Chapter 10
Nervous System
• Organs
– Brain, Spinal Cord (CNS), and Nerves
(PNS)
• Function
– Integration of all parts – organs - tissues cells
– Allows control of parts to enable
unification: communication - control 1
integration - homeostasis - survival
Chapter 10
Nervous System
Cell Types of
Neural Tissue
• Neurons
• Neuroglial cells
2
Divisions of the
Nervous System
• Central Nervous System
• brain
• spinal cord
• Peripheral Nervous System
• nerves
• cranial nerves
• spinal nerves
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Neuron Structure
Soma
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Neurons
Structure:
• Cell body - Soma
• Axon - sends messages away from soma
• Dendrite - receives messages from axon to soma.
Types of Neurons:
• Afferent (sensory) - to spinal cord or brain
• Efferent (motor) - away from spinal cord or brain
• Interneurons (synapse between 1 and 2) - from
afferent to efferent (from sensory to motor)
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Classification of Neurons –
Functional Differences
Sensory Neurons
• afferent
• carry impulse to CNS
Interneurons
• link neurons
• Found in CNS
Motor Neurons
•carry impulses
away from CNS
• carry impulses to
effectors
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See hand out
Divisions Nervous System
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Central Nervous System
Brain and Spinal Cord
1. Peripheral Nervous system
Spinal nerves and Cranial nerves
Somatic Nervous System
(Skeletal muscle)
Sensory and Motor Neurons
Outside environment
2. Autonomic nervous system
(internal environment – Smooth,
Cardiac muscle, Glands)
Parasympathetic Division
Sympathetic Division
Prepares body for emergency
‘Fight or Flight’
Salivation, Urination, Digestion,
etc. Active under ordinary, restful conditions.
Counterbalances effect of Sympathetic
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division
Divisions of Peripheral
Nervous System
Sensory Division
• picks up sensory information and delivers it to the CNS
Motor Division
• carries information to muscles and glands
Divisions of the Motor Division
• Somatic – carries information to skeletal muscle
• Autonomic – carries information to smooth muscle,
cardiac muscle, and glands
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Functions of Nervous System
Sensory Function
• sensory receptors gather
information
• information is carried to the
CNS
Integrative Function
• sensory information used to
create
• sensations
• memory
• thoughts
• decisions
Motor Function
• decisions are acted
upon
• impulses are
carried to effectors
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Myelination of Axons
White Matter
• contains myelinated
axons
Gray Matter
• contains
unmyelinated
structures
• cell bodies, dendrites
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Myelination of Axons
• Unmyelinated fibers conduct impulses
slower.
• Myelinated fibers conduct impulses faster
– Nodes of Ranvier (short region of exposed axon
between Schwann cells on neurons)
– The more myelin the faster the impulse
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Multiple Sclerosis
•
•
•
•
Most common disease of the nervous system
Loss of myelin sheath
Hard plaque lesions replace myelin
Nerve conduction is impaired and weakened, loss
of coordination, visual impairment and speech
disturbances.
• Most common in women between age 20-40
• No known Cure
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Reflex Arc
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Reflex Arc
• Conduction of an impulse to and from the
brain and spinal cord.
– Types:
• Two neuron arc - simplest form
– Consists of afferent and efferent neurons
• Three neuron arc - must common
– Consists of afferent, interneurons, and
efferent
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Two Neuron Arc
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Three Neuron Arc
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The Synapse
Nerve impulses pass
from neuron to
neuron at synapses
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Synaptic Transmission
Neurotransmitters are
released when impulse
reaches synaptic knob =
Acetylcholine or AcH
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Brain and Cord Coverings
• Bone is outer cover
– Brain - Cranium
– Spinal cord - Vertebrae
• Meninges - inner cover
– Dura Mater - outer, white fibrous tissue
– Arachnoid Membrane - cobwebby, middle
– Pia Mater - adheres to brain, transparent
• Meningitis is inflammation of meninges 21
Meninges
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Meninges
White matter
Grey matter
Spinal Cord
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Spinal Cord
• 17 - 18 in. in length
• Two bulges
– Cervical region - sends nerves to upper limbs
– Lumbar region - sends nerves to lower limbs
• Grey Matter
– Inner core, looks like an H in cross section, made of
interneurons and motor neuron somas
• White Matter
– Surrounds gray matter, consists of nerve fibers in
bundles (axons and dendrites)
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Spinal Nerves
• 31 pairs - they are numbered according to where
they are located.
