Physiology, Brain

Excerpt

The human brain is perhaps the most complex of all biological systems, with the mature brain composed of more than 100 billion information-processing cells called neurons. The brain is an organ composed of nervous tissue that commands task-evoked responses, movement, senses, emotions, language, communication, thinking, and memory. The three main parts of the human brain are the cerebrum, cerebellum, and brainstem.

The cerebrum is divided into the right and left hemispheres and is the largest part of the brain. It contains folds and convolutions on its surface, with the ridges found between the convolutions called gyri and the valleys between the gyri called sulci (plural of sulcus). If the sulci are deep, they are called fissures. Both cerebral hemispheres have an outer layer of gray matter called the cerebral cortex and inner subcortical white matter.

Located in the posterior cranial fossa, above the foramen magnum, the cerebellum's primary function is to modulate motor coordination, posture, and balance. It is comprised of the cerebellar cortex and deep cerebellar nuclei, with the cerebellar cortex being made up of three layers; the molecular, Purkinje, and granular layers. The cerebellum connects to the brainstem via cerebellar peduncles.

The brainstem contains the midbrain, pons, and medulla. It is located anterior to the cerebellum, between the base of the cerebrum and the spinal cord.