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22 Cards in this Set
- Front
- Back
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What is a bulb-shaped receptor found at muscle-tendon junctions?
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Golgi tendon organ (GTO)
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What is:
Narro encapsulated structure Approx. 1 mm in length diameter of about 0.1 mm Contains finely braided collagen fibers Connected in series with extrafusal, skeletal muscle fibers |
GTO
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What type of nerve innervates a GTO?
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A single Ib axon
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True/False: Golgi sensitivity can't be altered, like the muscle spindle.
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False
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True/False: The single Ib axoncontains sensory or afferent innervation only, no motor innervation.
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True
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What stimulates the GTO?
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Msucle stretch or voluntary muscle contraction.
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How do muscle spindles and the GTO differ interms of sensor types?
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The tendon organ functions as a sensor for muscle tension (not length or changes in length as with the spindle)
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Regulation of muscle tension: This circuity produces a ________ feedback system tha regulates the amount of tnetions produced by the msucle (GTO).
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Negative
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What effect does the GTO have on its agonist when its muscle has a rapid increase in motion?
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Excitatory synapse on Ib inhibitory interneuron increases its firing rate.
Inhibitory synapse of Ib interneuron on alpha motor neuron of the agonist muscle decreases the alpha motor neuron's firing rate and decreases muscle tension. |
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What basically does the GTO do complete with its interneuron set?
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It keeps the tension applied level and prevents the myotatic reflex.
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How does the GTO equalize muscle fiber tension?
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Fibers that exert excess tension are inhibited by the reflex whereas fibers that exert too little tension are more excited by the absence of reflex inhibiton allowing the repsad of muscle load over all the fibers.
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What causes spasticity?
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Abnoramlly brisk monosynatpic stretch reflexes.
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What causes the two parts of the clasp-knife reflex?
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Hyperactivity of teh stretch reflex loop is the reason for the increased resistance to stretch. The physiological basis for the inhibition that causes the sudden collapse of the stretch reflex and loss of muscle tone is thought to involve the inhibition of motor neurons by thea ctivation of the GTOs.
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Define: The neuronal circuit that causes reciprocal inhibition.
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Reciprocal innervation
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Define: Reciprocal relations often exist bewteen the muscles on the two sides of teh spinal cord, as illustrated by the flexor and extensor muscle reflexes.
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Reciprocal inhbition
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Define: Initiated by cutaneous receptors (noxious stimuli) and produces a general flexion of the entire limb its pathway must be spread over several spinal segments.
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Flexor Withdrawal Reflex
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True/False: The response to cutaneous afferent fibers from Nociceptor flexor withdrawal response involves at least 4 muscle groups.
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True (Two sets of extensors, and two sets of flexors)
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What is the purpose of the crossed extensor reflex?
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To activate the contralateral antigravity (extensor) muscles to support the entire body weight when the ipsilateral lower limb is withdrawn from the sharp object.
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What is activated at the same time as the crossed extensor reflex?
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The ALSTT due to Laminae I, IV and V are activated at the same time and they relay information to the thalamus then cerebral cortex to decode the location and nature of the initial stimulus
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What are the two clinical signs for decerebrate rigidity?
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Hyperactivity of extensors of all four limbs
Hyperactive deep tendon reflexes |
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What causes decerebrate rigidity?
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Produced by unopposed inputs to alpha and gamma motor neurons of the spinal cord from the vestibulospinal and pontine reticulospinal tracts.
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What is the effect of the transection of the brain stem at intercollicular midbrain levle?
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Lateral vestibular nucleus and pontine reticular formation are released from inhibition (by cerebral cortex input) thereby allowing facilitation of extensor mortor neurons of the arms and legs.
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