Membrane Potential & Excitation

Question 1

Outline structure of a UNIPOLAR SENSORY NEURON

Answer 1

One long axon, connects to receptors at spinal cord/brain.

Question 2

Outline structure of MULTIPOLAR INTER/MOTORNEURON

Answer 2

Many dendrites, one axon

Question 3

Outline structure of a BIPOLAR NEURON

Answer 3

One bunch of dendrites, one axon

Question 4

Where is concentration of Na+ highest?

Answer 4

Outside the cell

Question 5

Where is concentration of K+ highest?

Answer 5

Inside the cell

Question 6

Where is concentration of Cl- (chloride) highest?

Answer 6

Outside the cell

Question 7

Which ions is the resting membrane most permeable to?

Answer 7

K+ and Cl-

Question 8

Give the correct sequence of events that follow a threshold potential.

Answer 8

Na+ channels open, Na+ ions diffuse inward. Membrane depolarized. K+ channels open and K+ ions diffuse outward, while Na+ is actively transported out of the cell. Membrane repolarizes.

Question 9

What must be reached for an action potential to occur?

Answer 9

Threshold or ‘generator potential’

Question 10

In the resting potential state, which ion is the membrane more permeable to, K+ or Na+?

Answer 10

K+

Question 11

If the concentration of K+ increases in the ECF, what happens to the resting membrane potential?

Answer 11

It becomes less negative.

Question 12

What does the Nernst equation predict?

Answer 12

Equilibrium potential.

Question 13

What is the concentration of K+ inside a cell?

Answer 13

150mM

Question 14

What is the concentration of K+ outside a cell (in ECF)?

Answer 14

5mM

Question 15

What is the concentration of Na+ inside a cell?

Answer 15

15mM

Question 16

What is the concentration of Na+ outside a cell (in ECF)?

Answer 16

150mM

Question 17

What is the concentration of Cl- inside a cell?

Answer 17

10mM

Question 18

What is the concentration of Cl- outside a cell (in ECF)?

Answer 18

125mM

Question 19

On which side of the membrane is there a net positive charge?

Answer 19

Net positive charge on the outside of the membrane, net negative charge on inside. Creates electrical potential.

Question 20

Which two forces act upon K+ ions?

Answer 20

Concentration gradient and electrical potential. Together they form the electrochemical gradient.

Question 21

What maintains the resting membrane potential?

Answer 21

Sodium-potassium pump (Na-K pump)

Question 22

How many Na+ and K+ ions does the Na-K pump actively transport across the membrane?

Answer 22

3 Na+ out for every 2 K+ in.

Question 23

What does the permeability of a cell depend on?

Answer 23

The number and type of ion channels in its membrane.

Question 24

Give the voltage of a neuron at resting potential.

Answer 24

-70mV