Action Potentials: Generation And Propagation

Question 1

What does each domain/ subunit contain?

Answer 1

Voltage sensor

Question 2

What causes the initial depolarisation?

Answer 2

Opening of small capacitance cation channel

Question 3

How is an AP generated and restored?

Answer 3

Local potential change
Causes depolarisation so opening of sodium voltage gated Channel
Repolarisation occurs by closing sodium channel and opening potassium
Hyper polarisation occurs by potassium remaining opening past RMP - refractory

Question 4

What mainly effects ion movement?

Answer 4

Permeability

Question 5

What is ouabain and how does it work?

Answer 5

Na/k ATPase inhibitor

Reduces size of AP progressively until membrane sodium grad reduced where APs initiated but fail

Question 6

What is tetrodotoxin and how does it work?

Answer 6

Blocks neuronal VGSC so abolishes AP

Question 7

What is the refractory period due to?

Answer 7

Inactivation of the voltage gated sodium channel

Question 8

What is speed of conductance regulated by?

Answer 8

Temp
Axon diameter - fatter faster
Myelination

Question 9

What do oligodendocytes wrap CNS axons with?

Answer 9

Myelin

Question 10

What do Schwann cells apply myelin to?

Answer 10

Single peripheral axons

Question 11

What is saltatory conduction?

Answer 11

APs jumping from one node of ranvier to another

Question 12

What are esters and amides metabolised by?

Answer 12

Esters- cholinesterases

Amides- liver amidase

Question 13

What are the structural differences in Cav, Kv, Nav?

Answer 13

Ca - 4 domains 6 TM
K - 4 subunits of 6TM
Na - 4 domains of 6TM