Pons: A Detailed Overview and its Functions

The Pons term is derived from the Latin word meaning ‘bridge’ because it serves as a bridge between brain and body. It is a horseshoe-shaped structured part of the brainstem that consists of millions of nerve fibers.

• The pons is located between the midbrain and the medulla oblongata and are the major structure of the brain stem.
• It acts as a signal relay between the lower cerebellum, spinal cord, midbrain, cerebrum, and other upper brain regions. 
• Pons regulate the sensation signals of pain from the body parts below neck.
• It recieves the blood supply from posterior cerebral circulation.

Key Words: Pons, Brain, Central Nervous system, Brainstem, Nerves, Spinal cord, Midbrain.

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Pons in Brain

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The human brain represents an evolved system that connects neurons regulating and maintaining our physical responses and mental health. There are many parts of the brain like the frontal lobe, parietal lobe, occipital lobe, temporal lobe, brainstem, and cerebellum.

• With the help of three main parts cerebrum, cerebellum, and the brain stem the primary understanding of the brain can be easily done.
• The brain stem possesses a stalk-like structure and bridges the gap between the head and the body as it connects the cerebrum with the spinal cord. 
• Brain stem can further be classified into three parts- the midbrain, pons, and the medulla also known as the medulla oblongata.
• Controlling sleep cycles is one of the pons' key roles.

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Pons Anatomical Position

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In the anterior region of the posterior cerebral fossa, the pons is a horseshoe-shaped cluster of nerve fibers. The following are its anatomical relationships:

• The cerebellum is located posteriorly, divided by the fourth ventricle.
• The medulla oblongata is located beneath the medulla oblongata.
• The midbrain is just above the pons on the superior side.

Location of the Pons

As the pons is superior to the medulla oblongata, it lies above the medulla and as it is inferior to the midbrain, it lies below the midbrain.

• When a sectional portion of the pons is dissected it is seen that the pons lies anterior to the cerebellum (in front of it and behind) or posterior to the pituitary gland.
• The broad anterior bulge in the medulla is the pons which measures about the length of 2.5 cm in adults.
• It appears as a bridge that also connects the two hemispheres in the brain.

Structure of the Pons

Even though the pons appears as a bridge, the basal part of it is free and not connected to anything, and it is a collection of various tracts and nuclei.

• All help to serve the purpose of the pons’ function.
• The fibers of tracts and nuclei that travel down from the cortex are the pontine nuclei.
• When fibers of pontine nuclei from one side cross over to connect with the other side of the pontine nuclei, the middle cerebellar peduncles are formed.
• This forms the major pathways for information to travel to the cerebellum from the brain and brainstem.
• The main artery for the blood supply of the entire brain is present in the pons which is a basilar groove.
• It is a shallow groove that lodges the basilar artery and is situated in the middle of the fibers.

Anterior Pons

Pons also acts as the origin point for many nerves like the trigeminal nerve which is the fifth cranial nerve and the most complex of all cranial nerves.

• Apart from this, the abducens nerve is the sixth cranial nerve, the facial nerve, and the vestibulocochlear nerve are the seventh and eighth cranial nerves respectively.
• All of these nerves originating from the pons serve very specific functions. 

Posterior Pons

The posterior surface is displayed and the pons covers the upper half of the fourth ventricle when one separates the connection of the pons with the cerebellum.

• It shows the midline of the floor which is known as medial eminence.
• The facial colliculus is the fibers of the facial nerve that is looping around the abducens nucleus to form a bulge.
• It also clearly shows the stria medullaris forming the posterior border between the pons and the medulla.
• It is a bundle of nerve fibers crossing transversely from the lateral aspect into the midline. 

Also Check: Medulla Oblongata

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Nerves Emerging from Pons

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Four cranial nerves come from the pons, as follows:

• From the middle of the ventrolateral portion of the trigeminal nerve
• Abducent nerve: originates at the pons-pyramid junction.
• From the cerebellopontine angle, the facial nerve (angle between pons and cerebellum)
• From the cerebellopontine angle, the vestibulocochlear nerve

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Functions of Pons

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The pons, which is located above the medulla, is an important region of the brain. It belongs to the hindbrain category. Pons is a crucial component of the brain that regulates and controls a variety of key activities. It serves as a control center and also houses the nuclei of several essential cranial nerves.

