Question

Nissl’s granules are absent in
A) Dendrite
B) Cyton
C) Axon
D) Both A and B

Answer 1

Hint:Neurons are the basic working unit of the brain. It is designed to transmit information to other nerve cells, muscle, or gland cells. Most neurons have a cyton, axon, and dendrites.

Complete answer:
Nissl granules (Nissl bodies) are particles seen within the cell bodies of neurons, and consist of granular endoplasmic reticulum and free ribosomes. They were discovered by a German neurologist, F. Nissl. Neurons have a large number of Nissl granules in their cytoplasm. It helps in the synthesis and release of proteins and amino acids, for intracellular use. Nissl bodies can be illustrated by a method of selective staining developed by Nissl. Due to RNA's basophilic nature, it is stained blue. The cell body can be localized by this method.
They occur as free particles or are bound to the endoplasmic reticulum. During various functional activities of the brain, the distribution and staining properties of the granules change. For example, under various physiological conditions and pathological conditions like axonotmesis, they may dissolve and disappear in an attempt to upregulate protein synthesis for axonal repair and after a successful repair, Nissl bodies would reappear.
Cyton or cell body of the neuron has a large central nucleus and granules (Nissl granules). From the cell-body arises dendrites and axons.They are present in cyton and dendrites of the neurons.
Dendrites are branching extensions of a neuron that receive signals from other neurons. Axons take the message from cyton. It is a long, slender projection of the neuron and its distal end is branched. Each branch terminates as a bulb-like structure known as a synaptic knob consisting of synaptic vesicles in which chemicals called neurotransmitters are stored. The axons transmit nerve impulses away from the cell body to a synapse or a neuromuscular junction.
Hence, the correct option is C, ‘Axon’.

Note:Chromatolysis is the disappearance of Nissl bodies from the cell body of a neuron. It occurs due to various changes taking place in the brain. The trigger can come from cell exhaustion, virus infection, cell toxicity, etc.