+ channels open than Na+

Question 42

A-

Answer 42

Large negative molecules inside cells that are too big to diffuse and contribute to the negative charge of the inside of the cell

Question 43

what accounts for 80% of the membrane potential?

Answer 43

• K+ concentration gradient

- so, resting potential is due to the differences in K+ levels