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46 Cards in this Set
- Front
- Back
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Circuits that elicit movement without volition
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Pattern Movements
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Types of Pattern Movements
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Reflexes
Static (postural) or dynamic (righting) postural control complex motor activities (walking) using central pattern generators |
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Explain how volitional activities occur
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Initially intentional, use feedback and guidance until it becomes a learned motor behavior (programmed)
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What are the 3 Requirements of Motor Control?
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Selectively and quickly activate specific muscles or groups
Regulate strength of contraction and timing of activation Coordinate both postural and volitional movement simultaneously with control |
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Definition of central pattern generator
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Neural circuit, when activated produces a particular pattern of motor output which does NOT require afferent feedback
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How does muscle increase power?
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progressive recruitment of motor units (small first, then large)
shifting from twitch to tetany (tension development greater during tetany) |
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3 Inputs to motor neurons
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Supraspinal Inputs
Intersegmental Inputs Segmental Inputs |
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Supraspinal Inputs..
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Descend on discrete tracts from brainstem and telencephalon
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Intersegmental Inputs...
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Sensory input from periphery that enter spinal cord, send collaterals into ventral horn to form reflex connections.
Act as central pattern generators for walking/chewing |
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Segmental Inputs...
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Sensory fibers from periphery that enter spinal cord via dorsal roots within same segment of cord
FORM CIRCUITRY FOR SIMPLE SOMATIC REFLEXES |
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Large motor units work with muscles that...
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Don't require fine motor control
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T or F: properties of fast, intermediate, and slow twitch fibers depend on the motorneuron innervating them.
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TRUE
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What do gamma motor neurons innervate?
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muscle spindle
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What is so great about fast twitch muscle fibers?
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Most tension and most power with unfused tetanic contraction
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What is so great about slow twitch muscle fibers?
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Best endurance, least fatiguability
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In general, large motor units are innervated by...
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Large motorneurons
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In general, small motor units are innervated by...
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Small motorneurons
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Define DIVERGENCE
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Branching of afferent fibers inside the spinal cord so it can innervated multiple neuronal targets
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Define CONVERGENCE
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Different afferent fibers innervate common neuronal targets
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When stimulus increases, the number of responding receptors...
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Increases!
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What is the liminal fringe of mn? (discharge zone)
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These mn's are excited to threshold and produce AP's
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What is the subliminal fringe of mn?
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These mn's receive SUBthreshold synaptic excitation
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How do alpha motor neurons go from subliminal fringe to liminal fringe?
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If multiple afferent fibers are recruited simultaneously
(# of afferent fibers stimulated determines # of alpha mn in discharge zone |
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What is the receptor for the myotatic reflex?
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Muscle spindle
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Myotatic reflex is a ______ pathway
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monosynaptic
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What is type Ia fibers role in response to passive stretch?
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produce an increase in AP firing frequency
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Type Ia afferents monitors both muscle _____and rate of change in ______
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length, length
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What do Ia Afferents DO in the myotatic reflex?
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-Liminal excitation of muscle doing the action
-Subliminal excitation of mn that innervate synergists -Inhibition of antagonist motorneuron=reciprocal innervation |
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Where do Ia afferents project to?
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Through column of clarke (DSCT)- unconscious proprioception AND
DCML to sensory-motor areas: conscious proprioception |
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What is Ib's afferents roles in the GTO Reflex in the spinal cord??
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Inhibits alpha mn innervating the active muscle
Inhibits mn innervating synnergist muscles Excites alpha mn innervating ANTAGONIST muscles |
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How is the GTO reflex activated?
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By tension development during muscle contraction
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Myotatic Reflex is known as the _____ reflex
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Stretch
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GTO reflex is known as the _____ reflex
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Inverse Myotatic Reflex
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Where do Ib afferents ascend to?
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-Column of Clarke- DSCT (unconscious proprioception AND
DCML- conscious proprioception |
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What is the role of the Renshaw cell?
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Produces recurrent inhibition, inhibits EVERYTHING
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What is the function of the Withdrawl Reflex?
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Remove limb from harmful stimuli; protection
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What are the withdrawl reflex receptors?
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Cutaneus Nociceptors from C fibers
Receptors sense chemical factors derived from tissue damage and extreme temperatures |
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What is the needed reflex that occurs with the withdrawl reflex?
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Crossed extension reflex
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Define crossed extension reflex
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Activation helps maintain balance when withdrawl reflex happens
Secondary circuits (segmental and intersegmental circuits) cross to contralateral side of spinal cord. |
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What is the function of the fusimotor system?
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To get afferent info about muscle length to CNS motor centers continuously
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What happens when the muscle stretches and the muscle spindle stretches?
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the helical endings of the Ia fibers separate which increases the frequency of Ia discharge
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T or F: Only alpha motor neurons are stimulated during reflexes
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True
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Role of dynamic gamma motor neuron
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Influence response to phasic (quick!) stretches
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Role of static gamma motor neuron
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Influence response to static, steady stretches
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What would a silent period be?
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if an Alpha motor neuron was stimulated with contraction, but gamma mn was not
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How can locomotor circuits be activated?
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In spinal cord
Or by descending info from brainstem nuclei and cerebral cortex |
