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22 Cards in this Set
- Front
- Back
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TRUE or FALSE
Complex movements involve motor programs generated at various levels of the CNS. |
TRUE
CNS generates motor programs Spinal cord has more executive control of motor neurons |
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These neurons originate from the brain stem (cranial nerves) and the ventral horn of the spinal cord (spinal nerves). They are the final common pathway for motor commands.
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Lower Motor Neurons
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These neurons originate from the cerebral cortex, reticular formation and vestibular nuclei.
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Upper Motor Neurons
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Name the 2 higher order structures of the motor system that work with the association cortex to create motor programs that generate meaningful activity among upper motor neurons
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BASAL GANGLIA
CEREBELLUM they work out the details for the cortex. |
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Define motor unit.
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A motor unit is an alpha motor neuron and the muscle fibers it innervates.
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Name the motor unit:
Mixed fast twitch Fatique resistant Moderate force |
Intermediate unit
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Name the motor unit:
Slow twitch Red fibers Fatique resistant Less force |
Small unit
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Name the motor unit:
Fast twitch White fibers More force Fatigue easily |
Large unit
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TRUE or FALSE
Smaller motor neurons are activated first because they have higher AP thresholds. |
FALSE
Smaller motor neurons are activated first because they have LOWER AP thresholds. - fewer ion channels - less ionic current from postsynaptic potentials leaks out - more ionic current builds up on voltage sensitive Na+ channels to initiate AP's. |
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In the muscle spindles, which afferents detect changes in length and velocity?
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Ia (primary) and II (secondary)
The Ia afferents are the biggest, fastest and most myelinated |
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Love the stretch (myotatic) reflex. Can you tell me what it is? How would you test the integrity of this reflex circuit?
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The stretch (myotatic) reflex occurs when an increase in muscle length triggers homeostatic negative feedback to maintain limb in constant position.
Knee jerk reflex tests the integrity of reflex circuit |
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Gamma motor neurons regulate spindle sensitivity during movement. What will happen when the gamma neuron tautens the spindle?
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Tautening of spindle by the gamma neurons INCREASES sensitivity of Ia and II afferent neurons to muscle stretch.
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What is the "upshot" of alpha-gamma co-activation?
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Sensitivity to stretch maintained throughout range of motion.
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As speed and difficulty of a movement increase, sensitivity of spindles (increases or decreases)?
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INCREASES
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Are Golgi tendon organs innervated by gamma motor neurons?
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NO. They are innervated by Ib afferents.
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Name the reflex...
Ib afferents innervate interneurons that inhibit alpha motor neurons to the same muscle. |
INVERSE MYOTATIC REFLEX
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Which muscles are contracted during reciprocal innervation in the Inverse Myotatic Reflex?
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ANTAGONIST MUSCLES are contracted
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The propriospinal neurons interconnect spinal levels for complex reflexes. Which (medial or lateral) fit the following description?
- axons extend over whole spinal cord. - regulate proximal/axial muscles and full body posture |
MEDIAL propriospinal neurons
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The propriospinal neurons interconnect spinal levels for complex reflexes. Which (medial or lateral) fit the following description?
- extend fewer spinal segments - regulate distal muscles for independent control of fine movements |
LATERAL propriospinal neurons
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Are the flexor withdrawl and crossed extension reflexes examples of superficial or deep reflexes?
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SUPERFICIAL
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SUPERFICIAL or DEEP...
Stretch- and tension- induced reflexes use simpler Ia, II, Ib afferent pathways to elicit or inhibit muscle contraction. |
DEEP (tendon) reflexes
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SUPERFICIAL or DEEP...
Cutaneous, pain-induced limb withdrawl reflexes use complex excitatory, inhibitory and propriospinal pathways. |
SUPERFICIAL reflexes
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