Question

Draw a labelled diagram of a myelinated fibre. Explain the difference between sensory nerve and a motor nerve.

Answer 1

Myelinated fiber

1. The functional units of the nervous system are neurons. They have extensions of cell bodies called the axon and dendrites.
2. Neurons have protective insulation called neurilemma. The presence of a thin fatty sheath around nerve fibers is called the myelin sheath and such fibers are called myelinated fibers. They are present in a discontinuous fashion leaving gaps called the nodes of Ranvier.
3. The presence of myelination helps in faster and more efficient conduction of nerve impulses without loss of information. The image below shows a labeled myelinated fiber.

Difference between sensory and motor nerve

1. Sensory nerves- carry information from the sensory organs to the brain.
2. Motor nerves- carry information from the brain to different muscles in the body.

Sensory nerve	Motor nerve
They have a short axon and a long dendron.	They have a large axon and many dendrites.
They send impulses from the receptors to the central nervous system (CNS).	They send impulses from the CNS to the receptors.
They are unipolar.	They are multipolar.
They are also called receptor neurons.	They are also called effector neurons.
Eg.- auditory nerve (internal ear to brain)	Eg.- oculomotor nerve (brain to eye muscles)