The Nervous System

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The Nervous System
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Nervous System
A system that controls all of the activities of
the body.
The nervous system is made of
The brain
The spinal cord
The nerves
The senses
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The nervous system also allows you to react to a
stimulus.
Stimulus
A stimulus is a change in the environment.
Example A hot stove Or tripping over
a rock
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Your reactions are automatic.
Automatic
Automatic means that you do not have to think
about your reactions.
Example If a bug flies by your eye,
you will blink.
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Brain
An organ that controls your emotions, your
thoughts, and every movement you make.
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Central Nervous System
The Central Nervous System is made of the brain
and the spinal cord.
The Central Nervous System controls everything in
the body.
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Outer Nervous System
The Outer Nervous System is made of the nerves
and the sense organs.
Nerves
Sense organs
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Nerve Impulse
Messages carried throughout the body by nerves.
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You have a nerve along your whole arm.
"Funny Bone"
The funny bone is the only place on the arm
where the nerve is not protected. The funny
bone is on the elbow.
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The Nervous System
The Central Nervous System
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The Central Nervous System
The Central Nervous System controls all of the
bodys activities.
The Central Nervous System is made of two main
organs.
1. The brain
2. The spinal cord
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The Spinal Cord
The spinal cord sends messages to the brain.
The spinal cord is the part of the nervous
system that connects the brain to the rest of the
nervous system.
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The Brain
The brain controls everything in the body.
The brain is made of more than 10 billion
nerves!
The brain is divided into three parts and is
protected by the skull.
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The Three Parts of the Brain
The Brain has three main parts
1. The Cerebrum
2. The Cerebellum
3. The Brain Stem
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The Cerebrum
The Cerebrum is the largest part of the brain.
1. The cerebrum controls your thinking.
2. The cerebrum controls your memory.
3. The cerebrum controls your speaking.
4. The cerebrum controls your movement and
identifies the information gathered by your sense
organs.
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The Cerebellum
The cerebellum is below and to the back of the
cerebrum.
1. The cerebellum controls you balance.
2. The cerebellum controls your posture.
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The Brain Stem
The Brain Stem connects the brain to the
spinal cord.
The nerves in the brain stem control your
heartbeat, breathing, and blood pressure.
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The Vertebrae
The vertebrae are the many bones that protect
the nerves in the spinal cord.
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The Outer Nervous System
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Outer Nervous System
The outer nervous system carries messages
between the central nervous system and the rest
of the body.
The Outer Nervous Systems job is to connect
the Central Nervous System to the rest of the
body.
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Outer Nervous System
The outer nervous system is made of the nerves
and the sense organs.
Nerves
Eye
Skin
Ear
Tongue
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Reflex
An automatic reaction that happens without
thinking about it.
A reflex happens quickly in less than a second.
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Automatic Nervous System
The outer nervous system controls the bodys
activities that you dont think about.
The outer nervous system controls activities
in your small intestine, your breathing, and your
heartbeat.
controls
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How messages are sent
This is just for emphasis sake to remind us
how the brain receives the information

• We should note that these messages are sent in
  the form of chemical and electrical transmissions

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How messages are sent
Firstly our receptors receive the stimuli and
the information is sent as impulses through
the sensory neurons (nerves) These messages
are then sent to the brain where the information
is processed and an appropriate response is
constructed
The brain the sends the response
as impulses
to the motor neurones which in turn causes
the effectors (muscles) to react to the stimuli

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__ _____
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Sense Organs
Sense organs carry messages about the environment
to the central nervous system.
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Sense Organs
The eyes, ears, nose, tongue, and skin are
examples of sense organs.
The sense organs gather information (light,
sound, heat, and pressure) from the environment.
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Environment
The environment is everything outside the body.
The sense organs gather information from outside
the body, then send the messages to the brain.
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Vision is your ability to see.
Vision
Vision involves the eye and the brain.
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The Eye
The eye is one of your sense organs.
The eye is made of the iris and the
pupil.
The eye gathers pictures and sends them to the
brain.
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The Parts of the Eye
The colored part of the eye is the
iris.
The black part of the eye is the pupil.
The pupil becomes larger and smaller as it
controls the light coming into the eye.
Iris
Pupil
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Parts of the eye Function
Choroid Contains lots of blood vessels
Sclera Tough white fibrous coat protecting the eye ball
Retina Contains light sensitive cells
Iris Controls the amount of light entering the eye
Optic nerve Carries impulse from retina to brain
Ciliary muscles Alters the shape of the lens
Suspensory ligaments Attach lens to Ciliary muscles
Lens Focuses light unto the retina
Pupil Allows the light to enter the eye
Cornea Bends rays of light on entering the eye
Conjunctiva Protects the cornea


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How does the human eye work?

