Your brain is the portion of the central vertebrate nervous system that lies within the skull below it, which it is continuous with the spinal cord. The brain is enveloped by meninges in the same manner as the spinal cord. It almost completely fills the cranium; the remaining space is filled by cerebrospinal fluid. The brain is subdivided into a large rounded mass, the cerebrum, which consists of two lateral halves, the cerebral hemispheres, united across the midline, and a central core of nerve cells, the thalamus.
Between the thalamus and the spinal cord lie, successively, the midbrain, the pons, and the medulla oblongata. The cerebellum lies behind the pons and is attached to it as well as to the midbrain and medulla oblongata. The cerebellum is the portion of the brain that is reponsible for our emotions, thinking skills, and also motor skills. The term of brain stem is often applied collectively to the thalamus, midbrain, pons, and medulla oblongata,
The blood supply of the brain is derived from two sources which are, two vertebral arteries, one in each side of the vertebral or spinal column, which enter the skull where the spinal cord joins the medulla, and the internal carotid arteries, which approach the base of the skull very deeply and enter it through a complex course, part of which traverses a bony canal. On the inside of the human skull and lying upon the underside of the base of the brain, the internal carotid arteries communicate by means of short connecting links that form with the vertebral arteries, the so-called arterial circle of Willis. From this, two types of vessels supply the brain. The first of these vessels run upon the brain surface; the others either plunge deeply into the substance of the base of the brain as perforating arteries or take a course in the depths of fissures to reach its interior.
The medulla of the brain deals with the regulation of respiration and heart action, and also contains the central apparatus needed for swallowing. The auditory and vestibular nerves, which deal with hearing and equilibrium, enter the brainstem in the upper part of the medulla. The pons contains the central apparatus for chewing; through it the trigeminus, the principal sensory nerve of the face, enters the brain stem. The pons is also intimately connected with the cerebellum, impairment of which may result in a form of motor unsteadiness called ataxia. It is the mesencephalon that contains most of the central apparatus regulating the movements of the eyes.
The ventral part of the thalamus contains the hypothalamus, which is mostly concerned with the autonomic nervous system. The hypothalamus in our brain controls the blood pressures, body temperatures, our thirst and also cycles of sleeping.
