Varolio Bridge: structures, characteristics and functions

The Varolio Bridge, also known as the annular bulge or brainstem bridge, is one of the most important parts of the brain. In fact, a small injury to this structure could lead to sudden death or entry into a coma.

The reason for the importance of the Varolio Bridge is that it is one of the largest portions of a structure known as Brain stem, in charge, among other things, of keeping the automatic mechanisms that keep us alive.

Next we will look at the anatomy, parts and functions of the pons, as well as the problems that can be triggered if behavioral alterations appear due to injuries or diseases.

• Related article: "Parts of the human brain (and functions)"

What is the Varolio Bridge?

The brain stem bridge is the largest part of the brain stem, which is why it is also called an annular bulge. It is located between the other two main anatomical structures of this portion of the brain; by its upper part, it borders the midbrain, while its lower edge is in contact with the medulla oblongata.

The boundary separating the annular pons from the medulla oblongata is the pontine groove, while its border with the midbrain is the pontomesoencephalic sulcus.

Annular pons anatomy

Like any other region of the central nervous system, the pons is composed mainly of neurons and glial cells. However, in this region of the brain bundles of axons are especially important They run vertically from the brain to the spinal cord to the brain and vice versa. That is, the annular bulge acts in part as a communication pathway between two large portions of the central nervous system.

However, the bridge of Varolio also contains bundles of neurons that are distributed projecting sideways, forming the beginnings of the middle cerebellar peduncles, which are two of the areas where the brainstem connects with the cerebellum.

Another of the most notable anatomical characteristics of the Varolio bridge is that its front face, the closest to our face, is convex, bulging outward, which makes it stand out a lot over the other two main structures of the brainstem.

Inside the Varolio bridge the basilar groove is found, a small space through which the basilar artery crosses, one of the main responsible for keeping cells in large areas of the brain alive.

In addition, the pons forms the beginning of the trigeminal nerve, one of the most important cranial nerves.

Parts of the brainstem bridge

The annular bulge is formed by a set of cores, consisting of groups of associated neurons that are responsible for similar functions. They are as follows.

Somatic motor abductor nucleus

A nucleus of neurons linked to the cranial nerve known as the abducens nerve, responsible for the abduction movement of the eye.

Special trigeminal motor nucleus

The functions of this nucleus have to do with the trigeminal nerve, and basically consist of visceral movements.

Special motor core of the facial

Like the previous one, this one takes care of certain visceral movements.

Superior salivary nucleus

The functions of this nucleus are vegetative, and therefore automatic.

Its functions

The functions of the bridge of Varolio are diverse, although almost all of them are of great importance for survival.

1. Communication nexus

The annular bulge bridges groups of neurons that, if they did not pass through this structure, they would be cut off from each other. It allows information to flow from inside the skull to the outside and vice versa.

2. Motor coordination

The Varolio bridge works in conjunction with the cerebellum and other structures, Like the basal ganglia, to allow automatic and unconscious coordination of muscle groups. This makes it possible for us to balance in an upright position, for example.

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3. Homeostatic regulation

The annular bulge plays an essential role in functions such as the regulation of temperature and other basic physiological processes, like the heartbeat.

Regulation of consciousness

This region of the brainstem is traversed by the reticular formation, and for that reason it plays a role in the regulation of states of consciousness. It intervenes in the circadian cycles of sleep and wakefulness, and it also makes consciousness, itself, something possible.

Associated injuries and illnesses

The destruction or alteration of the normal functioning of the Varolio Bridge it has very serious consequences, since it affects very basic and necessary processes to stay alive.

This is so because a failure in this region of the brain can cause not enough blood or oxygen to get to the brain, resulting in death from hypoxia.

The diseases that can affect this structure are several, but stand out Alzheimer's disease and Parkinson's, since both damage large regions of the central nervous system and impede the normal functioning of neuron networks.