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Functions of the Nervous System
1. Sensory input – gathering information
 monitor changes both inside and outside
the body
 Changes = stimuli
2. Integration -- process and interpret
sensory input
3. Motor output
 A response to integrated stimuli
 The response activates muscles or glands
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Components of the Nervous System
Central Nervous System
brain, spinal cord
Peripheral NS
Sensory - input
afferent (approach)
Motor - output
efferent (exit)
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Figure 11.1
Organization of the Nervous System
 Motor (efferent) division
 Somatic nervous system =
voluntary
 Autonomic nervous system
= involuntary
Figure 7.2
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Communication Cells of System
 Neurons: specialized cells for
communication
 Types:
 sensory
 interneurons
 motor neurons
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Neuron Anatomy
 Cell body
 Dendrites
 Axon
 Neuroglial cells:
support and protect
neurons
 Schwann cells
 Wrap around
axon
Figure 7.4a–b
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Myelin Sheath on Neuron
 Myelin sheath: Schwann cells in PNS
 Functions:
 Saves the neuron energy
 Speeds up the transmission of impulses
 Helps damaged or severed axons
regenerate
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Nervous Tissue: Support Cells
 Oligodendrocytes - protection in CNS
 Produce myelin sheath around nerve fibers in
the central nervous system
Figure 7.3d
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Maintenance of the Resting Membrane
Potential
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Figure 11.4
Neurons Initiate Action Potentials
 Na-K pump: maintains resting potential
 Graded potential: alters resting potential,
either to depolarize or hyperpolarize
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Resting Membrane Potential, Graded
Potentials, and an Action Potential
Graded potentials can reach threshold and trigger an action potential
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Figure 11.5
Action Potential
 Depolarization: sodium moves into the axon
 Repolarization: potassium moves out of the
axon
 Re-establishment of the resting potential: the
normal activity of the sodium-potassium
pump
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Action Potentials
 All or none:
 individual neuron thresholds; when this
threshold is reached, it fires
 Self-propagating:
 electrical current reaches threshold
throughout axon during spread of the
action potential
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Summary of Synaptic Transmission
How does ON/OFF signal
create a graded potential?
1. AP moves Ca ++ into bulb
2. Ca++ causes vesicles to
release neurotransmitter
3. Neurotransmitter binds to
receptor, causing Na+
channel to open.
4. Na+ flows into cell, creating
graded potential
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Figure 11.7
Neurotransmitters
 Excitatory - depolarize postsynaptic cell.
 Acetylcholine - muscle cells
 Norepinephrine - areas of brain and spinal cord ANS
 Glutamate - major excitatory transmitter in brain
 Inhibitory - hyperpolarize postsynaptic cell.
 Serotonin - areas of brain, spinal cord. involved in sleep,
appetite, moods
 Dopamine - brain, parts of PNS. Involved in emotions.
 Endorphins - brain, spinal cord. Natural opiates that
inhibit pain
 Somatostatin - brain, pancreas. Inhibits pancreatic
release of growth hormone.
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Peripheral Nervous System
 Nerves and ganglia outside the central
nervous system
 Nerve = bundle of neuron fibers
 Nerves: carry signals to and from CNS
 Cranial nerves: connect directly to brain
 Spinal nerves: connect to spinal cord
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The Reflex Arc
Reflex arc – direct route from a sensory neuron, to an
interneuron, to an effector
 Crossed extensor reflex, stretch reflex, flexor
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Organization of the Nervous System
 Motor (efferent) division
 Somatic nervous system =
voluntary
 Autonomic nervous system
= involuntary
Figure 7.2
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Differences between Somatic and Autonomic NS
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Sympathetic – “fight-orflight”
Autonomic Nervous
System
“E” division =
exercise, excitement,
emergency, and
embarrassment

Parasympathetic –
housekeeping activites
Conserves energy
necessary body functions
“D” division - digestion,
defecation, and diuresis
Figure 7.25
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Central Nervous System
 CNS protection
 Bone: skull and vertebrae
 Meninges: dura mater,
arachnoid, and pia mater
 Cerebrospinal fluid: carries
nutrients and waste for
CNS Blood-brain barrier:
 Spinal cord: relays
information through nerve
tracts in white matter
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Spinal Cord
 Connects PNS to
brain; reflex center
 Extends from the
brain to lumbar region
 31 pairs of nerves
Figure 7.18
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Spinal Cord Anatomy
 Exterior white mater – conduction tracts
 Internal gray matter - mostly cell bodies
Figure 7.19
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Brain: Major Divisions
 Hindbrain: coordinates basic, automatic, vital functions
 Medulla oblongata: controls automatic functions of
internal organs
 Cerebellum: coordinates basic movements
 Pons: aids flow of information
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Hindbrain, Midbrain
 Midbrain: coordinates muscles related to
vision & hearing
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Brain: Processes and Acts on Information
 Forebrain: receives and integrates information
concerning emotions and conscious thought
 Hypothalamus: helps regulate homeostasis
 Thalamus: receiving, processing, and
transfer center
 Limbic system: neuronal pathways
involved in emotions and memory
 Cerebrum/cerebral cortex: higher
functions
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Specialized Areas of the Cerebrum
Figure 7.13c
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Sensory and Motor Areas of the Cerebral
Cortex
Figure 7.14
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Sleep
 Sleep center: reticular activating system
(RAS)
 Stages: based on electroencephalograms
(EEGs)
 Stage 1-4
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Limbic System: Emotions of Fear, Anger,
Sorrow, Love
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Figure 11.18
Psychoactive drugs
 Affect consciousness, emotions, behavior
 Cross blood-brain barrier
 Affect action of neurotransmitters
 Ex. Cocaine blocks reuptake of dopamine
Psychological dependence
Tolerance
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Disorders of the Nervous System
 Trauma: concussion, stroke, spinal cord
injuries
 Infections: encephalitis, meningitis, rabies
 Neural and synaptic transmission:
epilepsy
Parkinson’s disease
Alzheimer’s disease
 Brain tumors - growth of glial cells
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Alzheimer’s Disease
 Progressive, degenerative brain disease
 Structural changes in the brain include
abnormal protein deposits and twisted fibers
within neurons
Parkinson’s - lack of dopamine, such
that certain neurons are overactive,
cause jerky muscle contractions
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Development Aspects of the Nervous
System
 The nervous system is formed during the first
month of embryonic development
 Any maternal infection can have extremely
harmful effects
 The hypothalamus is one of the last areas of
the brain to develop
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Where Do You Stand Among Your Peers?
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Table 11.3
Cerebrum
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