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Brunnstrom’s Clinical Kinesiology Sixth Edition
Introduction
 Human motion results from the relationship
between anatomy and physiology.
 This chapter’s goal is to provide a basic
understanding of neural physiology as it
relates to kinesiology.
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Introduction
 Types of nerves
 Afferent (sensory)—incoming sensory
information
 Efferent (motor)—outgoing response to muscles
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Nervous System Anatomy
 Nerve fibers
 Motor and sensory nerves wrapped in myelin
 Myelin = phospholipid that speeds conduction
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Nervous System Anatomy
 Nerve fibers—motor classification in PNS
 Alpha motor neurons
 Innervate extrafusal muscle fibers
 Gamma motor neurons
 Innervate intrafusal muscle fibers
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Nervous System Anatomy
 Nerve fibers—classification
 Upper motor neurons
 Located within CNS
 Carry impulses from brain to spinal cord
 Lower motor neurons
 Carry impulses from spinal cord to muscle fibers
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscular System
 Muscle and muscle fiber structure
 Muscle is surrounded by epimysium.
 Perimysium subdivides muscle into sections.
 Each “section” is composed of muscle fibers.
 Muscle fibers = muscle cells.
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscular System
 Muscle and muscle fiber structure
 Muscle fibers are composed of myofibers.
 Myofibers are covered by the sarcolemma.
 Myofibers are composed of units—sarcomeres.
 Sarcomeres lie between to Z-lines.
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscular System
 Muscle and muscle fiber structure
 Myofibers or filaments are composed of:
 Actin (thin)—provides binding site for myosin
 Myosin (thick)—two crossbridges at each end
 Thick and thin filaments give “striated” appearance.
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscular System
 Muscle contraction and relaxation
 Sarcomeres decrease in length from 2.5 µm at rest
to 1.5 µm when contracted.
 Sarcomere may increase in length to 3.0 µm when
stretched.
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscular System
 Muscle contraction and relaxation
 Sliding filament model
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscular System
 Muscle relaxation
 Calcium concentration drops and relaxation occurs.
 Calcium is actively “pumped” back to SR.
 Troponin returns to its original shape.
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscular System
 Muscle fiber types
 Type I—postural muscles
 Dark in appearance (myoglobin and mitochondria)
 Small diameter; fatigue slowly
 Slow twitch, tonic, or slow oxidative
 Fibers depend on aerobic metabolism
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscular System
 Muscle fiber types
 Type II (subdivided into IIa and IIb)—rapid brief motion
 White
 Larger diameter; fatigue quickly
 Fast-twitch, phasic, fast oxidative
 Associated with anaerobic metabolism
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscular System
 The motor unit
 Alpha motor nerve and all the muscle fibers it
innervates
 Various sizes of motor units (5–1000 fibers)
 “All or none”
 Muscle fibers from respective motor units spread
throughout muscle
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Muscular System
 Gradation of contraction strength
 Size principle
 Recruitment principle
 Input/coding rate principle
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Joint, Tendon, and Muscle Receptors
 Joint receptors—sensory
 Found in joint capsule and ligaments
 Mechanically activated with motion
 Adapt after motion ceases
 Provide information related to joint position and rate of
movement
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Joint, Tendon, and Muscle Receptors
 Golgi tendon organs (GTOs)
 Located near muscle-tendon junction
 10–15 muscle fibers connected in series with GTOs
 Provide information related to muscle tension
 Send afferent information via BI axons
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Joint, Tendon, and Muscle Receptors
 Muscle spindle
 Embedded parallel within muscle
 Consists of intrafusal fibers (nuclear chain and bag)
 Provides information related to muscle length
 Transmits afferent information via IA and II axons
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Joint, Tendon, and Muscle Receptors
 Muscle spindle—stretch reflex
 Abrupt stretch activates spindle and ultimately
extrafusal muscle fibers of same muscle.
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Joint, Tendon, and Muscle Receptors
 Muscle spindle—motor function
 Gamma (γ) motor neurons innervate intrafusal
fibers
 Responsible for maintaining muscle tone
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Joint, Tendon, and Muscle Receptors
 Kinesthesia and proprioception
 Kinesthesia—dynamic joint motion
 Position sense—awareness of static position
 Proprioception—use of sensory input to detect
joint position and movement
Copyright © 2012 F.A. Davis Company
Brunnstrom’s Clinical Kinesiology Sixth Edition
Joint, Tendon, and Muscle Receptors
 Kinesthesia and proprioception
 Postural equilibrium
 Visual
 Vestibular
 Somatosensory
Copyright © 2012 F.A. Davis Company