The brainstem, of which the pons is the upper part, has three main functions,
It is a conduit - a superhighway - allowing nerve bundles to travel back and forth from the cerebrum to the cerebellum as well as nerve bundles to and from the body. Essentially all information from the brain to the body or vice versa must go through someplace in the brainstem.
- The brainstem serves as the origin for all the cranial nerves except the olfactory nerve (smell) and optic nerve (sight). The cranial nerves that originate in the pons are:
- 5th nerve - Trigeminal - This nerve has a sensory and motor component.
- The sensory part is responsible for the feeling of the face.
- The motor part innervates the muscles of the mandible responsible for biting, chewing and swallowing.
- 6th nerve - Abducens - This is a motor nerve that allows to eye to look to the side. Dysfunction of the nerve will cause the eye to drift in towards the nose potentially eventually becoming paralyzed in this position.
- 7th nerve - Facial - This is a motor nerve that affects the muscles of facial expression such as smiling showing ones teeth, raising the eyebrows, closing the eyes tightly or puffing out the cheeks.
- 8th nerve - Vestibularcochlear - This is a sensory nerve with two parts.
- The cochlear portion of this nerve allows for hearing transmitting sound from the ear to the brain. Problems with this part of the nerve can cause hearing loss.
- The vestibular portion transmits information from the inner ear about one's position in space which allows for balance and coordination. Dysfunction causes vertigo, motion sickness, nystagmus and a loss of equilibrium.
- The brainstem has influence over several automatic basic life functions. Here are a few examples involving the pons.
- Consciousness - The reticular formation is the dorsal part of the midbrain and brainstem (in the tegmentum). It is involved in the sleep/wake cycle affecting fatigue, alertness and motivation. Some theorize that the reticular formation has a role in dreaming.
- Respiration - There are two centers in the pons that affect respiration.
- The apneustic center in the lower pons that seems to stimulate and prolongs inspiration thereby controlling the intensity of breathing.
- The pneumotaxic center located in the upper pons that inhibits inspiration. It decreases the depth and frequency of breaths.