The human brain is composed of the two hemispheres and the brain stem and the cerebellum. Each hemisphere is connected to the other hemisphere by a membrane that is called the corpus callosum. The functional cells of the brain are called neurons. These are cells that are unable to divide. Other cells that form the connective tissue of the brain are called glial cells. These cells do divide and are the source of malignancy in brain tumors.
The cerebral cortex in the site of sensory and motor function. The anterior part of the cortex being respnsible for motor activity, while the posterior part is responsible for sensory function. The left hemipsphere receives sensory input from the right side of the body and the right hemisphere receives sensory input from the left side of the body.
The basal ganglia are a group of nuclei that are located deep in the hemispheres. They have a function related to regulating the movement coordination of the body. They usually secrete the neurotransmitter dopamine which is inhibitory in nature. Any damage to the basal ganglia such as occurs in parkinson's disease there is a motor disorder accompanied, which is manifested as tremor of the body muscles. This is so as result of the deficient secretion of dopamine mostly from the locus ceruleus in the basal ganglia.
An important part of the brain stem is called the reticular formation. This area of the brain stem is important for maintaining a state of consciousness. Any damage to the reticular formation can lead to coma and loss of consciousness.
The cerebellum is the posterior part of the brain. It is important as the basal ganglia in coordinating the movements of the body muscles. Any damage to the cerebellum can lead to ataxia or incoordinate movements of the body muscles.
The brain houses four ventricles or small rooms. These ventricles contain a fluid that is called the cerebrospinal fluid or CSF. The cerebrospinal fluid helps to protect the brain against trauma by absorbing the shock. The cerebrospinal fluid is produced by the choroid plexus that are located in the lateral ventricles. Between the lateral ventricle and the third ventricle there is a hole that is called the foramen of monroe. This hole permits the passage of the cerebrospinal fluid from the lateral ventricles to the third ventricle. Between the third and fourth ventricles there is a hole that is called the cerebral aqueduct. This hole permits the passage of the cerebrospinal fluid from the third to the fourth ventricle. In the fourth ventricle there are two holes that are called the foramen of luschka and the foramen of magendie. These two holes permit the passage of the cerebrospinal fluid from the fourth ventricle to the subarachnid space. In the subarachnoid space the cerebrospinal fluid is reabsorbed by the blood capillaries into the blood circulation. The cerebrospinal fluid is continuously formed and reabsorbed. Any obstruction to the flow of the cerebrospinal fluid leads to hydrocephalus or ventricles enlargement and to intracranial pressure.
Around the upper part of the brain stem there is the limbic system which functions in the sensation of emotions such as pain and pleasure and anger. The other important part of the brain is the hypothalamus which is situated at the bottom of the brain below the thalamus and above the pituitary gland. It is a very important gland in spite of its small size. It is connected to the pituitary gland by a neural network and controls the function of the pituitary gland by secreting releasing hormones which stimulates or inhibit the function of the pituitary gland. The hypothalamus controls the growth metabolism and sexual behavior and sleep and thirst and hunger behavior.