Transcript Unit_4 - pisscience

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 the
human nervous system
The nervous
system
Central
nervous
system
Peripheral
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 connect
Neuron with other neurons
To 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.
Central
nervous
system
The brain
The spinal
cord
The brain
1. 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
The brain
consists of
Cerebrum
Cerebellum
Medulla
Oblongata
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.
There are 2
types of
nerves
Cranial
nerves
Spinal nerves
Cranial nerves
Spinal nerves
1. 12 pairs.
1. 31 pairs.
2. Emerge from the brain.
2. Emerge from the spinal cord.
3. Some cranial nerves bring
3. Transmit kinetic responses
information from the sense
from the brain to the body
organs to the brain.
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.