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Nervous System
Chp 11
Components of the Nervous System
Figure 11.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Principle Parts of Nervous System
Central Nervous System (CNS)
• Components: brain and spinal cord
• Functions: receives, processes, and transfers
information
Peripheral Nervous System (PNS)
• Components: nerves outside CNS
• Sensory neurons: carry information toward the
CNS
• Motor neurons: carry information away from
CNS
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Types of Neurons in the Nervous
System
Sensory
Motor
Interneurons of CNS
Figure 11.2
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Communication Cells of System
Neurons: nerve cells, roles are in communication
• Cell adaptations: cell body, axon, dendrites
• Types: sensory, interneurons, motor neurons
• Neuroglial cells: cells specialized for support
and protection of neurons
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Myelinated Neuron- fast transmission of
signal
Figure 11.3
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Myelin Sheath on Neuron
Myelin sheath: found on Schwann cells in PNS
A) Functions:
• Saves the neuron energy
• Speeds up the transmission of impulses
• Helps damaged or severed axons regenerate
Myelin in CNS: formed by oligodendrocytes
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How Neurons Work: at Rest they are
said to be polarized
Figure 11.4
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Neurons Initiate Action Potentials
Sodium-Potassium pump:
1. maintains Resting Potential
•
more Na+ outside axon of neuron than inside
•
Slight negative charge inside neuron due to
negatively charged proteins in cell membrane
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Action Potential
• Wave Depolarization: sodium moves into axon
• Repolarization: potassium diffuses out of axon
• Reestablishment of the resting potential: the
normal activity of the sodium-potassium pump
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
All or None and Self-Propagating
Action Potentials
• All or none concept: once a wave of
depolarization started it can’t be stopped
• Self-propagating: electrical current reaches
threshold throughout axon during spread of the
action potential--wave moves down axon
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Summary of Synaptic Transmission
Figure 11.7
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Transfer of Information from Neuron
to Target
• Synaptic transmission
• Release of neurotransmitter
• Effects of neurotransmitter:
• Excitatory: depolarize postsynaptic cell
• Inhibitory: hyperpolarize postsynaptic cell
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Peripheral Nervous System:
Relay Information between Tissues
and CNS
Nerves: carry signals to and from CNS
• Cranial nerves: connect directly to brain
• Spinal nerves: connect to spinal cord
Sensory neurons: provide information to CNS
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Motor Neuron Divisions of PNS
• Somatic division
• Functions:
• Voluntary: conscious control of skeletal muscles
• Involuntary: spinal reflexes; flexor (withdrawal),
crossed extensor, stretch
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Motor Neuron Divisions of PNS
• Autonomic division: controls automatic body
functions
• Sympathetic division
• Origin: thoracic or lumbar regions
• Function: releases norepinephrine for fight or
flight reaction; opposes parasympathetic division
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Motor Neuron Divisions of PNS
Parasympathetic division
• Origin: brain or sacral region
• Function: releases acetylcholine to relax the
body; opposes sympathetic division
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Central Nervous System
CNS protection
• Bone: skull and vertebrae
• Meninges
• Cerebrospinal fluid
• Blood-brain barrier: carries nutrients and waste for
CNS
Spinal cord: relays information through nerve tracts in
white matter
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Brain: 5 Major Divisions
1. Hindbrain: coordinates basic, automatic, vital
functions
2. Medulla oblongata: controls automatic functions of
internal organs
3. Cerebellum: coordinates basic movements
4. Pons: aids flow of information
5. Midbrain: coordinates muscles related to vision &
hearing
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Brain: Processes & Acts on
Information
1. Forebrain: receives and integrates information
concerning emotions and conscious thought
2. Hypothalamus: helps regulate homeostasis
3. Thalamus: receiving, processing, and transfer center
4. Limbic system: neuronal pathways involved in
emotions and memory
5. Cerebrum/cerebral cortex: higher functions
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Limbic System: Emotions of Fear,
Anger, Sorrow, Love
Figure 11.18
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Sleep
Sleep center:
• Stages: based on electroencephalograms (EEGs)
• Stage 1: transitional, random small waves on EEG
• Stage 2: skeletal muscles relax, little eye or body
movement, EEG shows sleep spindles
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Sleep
• Stage 3: heart and respiration slower, EEG shows
slow wave sleep
• Stage 4: difficult to awaken, heart and respiration
slowest, body temperature decreased
• REM (rapid eye movement) Sleep: dreaming, EEG
same as awake
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Memory: Storing and Retrieving
Information
• Short term: working memory, information from
previous few hours
• Long term: information from previous days to
years
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Disorders of the Nervous System
• Trauma: concussion, spinal cord injuries
• Infections: encephalitis, meningitis, rabies
• Neural and synaptic transmission: epilepsy,
Parkinson’s disease, Alzheimer’s disease
• Brain tumors
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.