Download The Nervous System

The Nervous
System
C-Scope 2010
Unit 5, Lesson 2
The Nervous System
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Fun Facts:
The brain is composed of 85%
water.
 The brain uses 25% of the
body’s oxygen supply.
 The average brain has a mass
of 1.6 kg (about 3 pounds)
 Your brain could power a 10
watt light bulb!
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The Nervous System
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The nervous system is the
body’s control center and
communication network.
The nervous system allows us
to think, evaluate, and
remember information.
The most important part of the
nervous system is the neuron
or nerve cell.
Neurons
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This is the working unit (cell) of the
nervous system.
The neuron is made up of a cell body and
branches called dendrites and axons.
Dendrites receive messages and send
them to the body cells.
Axons carry messages away from the
neuron.
A message received is called an impulse.
Neuron
Dendrite
Nucleus
Axon
Direction of
Impulse
The Nervous System
 There
are three functions of the
nervous system:
Sensory Input
 Integration
 Motor Input
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Sensory Input
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When the eyes see something or hands
touch a warm surface, the neurons send a
message straight to the brain.
This action of getting information from the
surrounding environment is called sensory
input because things are being sent to the
brain by way of the senses.
Sensory Neurons
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Receives sensory input and sends an
impulse TO the spinal cord or brain.
The input comes from structures in the
skin called receptors (your nerves).
Integration
The interpretation, or
translation, of things that
have been felt, tasted,
and touched with the
sensory neurons into
responses that the body
recognizes.
 This process is
accomplished by the brain.
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Interneurons
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Through out the brain and spinal
cord
Relays impulses from sensory
neurons to motor neurons.
“The Middle Man”
There are more of these than
sensory and motor neurons.
Motor Output
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Once your brain has
interpreted all that
has been sent by
using any of the
senses, then your
brain sends a
message through
neurons to muscle or
other cells, which
work to perform the
response.
Nervous System
Nervous System
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The human nervous system is divided into
two parts:
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The Central Nervous System
The Peripheral Nervous System
Central Nervous System
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It is the body’s most rapid means of
maintaining homeostasis.
Regulates vital bodily functions by sensing
changes within the body and from the
environment.
Interprets the changes and makes
adjustments in a split-second by delivering
electrochemical impulses. These impulses
result in muscular contractions and/or
glandular secretions.
Central Nervous System
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The central nervous system
consists of the brain and the
spinal cord and association
neurons.
These neurons make up most
of the spinal cord and change
the input impulse to output
impulses and cause the body
to respond.
Peripheral Nervous System
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Peripheral nervous system– There are
two types of neurons in this system.
Sensory Neurons
 Motor Neurons
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More on Sensory Neurons
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Send information to
the central nervous
system from internal
organs, from the
environment, and
motor neurons;
which send impulses
to the voluntary and
involuntary muscles.
More on Motor Neurons
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Divided into the somatic nervous system and the
autonomic nervous system
Somatic – controls the skeletal muscles and
external sensory organs such as the skin
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This system is said to be voluntary because the
responses can be controlled consciously. An exception
is the reflex reactions of skeletal muscle. These are
involuntary reactions to external stimuli.
Autonomic Nervous System controls involuntary
muscles such as smooth and cardiac muscle.
This system is also called the involuntary
nervous system.