Brain




 
  Brain lies in the cranium of skull. The human brain has wrinkled surface and appears as a large, soggy, pinkish grey walnut. Adult brain, on average, weights two per cent of their body weight, growing from the quarter of its size at the time of birth.  the reaches between 75 and 80 percent of adult size at the size of 6 years. Human brain composed of about 30 billion neurons. It weights about 15- 17% of cardiac output. It also receives about 20% of the oxygen consumed by the body. The left hemisphere of the brain controls the right side of the body and vice-versa.

 Regions of the brain:
 Fore-brain: It  consist of three parts Olfactory lobe, Cerebrum, Hypothalamus
The cerebrum is the largest part of the human brain. the cerebral cortex is roughly 80% of total brain mass. the Cerebrum is the most complex and specialized  part of the brain. It consists of two cerebral hemispheres. The  cerebrum has a sensory area where information is received from sense of organs. Similarly, there is the motor area from where impulse are sent to muscle. In the cerebrum, specific organs for each kind of stimulus and its response are located. For Example occipital lobe is the region for visual reception, parietal lobe for touch, smell, temperature and conscious association and frontal lobe for muscular activities.
  Hypothalamus contains higher nerve centers for temperature regulation, hunger, thrist and emotional reactions. It secrets neurohormones which controls the secretion of anterior pituitary hormones. Hypothalamus synthesizes the posterior pituitary hormones and control their release into blood.

MidBrain: Mid brain controls the muscle tone and modify some motor activities initiated by the cortex.


HindBrain: It consist of three parts Cerebellum, Pons Varolii, Medulla Oblongata
  Cerebrum, contains centers for the maintenance of posture equilibrium of body. It also coordinate the voluntary movements. It controls rapid muscular activities such as runnin, typing, talking, etc.
Medulla oblongata is the regulating center for swallowing, coughing, sneezing and vomiting. It also controls involuntary function of the body.
The brain stem consist of pons varolii and medulla ablongata, the latter continuing into the spinal cord.

Meninges:
Brain and spinal cord are surrounded by three meninges (duramater, arachnoid and piamater). Duramater is outermost, thick, tough non vascular menix applied to the inner surface of bone. Piamater is the thinnest of all the meninges, which is highly vascular and closely adhered to the surface of the brain.

 Maningitis:
This refers to infection of Meninges resulting in severe headache, vomiting and pain and stiffness of the neck. The most common cause of meningitis is the infection of bacteria.

Cerebrospinal Fluid: Fluid present around brain and spinal cord id known as Cerebrospinal Fluid. An average of some 150cc of Cerebrospinal Fluid is usually present in adult neurvous system of man. The main function of Cerebrospinal Fluid is to absorb any shock or jerk to brain and spinal cord. It also helps in the nutrition and excretion of neurons in CNS.

Spinal cord:
medulla oblongata continues behind as spinal cord. Spinal cord is located in the neural canal of vertebral column. In spinal cord white matter is found outside the gray matter. the cavity of spinal cord is known as central canal.

 Spinal cord is a cylindrical structure. If begins in contribution with the medulla oblongata and extends downwards, enclosed within vertebral column. It also surrounded by meninges. A total of thirty one pairs of spinal nerves arises from the spinal cord.






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