Which component is responsible for releasing neurotransmitters into the synaptic cleft?

Which component is responsible for releasing neurotransmitters into the synaptic cleft?

• A. Terminal buttons
• B. Axon
• C. Soma
• D. Myelin sheath

Answer: (A)

Neurotransmitter release into the synaptic cleft happens at the presynaptic terminal, specifically the terminal buttons at the end of the axon. These buttons contain synaptic vesicles filled with chemical messengers. When an action potential arrives, the membrane at the terminal depolarizes and opens voltage-gated calcium channels. Calcium influx triggers the vesicles to fuse with the presynaptic membrane and release their contents into the synaptic cleft via exocytosis. The neurotransmitters then cross the gap and bind to receptors on the postsynaptic neuron, continuing the signal or modulating it. The axon's job is to carry the electrical signal to the terminal, the soma mainly integrates incoming signals, and the myelin sheath insulates and speeds conduction along the axon—none of these release neurotransmitters themselves.

Neurotransmitter release into the synaptic cleft happens at the presynaptic terminal, specifically the terminal buttons at the end of the axon. These buttons contain synaptic vesicles filled with chemical messengers. When an action potential arrives, the membrane at the terminal depolarizes and opens voltage-gated calcium channels. Calcium influx triggers the vesicles to fuse with the presynaptic membrane and release their contents into the synaptic cleft via exocytosis. The neurotransmitters then cross the gap and bind to receptors on the postsynaptic neuron, continuing the signal or modulating it.

The axon's job is to carry the electrical signal to the terminal, the soma mainly integrates incoming signals, and the myelin sheath insulates and speeds conduction along the axon—none of these release neurotransmitters themselves.