The%20Nervous%20System

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The Nervous System

• Functions, Divisions, Neurons

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Functions

• Sensory Input
• Integration
• Motor functions

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Divisions of Nervous System

• Central nervous system (CNS)
• Peripheral nervous system (PNS)

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Central Nervous System

• Brain
• Spinal cord

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Peripheral Nervous System

• Consists of nerves and ganglia
• Further divided
• Afferent division (sensory)
• Efferent division (motor)

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Efferent Division of PNS

• Further divided
• Somatic nervous system (voluntary)
• Autonomic nervous system (involuntary)

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Autonomic nervous system

• Further divided
• Sympathetic
• Parasympathetic

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Nerve Tissue

• Neuron
• Neuroglia (glial cell)

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Neuron
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Types of Neurons

• Afferent (sensory)
• Efferent (motor)
• Inter-neurons (association neurons)

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Neuroglia

• Do not conduct nerve impulses
• Serve as protection and nourishment for neurons

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Nerve Impulses

• Resting membrane
• Stimulation of neuron

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Resting membrane

• Non-conducting neuron
• Lots of Na outside neuron
• Lots of K inside neuron, but even more negative
  ions found inside
• Membrane is polarized

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Stimulation of Neuron

• A stimulus changes the membrane to allow passive
  movement of ions.
• Stimulus must be strong enough to make membrane
  highly permeable (threshold).

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Action Potential Nerve Impulse

• Depolarization
• Reverse polarization
• Repolarization

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Action Potential Animation

• Nerve Impulse

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Conduction of Impulse

• Action potential must continue the length of a
  neuron
• Neurotransmitters carry impulse across the
  synaptic cleft to new neuron

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Continuous vs Saltatory Action Potentials
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Reflex Arcs

• Functional unit of nervous system
• Allows for rapid response to stimulus
• Components
• Receptor
• Sensory neuron
• Integration center
• Motor neuron
• Effector