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The function of the pons, a structure located in the upper part of the brain stem, can be divided into three segments. It first acts as a pathway, allowing nerve bundles to pass between the cerebrum and cerebellum, and also between the body and the brain. This structure also has influence over the involuntary basic life functions of respiration and levels of consciousness. Additionally, it serves as the point of origin for four cranial nerves involved in various purposes such as chewing and hearing.
Consciousness is a function of the pons influenced by the area of this structure called the reticular formation. It regulates the sleep/wake cycle, which influences fatigue, motivation, and degree of alertness. Some members of the medical community postulate that this area also plays a role in dreaming.
Another function of the pons is respiration, which is influenced by two different centers within this structure. The apneustic center in the lower portion of the structure appears to regulate breathing intensity by stimulating and prolonging the inspiratory part of respiration. A portion of the pons called the pneumotaxic center exerts an inhibitory influence on inspiration. This inhibition is accomplished by decreasing the depth and frequency of breaths.
In addition to regulating some involuntary basic life functions, the pons is also involved in the control of motor and sensory capabilities of the face and head. This function of the pons is due to the fact that it is the originating spot of every cranial nerve except the optic and olfactory nerves. The mid-portion of the pons contains the trigeminal nerve, while the lower portion contains the abducens, facial, and vestibularcochlear nerves, which provide a variety of bodily services.
The fifth cranial nerve is called the trigeminal nerve, the sixth is referred to as the abducens nerve, and the seventh nerve is known as the facial nerve. Trigeminal nerve function can be divided into two parts: the sensory part, which provides feeling for the face, and the motor part, which innervates muscles involved in biting, chewing and swallowing. The abducens nerve is strictly a motor nerve that allows the eye to look to the side, while the facial nerve function involves motor control of all muscles involved in facial expression.
Vestibularcochlear function is provided by the eighth cranial nerve, which is a sensory nerve with two components. The cochlear part provides hearing by sending sound transmissions from the ear to the brain. A dysfunction of this part of the nerve can result in hearing loss. The vestibular part of this nerve sends information from the inner ear regarding spatial position in order to facilitate balance and coordination. Malfunctioning of this portion is manifested by dizziness and motion sickness.
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