Assistant Professor Department of Neurobiology and Anatomy University of Texas Health Science Center at Houston Houston TX MichaelSBeauchamputhtmcedu Motor Control Lecture 1 Muscles what are they good for ID: 374902
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Michael S. Beauchamp, Ph.D.Assistant ProfessorDepartment of Neurobiology and AnatomyUniversity of Texas Health Science Center at HoustonHouston, TX
Michael.S.Beauchamp@uth.tmc.edu
Motor Control: Lecture 1Slide2Slide3
Muscles, what are they good for?Slide4
Muscle modelSlide5
Body as machineSlide6
Cognition
Action
ENVIRONMENT
Senses
MOTOR CONTROLSlide7Slide8
Necessary Components of Proper Motor Control Volition Coordination of signals to many muscle groups Proprioception Postural adjustments Sensory feedback Compensation for body and muscles Unconscious processing AdaptabilitySlide9
Motor control requires sensory input The case of Ian Waterman Lost all somatosensory and proprioceptive input Initially unable to make any coordinated movement After years of practice he trained himself to make movement under visual guidance Requires total concentration to move and even maintain posture Collapses to ground when lights unexpectedly go outJonathan Cole, Pride and a Daily Marathon, MIT Press, 1995.Slide10
The Man Who Lost His Body 1998 BBC documentaryIan Waterman, age 19 Lost all somatosensory and proprioceptive input Initially unable to make any coordinated movement After years of practice he trained himself to make movement under visual guidance Requires total concentration to move and even maintain posture Collapses to ground when lights unexpectedly go outSlide11
Hierarchical Organization and Functional Segregationof Central Motor StructuresLevel 4: Association CortexLevel 2: Brain Stem (Red Nucleus, Reticular Formation, Vestibular Nuclei, Tectum, Pontine Nuclei, Inferior Olive)Level 1: Spinal CordLevel 3: Motor Cortex
Side Loop 1:
Basal Ganglia
(Caudate Nucleus,
Putamen
,
Globus
Pallidus
,
Substantia
Nigra
,
Subthalamic
Nucleus)
Thalamus
(VA,VL,CM)
Side Loop 2: CerebellumSlide12Slide13
Alpha motor neuronSlide14
Alpha Motor Neurons Innervate skeletal muscle and cause muscle contractions Isometric contraction (equal size) Isotonic contraction (equal force) Release acetylcholine at the neuromuscular junctionSlide15
Motor Neuron Pool (Motor Nucleus) The group of motor neurons that innervate an individual muscleSlide16
From J. Nolte (2002) The Human Brain, 5th EditionMotor Neuron PoolSlide17
Motor Neuron Pool (Motor Nucleus)The group of motor neurons that innervate an individual muscleMotor UnitAn individual motor neuron and all the muscle fibers that it innervatesSlide18
Motor Neuron Pool vs. Motor UnitSlide19
Motor Neuron Pool (Motor Nucleus)The group of motor neurons that innervate an individual muscleMotor UnitAn individual motor neuron and all the muscle fibers that it innervatesInnervation RatioThe number of muscle fibers innervated by a single motor neuronSlide20
Control of muscle forceRate Code: Increases in rate of action potentials of motor neuron cause increases in muscle forceSize Principle: With increasing strength of input, motor neurons are recruited from smallest to largestSlide21
Rate CodetetanusSlide22
Control of muscle forceRate Code: Increases in rate of action potentials of motor neuron cause increases in muscle forceSize Principle: With increasing strength of input, motor neurons are recruited from smallest to largestSlide23
Size PrincipleV = IRFrom G. E. Loeb & C. Ghez (2000), in Principles of Neural Science, 4th Edition (Kandel, Schwartz, & Jessel, Eds.)Slide24
Size PrincipleSmall motor neurons innervate slow-twitch muscle fibersMedium motor neurons innervate fast-twitch, fatigue-resistant muscle fibersLarge motor neurons innervate fast-twitch, fatigable muscle fibersSlide25
ProprioceptionSpecialized receptors provide informationabout muscle: length velocity (change in length) load (force)Slide26
Receptors Involved in Proprioception Muscle Spindles Golgi Tendon OrganSlide27
Muscle modelSlide28
Intrafusal fibersExtrafusal fibersSlide29
Typical muscle spindle = 1 dynamic nuclear bag fiber 1 static nuclear bag fiber ~ 5 nuclear chain fibersMuscle Spindles are made of intrafusal muscle fibersSlide30
Sensory Fibers Involved in ProprioceptionMuscle Spindles Group Ia (primary): velocity and length Group II (secondary): lengthSlide31
Type Ia afferents signal velocity and length, Type II afferents signal length onlySlide32
Gamma motor neurons maintain sensitivity of muscle spindle Slide33
Receptors Involved in Proprioception Muscle Spindles Golgi Tendon OrgansSlide34Slide35
Golgi Tendon OrganSlide36
Sensory Fibers Involved in ProprioceptionMuscle Spindles Group Ia (primary): velocity and length Group II (secondary): lengthGolgi Tendon Organs Group Ib: Tension or forceSlide37
Next Lecture: Spinal ReflexesMyotatic reflex Muscle spindles (Ia) + alpha motor neuronsAutogenic inhibition Golgi tendon organs (Ib) - alpha motor neurons