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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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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) Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Functional Organization (cont’d) Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Nervous Tissue: Neurons Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Nervous Tissue: Neurons (cont’d) • 3 structural types of neurons: – Multipolar neurons – Bipolar neurons – Unipolar neurons Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Nervous Tissue: Neurons (cont’d) • 3 functional types of neurons: – Sensory neurons in PNS – Motor neurons in PNS – Interneurons (associative neurons) in CNS Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Nerves Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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) Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Central Nervous System: Brain • 4 major regions of brain Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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) Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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) Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Common Areas of Referred Pain Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins