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34 Cards in this Set
- Front
- Back
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How are limb movements produced?
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By the coordinated contraction of groups of muscles working together.
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What happens as synergists contract?
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Antagonists relax.
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2 types of muscles:
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-Extensors
-Flexors |
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What is the Stretch Reflex? (clinical name?)
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A monosynaptic excitatory reflex
-Deep tendon reflex |
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What is the common example of a stretch reflex?
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The patellar reflex
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What is the STIMULUS in the stretch reflex? Receptor?
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-STRETCH of muscles which increases its length
-Receptor is Muscle spindles |
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What is the AFFERENT in the stretch reflex?
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Ia afferents from the muscle spindle.
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Where does the Ia afferent project? (3 places)
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-To almost all a-motor neurons that control the muscle where the Ia afferent signal started
-To synergistic muscles -To inhibitory interneurons that inhibit motor neurons to antagonist muscles |
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What do we call that muscle where it all started?
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Homonymous muscle
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What is the Efferent in the stretch reflex?
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The alpha motor neurons that excite the homonymous and synergist muscles to cause contraction.
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What is this Reciprocal innervation?
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Simultaneous excitation of a group of synergistic muscles and inhibition of their antagonists.
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Why do we need the monosynaptic reflex?
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To maintain muscle tone for posture, to hold still, to smooth out movements.
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What is the function of the Flexion and Crossed-Extension reflex?
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Withdrawal from a painful stimulus.
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Is the Flexor reflex monosynaptic?
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No it is polysynaptic
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What is an example of the flexor reflex?
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A nail in the knee makes you draw back and shift weight to your other leg.
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What is the receptor that is stimulated in the flexor reflex?
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Nociceptors
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What happens with the afferent information from nociception?
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It goes to interneurons in the spinal cord that do 2 things:
-excite ipsilateral flexor muscle -inhibit extensor muscle |
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What is achieved by exciting the ipsilateral flexor and inhbiting the extensor muscles?
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You withdraw
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What do contralateral interneurons do?
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-Excite contralateral extensor
-Inhibit contralateral flexor |
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What is achieved by exciting the ipsilateral extensor and inhbiting the flexor muscles?
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You have a leg to stand on!
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What's pretty remarkable about the Flexor Reflex?
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It remains even if you completely transect the spinal cord.
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So what does a Muscle spindle activate?
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Alpha motor neurons
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What does a Golgi tendon organ reflex in contrast do?
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Inhibits alpha motor neurons via inhibitory interneurons.
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What is the stimulus for the Golgi tendon organ reflex?
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Tension on the Golgi tendon organ receptor
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What is the afferent in the Golgi tendon organ reflex?
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Ib afferent inhibitory interneurons.
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Do these Ib afferent inhibitory interneurons stand alone?
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NO! they also get convergent info from muscle spindle afferents, low-threshold cutaneous afferents, joint afferents, and UMN pathways.
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What does activation of inhibitory Ib interneurons do ultimately?
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Inhibits the homonymous muscle - the original one - that was stretched.
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What is this inhibition called?
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Autogenic inhibition.
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What is the FUNCTION of the Golgi tendon reflex?
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To prevent overly forceful movements, and precisely control fine movements.
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What do Ia afferents inhibit during the stretch reflex?
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Antagonist muscles
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What do Ib afferents inhibit in the Golgi tendon reflex?
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Agonist muscles
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What are Renshaw cells?
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Interneurons
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What do Renshaw cells do?
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Inhibit the same motor neurons that excite Renshaws in the 1st place, to give negative feedback.
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Why do we have Renshaw cells?
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To regulate the firing pattern of motor neurons, and make sure the a-motor neurons in our motor pools TAKE TURNS.
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