Neuronal electrophysiology

Question 1

Length (space) constant definition

Answer 1

Distance over which a subthreshold depolarization will spread and influence the next segment of membrane

Question 2

The longer the space constant …

Answer 2

The faster the conduction

Question 3

Equation for length constant

Answer 3

Square root of (membrane resistance over internal resistance)

Question 4

All-or-none response

Answer 4

A stimulus will either elicit an action potential or fail to do so

Question 5

Length of Na+ channel upstroke

Answer 5

0.5 ms

Question 6

Upstroke of action potential chart

Answer 6

Caused by increase in Na+ channel conductance

Question 7

Causes repolarization of membrane

Answer 7

Delayed increase in K+ channel conductance along with the decrease in Na+ channel conductance

Question 8

Deactivation of K+ channel conductance

Answer 8

Caused by repolarization of the membrane potential

Question 9

Where on the scale of Em does action potential take place?

Answer 9

Between E(na) and E(k)

Question 10

Resting channel (w/r/t m and h)

Answer 10

M activation gate closed, H inactivation gate open

Question 11

Activated channel (w/r/t m and h)

Answer 11

Both m and h open to allow Na+ influx

Question 12

Inactivated channel (w/r/t m and h)

Answer 12

m gate open, h gate closed

Question 13

Regenerative depolarization

Answer 13

“Positive feedback mechanism” that allows for more influx of sodium when some gates have already opened

Question 14

When do Na+ channels close?

Answer 14

Rapidly at depolarization

Question 15

What is the main difference between Na+ and K+ channels?

Answer 15

K+ channels are never deactivated during depolarization, and will only shut off once it has reached repolarization

Question 16

Absolute vs. relative refractory period

Answer 16

Absolute: another AP cannot be elicited no matter what Relative: it can make a new AP, it just takes extra stimulation than normal

Question 17

What happens to the resting membrane potential with hyperkalemia?

Answer 17

Becomes more positive

Question 18

As a result of hyperkalemia, what happens to Na+ channels?

Answer 18

They become less available (they inactivate) and conduction slows

Question 19

Signs and symptoms of hyperkalemia

Answer 19

Slow mentation, muscle weakness

Question 20

How Ca2+ affects Na+

Answer 20

Modulates channel activity by altering membrane surface charge

Question 21

Effect on Na+ channels during hypercalcemia

Answer 21

Extra Ca2+ raises threshold for Na+ channel activation and decreases membrane excitability

Question 22

Effect on Na+ channels during hypocalcemia

Answer 22

Lowers threshold for Na+ channel activation and increases membrane excitability

Question 23

Hyperventilation and Ca2+

Answer 23

Decreases free plasma calcium to increase neuronal membrane excitability

Question 24

Hypoventilation and Ca2+

Answer 24

Increases free plasma calcium to decrease neuronal membrane excitability

Question 25

Myelinated axons are ___x less in diameter than unmyelinated axons

Answer 25

100

Question 26

Myelin sheath increases ___, therefore also increasing ___

Answer 26

membrane resistance, length constant

Question 27

Internodal distance

Answer 27

1-2 mm

Question 28

Commonalities between MS and diabetic neuropathies

Answer 28

Both destroy myelination and severely slow neuronal conduction

Question 29

Post-synaptic potentials

Answer 29

Local, graded responses propagated passively

Question 30

Excitatory neurotransmitters

Answer 30

ACh, glutamate

Question 31

Inhibitory neurotransmitters

Answer 31

GABA, glycine

Question 32

EPSP ion influx

Answer 32

Cations (Na in, K out)

Question 33

IPSP ion influx

Answer 33

Anions (Cl- in)

Question 34

EPSP membrane potential change

Answer 34

Positive; toward E(Na,K)

Question 35

IPSP membrane potential change

Answer 35

Negative; toward E(Cl)

Question 36

Temporal summation

Answer 36

Different locations stimulated at the same time

Question 37

Spacial summation

Answer 37

Same area affected in a short timespan