Action and membrane potential

Question 1

Cell membrane channels

Answer 1

1. Leaky ion- selectively permeable to ions
2. Water pores(aquaporins)- movement of water

Question 2

Gated protein channels

Answer 2

1. Ligand gated- bind to receptor e.g acetylcholine
2. Voltage gated- opens in response to change in membrane voltage
3. Gap junction-open to allow passage of ions between cells

Question 3

How to measure membrane potential

Answer 3

Voltmeter with microelectrodes connected

Question 4

Cell types and measuring RMP

Answer 4

1. Smooth muscle: -50 to -60
2. Neurons: -60 to -70
3. Cardiac muscle; -80 to -90
4. Skeletal muscle: -85 to -95

Question 5

Initiation and termination of action potential

Answer 5

Begins by the rise in MP towards zero
Open voltage gated sodium channels
Sodium inflow
Ends by rising MP which causes sodium channels to close and opening of potassium channels> voltage gated potassium channels.

Question 6

Summary

Answer 6

sodium channels open during depolarization, allowing sodium to diffuse inside the axon to the cell.
Reaches peak and close.
Opens potassium channels and potassium ions diffuse to the exterior TO RE-ESTBLISH NORMAL NEGATIVE RESTING MEMBRANE POTENTIAL

Question 7

Propagation of AP in myeinated nerves

Answer 7

In nodes of ranvier
Saltatory conduction- fast and energy effecient

Question 8

Propagation of AP in unmyelinated nerve

Answer 8

AP travels away from the stimulus

Question 9

What is refractory

Answer 9

Where it is impossible to begin the second AP

Question 10

Relative refractory

Answer 10

Second AP can be evoked but requires larger than normal stimulus
Occurs after absolute refractory

Question 11

All-or-non principle

Answer 11

AP is full response. It is either it happens or not at all.