• Emerge from cord through foramen of vertebrae.
• Each nerve level attaches to a body section
– Dermatone - patches of skin that correspond to each
nerve.
• Herpes Zoster - (causes chicken pox and shingles)
lies dormant at the ends of nerves.
– Causes eruptions of red swollen patches which are26 very
painful
Spinal nerves
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Dermatomes
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Spinal
Spinal nerves
Nerves
• Broken neck at 3, 4, or 5 vertebrae
= damage to phrenic nerve
– This nerve controls the diaphragm
– Without artificial respiration, patient
will die.
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Brain
• Size
– 3 pounds
– Larger in men than women
– Larger in young than old
– Full size by age 18
– Contains 100 billion neurons
http://www.cbsnews.com/2100-500165_162-6890474.html
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Brain
31
oblongata
Brain stem
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Divisions of the Brain
• Brainstem
– Midbrain
– Pons
– Medulla oblongata
• Cerebellum
• Diencephalon
• Cerebrum
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Divisions of the Brainstem
• Medulla Oblongata
–
–
–
–
Most vital part of the brain
Injury or disease proves fatal
Lowest part of brainstem
Function
• Vital centers - cardiac, dilates blood vessels (drops
and increases blood pressure), respiratory
• Nonvital centers - vomiting, coughing, sneezing,
hiccupping, swallowing.
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Divisions of the Brainstem
• Pons
–Above the medulla oblongata
–Function
• Helps regulate respiration gases,
chewing, saliva secretion, hearing
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Divisions of the Brainstem
• Midbrain
– Located above the pons and below
the cerebrum
– Function
• Reflex center: eye movements, hearing
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Cerebellum
• Second largest part of the brain
• Function
– Maintains equilibrium
– Helps control posture
– Smoothes movements instead of being jerky, trembling
or uncoordinated
• Diseases (hemorrhage, tumor)
– Cause ataxia - muscle incoordination
• Diagnose with a finger to nose test
– Tremors
– Disturbances of walk and balance
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Diencephalon
• Located between the midbrain and
cerebrum
• Consists of the hypothalamus and thalamus
– Hypothalamus: regulator of autonomic
activities; mind-body link (tears); maintains
water balance, waking state, appetite, and body
temperature
– Thalamus: recognizes sensations of pain,
temp., and touch; relays sensory impulses to
cerebrum; associates sensory impulses to
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emotions, arousal or alerting mechanism
Cerebrum
Gyrus/ fold
Cerebellum
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Cerebrum
• Largest part of the brain
• Consists of two halves and 5 lobes
– Right hemisphere
• Spatial abilities - see whole picture
– Left hemisphere
• Analytical skills
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Cerebrum
• Five Lobes
– Frontal - forehead
– Parietal - posterior top
– Temporal - temples
– Occipital - posterior base
– Insula - hidden from view
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Cerebrum
• Function
– Sensory: visual and auditory
– Motor ability: movement of muscles
– Integrative ability:
• Ability to receive sensory impulses and send motor
impulses.
• Consciousness: state of awareness
• Memory: major mental activity
• Use of language: ability to speak and write words
and understand words
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• Emotions
Cerebrum
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http://www.pbs.org/wgbh/nova/assets/swf/1/mapping-thebrain/mapping-the-brain.html
http://www.pbs.org/wgbh/nova/body/brain-trauma.html
http://www.pbs.org/wgbh/nova/body/psychology-magic.html
http://www.pbs.org/wgbh/nova/body/mirror-neurons.html
http://www.pbs.org/wgbh/nova/body/how-memoryworks.html
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