Sympathetic postganglionic neurotransmitter in sweat gland
**Core Concept**
The sympathetic nervous system plays a crucial role in regulating various involuntary functions, including sweating. The sympathetic postganglionic fibers release neurotransmitters that stimulate or inhibit target organ functions. In the context of sweat glands, the sympathetic postganglionic neurotransmitter is responsible for stimulating sweating.
**Why the Correct Answer is Right**
The sympathetic postganglionic neurotransmitter that stimulates sweat gland function is acetylcholine (ACh). ACh acts on muscarinic receptors (M3 subtype) on sweat gland cells, leading to increased sweat secretion. This is in contrast to the sympathetic postganglionic neurotransmitter for most other target organs, such as the heart or blood vessels, which is norepinephrine (NE). The use of ACh in sweat glands is an example of a unique exception in the sympathetic nervous system.
**Why Each Wrong Option is Incorrect**
* **Option A:** Norepinephrine (NE) is the primary sympathetic postganglionic neurotransmitter for most target organs, including the heart and blood vessels, but not sweat glands.
* **Option B:** Dopamine is a neurotransmitter involved in various functions, including motor control and reward processing, but it is not the primary sympathetic postganglionic neurotransmitter for sweat glands.
* **Option C:** Serotonin is a neurotransmitter involved in mood regulation, appetite, and sleep, but it is not the primary sympathetic postganglionic neurotransmitter for sweat glands.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the sympathetic postganglionic neurotransmitter for sweat glands is acetylcholine, which is an exception in the sympathetic nervous system. This knowledge can help you distinguish between different types of neurotransmitters and their effects on various organs.
**Correct Answer:** A. Acetylcholine