Anatomy of the Brain - Pons

Brain: Pons
Brain Anatomy Showing the Pons, Pituitary gland, Olfactory bulb, and Cerebral Hemispheres. Credit: MedicalRF.com/Getty Images

In Latin, the word pons literally means bridge. The pons is a portion of the hindbrain that connects the cerebral cortex with the medulla oblongata. It also serves as a communications and coordination center between the two hemispheres of the brain. As a part of the brainstem, the pons helps in the transferring of nervous system messages between various parts of the brain and the spinal cord.

Function

The pons is involved in several functions of the body including:

  • Arousal
  • Autonomic Function: Breathing Regulation
  • Relaying Sensory Information Between the Cerebrum and Cerebellum
  • Sleep

Several cranial nerves originate in the pons. The largest cranial nerve, the trigeminal nerve aids in facial sensation and chewing. The abducent nerve assists in eye movement. The facial nerve enables facial movement and expressions. It also aids in our sense of taste and swallowing. The vestibulocochlear nerve aids in hearing and helps us maintain our equilibrium.

The pons helps to regulate the respiratory system by assisting the medulla oblongata in controlling breathing rate. The pons is also involved in the control of sleep cycles and the regulation of deep sleep. The pons activates inhibitory centers in the medulla in order to inhibit movement during sleep.

Another primary function of the pons is to connect the forebrain with the hindbrain. It connects the cerebrum to the cerebellum through the cerebral peduncle.

The cerebral peduncle is the anterior portion of the midbrain that consists of large nerve tracts. The pons relays sensory information between the cerebrum and cerebellum. Functions under the control of the cerebellum include fine motor coordination and control, balance, equilibrium, muscle tone, fine motor coordination, and a sense of body position.

Location

Directionally, the pons is superior to the medulla oblongata and inferior to the midbrain. Sagittally, it is anterior to the cerebellum and posterior to the pituitary gland. The fourth ventricle runs posteriorly to the pons and medulla in the brainstem.

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Pons Injury

Damage to the pons can result in serious problems as this brain area is important for connecting areas of the brain that control autonomic functions and movement. Injury to the pons may result in sleep disturbances, sensory problems, arousal dysfunction and coma. Locked-in syndrome is a condition resulting from damage to nerve pathways in the pons that connect the cerebrum, spinal cord, and cerebellum. The damage disrupts voluntary muscle control leading to quadriplegia and the inability speak. Individuals with locked-in syndrome are consciously aware of what is going on around them, but are unable to move any parts of their bodies except for their eyes and eye lids. They communicate by blinking or moving their eyes. Locked-in syndrome is most commonly caused by decreased blood flow to the pons or bleeding in the pons.

These symptoms are often the result of blood clot or stroke.

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 help neurons conduct nerve impulses more efficiently. Central pontine myelinolysis can result in difficulty swallowing and speaking, as well as paralysis.

A blockage to the arteries that supply blood to the pons can cause a type of stroke known as lacunar stroke. This type of stroke occurs deep within the brain and typically only involves a small portion of the brain. Individuals suffering from a lacunar stroke may experience numbness, paralysis, loss of memory, difficulty in speaking or walking, coma, or death.

Divisions of the Brain

  • Forebrain - encompasses the cerebral cortex and brain lobes.
  • Midbrain - connects the forebrain to the hindbrain.
  • Hindbrain - regulates autonomic functions and coordinates movement.