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Annular pons, pons, pons, and pons are the names given to the portion of the brainstem that connects the cerebral cortex to the medulla oblongata. The pons also serves as the communication and coordination center between the two hemispheres of the brain. Being part of the brain stem, the pons aid in the transfer of nervous system messages between various parts of the brain and spinal cord.
The pons is located in the upper part of the medulla oblongata and in the lower part of the midbrain. In a frontal plane, it is in front of the cerebellum and behind the pituitary gland, as shown in the figure below.
The pons perform various functions of the central nervous system, such as sexual arousal and sleep; it is also part of the regulation of breathing and is involved in the transmission of sensory information between the cerebrum and the cerebellum.
Several nerve connections originate from the pons. The largest nerve connection, the trigeminal nerve, aids in facial sensations and chewing. The abducens nerve or external oculomotor nerve participates in the movement of the eyes. The facial nerve enables movement and facial expressions, and also aids in the sense of taste and swallowing. The vestibulocochlear nerve, auditory nerve or statoacoustic nerve, participates in the hearing process and helps maintain balance.
The pons helps regulate the activity of the respiratory system by participating in the control of the respiratory rate carried out in the medulla oblongata. It also participates in the control of sleep cycles and in the regulation of deep sleep; the pons activate inhibitory centers in the spinal cord to turn off movement during sleep.
Another important function of the pons is to connect the forebrain, or forebrain, with the rhombencephalon, or hindbrain. It connects the cerebrum with the cerebellum through the cerebral peduncle. The cerebral peduncle is the anterior portion of the midbrain or midbrain, consisting of large nerve tracts. The pons transmits sensory information between the cerebrum and the cerebellum. Functions under the control of the cerebellum include coordination and control of fine motor skills, balance, muscle tone, and sense of body position.
Consequences of annular pons lesion
An injury to the pons can cause serious problems, as it is an organ that connects areas of the brain that control autonomic functions and movement. Injury to the pons can cause sleep disturbances, sensory problems, sexual arousal dysfunction, and coma. Locked-in syndrome is a pathology resulting from damage to the nerve connections in the pons that connect the brain to the spinal cord. The damage disrupts voluntary muscle control, leading to quadriplegia and the inability to speak. People with locked-in syndrome are aware of what is going on around them, but they cannot move any part of their body except their eyes and eyelids. They communicate by blinking or moving their eyes.
Damage to the myelin sheath of nerve cells in the pons results in a condition called central pontine myelinolysis. The myelin sheath is an insulating layer of lipids and proteins that helps neurons conduct nerve impulses. Central pontine myelinolysis can cause difficulty swallowing and speaking, as well as paralysis. On the other hand, damage to the myelin of peripheral nerves is the cause of multiple sclerosis.
Blockage of the arteries that supply blood to the pons can cause a type of stroke called a lacunar stroke . This type of pathology occurs deep in the brain and usually only involves a small portion of it. People who have a lacunar stroke may experience numbness, paralysis, memory loss, difficulty speaking or walking, coma, and in some cases death.
Sources
Gray’s Clinical Neuroanatomy . Editors Elliot L. Mancall and David G. Brock, Elsevier, United States, 2011.
