Lecture 8 - Changing Membrane Potential

Question 1

What is the definition of depolarization?

Answer 1

Decrease in the size of the membrane potential from its normal value, when cell interior becomes less negative

Question 2

What is the definition of hyperpolarization?

Answer 2

Increase in the size of the membrane potential from its normal value, cell interior becomes more negative

Question 3

What are the mechanisms that lead to depolarization?

Answer 3

Opening Na+ or Ca2+ channels, influx of positive ions decreases the membrane potential

Question 4

What are the mechanisms that may lead to hyperpolarization?

Answer 4

Opening K+ or Cl- channels, efflux of K+ or influx of Cl- increases membrane potential

Question 5

How do changes in ion channel activity lead to changes in membrane potential?

Answer 5

Excitatory and inihibitory transmitters open ligand-gated channels, allowing movement of ions which causes changes in membrane potential

Question 6

What are some roles of membrane potential in signaling within and between cells?

Answer 6

1. Action potentials in nerve and muscle cells
2. Triggering and control of muscle contraction
3. Control of secretion of hormones and neurotransmitters
4. Transduction of sensory information into electrical activity by receptors
5. Postsynaptic actions of fast synaptic transmitters

Question 7

How can ligand-gated channels give rise to synaptic potentials?

Answer 7

2 ways: slow and fast synaptic transmission

Question 8

How do ligand-gated ion channels participate in fast synaptic transmission?

Answer 8

At synapse, chemical transmitter released from the presynaptic cell binds to receptors. In fast synaptic transmission, receptor protein is an ion channel, transmitter binding causes it to open.

Question 9

How do ligand-gated ion channels participate in slow synaptic transmissions.

Answer 9

At synapse, chemical transmitter released from the presynaptic cell binds to receptors on the postsynaptic membrane. In slow synaptic transmission, receptor and channel are separate proteins.

Question 10

What are the 2 basic patters of receptor-channel in slow synaptic transmission?

Answer 10

1. Direct g-protein gating

2. Gating via an intracellular messenger

Question 11

How does direct G-protein gating work?

Answer 11

Localized, quite rapid, ligand binds to GPCR, signal travels across membrane and then opens channel

Question 12

How does gating via an intracellular messenger work?

Answer 12

Ligand binds to receptor, g-protein activates enzyme, which causes a signalling cascade then intracellular messengers or protein kinases open the channels

Happens throughout the cell