MT - Neuronal Function (Part 1)

Question 1

What structures make up the CNS?

Answer 1

The brain and spinal cord.

Question 2

What structures make up the PNS?

Answer 2

The neurons and glia that aren’t part of the CNS.

Question 3

Define depolarization, repolarization, and hyperpolarization.

Answer 3

Depolarization: membrane potential becomes more +ve
Repolarization: membrane potential returns to resting value
Hyperpolarization: membrane potential becomes more -ve than resting value.

Question 4

What 2 components influence the membrane potential of a cell?

Answer 4

1. Relative ion permeabilities

2. Relative ion concentrations inside and outside the cell

Question 5

For the Nernst equation, what is RT/zF at 22C?

Answer 5

58 mV.

Question 6

For the Nernst equation, what is RT/zF at 37C?

Answer 6

61.5 mV.

Question 7

What transporter maintains the concentration gradients of Na+ and K+?

Answer 7

The Na+ / K+ ATPase.

Question 8

For every ATP that gets hydrolyzed by the Na+ / K+ ATPase, what is the net movement of ions?

Answer 8

3 Na+ ions transported out and 2 K+ ions transported in

Question 9

What happens to the membrane potential when Na+ channels are opened?

Answer 9

The membrane depolarizes.

Question 10

What happens to the membrane potential when the K+ channels are opened?

Answer 10

The membrane hyperpolarizes.

Question 11

What equation gives the conductance of a membrane?

Answer 11

Conductance = 1/Resistance

Question 12

What equation gives the electrochemical driving force?

Answer 12

Driving force = conductance (charge-equilibrium potential)

Question 13

Define the “electrochemical driving force”.

Answer 13

How far the membrane potential is from equilibrium.

Question 14

What ion channels are voltage-gated?

Answer 14

Na+, K+, and Ca 2+ channels.

Question 15

What ion channels are ligand-gated?

Answer 15

Glutamate receptors, GABA receptors, nicotinic acetylcholine receptors, 5-HT3, P2X

Question 16

What is the equation for Ohm’s law?

Answer 16

Voltage = current * resistance

Question 17

What is the capacitance of a membrane?

Answer 17

The ability of a membrane to store charge when a voltage difference occurs.

Question 18

What equation gives the capacitance of a membrane?

Answer 18

Capacitance = charge difference / voltage difference

Question 19

What are the 3 features of a capacitor that define its function?

Answer 19

1. Material properties
2. Area of the conducting surfaces
3. Thickness of the insulating layer

Question 20

What effect does the area of the conducting surfaces have on membrane capacitance?

Answer 20

Larger area = greater capacitance

Question 21

What effect does the thickness of the insulating layer have on membrane capacitance?

Answer 21

Thicker = greater capacitance

Question 22

What quality of membrane electrophysiology is described by the time constant?

Answer 22

The time over which the membrane potential will decay to 37% of its maximal value (how well does it hold charge).

Question 23

What variables affect the time constant of a membrane?

Answer 23

1. Resistance of the cell membrane

2. Capacitance of the cell membrane

Question 24

What effect does having a low membrane resistance have on the time constant of a membrane?

Answer 24

The capacitor becomes full faster, depolarizes faster, and conducts faster (lower time constant).

Question 25

How is the change in membrane potential in an unmyelinated axon affected by distance?

Answer 25

It decreases rapidly with distance.

Question 26

What equation describes conduction decrement in an axon with distance?

Answer 26

decrement =sqrt((membrane resistance)/(internal resistance + external resistance))

Question 27

What effect does increasing the resistance of intracellular/extracellular fluids have on the decrease in voltage along an axon?

Answer 27

Higher fluid resistance = greater decrease.

Question 28

What effect does decreasing the membrane resistance have on the decrease in voltage along an axon?

Answer 28

Lower membrane resistance = greater decrease.