ICPP - Changing Membrane Potential

Question 1

What is depolarisation?

Answer 1

A decrease in the size of the membrane potential from its normal value - the cell interior becomes less negative.

Question 2

What is hyperpolarisation?

Answer 2

An increase in the size of the membrane potential from its normal value - cell interior becomes more negative.

Question 3

True or false - increasing membrane permeability for a particular ion moves membrane potential away from that ion?

Answer 3

False - it moves it towards

Question 4

What is the main way that changes in the membrane potential can be caused?

Answer 4

Changes in the activity of ion channels

Question 5

What is the Goldman-Hodgkin-Katz equation used to calculate?

Answer 5

Membrane permeability for each ion

Question 6

Why are nicotinic acetylcholine receptors viewed as less specific?

Answer 6

When 2 ACh molecules bind, the ion channels opens which lets through both Na+ and K+ (not anions though).

Question 7

What are the three types of ion channel gating?

Answer 7

• Ligand gating (opens due to binding of ligand eg ACh)
• Voltage gating (opens due to changes in membrane potential eg action potential changes)
• Mechanical gating (opens due to membrane deformation)

Question 8

What sort of gated ion channel is present in the inner ear?

Answer 8

Mechanical gating

Question 9

How does the mechanical gating in the inner ear work?

Answer 9

• pressure from sound waves makes K+ channel close
• membrane depolarises
• Ca2+ channel opens
• vesicles containing neurotransmitter fuse with basement membrane
• neurotransmitter binds to receptor and generates action potential

Question 10

Give some examples of places where synaptic transmission takes place.

Answer 10

Nerve cell - nerve cell
Nerve cell - muscle cell
Nerve cell - gland cell
Nerve cell - sensory cell

Question 11

What is different about the receptor protein in fast synaptic transmission?

Answer 11

It is also an ion channel, and transmitter binding causes it to open

Question 12

What do excitatory synapses do?

Answer 12

Open ligand-gated channels that cause membrane depolarisation.

Question 13

What is the change in membrane potential caused by excitatory synapses called?

Answer 13

Excitatory post-synaptic potential

Question 14

Give some examples of excitatory transmitters.

Answer 14

Acetylcholine, glutamate, dopamine

Question 15

What do inhibitory transmitters do?

Answer 15

Open ligand-gated channels that cause hyperpolarisation. Eg. Glycine, GABA

Question 16

What are the two patterns of slow synaptic transmission?

Answer 16

• direct G-protein gating (rapid, localised)

- gating via an intracellular messenger (throughout cell, amplification by cascade)

Question 17

Give two factors other than action potentials that can influence membrane potential.

Answer 17

• changes in ion concentration

- electrogenic pumps (Na/K-ATPase)

Question 18

Give three properties of cardiac ion channels.

Answer 18

• selectivity (only permeable to single type of ion)
• voltage sensitive gating
• time dependence

Question 19

Explain the stages of action potential of cardiac muscles

Answer 19

Phase 4 - resting potential of cardiomyocyte is -90mV
Phase 0 - action potential triggers Na+ channels to open and cell depolarises rapidly. At -40mV, long-opening Ca2+ channels open.
Phase 1 - K+ flows out and repolarises to 0 mV.
Phase 2 - MP is maintained at plateau
Phase 3 - Ca2+ channels deactivated, pumps return normal ionic concentration gradients