Brain

The brain is encased in a  bony shell and is further protected by three membranes or meninges. The inner part of these, covers the brain and is richly supplied with blood vessels. It brings oxygen and nutrition to underlying brain and protects it. The cerebrospinal fluid (CSF) lies between the inner and middle layers, which provides cushioning and ions to the brain and spinal cord. The outer most layer is laugh and fibrous and provide mechanical support.

       The vertebrate brain is divided into three basic regions, the hindbrain, the midbrain, and the forebrain.

       The hind brain is chiefly concerned with involuntary, mechanical process. It consists of three primary medulla oblongata which lies on top of the spinal cord and contain many of the centres that control involuntary process like breathing, blood pressure and heart beat. All communication between and spinal cord pass through the medulla. (2) the Pons that is present on the top of the medulla and contains the longitudinal bundles of myelinated fibres running between brain and spinal cord and controls balance and muscle coordination. (3) the cerebellum lies behind the medulla and controls and muscle coordination.

structure. (1) the

       The midbrain lies between the hindbrain and forebrain and connects the two. It processes the visual and auditory information from the eye and ears before sending them to the forebrain.

   The forebrain is most advanced in human. Its lower most part which lies above the midbrain is called hypothalamus which control, heart rate, blood pressure, body temperature, hunger, thirst, sex and anger in thalamus which provides connections between many parts of brain and between sensory system and cerebrum. It may also control moods and feelings. Sleep may be influenced by thalamus centre along with the midbrain and hindbrain. It is concerned to keep the body alert. The cerebrum is the top most and the largest part of the forebrain. It is divided into two hemispheres comprising 15 billion nerve cells.

addition to its hormonal role. Resting above the hypothalamus is the

(I)                   At the back are the occipital lobes which receive and analyze visual informations.

(II)                At the lower sides of the brain are the temporal lobe which are primarily concerned with heating.

(III)              At the front of the brain are the frontal lobes which regulate fine motor control including movements involved in speech.

            Above the temporal lobe and behind the frontal lobe are the parietal lobes which receive stimuli from the skin and also provide awareness of the body position. Memorytrack are also supposed to be present in the cerebrum.