Question

How do pons act as a relay centre?(3 marks)

Answer 1

It acts as an important sensory relay system which provides information to different parts of the nervous system like the cerebellum, cerebrum, and even the spinal cord. Its function is mostly to provide input to the cerebellar cortex through structures known as the pontine nuclei, which allow the cerebellum to coordinate most of its control.
The main function of pons is to basically act as a bridge or highway for relay of many signals to and from the cerebrum and the cerebellum. This is the center that acts as the point of origin for various nerves in the body, including the important cranial nerves.
The different nerves that emerge from the pons include:

• Trigeminal nerve ― This is the fifth cranial nerve which is both sensory and motor in nature. It is responsible for sensation on the face and it also innervates the muscles of the mandible, which are responsible for biting, chewing, and swallowing food.
• Abducens nerve ― This is a motor nerve which is responsible for sideways movement of the eyes.
• Facial nerve ― This is a motor nerve which affects the muscles of facial expression, like muscles that help in smiling, raising eyebrows, and bringing about various expressions on the face, like shock, fear, joy, etc.
• Vestibulocochlear nerve ― This is a sensory nerve which has two parts ― the cochlear portion, which is involved with transmission of sound from the ear to the brain. The other part is the vestibular portion, which transmits information from the inner ear and helps in maintaining balance and coordination.

The primary function of pons is also to act as a motor relay center. Many of the descending nerve fibers of various tracts synapse in the region of the pons, which only go on to show how important pons function is.
The importance of the pons cannot be underplayed for the simple reason that it is so closely associated with the brain stem. This is the region that is involved in basic life sustaining activities, like respiration, reflexes, etc.
The apneustic center, which is located in the lower pons is the center that stimulates inspiration of air and the pneumotaxic center, located in the upper pons, inhibits inspiration by decreasing the activity of the phrenic nerve.
As a part of functions, it is said that the dorsal part of the midbrain and the brain stem is also an important center for consciousness and for maintaining alertness and fatigue levels of an individual.
Hence, some experts believe that the pons may play a vital role in REM sleep cycle and in arousal as well. This is the reason why brain stem injury is said to be a possibly life-threatening injury.