The three primary functions of the pons are acting as a pathway for signals transferring between the cerebrum and the cerebellum; helping transmit cranial nerve signals out of the brain and into the face and ears; and controlling certain involuntary functions like respiration and consciousness. Though the pons is a small part of the brain it is a very important one. Its location in the brain stem makes it ideally suited to conduct signals in and out, and it serves as the point of origin for many important cranial nerves. Any time people chew, swallow, breathe, and sleep they are, in most cases, using their pons. The pons also plays a role in hearing.
Location in the Brain
In humans and most other animals, the pons is located in the upper part of the brain stem. It sits between the medulla oblongata and the thalamus, and in many ways acts as a sort of link between these two areas. The pons is made primarily of what is known as “white matter,” which is different, both functionally and biologically, from the “grey matter” of the cerebral brain, and it’s generally pretty small, measuring about an inch (2.5 cm) in most adults. Its size and location make it idea for controlling and directing many nerve signals, most of which relate to the face and respiratory system.
As a Nerve Pathway
The pons serves as the point of origin for four of the twelve major cranial nerves: the trigeminal, the abducens, the facial, and the vestibularcochlear. It acts as a pathway for these nerves and carries their signals into the main cortex. Most of these signals relate to facial functions, including movement and sensation in the eyes and ears.
In most cases the trigeminal nerve, which is the fifth cranial nerve, controls feeling in the face and also controls many of the muscles involved in biting, chewing, and swallowing. General facial expressions and muscular contractions are controlled by the facial nerve, though, which is the seventh sequential cranial nerve. The abducens, or sixth, nerve is a bit more specific in that it is strictly a motor nerve, and its primary function is eye movement. It is credited with allowing the eye to look far to either side. In none of these tasks does the pons itself actually play an active role, but it is essentially the pathway for signals to get from the nerves to the brain — which is a crucial step.
In a similar way the pons plays a role in hearing, too, in that it also conducts signals from the vestibularcochlear nerve. This sensory nerve has two components. The “cochlear” part provides hearing by sending sound transmissions from the ear to the brain, while the “vestibular” part sends information from the inner ear regarding spatial position in order to facilitate balance and coordination. If the nerve is damaged or if the pons crosses its signals, a person might feel dizzy or motion sick.
Conducting Signals Out
Just as the pons carries signals from the nerves into the brain, so also does it take commands from the brain and relay them to the nerves. As a result it serves as something of a clearinghouse for information traveling both to and from the largest areas of the face. The main role of the white matter here is to organize the signals, prioritize them, and translate them completely and accurately.
Controlling Involuntary Functions
This structure also has influence over a number of involuntary basic life functions related to respiration and consciousness. An area of the pons known as the reticular formation controls regulates the sleep/wake cycle, for instance, which influences fatigue, motivation, and degree of alertness. Some members of the medical community think that this area may play a role in dreaming and the formation of dreams, too, but not much research has been done to prove this.
Another function of the pons is respiration. Its apneustic center in the lower portion of the structure appears to regulate breathing intensity by stimulating and prolonging the inspiratory part of respiration. At the same time, the pneumotaxic center exerts an inhibitory influence on inspiration which can decrease the depth and frequency of breaths.