• Four cranial nerves begin or terminate from this structure are critical for conveying sensory and motor information to the brain and face regions in both directions.
• Pons thus serves as a conduit for nerve fibers connecting the cerebellum and the cerebral cortex.
• Pons is a critical component of the neurological system of vertebrates.
• It's a location where all information passing through the nervous system must pass through at some time.
• Pons is a component of the brainstem and is involved in several essential peripheral and central nervous system activities.
• It plays a role in fine motor control, arousal, maintaining homeostasis, respiratory functions, muscular tone, and the circadian cycle are all sensory and autonomic processes.
• Pons is related to several cranial nerves, including the facial, abducens, trigeminal, and vestibulocochlear.
• The facial nerves are in charge of facial emotions and taste, the abducens is in charge of eye movement, and the vestibulocochlear is in charge of regulating auditory experiences and maintaining equilibrium.

In addition, the pons contains a cluster of neurons that are important for the brain's primary neurotransmitter system. The locus coeruleus, for example, is the largest concentration of norepinephrine-producing nerve cells in the central nervous system.

• Protrusions from the locus coeruleus to the sub coeruleus region of the pons aid in the regulation of REM sleep.
• This portion of the pons is thought to be the most important in the brain for REM sleep.
• Any damage to this might cause REM sleep to be disrupted.
• The raphae nuclei, a collection of cells that contain serotonin, are found in the pons.
• The pons also controls bladder control, swallowing, and hearing.

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Pons Pathology and Injury

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Damage in pons can be responsible for many problems since there are many nerves and nuclei possessed by it and they connect and intersects many networks. The diseases or damage can result in severe damage.

• If an individual is suffering from quadriplegia, it will disrupt voluntary muscle control.
• If there is damage to the nerve pathways in the pons that connect the cerebrum, spinal cord, and cerebellum, they will also lose the ability to speak and this is called the Locked-in syndrome.
• The locked-in syndrome takes place also because of reduced blood flow, which can also result in strokes, clots, or sometimes even bleeding in the pons.
• Central pontine myelinolysis happens as a result of the damage in the myelin sheath of nerve cells in the pons and results in paralysis.
• When the arteries that supply blood to the pons are blocked due to any reason Lacunar stroke is caused.
• This results in loss of memory, inability to speak and walk, paralysis, coma, or even death.
• Pons tumors cause sensory defects of the trunk and limbs, weakness in the facial muscle, and sometimes hearing impairment when the cochlear nerve is affected.

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Significance of Pons

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While people can live without a gallbladder, lung, or even a kidney, there are some organs and portions of our body that we simply cannot live without. One of the parts that we can't live without is the Pons.

• The body could conceivably survive if anything above the brainstem was removed, but if anything below the brainstem was removed, the body would perish.
• All of essential functions, such as breathing, are "housed" in the brainstem, which is controlled by the Pons.
• The Pons is not something a person could live without because of its role in hearing, feeding, facial expression, and eye movement.

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Conclusion

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Pons is a portion of the hindbrain that is located in the brain stem just above the medulla oblongata. The pons has a convex anterior surface with a shallow groove in the middle for the basilar artery on gross inspection. The roof of the fourth ventricle is formed by the middle cerebellar peduncles on all sides. Pons appear to have pear-shaped transverse parts. It is investigated on two levels: the face colliculus and the trigeminal nuclei.

The trigeminal nerve (CN V), abducent nerve (CN VI), facial nerve (CN VII), and vestibulocochlear nerve (CN VIII) all arise from the pons (CN VIII).

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Things to Remember

• Pons is important for the body's sensory, autonomic, and motor processes.
• It is the most important structure since it is through it that the peripheral and central nervous systems communicate.
• Any damage to the pons can result in a loss of facial sensibility, the inability to stare, and the lack of a corneal reflex.
• The signs of pons injury are similar to those of a stroke, such as a loss of facial muscle control, leading the face to droop.
• As a bridge, pons forms a vital part of the different critical survival processes.
• The main functions of pons are in signaling the pain sense to body part, hearing, feeding, eye movement and facial expression. 

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