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Chapter 7:
The Nervous System
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Introduction
• Nervous system: major regulatory system of body
• Along with endocrine system, directs and coordinates
functions of every other system
• In manual therapy, important to understand impact of
touch, pressure, and movement on nervous system
• Many therapists need to avoid irritating major nerves to
them with deep tissue manipulation
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Functional Organization
• Sensory functions: ability to detect broad spectrum of
stimuli
• Integrative functions: capacity to process sensory
information and direct body responses
• Motor functions: commands from brain via nerves to
activate muscles, glands, and organs
• 2 major divisions:
– Central nervous system (CNS)
– Peripheral nervous system (PNS)
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Functional Organization (cont’d)
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Nervous Tissue: Neurons
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Nervous Tissue: Neurons (cont’d)
• Nervous tissue: composed of impulse-conducting
neurons, held together and protected by glial cells
• 3 structural elements of neurons:
– Dendrites receive stimulus
– Cell body houses nucleus and organelles
– Axon carries nerve impulses away from cell body
• Impulse conduction: dendrite to cell body to axon
• See Figure 7-3
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Nervous Tissue: Neurons (cont’d)
• 3 structural types of neurons:
– Multipolar neurons
– Bipolar neurons
– Unipolar neurons
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Nervous Tissue: Neurons (cont’d)
• 3 functional types of neurons:
– Sensory neurons in PNS
– Motor neurons in PNS
– Interneurons (associative neurons) in CNS
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Nervous Tissue: Neuroglia
• Support and protect neurons
• CNS glial cells: astrocytes, oligodendrocytes, microglia,
ependymal cells
• PNS glial cells: Schwann cells, satellite cells
• See Figure 7-4
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Pathology Alert: Multiple Sclerosis
• Degenerative condition
– Myelin destroyed and replaced by scar tissue
– Neuronal impulse conduction impaired
– Believed an autoimmune disorder
– Alternating acute inflammation and remission
• Manual therapies contraindicated in active cycles
– Can be helpful during remission
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Nerves
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Cranial Nerves
• 12 pairs of cranial nerves originating from brain
• Deliver sensory information from sense organs,
abdominal viscera, and areas of neck, chest, and face
• Some provide motor control for certain muscles
• Designated by Roman numerals in descending order
• Each named according to function, location, or
appearance
• See Figure 7-6 and Table 7-1
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Pathology Alert: Bell Palsy
• Paralysis of facial muscles
• Caused by inflammation or damage to cranial nerve VII
• Most cases caused by viral infection
• Signs and symptoms: sudden onset of weakness,
drooping muscles on one side, and other symptoms
• Manual therapy indicated to help maintain circulation and
tissue flexibility
– Avoid deep or vigorous manipulation of tissue
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Spinal Nerves
• Named and numbered according to location along spinal
column (see Figure 7-10)
• 31 pairs of spinal nerves:
– 8 cervical
– 12 thoracic
– 5 lumbar
– 5 sacral
– 1 coccygeal
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Spinal Nerves (cont’d)
• Converge into common networks that innervate body
regions
• 4 major plexuses:
– Cervical: innervates neck, head, face
– Brachial: innervates upper extremities
– Lumbar: innervates lumbar region of back and
gluteals region
– Sacral: innervates hips and lower extremities
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Impulse Conduction: Action Potentials
• Nerve impulses: electrochemical signals carried by
neurons
• Neurotransmitters build chemical bridge between one
neuron and another
• With threshold stimulus, neuron generates impulse
(action potential)
– Depolarization
– Refractory period
– Repolarization
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Impulse Conduction:
Synaptic Transmission
• Synapse: junction where electrical signal passes from
one cell to another
• Neurotransmitters cross synaptic cleft
– Chemicals such as acetylcholine, norepinephrine,
dopamine, serotonin, and endorphins
– Excitatory or inhibitory effect
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Impulse Conduction: Neuronal Pathways
• Neuronal pathways: one-way routes from one region to
the next
• Afferent or efferent
• Reflex arcs: simple neuronal pathways for reflexes (see
Figure 7-14)
• Neuronal pools and circuits: complex networks of
sensory, associative, and motor neurons
– Convergent: voluntary and involuntary control
– Divergent: systemic effects
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Pathology Alert: Neural CompressionTension Syndromes
• Conditions such as sciatica, thoracic outlet syndrome
(TOS), and carpal tunnel syndrome (CTS)
• Tight fascia and/or muscle spasms cause peripheral
nerves to be compressed
• Signs and symptoms: numbness or tingling, muscle
weakness, decreased coordination, chronic aching, pain
• Manual therapy can help relieve pain and dysfunction
– Rule out more severe neurologic causes
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Peripheral Nervous System
• Sensory components detect and carry sensory
information to CNS
• With sustained stimulus, receptors undergo adaptation
• 2 categories of sensory receptors:
– General receptors
