Homework Sourse1 At a chemical synapse which of the following occurs first
1. At a chemical synapse, which of the following occurs first?
2. How does increased frequency of action potentials result in increased release of neurotransmitter?
| a. receptor-ligand binding at the postsynaptic membrane |
| b. exocytosis of secretory vesicles |
| c. opening of voltage-gated calcium channels |
| d. re-uptake of the neurotransmitter or parts of the neurotransmitter |
Solution
1. Answer : B
At a chemical synpsis exocytosis of secretory vesicles happens. The neurotransmitter present in the vesicles will release into synaptic cleft by exocytosis.
2. Answer : C
Increased release of neurotransmitters results in increased firing frequency, the axon terminal is depolarized for longer, allowing more Na+ to rush into the cell. When the wave of depolarization reaches the axon tip, voltage-gated Ca+ channels open , allowing Ca+ entry. The resulting increase in internal Ca2+ triggers exocytic release of neurotransmitter acetylcholine into the synaptic cleft.
