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27 Cards in this Set
- Front
- Back
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What is an agonist of the biceps? Antagonist?
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Agonist: Brachialis
Antagonist: Triceps (both allow for flexion/extension and joint stabilization via co-contraction) |
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Fast Muscle vs Slow Muscle
-Color -Speed of Tension Rise -Speed of Tension Decay -Fatigability -Energy Source -Mitchondria Count -Vascularization |
Fast:
White Fast rise in tension Fast decay in tension Rapid fatigue Glycolysis (anaerobic) Sparse mitochondria Poor capillary supply Slow Muscle: Red Slow rise in tension Slow decay in tension Slow fatigue Oxidative metabolism Plentiful mitochondria Rich capillary supply |
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Soleus: muscle type
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strong, slow
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Gastrocnimeus: muscle type
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Fast, fatigue-resistant (intermediate--some mitoch, some ATPase)
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Extraocular muscles: muscle type
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Fast, fatigable
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Where are alpha-MN cell bodies located?
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Ventral horn of SC
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Motor Unit vs Motor Neuron Pool
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Motor Unit: 1 alpha-motor neuron + all mm fibers it innervates
Motor Neuron Pool: all alpha-MN's that innervate the same muscle |
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What is the relationship of motor unit size and muscle control?
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The smaller the motor unit size (smaller ratio of alpha-MN's to muscle fibers) the more fine tuned control you'll have
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What determines a muscle fiber's slow/fast properties?
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The alpha-MN innervating it (determines twitch props, number of mitcoh, etc)
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How do motor neurons dictate muscle force?
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1) Firing rate of active MN's (1AP-->twitch; 2AP-->Temporal Summation; Multiple AP-->Tetany)
2) Recruit more active MN's in pool |
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What are fibrillations? When are they visible?
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Fibrillations are muscle contractions that are only visible on EMG; they're abrnoraml and usually result of denervation
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What are fasciulations? When are they visible?
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Visible abnormal contractions
Can be seen in those with Polio |
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What types of neurons converge onto alpha-motor neurons in the spine?
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1) Sensory inputs (Ia, II axons) from muscle spindles
2) Same/nearby segments via spinal IN's 3) Propriospinal input 4) Supraspinal control from BS and brain |
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What are the afferent innervations of muscle?
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Muscle spindles (stretch receptors): sense length of m (Ia axons)
Golgi Tendon organs: sense force generated by m (Ib axons); sensitive to length |
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Extrafusal vs Intrafusal fibers
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Extrafusal: innervated by alpha-MN; generate power
Intrafusal: innerv by gamma-MNs (not for contraction; for determining stretch) |
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Function of golgi tendon organs.
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Measure tension of muscle via
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List two ways stretch receptors can be activated.
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1) Contract muscle
2) Contract intrafusal fibers of stretch receptor (no contraction necessary) |
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What types of neurons fire in response to muscle stretching?
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Gamma motor neurons
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Describe alpha-gamma co-activation.
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When muscles contract (via alpha MN's), Stretch receptors slacken, goes offline.
BUT co-contraction of stretch receptors via gamma neurons keep stretch receptors taught and online Thus muscles are always sensitive to stretch |
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Provide an example of a monosynaptic and polysynaptic reflex.
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Monosynaptic: stretch reflex (myotatic, knee-jerk, tendon-jerk)
Polysynaptic: withdrawal reflex |
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Stretch Reflex Circuit acts directly on ______________ muscle
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homonymous (muscle that's being stretched)
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Function of Jendrassik’s maneuver?
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Increases briskness of reflex jerk (demonstrates that reflex circuits can be modulated)
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How does the Hoffman reflex work?
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Shock afferent and efferent muscle nerves, should expect two jerks:
Immediate jerk (M wave) is due to direct activation of efferent fiber Delated jerk (H wave) due to activation of Ia afferent fiber (tests reflex) |
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Explain automatic load adjustment.
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Ex: pour beer into glass, increased Fg, increased stretch
Thus: Increase activity (contraction) of agonist (Ia fibers) Decreased activity (relaxation) of antagonists (IIb fibers) |
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Explain the use of servo control when muscle contraction doesn't meet expectations.
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If m contraction doesn't meet expectations, muscle spindles provide corrective feedback
Causes alpha-gamma MN's to coactivate, fire together, and contract muscle. |
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Treatment for rigidity. Side effect?
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Alternating dorsal risotomy to decrease descending gamma activity
Would lose reflex arc |
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Describe the events of the withdrawal reflex of the legs.
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Nociceptive stimulus
-->IM Horn -->Ventral Horn -->Activate flexors and inhibit extensors on affected limb -->Inhibit flexors and activate extensors on opposite limb -->Inhibit extensors |
