Question

Nissl Granules are absent in:
(a) Axon
(b) Cyton
(c) Dendron
(d) Both (a) and (b)

Answer 1

Hint: Nissl’s granules are the large granular body found in Neurons. Nissl’s granules are present only in the cytoplasm of the cell body of neurons.

Complete answer:
These granules are rough endoplasmic reticulum with rosettes of free ribosomes that synthesize proteins in the body of the neuron. The cell body of the neuron is the controlling part and is known as Cyton. It contains a cytoplasm with a nucleus in the center. The cytoplasm of the cell body contains typical cell organelles like the Golgi apparatus, endoplasmic reticulum, ribosomes, mitochondria, etc. The cytoplasm also contains Nissl’s granules which gives a slightly cooler appearance to the cytoplasm of the cell body. The Nissl’s granules are also present in dendrites of neurons. These are absent in axons and axon hillocks.
So, the answer is, ‘Axon.’

Additional Information:
- It was named after Franz Nissl, a German neuropathologist who invented the Nissl’s staining method. This method is useful to localize the cell body and dendrites.
- Since Nissl staining localizes Nissl granules, cyton and dendrites are stained and axons are excluded.
- These granules show changes under various physiological conditions as well as pathological conditions.

Note:
- Nissl’s granules are also found in dendrites.
- These are absent in axon or axon terminals.
- Nissl’s granules are thought to be similar to that of Rough Endoplasmic Reticulum and Golgi bodies as they produce protein and amino acids as well as help in their transport within the neuron.
- These granules are basophilic due to the presence of RNA in it. Thus, will staining with aniline die only dendrites and cyton are stained and axons are not stained as they lack Nissl’s granules.