Midbrain, Cerebellum, and Brain Stem

Cerebellum
Cerebellum is located below the cerebrum and at the upper back of the brainstem. Its
name connotes its small size. Its mass is 1/10 of the whole brain. However, in terms of
the number of neurons it contains, it exceeds that of the remaining parts of the central
nervous system combined. This lump of nerve tissues, bearing the look of something cut
in half, covers most of the back of brainstem. With the help of three pairs of fibers,
collectively called cerebral peduncles, the brainstem is bound to the cerebellum. Like the
cerebrum, it also has a wrinkled surface, but its grooves and bulges are finer and
organized into more regular patterns. In terms of its physical structure, this too has a long
groove in the center, with two large lateral lobes, one on each side. These lobes are
reminiscent of the two hemispheres of the cerebrum and are sometimes termed cerebellar
hemispheres. The cerebellum has a similar layered microstructure to the cerebrum. The
outer layer, or cerebellar cortex, is gray matter composed of nerve-cell bodies and their
dendrite projections. Beneath this is a medullary area of white matter consisting largely
of nerve fibers. As of now, it has been established that cerebellum’s main function is in
coordinating the body movement. Although, it may not initiate the movements, however
it helps in the coordination and timely performance of movements, ensuring their
integrated control. It receives data from spinal cord and other parts of the brain, and these
data undergo integration and modification, contributing to the balance and smooth
functioning of the movements, and thus helps in maintaining the equilibrium. Therefore, whenever this part of the brain is plagued by a disorder, the person may not lose total
movement, but their ability of performing measured and steady movements is affected as
also their ability to learn new movements. Within the division of entire brain into
forebrain, midbrain, and hindbrain—cerebellum forms part of the hindbrain.

Brainstem
Brainstem is located below the cerebrum and in front of cerebellum. Its lower end
connects with the spinal cord. It is perhaps misnamed. It is not a stem leading to a
separate brain above, but an integral part of the brain itself. Its uppermost region is the
midbrain comprising an upper “roof” incorporating the superior and inferior colliculi or
bulges at the rear, and the tegmentum to the front. Below the midbrain is the hindbrain.
At its front is the large bulge of the pons. Behind and below this is the medulla which
narrows to merge with the uppermost end of the body’s main nerve, the spinal cord. This
part of the brain in associated with the middle and lower levels of consciousness. The eye
movement involved in following a moving object in front of the eye is an example. The
brainstem is highly involved in mid-to low-order mental activities, for example, the
almost “automatic” scanning movements of the eyes as we watch something pass by. The
gray and white matter composites of the brainstem are not as well defined as in other
parts of the brain. The gray matter in this part of the brain possesses some of the crucial
centers responsible for basic life functions. For example, the medulla houses groups of
nuclei that are centers for respiratory (breathing), cardiac (heartbeat), and vasomotor
(blood pressure) monitoring and control, as well as for vomiting, sneezing, swallowing,
and coughing. When brainstem is damaged, that will immediately trigger danger to life
by hindering heartbeat and respiratory processes.