What is the nervous system?

• Communication and controlling device.

• Consists of: the brain – the spinal cord – nerves.

Why this system is important?

• Because :1.The system receives information from the

surrounding environment and from your body.

2.The system interprets this information and make your body responds to it.

3.You nervous system lets you know if things are hot, cold, rough, smooth or bitter.

4. The nervous system adjusts your movements and keep you from harm.

5. The system makes you feel pain, solve problems and learn music.

6. The nervous system adjusts the responses which require emotions. The system makes you sad, happy, angry or calm.

Structure and functions of thehuman nervous system

The neuron consists of:• First: The body cell:- It contains nucleus, cytoplasm and cell

membrane.- There are some branches extending from the

neuron’s body called dendrites.- The dendrites connectNeuron with other neuronsTo form synapse.

• Second: The axon:- Cylindrical axis covered with fatty layer called

myelin sheaths.

- The axon ends with nerve endings called axon terminals.

- Axon terminals are connected to the muscles or to form synapse.

The brain1. The main control center in the body.

2. Directs and coordinates all the processes, behaviors and emotions.

3. It is a huge computer.

4. It is also a nerve block which contains millions of nerve cells.

How the brain is protected?

• The brain is located inside a bony box called the skull to protect it

Cerebrum • The largest part of the brain.• Divided into two halves which are called the

cerebral hemispheres.• The outer surface of the hemisphere is called

the cerebral cortex and it is grey.

• The hemispheres are characterized by having convolutions (twists) and folds on the surface.

The most important functions of the hemispheres

1. Controlling voluntary movements of the body such as ………………………

2. Receiving nerve impulses from sense organs and send the appropriate response.

3. Contains the center of thinking and memory.

Cerebellum 1. Lies at the back area of the brain.2. Below the hemispheres.

The main function of the cerebellum is to maintain the balance of the body during

movement.

Medulla oblongata

1. Located in front of the cerebellum.

2. Connects the brain with the spinal cord.

3. Control the involuntary processes such as …………………………………………………………

The Spinal Cord

• Extends in a channel of vertebrae (back bone).

• Cylindrical.

• The spinal nerves extend from the spinal cord.

The Structure of a cross section of the spinal cord

• The spinal cord consists of an internal grey matter I the shape of the letter (H).

• The grey area is surrounded with white matter.

Functions of the spinal cord

1. Delivers the nerve messages from the body organs to the brain.

2. Deliver the appropriate responses from the brain to the body organs.

3. Responsible for the reflexes.

The Peripheral nervous system

• The nerves which emerges from the central nervous system.

The functions of these nerves:1.Transmit sensory information from the body

organs to the central nervous system.2. transmit the kinetic responses from the

central nervous system to the body organs.

Cranial nerves

1. 12 pairs.2. Emerge from the brain.3. Some cranial nerves bring

information from the sense organs to the brain.

Spinal nerves

1. 31 pairs.2. Emerge from the spinal cord.3. Transmit kinetic responses

from the brain to the body organs.

Reflex Action• A voluntary response done by the body when

the body is subjected to an external stimuli.Examples of reflex actions:1.Withdrawing the hand quickly when it touches

a hot surface.2.Blinking when something gets close to your

eye.Search the internet for other examples of reflex

actions.

The stages of reflex actions

1. The severity of the external stimuli affects the nerve endings resulting nerve impulses.

2. The nerve impulses are transmitted to the spinal cord through the sensory nerve fiber.

3. The spinal cord send the appropriate action to the arm muscle through the motor fiber without the brain intervention .

Ways of maintaining human nervous system

1. Reduce the intake the stimulating substances such as coffee, tea and soda drinks.

2. Stays away from tranquilizers and stimulants.3. Don’t exhaust by your sensory organs by

sitting for a long time in front of the computer and television.

4. Avoid extreme exciting.5. Do physical exercises and stay away for

sources of pollution.