Transcript Nervous System

Nervous System
Nervous System
Structures
 Brain, spinal cord, peripheral nerves
 Function
 Recognizes and coordinates the
body’s response to changes in its
internal and external environment
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Neurons
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Basic unit of structure & function in the nervous system
The messages carried by the nervous system are
electrical signals called impulses.
Neurons – cells that transmit the signals (impulses)
3 Types of Neurons:
1. Sensory neurons – carry impulses from the sense
organs to the spinal cord & brain
2. Motor neurons – carry impulses from the brain &
spinal cord to muscles & glands
3. Interneurons – connect sensory & motor neurons
and carry impulses between them
Diagram of Neuron
CELL BODY
AXON
NUCLEUS
DENDRITES
MYELIN
SHEATH
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2 Divisions of the Nervous System
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1. Central Nervous System
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Consists of the brain and spinal cord
Relays messages, processes information and
analyzes information
2. Peripheral Nervous System
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Consists of all the nerves and cells not part of the
brain and spinal cord (includes ganglia)
Transmits impulses from sense organs to the central
nervous system
Transmits impulses from the central nervous system
to muscles or glands
Reaction to a Stimulus
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The peripheral nervous system transmits impulses
from sense organs to the central nervous system
and back to muscles or glands.
Reflex – a quick, automatic (involuntary) response to
a stimulus; allows your body to respond to danger
immediately without spending time thinking about a
response
Example: When you step on a tack, sensory
receptors in your foot stimulate a sensory neuron,
which relays the signal to an interneuron within the
spinal cord. The signal is then sent to a motor
neuron, which in turn stimulates a muscle in your leg
to lift your leg.