Neurons and Synapses: Topic 6.5

Question 1

Outline the steps of an action potential.

Answer 1

Depolarization: Voltage-gated Na channels open (when threshold of -55mv is reached) and Na rushes into the axon causing more Na channels to open (propagation) membrane potential +
Repolarization: K channels open (Na close) and K rushes out of the axon membrane becomes hyperpolarized (super negative)
Refractory Period: resting potential is restored through the Na K pumps that pumps 3 Na out of the axon for every 2 K into the axon, another action potential can’t occur until balance restored

Question 2

Outline the role of myelin.

Answer 2

Myelin speeds up the signal along the axon this is called saltatory conduction

Question 3

Explain the process of synaptic transmission at the neuromuscular junction (including the role of acetylcholinesterase)

Answer 3

Action potential gets to the end of the axon terminal, Ca channels open and Ca ions rush into the axon terminal, Ca ions interact with vesicles causing them to move and use with the membrane of the axon terminal, Ach is released by exocytosis into the synaptic cleft and diffuses across to bind to receptor proteins on the postsynaptic membrane, binding of ach causes ion channels to open Na ions rush into the postsynaptic cells or ca ions rush out , enzymes break down ach into two or more fragments and their pieces diffuse back together

Question 4

Outline how neonicotinoid pesticides affect synaptic transmission in insects.

Answer 4

Neonicotinoid pesticides bind permanently to ach receptors in postsynaptic fiber cells in insects, the block the binding of ach and ache isn’t able to break down neonicotinoids so the effect is permanent and leads to paralysis and death