5. Ligand Gated Channels & Calcium Regulation

Question 0

How does calcium entry at the motor neurone terminal initiate exocytosis?

Answer 0

Ca2+ binds to Synaptotagmin
Vesicle descends
Snare complex forms a fusion pore
Transmitter released through the pore

Question 1

When an action potential arrives at the motor neurone terminal what channels does it open?

Answer 1

Voltage Gated Ca2+ channels

Question 2

How many molecules of acetyl choline bind to nicotinic receptors on the end plate?

Answer 2

2

Question 3

What does binding of Acetyl Choline on the end plate lead to?

Answer 3

Depolarisation leading to Voltage gated Na+ channels opening initiating and action potential on the effector

Question 4

Name a competitive blocker for nicotinic Acetyl Choline receptors

Answer 4

Tubocurarine

Question 5

How do depolarising blockers work?

Answer 5

Bind to nicotinic receptors but not broken down, this slow depolarisation of the membrane leads to accommodation hence inactivation of voltage gated Na+ channels adjacent to the end plate

Question 6

Name an advantage of the large calcium gradient across the cell membrane.

Answer 6

Changes can occur quickly as it calcium diffuses rapidly across

Question 7

Name a protein that transports calcium that has high affinity but low capacity.

Answer 7

Ca2+ATPase

Question 8

Name a protein that transports calcium that has low affinity but high capacity.

Answer 8

Na+Ca+ exchanger

Question 9

Name four proteins that raise intracellular calcium when activated

Answer 9

Voltage gated calcium channels
Receptor operated calcium channels
G protein coupled receptors (Gq)
Ryanodine receptors in CICR

Question 10

Why do mitochondria take up Calcium?

Answer 10

To protect the cell
Buffering
Stimulate ATP Production
Participate in signalling in micro domains

Question 11

How are calcium levels returned to normal?

Answer 11

Signal terminated
Calcium remove
Calcium store refilling