– Special receptors
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Types of Sensory Receptors
• Photoreceptors: sensitive to light
• Chemoreceptors: sensitive to chemical changes
• Thermoreceptors: stimulated by temperature changes
• Nociceptors: pain receptors
• Mechanoreceptors: stimulated by pressure and
movement
• Proprioceptors: specialized mechanoreceptors in skeletal
muscle and joints
• See Table 7-2
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Sensory Receptors: Proprioceptors
• Important to manual therapists
• Major types:
– Joint receptors: pressure, tension, movement
– Muscle spindles: stretch reflex
– Golgi tendon organs: inverse stretch reflex
• Combine to create kinesthetic sense
• See Figure 7-19
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Central Nervous System:
Meninges and Cerebrospinal Fluid
• Meninges: collective name for brain/spine membranes
– Dura mater: outer layer
– Arachnoid mater: middle layer
– Pia mater: inner layer
• Cerebrospinal fluid: circulates through meninges, spinal
cord, and brain ventricles
• See Figures 7-20 and 7-21
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Pathology Alert: Meningitis
• Inflammation of meninges caused by bacterial, viral,
fungal, or parasitic infection or other causes
• Signs and symptoms: high fever, severe headache, rash,
stiff neck, and more
• Manual therapists should rule out meningitis in clients
with similar symptoms
– Otherwise refer to physician
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Central Nervous System: Spinal Cord
• Located within vertebral foramen of spinal column
• Relays information between brain and body
• Serves as body’s primary reflex center
• Posterior (dorsal) portion houses sensory/ascending
tracts
• Anterior (ventral) portion contains motor/descending
tracts
• White and gray matter (see Figure 7-22)
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Central Nervous System: Brain
• 4 major regions of brain
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Central Nervous System: Brain (cont’d)
• Brain stem: junction point, relays information
• Diencephalon: thalamus, hypothalamus
• Cerebrum: cognition, consciousness, motor activity
• Cerebellum: voluntary muscle activity, muscle tone,
posture, equilibrium
• Limbic system: memories, emotions, unconscious
survival responses
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Pathology Alert: Headaches
• 3 general categories of headaches:
– Stress or tension headaches
– Cluster headaches
– Migraine headaches
• Headache can be warning sign of serious pathology
• Manual therapy often provides effective treatment
• Note cautions and contraindications
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Peripheral Nervous System:
Somatic Division
• Sensory neurons carry information from receptors
• Motor neurons for voluntary movement
• One motor neuron between spinal cord and effector
• Only one type of effector: skeletal muscle
• See Figure 7-29
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Peripheral Nervous System:
Autonomic Division
• 2 motor neurons and ganglion at synapse
• Autonomic effectors: glands, organs, and smooth
muscles
• 2 branches of autonomic motor division:
– Sympathetic: body-wide response to stress (“fightor-flight”)
– Parasympathetic: maintains and returns body to
homeostasis after stress (“rest and digest”)
• Most visceral effectors have dual innervation
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The Nervous System at Work
• Each component functions within integrated whole
• Afferent sensory neurons monitor internal and external
environments
• Spinal cord and brain receive and organize data and
formulate responses
• Efferent neurons deliver motor commands to body
effectors
• Repetition strengthens neuronal connections
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Theories of Pain
• Pain: warning sign to withdraw from damaging stimulus
and then to guard injured tissue
• Gate control theory: signal, message, perception stages
• Melzack-Casey conceptual model: pain result of
interactions within nervous system:
– Sensory (sensation)
– Cognitive (thinking)
– Affective (emotional/feeling)
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Types of Pain
• 2 broad categories based on underlying cause
– Somatogenic pain (arising from the body)
• Includes superficial, deep somatic, and visceral
pain
• Referred pain: visceral pain felt in body areas
separate from affected organ
– Psychogenic pain (arising solely from mind)
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Common Areas of Referred Pain
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Pain Management
• Drug therapy widely used
• Other effective methods: surgery, acupuncture,
hydrotherapy, biofeedback, hypnosis, art, music,
meditation, visualization, prayer, deep breathing,
laughter
• Assess pain: acute or chronic
• Manual therapy has proven effective treatment
– Different techniques at different stages of pain
experience
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Aging and the Nervous System
• Slight decay of myelin sheaths and slowing of impulse
conduction
• Decrease in brain mass and synaptic connections
• Gradual declines in thought processes, memory, balance,
and coordinated movement
• Rate of changes influenced by lifestyle choices
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Pathology Alert: Dementia
• Caused by degeneration of neural tissue in frontal and
temporal lobes
• Characterized by progressive loss of intellectual ability
• May be accompanied by personality changes
• Signs and symptoms associated with pathologies such as
Alzheimer disease
• Not normal age-related changes
• Manual therapy neither indicated nor contraindicated
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