True about Nissl granulea) Involves in RNA synthesisb) Present in axonc) Present in dendrited) Involves in protein synthesise) Structurally they are endoplasmic reticulum
**Core Concept**
Nissl granules are specialized organelles found in neurons, composed of rough endoplasmic reticulum (RER) and ribosomes. They play a crucial role in protein synthesis in neurons.
**Why the Correct Answer is Right**
Nissl granules are involved in protein synthesis, as they contain ribosomes that translate messenger RNA (mRNA) into proteins. This process is essential for neuronal function and maintenance. The presence of rough endoplasmic reticulum in Nissl granules allows for the synthesis of proteins, which are then transported to other parts of the neuron or released as neurotransmitters.
**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because Nissl granules are not primarily involved in RNA synthesis, which occurs in the nucleus.
* **Option B:** Incorrect because Nissl granules are not found in axons, but rather in the cell bodies of neurons (somata).
* **Option C:** Incorrect because Nissl granules are not exclusive to dendrites, but are found in the cell bodies of neurons.
* **Option D:** Incorrect because while protein synthesis is a function of Nissl granules, it is not the only process they are involved in.
**Clinical Pearl / High-Yield Fact**
Nissl granules are a hallmark of neuronal cells and can be stained with specific dyes to visualize them in histological preparations.
**Correct Answer: D. Involves in protein synthesis**