Sesh 4: Resting Membrane Potential

Question 1

What is membrane potential?

Answer 1

The magnitude of an electrical charge across a plasma membrane. Always expressed as potential inside the cell, relative to the outside.

Question 2

What is the basis of signalling in all cells?

Answer 2

Changing the electrical potential difference across the membrane.

Question 3

What 2 general factors are essential for establishing a membrane potential?

Answer 3

1. Asymmetric ion distribution across membrane
2. Selective permeability of membrane
   * both allow charge separation

Question 4

In most cells, what dominates the membrane ionic permeability at rest?

Answer 4

Open K+ channels.

Question 5

What is the equilibrium potential of an ion?

Answer 5

The membrane potential at which the electrical and chemical gradients across the membrane balance i.e. There is no NET movement of that ion.

Question 6

What does the Goldman-Hodgkin-Katz equation describe?

Answer 6

Uses relative ion permeabilities of the membrane to calculate the membrane potential.

Question 7

What is conductance?

Answer 7

How permeable the membrane is to a particular ion, which depends on how many channels for that ion are open in the membrane.
Determines how much an ion contributes to the membrane potential.

Question 8

What is the post-synaptic ion channel at the neuromuscular junction, and what ions does it conduct?

Answer 8

Nicotinic Acetylcholine receptor (nAChR).

Is cation selective- conducts Na+ and K+.

Question 9

List the 3 types of channel gating that can occur.

Answer 9

1. Ligand gating
2. Voltage gating
3. Mechanical gating

Question 10

How does activation of mechanoreceptors of the hair cells in the inner ear cause firing of the afferent nerve?

Answer 10

Fluid flow opens K+ mechanoreceptors on the stereocilia, causing K+ influx and depolarisation of the hair cell.
Opens v-gated Ca2+ channels, causing DA/dynorphin vesicle fusion and release.
NT binds post-synaptic R’s on the afferent nerve, to cause an EPSP, which may cause an action potential.
In this way, rate of fluid flow determines rate of firing in the afferent nerve.

Question 11

Name fast NTs that act at excitatory synapses.

Answer 11

• ACh
• Glu
• DA

Question 12

Name fast NTs that act at inhibitory synapses.

Answer 12

• GABA

- Glycine

Question 13

In the cardiac action potential, what is the plateau phase due to?

Answer 13

-L-type Ca channels are open (allow excitation contraction coupling)