Release of neurotransmitter from presynaptic vesicles is an example of –
**Core Concept**
The release of neurotransmitters from presynaptic vesicles is a fundamental process in neurotransmission, allowing chemical signals to be transmitted across synapses between neurons. This process involves the fusion of vesicles with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft.
**Why the Correct Answer is Right**
The release of neurotransmitters from presynaptic vesicles is an example of exocytosis, a process in which vesicles fuse with the cell membrane to release their contents. In the context of neurotransmission, this process is triggered by the influx of calcium ions into the presynaptic neuron, which binds to and activates proteins such as synaptotagmin, leading to the fusion of vesicles with the membrane and the release of neurotransmitters. The released neurotransmitters then bind to receptors on the postsynaptic neuron, transmitting the signal.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the process of neurotransmitter release. Endocytosis is the process by which cells take in substances from outside the cell, not release them.
* **Option B:** This option is incorrect because it does not accurately describe the process of neurotransmitter release. Passive transport refers to the movement of substances across a cell membrane without the use of energy, which is not relevant to the release of neurotransmitters.
* **Option C:** This option is incorrect because it does not accurately describe the process of neurotransmitter release. Active transport refers to the movement of substances across a cell membrane using energy, but it is not the primary mechanism by which neurotransmitters are released.
**Clinical Pearl / High-Yield Fact**
It's worth noting that the release of neurotransmitters is a highly regulated process, and disruptions in this process can lead to various neurological disorders, such as Parkinson's disease, which is characterized by the degeneration of dopamine-producing neurons in the substantia nigra.
**Correct Answer: D. Exocytosis**