Nervous system 1. A newborn baby's brain grows almost 3 times during the course of its first year. 2. The left side of human brain controls the right side of the body and the right side of the brain controls the left side of the body. 3. A New born baby loses about half of their nerve cells before they are born. 4. As we get older, the brain loses almost one gram per year. 5. There are about 13, 500, 00 neurons in the human spinal cord. 6. The total surface area of the human brain is about 25, 000 square cm. 7. The base of the spinal cord has a cluster of nerves, which are most sensitive. 8. An average adult male brain weighs about 1375 grams. 9. An average adult female brain is about 1275 grams. 10. Only four percent of the brain's cells work while the remaining cells are kept in reserve.

11. The Brain utilizes 20 % of our body's energy ie,it uses 20% of one's blood and oxygen and makes up only 2 % of our body weight.
12. The Human brain stops growing by 18 years of age.
13. The human brain is very soft like butter.
14. Sixty percent of the human body's nerve ends in the forehead and the hands.
15. The brain continues to send out electric wave signals until approximately 37 hours after death
16. It is estimated that there are over 1, 000,000,000,000,000 connections in the human brain.
17. Human brain constitutes 60 % of white matter and 40 % of grey matter.
18. The average length of the human brain is about 167 mm and its average height is 93mm.
19. On an average, 100, 000 to 1000, 000 chemical reactions take place in our brain.

20. The Nervous system transmits messages to the brain at the speed of 180 miles per hour.

21. The spinal cord, which controls over 10 billion nerve cells, is less than two feet in length and its diameter is same as that of the index finger.
22. Reading aloud to children helps to stimulate brain development.
23. The right side of the human brain is responsible for self-recognition.
24. Men listen with the left side of the brain and women use both sides of the brain.
25. The human brain is made up of a staggering 15 billion cells with about thousand billion connections between these cells. It however weighs less than 3 pounds.

Nervous System

The Central nervous system consists of the brain, the spinal cord, and the body’s nerve network. This complex system is based on one kind of cell the neurons. The brain, the mass of tissue inside the head, has the greatest number of these cells, most of which are in it’s outer part, the cerebrum. Below the cerebrum is the cerebellum and the brain stem, which is linked to the spinal cord.

The Brain: The brain has been compared to a giant telephone exchange or to a computer. It functions as both, handling incoming and out going calls, and making decisions, as diverse as whether to laugh or cry and whether the temperature of the body should be higher or lower, on the basis of information fed into it.

Cerebrum: The brain’s most obvious external features are two soft hemispheres, which make up the cerebrum. These hemispheres make up 70% of the whole brain and nervous system. They are “mirror images” of each other, and each is chiefly concerned with the movements and sensations of only one side of the body. Sensations on the right side of the body and the control of the muscles on that side are functions of the left hemisphere, and vice versa. It consists of 2 layers: (1) outer cortex or grey matter - which is the decision maker of the brain, (2) Inner layer of white matter - made up of nerve fibers.

Cerebellum: The cerebellum functions below the level of consciousness. It is concerned with balance, and is the center for the co-ordination of complex muscular movements

Brain Stem: Links the spinal cord to the brain. They lie below the cerebral hemispheres.

The Spinal Cord: The spinal cord is the body’s main nerve trunk-a cylinder of nerve tissue 18 inches long about as thick as a man’s little finger. It runs down the back from the medulla oblongata, at the base of the brain. It is enclosed in a set of 3 membranes, similar to those surrounding the brain. Between the layers of membranes, Cerebro-spinal fluid acts as a cushion, to protect the cord from damage.

Nerve Fibres: The spinal cord is a column of nervous tissue, which is spread throughout the body; they carry impulses to and from the brain. Nerve fibres from the brain and spinal cord are bundled together to form 12 pairs of cranial nerves, connected to the brain and 31 pairs of spinal nerves

Spinal Nerves: 1) CERVICAL NERVES - (8 pairs) serve mainly the arms.

2) THORACIC NERVES - (12 pairs) lead to the sternum, internal organs and muscles of the chest.

3) LUMBAR NERVES - (5 pairs) serve the abdominal wall and legs.

4) SACRAL & COCCYGEAL NERVES - (6 pairs) lead mainly to the legs.

Carnival Nerves: The brain has links with the sense organs and the muscles of the head by means of 12 pairs of cranial nerves

1) OLFACTORY: - sense of smell

2) OPTIC: - sense of sight balance

3) OCULOMOTOR: - Focusing, regulating the size of the pupil, balance

4) TROCHLEAR: - movement of the eyeball.

5) TRIGEMINAL: - Chewing, sensation from the face

6) ABDUCENT: - movement of eye, sense of taste

7) FACIAL: - movements of facial expression

8) VESTIBULOCOCHLEAR: - maintenance of balance, sense of hearing

9) GLOSSOPHARYNGEAL: - secretion of saliva, sense of taste, movement of pharynx

10) VAGUS: - movement and secretion

11) ACCESSORY: - movement of the head, shoulders, pharynx and larynx

12) HYPOGLOSSAL: - movement of tongue.

Autonomic Nervous System: The autonomic system controls glands, such as the salivary glands, and the internal organs-the bladder, heart, intestines, liver, lungs and sexual organs. Nearly all the actions of the autonomic system are outside voluntary control eg. You cannot normally “will” your heart to beat faster; but if you are given a fight, your pulse involuntarily speeds up. The autonomic division of the nervous system consists of two opposing parts,

The sympathetic; The parasympathetic; which operate below the level of consciousness The sympathetic nerves: - Through the sympathetic nerves, the brain mobilizes the body for action to meet possible danger.

1) IRIS- Changes size, when someone is frightened or angry, the brain stimulates the sympathetic nerves to their part of the eye, causing the pupils to open wide.

2) SALIVARY GLANDS- produces less saliva, so that the mouth goes dry.

3) LUNGS & WINDPIPE- are affected under stress; breathing becomes faster, so that the body gets more oxygen.

4) HEART- pumps faster, during times of fear & anger. Normally you are unaware of the beating of the heart, but its increased activity in times of excitement raises the blood pressure, pumping more blood to supply energy for muscles.

5) ADRENAL GLANDS- at the top of the kidneys secrete the hormone adrenaline, which prepares the body to fight or run away

6) LIVER-releases glucose under emotional stress, providing extra energy for muscles.

7) STOMACH & INTESTINES- have their blood diverted to the heart, CNS and muscles, so that they can operate under stress. The wave like movements of the intestinal walls stop, and the various sphincters close. ·

Parasympathetic Nerves: - are concerned with restoring the body to peaceful activity after an emergency

1) Heart - slows down & the blood pressure falls after the danger is over.

2) Bladder - can be contracted and it’s sphincter may open, causing urination.