• The individual components of the eye work in a
  manner similar to a camera. Each part playsa
  vital role in providing clear vision. So think of
  the eye as a camera with the cornea,
  behavingmuch like a lens cover. As the eye's
  main focusing element, the cornea takes widely
  divergingrays of light and bends them through
  the pupil, the dark, round opening in the center
  of thecolored iris. The iris and pupil act like
  the aperture of a camera.

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Lets compare the camera and the eye
Light sensitive areas retina and the
film Focusing both camera and eye has lens to
focus Amount of light entering diaphragm and
shutter.eye lids and iris
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How does the human eye work?

• Next in line is the lens which acts like the lens
  in a camera, helping to focus light to the
  backof the eye. Note that the lens is the part
  which becomes cloudy and is removed during
  cataractsurgery to be replaced by an artificial
  implant nowadays.

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Eye defects

• Accommodation is the adjustment of the thickness
  of the lens of the eye to see near of far
• Shortsightedness (myopia)

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Shortsightedness (myopia)

• What is myopia?
• Myopia, also known as short sightedness or near
  sightedness, is the condition in which distant
  objects appear blurry. A shortsighted person may
  have good vision at close range, but will usually
  experience difficulties seeing details or objects
  that are far away.

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With myopia, light entering the eye
focuses in front of the retina. This occurs
because either the eye has grown too long, or the
focusing components of the eye are too strong.
A diagram of a normal eye v a
shortsighted eye.As you can see, in the diagram
of the normal eye, light enters the eye, and
focuses perfectly onto the back of the eye (the
retina). With a shortsighted eye, the light
focusses in front of the retina, and causes the
image that forms on the retina to be blurred.
Thus, causing distance vision to be blurred.
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Longsightedness (hypermetropia) What
is hypermetropia? Hypermetropia, also known as
long-sightedness or far-sightedness, is the
condition in which close objects appear blurry. A
longsighted person may have good distance vision
but will have trouble with close objects.
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• With hypermetropia, light entering the eye
  focuses in behind the retina. This occurs because
  either the eye is too short (in length), or the
  focusing components of the eye are too weak.
• A diagram of a normal eye v a longsighted
  eye.
• As you can see, in the diagram of the normal eye,
  light enters the eye, and focuses perfectly onto
  the back of the eye (the retina). With a
  longsighted eye, the light focuses in beyond the
  retina, and causes the image that forms on the
  retina to be blurred. This causes near vision to
  become blurred.

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When a sound is made, the air around the sound
vibrates.
Hearing
Hearing starts when some of the sound waves go
into the ear.
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Parts of the Ear
There are nine main parts of the ear.
1. Pinna
5. Anvil
2. Ear canal
6. Stirrup
3. Ear drum
7. Cochlea
4. Hammer
8. Eustachian tube
9. Auditory nerve
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____ __ ___ __
The pinna is the part of the ear
that you can see.
The ear canal is the tube between the outside of
the ear and the ear drum.
The ear drum is in the middle ear. It vibrates
when sound waves hit it.
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Parts of the Ear
The three smallest bones in the body, the hammer,
the anvil, and the stirrup, are in the
middle ear.
The hammer gets the vibrations from the eardrum,
then sends them to the anvil.
The anvil passes the vibrations to the stirrup.
The stirrup passes the vibrations
to the inner ear.
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____ __ ___ __
The Eustachian tube controls the amount of
pressure in the ear.
The inner ear is made of
the cochlea and liquid.
The cochlea is in the inner ear. The cochlea
looks like a shell.
The auditory nerve carries the hearing
information to the brain and the brain
tells us what we heard.
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The Ear and Balance
The ear works with the brain to control your
balance.
All of your movements are controlled by balance
and muscles.
The liquid in your inner ear is responsible for
your balance.
The liquid in your ear moves when we move. The
liquid movement sends information to the brain to
tell it how we are moving.
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The sense of touch is located in the skin.
Touch
The nerves in the skin allow us to feel texture,
pressure, heat, cold, and pain.
Texture is how something feels.
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The nose controls your sense of smell.
Smell
The nose is able to smell 80 different kinds of
smells.
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Your sense of taste comes from the taste buds in
the tongue.
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Taste buds are the parts on the tongue that allow
us to taste.
The four kinds of taste buds are sweet, sour,
bitter, and salty.
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Flavors
Tastes and smells work together to
make flavors.
Flavors are the tastes of food and
drinks.