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Neuro3 Motor System

Neuro3 Motor System II

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Review the Alpha motor neuron topography in the Ventral Horn (Laterally) Hand, forearm, arm, shoulder, trunk (medially). Flexors Posteriorly, Extensors anteriorly. **Alpha & gamma motor neurons for inidividual muscles will extend down certain spinal levels in a column (biceps: C5-6).
Which nerve type innervates intra Vs extrafussal muscle fibers? 1.Aplha: Extrafussal. 2.Gamma: Intrafussal.
What is occuring around a muscle spindle during and following stretch? 1.Muscle stretch. 2.Group 1a afferents relay stretch from spindle to spinal cord. 3.Synapse on Nucleus of Clark, Aplha & Gamma motor neuron. 4.Alpha Motor neuron will cause muscle contraction, Gamma will adjust spindle so they maintain sensitivity.
6 main characteristics of Flaccid Paralysis (Lower Motor Neuron Syndrome) 1.Weakness. 2.Dec or absent muscle tone (hypotonia). 3.Dec or absent tendon reflexes (hyporeflexia). 4.fasciculations. 5.Atrophy. 6.Dec or absent resistance to passive ROM
What is responsible for generating the Velocity-dependent resistance to passive ROM seen with an Upper Motor Neuron Syndrome? No longer have control over gamma motor neurons, thus they do not adjust: 1.Muscle is stretched. 2.Spindles do not adjust (relax). 3.Will cause a reflex contraction in that muscle percieved as resistance to the passively induced ROM.
List the 4 Descending Brainstem systems. Which ones fascilitate flexion? extension? 1.Rubrospinal System. 2.Medullary Reticulospinal System. 3.Pontine Reticulospinal System. 4.Lateral Vestibulospinal System. **1&2 favor flexion, inh extension. **3&4 favor extension, inh flexion.
Where does the Rubrospinal System originate? what muscles does it influence? RED NUCLEUS in midbrain. Controls more the upper extremity muscles b/c it runs laterally down the spinal cord only in the CERVICAL spine. **Flexion Drive.
Of the two Reticulospinal Systems, which runs laterally? medially? LATERAL: Medullary (Flexion Drive in extremities). MEDIAL: Pontine (Extension Drive in axial muscles)
Where does the Lateral Vestibulospinal system originate? what muscles does it influence? 1.Originates: Lateral Vestibuli nucleus. 2.Controls: axial muscles & proximal limb muscles. 3.Drive: Extension.
What is the MAIN function of the 4 descending brainstem systems? Keep the alpha motor neurons close to their threshold of activation. **Allows cortex to have instant impact when it wants a contraction.
Which of the 4 descending brainstem systems would be more involved with standing? Sitting? STANDING: Lateral Vestibulospinal System & Pontine Reticulospinal Sytem. SITTING: Medullary Reticulospinal System.
What can modulate/regulate all 4 descending brainstem systems? Cortex, depending on the action we want to carry out.
How will a patient's posture present if they lose cortical control over the descending brainstem systems? (due to a stroke) DECORTICATE POSTURING: 1.Upper extremities: Flexed (due to strong flexion drive). 2.Lower extremities: Extended (due to stronger extension drive). **The brainstem is the only control at this point.
How will a patient's posture present if they lose cortical and midbrain control over the descending brainstem systems? (due to a stroke) DECEREBRATE POSTURING: 1.Upper extremity: Extended (lose of Rubrospinal System). 2.Lower Extremities: Extension (due to stronger extension drive)
As damage increases from Increased Intracranial pressure, what will result once the brainstem is destroyed? SPINAL SHOCK: 1.Complete release of all synaptic tone on the ventral horn neurons. 2.Hyperpolarization of the ventral horn neurons. 3.Gradual return to normal resting membrane potential in a few weeks
Created by: WeeG
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