Question

Which of the following is not strictly considered a part of the neuron?

• A. Dendrites
• B. Myelin sheath
• C. Nissl’s granules
• D. Synaptic knob

Answer 1

The correct option is B Myelin sheath

Myelin sheath is not considered strictly as a part of the neuron. This is because there are neurons which are devoid of myelin sheath such neurons are called unmyelinated neurons. The neuron is of two types: myelinated neuron and unmyelinated neuron. The myelinated neurons consist of Schwann cells, which form a myelin sheath around the axon. Unmyelinated neuron is enclosed by Schwann cells but that does not form a myelin sheath around the axon. Unmyelinated neurons are found in autonomous and somatic neural systems.
The neuron is composed of three major parts- dendrites, cell body and axon. Dendrites are short branched fibres arising from the cell body. They transmit impulses to the cell body. Cell body also known as soma is composed of cytoplasm having cell organelles and granules called Nissl’s granules. Nissl’s granules are the site of protein synthesis. Axon is a long process of neuron, its distal end is branched, having a bulb-like structure at the end called synaptic knob. Synaptic knobs are composed of synaptic vesicles containing neurotransmitters.