About 2.5 cm in length, Pons Varolli is the part of the brainstem found just over the medulla oblongata and below the cerebellum. This horseshoe-shaped mass of nerve fibres is a critical part of the hindbrain. In Latin, pons means “bridge” which also corresponds to the function it carries out, linking both the hemispheres of the cerebrum. Additionally, it also links the cerebral cortex to the medulla oblongata through the cerebral peduncles.
It is from this structure, the Pons, that four cranial nerves originate or terminate which are crucial for transferring sensory and motor information both ways to the brain and the facial regions. Pons hence provides a pathway for the nerve fibres to connect the cerebellum and the cerebral cortex.
Pons is a pivotal structure of the vertebrate nervous system. It is a juncture at which all the information travelling through the nervous system must pass through it at some point. Since Pons is a part of the brainstem, it is involved in carrying out some important processes of the peripheral and central nervous system.
It participates in many sensory and autonomic processes such as fine motor control, arousal, maintaining equilibrium, respiratory functions, muscle tone and the Circadian cycle. Pons is connected to many cranial nerves such as facial, abducens, trigeminal and vestibulocochlear nerves.
The basilar groove, an indentation in the centre of the pons is the location from where all the cranial nerves emerge from the same side. The trigeminal nerve, however, is an exception. This nerve is the largest cranial nerve whose name is derived from its branches – maxillar, ophthalmic and mandibular nerves. These bunch of nerves regulate the sensory information accumulated from structures of the face and the motor control of chewing.
The facial nerves control the facial expressions and sense of taste, the abducens control the eye movement and the vestibulocochlear is responsible for regulating the auditory sensations and maintaining equilibrium.
The pons is better thought of as a collection of many nuclei and tracts performing their individual functions. The basal pons is not directly associated with the two cerebral hemispheres, however, the fibres pass down the cortex synapse on many nuclei and are known as pontine nuclei. From here, a cluster of fibres emerges on one side of the pons crossing its other side, uniting for the formation of the middle cerebellar peduncles.
These peduncles connect the cerebellum thereby forming the connecting link or the “bridge”. This serves as the main pathway for the passing of information from the brain, then the brainstem all the way to the cerebellum.
Additionally, the pons comprises a cluster of neurons significant for the prime neurotransmitter system of the brain. For instance, the locus coeruleus, is the biggest collection of the norepinephrine having nerve cells in the central nervous system. Protrusions from the locus coeruleus to the subcoeruleus region of the pons assists in regulating REM (rapid eye movement) sleep. This section of the pons is deemed to be the most pivotal section for REM sleep in the brain. Any harm to this can destruct REM sleep. The group of cells containing serotonin, the raphae nuclei is found to be present in the pons. Additionally, pons regulates bladder control, swallowing and hearing.
The pons functions as a channel for several tracts moving to and fro the brainstem as it is located between the spinal cord and the brain. Pons is a point of passing for the anterolateral system for pain sensation, medial lemniscus for proprioceptive and tactile sensations and the corticospinal tract for voluntary actions.
Consequently, owing to the range of nuclei and tracts found in the pons, it is associated with a myriad of functions. Hence, the pons is not only the most distinguished structure of the brain, (as a result of its bridge-like appearance of the basal pons) but is also a critical structure for relaying information.
Pons is key for sensory, autonomic and motor functions of the body. It is the most critical structure as it is through this that the transmission of peripheral and the central nervous system takes place.
Any damage to pons can cause a loss of sensation in the face, loss of ability to gaze and loss of a corneal reflex. Also, the damage of pons poses similar symptoms as that of a stroke such as a lack of control of facial muscles causing the facial appearance to droop. Hence, pons being a bridge becomes an integral part of the various critical processes for survival.
This was a brief on the functions of Pons. For more on NEET, visit us at BYJU’S.