Question

a. Identify the given diagram. (refer image)
b. Name the parts labelled as A, B, C, and D

Answer 1

The central nervous system of the human body is a long cylindrical structure that arises from the medulla oblongata. It is a segmented pipe-like structure with a pair of roots that contain nerve fibres.

Complete answer: The given figure is of the spinal cord, which is a tube-like cylindrical structure that originates from the base of the medulla oblongata. The medulla oblongata is the base of the brainstem of the brain. Nerve fibres come together and enter the spinal cord.

The spinal cord is usually 40 cm long with a width of 2 cm. it forms an essential connection between the brain and body. The spinal cord is further divided into five regions. The uppermost region is called the cervical region made of 8 segments. The next is called thoracic with 12 segments, then lumbar with 5 segments, and then sacral with 5 segments. The tip of the spinal cord is called the coccygeal part which is a single pair of spinal nerves. Each segment of the spinal cord has several spinal nerves emerging from it. These spinal nerves carry signals from all body parts towards the brain. Each segment consists of grey matter which is a butterfly-like structure shown as D in the figure. It is surrounded by white matter. The pore in the grey matter is called the central canal depicted by C in the figure. It is filled with cerebrospinal fluid. The upper section of grey matter forms two dorsal horns. The lower sections form two ventral horns. The grey matter contains the cell bodies of spinal neurons and white matter contains axons of spinal neurons. The spinal nerves are attached to the spinal cord through two root fibres. These are called dorsal sensory roots represented by A in the figure and ventral motor root represented by B in the figure. The former lies at the side of the dorsal horn and the latter lies on the side of the ventral horn.

Note: The spinal cord is the main link between the brain and peripheral nervous system or PNS. It provides structural support to the body and maintains the posture. It also facilitates the flexible movements of the body. The main function of the spinal cord is communicating messages to and from the brain and body.