Download File

Body Balance
Year 9 Science
The Nervous System
Central Nervous System (CNS)
The central nervous system is divided into
two parts: the brain and the spinal cord.
Central Nervous System (CNS)
The CNS acts as the
control centre,
receiving messages
from all parts of the
body.
It examines the
information and then
sends out messages
to the body telling it
what to do.
Peripheral Nervous System (PNS)
The PNS consists of nerves which
connect the brain and spinal cord with
other parts of the body. The PNS is
made up of sensory receptors and
nerves.
Simplified Summary
Nervous System
Central Nervous
System
Brain
Spinal
Cord
Peripheral
Nervous System
Motor
Nerves
Sensory
Nerves
• Cerebellum controls and coordinates
movements of the muscles, like walking or
swinging the arms.
• This means that the movement is smooth and
controlled and you don’t fall over when you
turn around.
• Cerebrum has special areas, which receive
messages about sight, touch, hearing and
taste. Other areas control movement,
speech, learning, intelligence and personality.
• The brain stem is in charge of keeping the
automatic systems of your body working.
Nerves
• Movement is directed and controlled by the
action of the nervous system.
• Nerves act as messengers inside the body,
carrying information from one part of the
body to another
• Nerves are made up of bundles
of nerve fibres or nerve cells.
Source: HSL3 (2006) pp 191
• Messages are passed through the nervous
system by nerve cells called NEURONS.
Neuron
• Neurons transmit and receive
messages in the form of electric
impulses called “nerve impulses”.
• Nerve impulses travel at very high
speeds and normally only travel in one
direction.
• There are two types of neurons: Motor
neurons & sensory neurons
Motor Neurons
• Send information/messages AWAY from the
CNS to effector organs such as muscles.
• Muscles and glands are called Effectors
because they put the messages into effect.
AWAY from CNS
Sensory Neurons
• Sends information/messages from sensory
receptors (such as skin, eyes, nose, tongue,
ears) TOWARDS the CNS.
• Sensory neurons have specialised endings
that are sensitive to a particular stimuli such
as heat, pressure or light called Receptors.
• Messages are sent as an electrical impulse
along the neuron.
• This carries the messages from the axon of
one neuron to the dendrite of the next
neuron.
Reflexes
Reflexes
• A reflex action is an involuntary, or
automatic, action that your body does
in response to something - without you
even having to think about it.
• Reflexes protect your body from things
that can harm it.
For example:
if you put your hand on a hot stove, a
reflex causes you to immediately
remove your hand before the message,
"Hey, this is hot!" even gets to your
brain.
Reflex Action
• Sometimes your body reacts very fast without
waiting for instructions from the brain. Such as
blinking, sweating, coughing, knee jerking.
What happens?
• An impulse is sent to the spinal cord and acted
on immediately. This impulse uses a pathway
know as a reflex arc which does not involve the
brain directly.
• A message is sent to the brain shortly
afterwards.
• Actions that need to be carried out automatically
and without thinking are very fast because they
involve only a few neurons.
There are five main senses
that correspond to specific
organs.
What are they?
Five Senses and the nervous system
• There are five main senses that correspond to
specific organs.
The sense of
• Touch (skin)
• Sound (ear)
• Light (eye)
• Chemicals in air (nose)
• Chemicals in food ( tongue)
The tongue
Receptors
• Information is collected from cells
called receptors.
• There are many different types of
receptors that respond to different
types of stimuli.
Mechanoreceptors
Sensitive to touch
e.
.
i
s
e
ur
Text smooth
h,
ro u g
Receptors
Photoreceptors
Sensitive to light
n)
Nig
u
ht
(S
t
h
g
i
l
y
Da
Thermoreceptors
Chemoreceptor
Sensitive to chemicals
Sensitive to temperature
Food
Tast
e
Su
m
me
Win
r (H
ea
t)
old
C
(
r
te
)