In chemical synaptic transmission, the opening of what type of channel results in ion influx and eventual vesicle fusion with the presynaptic terminal membrane?
The correct answer and explanation is:
The correct answer is voltage-gated calcium (Ca²⁺) channels.
In chemical synaptic transmission, the process begins when an action potential travels along the axon to the presynaptic terminal. As the action potential reaches the presynaptic terminal, it causes the depolarization of the membrane. This depolarization triggers the opening of voltage-gated calcium channels located in the presynaptic membrane. The calcium ions, which are present in higher concentrations outside the neuron, rush into the cell due to their electrochemical gradient.
The influx of calcium ions plays a crucial role in the synaptic transmission process. The increase in intracellular calcium concentration is the signal that leads to the next step in the transmission process: vesicle fusion. Synaptic vesicles, which contain neurotransmitters, are now able to fuse with the presynaptic membrane. This fusion occurs through a complex process involving several proteins, such as synaptotagmin, which senses the calcium ions and triggers the vesicle’s attachment and fusion with the membrane.
Once the vesicle fuses with the presynaptic membrane, it releases its neurotransmitter content into the synaptic cleft. This neurotransmitter then binds to receptors on the postsynaptic membrane, continuing the signal transmission across the synapse.
In summary, the opening of voltage-gated calcium channels is essential for the influx of calcium ions, which enables vesicle fusion and neurotransmitter release, allowing for communication between neurons in chemical synaptic transmission. Without this crucial step, the transmission of the electrical signal would not continue beyond the presynaptic neuron.