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The Nervous System
Unit 7
> Communication via electrochemical signals
> Rapid, immediate responses
I. Functions of the Nervous System
> Sensory Input: Monitors body's internal and external enviornments
> Integration: Processes & interprets sensory input
> Motor Output: Coordinates voluntary & involuntary responses of many other organ systems
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II. Divisions of the Nervous SystemA. Structural Divisions
> CNS: Central Nervous System» Brain & Spinal Cord
> PNS: Peripheral Nervous System» Cranial (12 pairs) & Spinal (31 pairs) nerves
II. Divisions cont.B. Functional Divisions of PNS
> Sensory/Afferent: send info to CNS– Somatic Sensory Fibers:
« Impulses from skin, skeletal muscles
– Autonomic Sensory Fibers: « Impulses from viscera
> Motor/Efferent: send info from CNS– Somatic Nervous System:
« Connects CNS to skeletal muscles» Voluntary
– Autonomic Nervous System:« Connects CNS to viscera, smooth & cardiac muscle,
and certain glands» Involuntary
« 2 subdivisions:
» Sympathetic: "fight-or-flight" system• Prepares body for physical activity
» Parasympathetic: "resting & digesting" system• Promotes normal digestion, elimination &
conserving body energy
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III. Cells of the Nervous System
1. Neurons– Receive stimuli and
conduct action potentials
2. Neuroglia (non-neural)– Protects neurons
and perform other functions
A. Two Types
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III. Cells of the Nervous System cont.
B. Neuron Structure
III. Cells of the Nervous System cont.
C. Structural Variation in Neurons
> Multipolar– Many fibers (dendrites) to cell body, only 1 axon
carrying impulse away
> Unipolar– Single fiber from cell body, dendrite connects to
peripheral and axon to the brain or spinal cord
> Bipolar– 2 fibers, axon & dendrite (eyes, nose, ears)
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III. Cells of the Nervous System cont.
D. Functional Variation in Neurons> Sensory Neurons (afferent neurons)
– Carry AP's from peripheral receptors to CNS
> Interneurons (association neurons)– Lie within CNS, distribute sensory info &
coordinate response
> Motor Neurons (efferent neurons)– Carry AP's from CNS to effectors
