Myelin sheath is produced by

Afferent nerve fibres carry impulses from

Which of the following statements are correct for a nerve cell?
$(I)$. Each neuron has a cell body
$(II)$. Each neuron has a single axon
$(III)$. Neurons are the functional units of the nervous system
Select the correct option.

The largest cell in the human body is:

The supporting and nutritive cells found in the brain are

Define the location and function of the following:
$(1)$ Nerve net
$(2)$ Dendrites