Action Potential Conduction And Nureomusclular Junction

Question 1

How does the action potential propagate along the axon

Answer 1

Is initiated at the axon hillock by EPSP
It travels down axon. Without loss of amplitude
One direction
Propagation of action potential depends on local current spread depolarising the membrane potential adjacent sections of axon above threshold

Question 2

Saltatory conduction in myelinated axons

Answer 2

Myelin sheath acts as insulator causing localmcircuit currents to depolarise next node above threshold and initiate action potential
Action potential jumps from node to node much faster conduction velocity

Question 3

How is signal passed from nerve to muscle

Answer 3

Neuromuscular junction is syngasses between nerve and skeletal muscle fibres
Is a chemical synapses

Question 4

Synaptic transmission at a chemical synapse occurs in 7 steps

Answer 4

1) synthesis of neurotransmitter and packaging into vesicles
2) action potential arrives at nerve terminal
3) voltage-gated ca2+ channels open
4) Rise in ca2+ in nerve terminal triggers release of transmitter
5) transmitter diffuses across synaptic cleft and bind to receptors in postynaptic membrane
6) transmitter activated receptors cause a response in posysnaltic cell
7) transmitter diffuses away is broken down by enzymes or taken up by cells which terminate the response

Question 5

Transmitter release

Answer 5

1) ca2+ enter through ca2+ channels
2) vesicle brought close to membrane
3) vesicles fuse with membrane l4) trNsm8tter released my exocytosis

Question 6

Transmission at neuromuscular junctions

Answer 6

Action potential arrives at the motornueurone terminal where it open voltage gated ca2+ channels
Ca2+ entry initiates exocytosis of vesicles containing ACH
ACH binds to nicotine ACH receptors on muscle end plate causing them to open and the flow of cations causes depolarisation called end plate potential
End plate potential depolarises the adjacent muscle membrane activates voltage gated na+ channels thereby initiating an action potential in muscle fibre
Muscle then contracts due to process called excitation contraction coupling
Nach receptors can be blockedcomoetatovely by d-tubocurarine this causes paralysis