Action Potential

Question 1

Is intracellular fluid positive/negative with respect to ECF?

Answer 1

Negative

Question 2

Is Na+ concentration higher in extracellular fluid or intracellular fluid?

Answer 2

Extracellular fluid

Question 3

Is K+ concentration higher in extracellular fluid or intracellular fluid?

Answer 3

Intracellular fluid

Question 4

What charge does the diffusion of K+ leave inside cell?

Answer 4

Negative

Question 5

How does resting membrane potential arise?

Answer 5

From the seperation of charges on either side of the membrane

Question 6

Is RMP due to mainly diffusion of K+ from cell interior or from Na+ leaking into the cell?

Answer 6

K+ diffusion

Question 7

How is Na+ that leaked into the cell expelled?

Answer 7

Na+/K+ pump- 3 Na+ out, 2K+ in

Question 8

The Na+/K+ pump is ‘electrogenic.’ What does this mean?

Answer 8

Generates a charge on the outside of the cell

Question 9

What is the ‘threshold’ for rising phase to occur?

Answer 9

-55mV

Question 10

What happens during rising phase?

Answer 10

Voltage gated channels open, Na+ influx into the neuron

Question 11

What happens during falling phase?

Answer 11

K+ moved out of the axon via voltage gated channels

Question 12

What are ion channels?

Answer 12

Transmembrane proteins, aqueous channels with gated opening: voltage gated or ligand gated

Question 13

At resting potential, in the voltage-gated sodium channel, what are the gates doing?

Answer 13

M gate closed
H gate open

Question 14

When the threshold is reached, what do the gates of the voltage gated sodium channel look like?

Answer 14

M gate open
H gate open

Question 15

During hyperpolarisation, what do the gates of the voltage gated sodium channel look like?

Answer 15

M gate open
H gate closed