2. The nervous system is a group of organs that process information. Parts and functions of the Nervous System The nervous system can be divided into two main parts. 1.Central nervous system- includes the brain and spinal cord. Spinal cord relays messages between the brain and all parts of the body. 2.Peripheral nervous system- all the nerves that connect the brain and spinal cord with other parts of the body. Example: nerves that connect the brain with the eyes. Nerves from muscles to spinal cord.

3. The nervous system performs several important jobs for your body. 1.It receives information from the environment through special nerve endings. (receptors) 2.Directs your thought processes. Remembering a phone number 3.Controls the movement. Example: throwing a ball, riding a bike.

4. The brain, spinal cord, and nerves are made of nerve cells or neurons. A nerve cell has a special shape. It looks something like a spider hanging from the ceiling. The long arm is called axon. The shorter ones are called dendrites. The message always travels through the cell dendrite to axon.

5. What we call a nerve is actually a bundle of the many-armed cells, which make up long strings of nerve fibers. These link up all parts of the body. The nerve highway system is made up of 12,000 million nerve cells. In less than a second, 100,000 nerve cells relay 100 meters a second.

6. The message that a nerve sends is called an impulse. The space between the axon of one neuron and the dendrites of another is called a synapse. In order for the impulse to move across the synapse, the synapse must be filled with a chemical called a transmitter.

7. Nerve tissue is soft and easily damaged. If a nerve in the CNS is cut, it usually cannot grow back together. Re-growth of damaged nerves almost never occurs. For this reason, any damage to the brain or spinal cord is almost certainly permanent, and may result in loss of body control or loss of senses in the area beyond the damaged nerves. Most of it is behind bony protections or deep within muscle tissue. One exception is the ulnar nerve, which occupies the little hollow at your elbow Ever knock your elbow and get that electric needles and pins feeling as if you have been shocked? Well in a way you have.

8. Three types of neurons: 1.Sensory neurons: Carry signals towards the brain. They begin at sense organs (eyes, nose, ears, tongue, skin) and carry information from the sense organs to the brain. 2.Association neurons: Carry signals between sensory and motor neurons in spinal cord and brain. 3.Motor neurons: Once the brain has received information from the sense organs about what to do, it sends signals back out to the body in a different set of nerves called motor neurons. Motor neurons are always attached to either muscles or glands, so the brain’s orders results in either movement or the production of body chemicals.

9. In order for you to perform any movement, no matter how simple, impulses must travel along sensory, motor and association neurons in definite pathways. There are two main kinds of impulse pathways- long and short. A long impulse pathway is controlled by the brain. Most of your action are the result of long impulse pathways.

10. Long Pathway response For example, the pathway begins when a raindrop hits a receptor in the skin. The receptor sends a “rain” impulse along a sensory neuron to an association neuron in the spinal cord. The association neuron picks up the “rain” impulse and carries it up the spinal cord to the brain. The brain interprets the “rain” impulse and makes the decision to open the umbrella. The brain sends an “open umbrella” impulse along an association neuron down the spinal cord to a motor neuron. The motor neuron picks up the “open umbrella” impulse and carries it to a muscle in the hand. The impulse then directs the muscle to open the umbrella. The entire long pathways beginning at the receptor and ending at the muscle, takes three for four tenths of a second to occur.

11. Short impulse pathways Sometimes your body needs to react more quickly. Certain quick movements are the result of short impulse pathways. This movement is controlled by the spinal cord. The brain is not involved in the pathway. In fact, you don’t realize the injury until you’ve already reacted. The entire short pathway takes only one tenth of a second to occur. Movements controlled by the spinal cord through short impulse pathways are called reflexes. A reflex is a quick, automatic reaction to the environment.

12. Sense organs- each only recognizes one type of signal. 1.Eye: it receives light onto the retina so you can form an impulse of the world around you. 2.Ear: Ears pick up sound waves which stimulate special receptors. 3.Nose: Sense odors that dissolve in the mucus layer and stimulates the receptors. 4.Tongue: has taste buds that are stimulated by the flavors in food. 5.Skin detects pain, heat, cold, pressure or touch.

13. All signals from sense organs are sent to the brain. The brain is the control center of the entire nervous system. It is about the size of a grapefruit. Three parts of the brain: 1.Cerebrum- largest region Jobs: a. Impulses from your sense organs travel over sensory neurons to your cerebrum. The cerebrum interprets these impulses. b. Controls many of your body movements.

14. c. It allows you to learn, to reason, to understand and to remember. d. It enables you to make decisions. e. It allows you to solve problems The cerebrum is divided into right and left halves. The right side controls the left side of the body and vice versa. Right sideLeft side DrawingReading Singingwriting organizing

15. Cerebellum: second largest region of the brain. Jobs: a.Keeps balance and muscle tone. b.Coordinates your movements Example: if your cerebrum directs you to hammer a nail, your cerebellum makes sure your movements are smooth and organized

16. 3. Medulla: located where your brain joins your spinal cord. Nerves traveling up the spinal cord to the cerebrum cross over to opposite sides in the medulla. Job: a. Controls the functions of your internal organs. It regulates your heart and breathing rates. It controls peristalsis. It even handles certain reflexes such as sneezing and coughing

17. Your spinal cord is about as wide as your index finger. It contains billions of association neurons. 31 pairs of spinal nerves branch off the spinal cord. The spinal nerve contain both sensory and motor neurons. They carry impulses both to and away from the spinal cord.

18. Disorders of the nervous system: 1.Concussion- temporary loss of brain function caused by a blow to the head. 2.Paralysis- loss of muslce movement and feeling often caused by injury to the spinal cord. 3.Epilepsy- muscular seizures and body convulsions caused by abnormal impulse activity. 4.Multiple sclerosis- loss of muscle control caused by the hardening of nerve tissue in the brain or spinal cord.