M&R - Cellular Response to APs

Question 0

Describe the process of neurotransmitter release?

Answer 0

Depolarisation opens voltage gated calcium channels
Calcium influx into the cell
Calcium binds to synaptotagmin
Vesicle brought to membrane
Release of neurotransmitter via snare complex pore

Question 1

What channels are present at the nerve terminal?

Answer 1

Sodium, potassium, and calcium

Question 2

What is the structure of a calcium channel?

Answer 2

One peptide, four homologous repeats each with 6 TM domains

Question 3

What is the equilibrium potential for calcium?

Answer 3

122mV

Question 4

What happens on the motor end plate After ACh release?

Answer 4

The ACh activates nicotinic receptor channels

A conformational change causes the movement of sodium and potassium - this leads to depolarisation

Question 5

What is the end plate potential?

Answer 5

This is the brief depolarisation (to about -10mV) caused by ACh binding to nicotinic receptors.
This activates adjacent sodium channels causing a muscular AP

Question 6

What is a competitive blocker of nicotinic ACh receptors?

Answer 6

This is something that sits in the ACh binding site
The ACh cannot bind to the nicotinic receptors so the channel remains closed.
E.g d-tubocurarine

Question 7

What is a depolarising blocker of ACh nicotinic receptors?

Answer 7

This causes receptor to open and remain open
This leads to a maintained depolarisation but one that will fail to activate adjacent sodium channels
e.g succinylcholine

Question 8

What is myasthenia gravis?

Answer 8

Autoimmune disease targeting nicotinic ACh receptors - leads to loss of functional ACh receptors
End plate potentials are reduced in amplitude
Patients suffer profound weakness and fatigue