The human brain is such a complex organ that in order to function properly it must have the participation of a large number of parts and structures in its anatomy. Several of these parts of the brain are large and easy to see with the naked eye, such as the frontal lobes, but others are very small and located below those surface folds.

This is the case of the cerebral peduncles , small regions of the brain that, despite their size, are very important. Below you can learn more about these anatomical structures.

What are brain stalks?

The human brain is composed, roughly speaking, of two main types of “material”: grey matter and white matter.The former contains a greater concentration of neuronal somas (i.e. the “bodies” of neurons, the area in which the nucleus of these cells is found), while the white matter areas are dominated by other anatomical zones of the neuron: the axons, narrow and elongated elements which when grouped together in the form of bundles form nerve fibres.

The brain stalks are two small cylindrical shaped white structures that are composed of white matter. They are born from the brain stem, specifically above the Varolio bridge, and reach the cerebral cortex by projecting vertically.

Between the peduncles of the brain is the interpeduncular fossa, a space that acts as a physical separation between these two structures as if it were a kind of tunnel. In addition, the ventral and dorsal sides of each peduncle are separated from each other by a sheet of something that is not white matter, but something known as a black substance.

They are not the same as cerebellar peduncles

It’s easy to believe that brain stalks are the same as cerebellar stalks, but they’re not. These second structures have a similar function , as they also function as important nerve pathways that collect information from various regions. However, both their location and the type of information that these neural signal pathways integrate are different.

Brain stem functions

Brain stalks are primarily “self-pikes” of nerve impulses that travel through the brain. Because they are made of white matter, this information passes through them quickly, as the myelin that covers the axons (and gives these structures that white hue) makes these electrical signals go at a high speed.

The main function of the brain’s peduncles, therefore, is to communicate two areas of the brain : the midbrain (located at the top of the brain stem) and the cerebral cortex. In fact, these nerve fiber ducts reach the division that is created between the two cerebral hemispheres.

In fact, the peduncles contain several pathways. One of them is the corticospinal, which as its name indicates communicates the cortex with the spinal cord, and the other is the corticopontinal tract , which links the cortex with the pons.

As the brain stem is in charge of executing automatic and stereotypical actions useful or necessary for our survival, the role of the brain stem is also related to this task.

Thus, the main functions of these bundles of nerve fibres are the regulation of motor impulses and the transmission of reflex acts, two very useful mechanisms for keeping us alive, as they allow us to react quickly to significant events (especially if they are dangerous or harmful).

Specifically, the peduncles play an important role in the reflex movements of the eyes , necessary for them to work well, and in coordinating these acts with other movements of the head and neck.

Specifically, these structures are involved in the reflex control of reflex movements. Normally this occurs when commands from the motor cortex reach the brain’s peduncles, and from these go to various nuclei of a structure known as the thalamus, located deep in the brain in an area known as the diencephalon.

Parts of this pair of structures

The brain stem receives connections from the cerebellum, the cerebral cortex, and the lower parts of the brain stem and spinal cord.

On the other hand, the brain stem is composed of several parts or sections . One of them is the midbrain tegment, to which the brain crus succeeds, and the other region is called the pretectum. The tectum extends beyond the brainstem to the cortex of the brain.

The complexity of the different components of the peduncles has to do with the fact that they are located in an area of the central nervous system where all kinds of functions of control and coordination of specialized actions are carried out and created by millions of years of evolution and natural selection. In a small space, the brain stem has tiny zones in charge of performing such vital actions as the regulation of the heartbeat or the control of body temperature.