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40 Cards in this Set
- Front
- Back
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What is the most basic circuit in the neuromotor system?
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reflex
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Define reflex.
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a rapid, automatic response to a stimuli
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What is a reflex arc?
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-the "wiring" of a particular reflex
-the simplest level of sensorimotor integration |
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True or false: A reflex's reponse is unpredictable
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False, predictable (stereotyped)
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What is the most basic circuit in the neuromotor system?
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reflex
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What is the response latency of a reflex?
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-the time it takes for the stimulus to elicit the response
-typically short (msecs) -relatively invariable (same from trial to trial) |
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True or false: In some reflexes, the subject cannot prevent the stimulus from causing the reflex response.
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True
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What is the purpose of postural reflexes? AND what are the primary receptors for this?
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-essential for maintaing normal posture, or to recover stability when unexpectedly destabilized
-primary receptors: muscle (spindles), joint, and vestibular receptors |
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What do autonomic reflexes respond to?
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automatic responses to changes in blood pressure, blood gas levels, contents of the stomach, etc.
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What are the components of a reflex arc?
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-sensory receptor (sensitive to specific stimulus. depolarizes when stimulated)
-afferent neuron -interneuron (not every reflex employs an interneuron) -efferent neuron (motor or secretory) -effector organ (muscle or gland) |
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What is proprioception? AND what do these include?
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-transducers (sensory receptors) in muscles and tendons that information about the relative configuration of a body segment
-muscle spindles (intrafusal muscle fiber), golgi tendon organs, joint receptors |
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What is a muscle spindle? AND where is it found?
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-(aka stretch or extensor receptor) a proprioceptor in skeletal muscle
-found within the belly of muscles and run in parallel with the main muscle fibers (extrafusal) |
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What does the muscle spindle do?
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-senses muscle length and changes in length (sensor for stretch or extensor reflex. part of gamma reflex loop)
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What are extrafusal muscle fibers?
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-main body of muscle
-served by axons of alpha motor neurons |
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What are intrafusal muscle fibers?
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-muscle spindle
-specialized organs that are served by 3 axons |
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What are the 3 axons that serve intrafusal muscle fibers?
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-sensory (Ia and II)
-motor (gamma) |
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What is the primary function of the muscle spindle?
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primary function is excitatory to extrafusal muscle
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When do intrafusal receptors fire?
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when muscle lengthens
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When the muscle lengthens, what messages does Ia send to the spinal cord from the muscle spindle?
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-activates agnoist muscle fibers
-inhibits antagonist muscle fibers |
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What are the two types of fibers in the intrafusal muscle fiber?
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-nuclear bag
-nuclear chain fibers |
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Describe Ia of intrafusal muscle.
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-afferent fiber
-fastest sensory nerve in body -very sensitive to dynamic phase of stretch (responds to change in length) -considered velocity-sensitive due to large increase in firing rate when stretch is detected |
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Describe II of intrafusal muscle fiber.
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-afferent fiber
-smaller diameter neurons -considered more length-sensitive -fires as long as muscle is stretched |
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Describe the gamma motor neuron of intrafusal muscle fiber.
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-efferent fiber
-anterior gray of spinal cord -causes intrafusal muscle fiber to contract -function is to modify the sensitivity of the fibers afferent ending to stretch |
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What are the two ways in which muscle spindle can be stretched?
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-passive activation (e.g., extend a limb)
-active activation (thru gamma) --both methods activate the nuclear bag and nuclear chain fibers |
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Describe passive activation.
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-way in which muscle spindle can be stretched
-stretch of extrafusal muscle stretches spindles and its sensory endings |
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Describe active activation.
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-way in which muscle spindle can be stretched
-gamma activity causes contraction of the intrafusal fibers on either side of the central region -this stretches the central sensory region |
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True or false: Contraction of extrafusal fiber makes intrafusal fiber contract as well and results in increased sensitivity of spindle.
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False, makes intrafusal fiber flaccid and decreases sensitivity of spindle
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Gamma motor stimulation causes local intrafusal contraction which:
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-stiffens the polar regions
-causes the center region to stretch -causes muscle spindle activation |
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Describe gamma initiated movement.
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-gamma activated ends of intrafusal fibers causing spindle to activate
-contraction of both extrafusal and intrafusal fibers |
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The sensitivity to both length and velocity can be altered by the CNS via the __________ _________ _________, which controls sensitivity of the muscle spindle.
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gamma motor system
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In what way are golgi tendon organs opposite of muscle spindles?
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-fire when muscle contracts
-respond to changes in muscle tension |
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What are golgi tendon organs?
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a proprioceptive receptor located at the junction of the muscle and tendon
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True or false: Golgi tendon organs respond to changes in muscle length.
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False, respond to changes in muscle tension
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How do GTOs encode the degree of muscle tension?
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by rate of firing
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What is the primary function of GTOs?
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primary function is inhibitor
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True or false: GTOs have a greater threshold than muscle spindles.
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True
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Are GTOs responsive to rate of force change?
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No
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Afferent nerves synapse on interneurons in spinal cord and inhibit the agonist muscle. What NT is released to do this?
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release of glycine onto alpha-motoneuron (IPSP)
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What do disynaptic reflexes of the stretch reflex do?
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inhibits antagonist
-has an inhibitory neuron that inhibits the antagonist muscle |
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What do monosynaptic reflexes of the stretch reflex do?
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excites own muscle
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