What structures is not part of the central nervous system?

Option D

Explanation:

Complete question-

Which of the following structures is not part of the central nervous system?

A. Optic tract

B. Mammillary body

C. Optic chiasm

D. Optic nerve

Solution-

All nerves with in the brain and spinal cord are considered to be part of central nervous system. Since, optic nerve is an extension of the brain and not a part of the brain, it is considered to be the part of peripheral nervous system and hence, found as bundles of axons with in the PNS.

Hence, option D is correct

The question is incomplete.

The complete question is:

Which of the following structures is not part of the central nervous system?

a) the brain

b) a nerve

c) the spinal cord

d) a tract

Answer: b) a nerve

Explanation:

Nervous system is divided into Central nervous system (CNS) and Peripheral nervous system (PNS).

The Central nervous system (CNS) is primarily consist of the brain and spinal cord and also consist of tracts which functions to receive the information from all the parts of the body and coordinate accordingly.

The Peripheral nervous system (PNS) consists of all of the nerves which are connected to the brain and spinal cord and send signals to the CNS.

Hence, the correct option is b. Nerve