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Nervous System

True/False: Motor control

True/FalseAnswer
Upper motor neuron lesions produce weakness. True, this is in a pyramidal distribution (weakness of the arm extensors and leg flexors so the patient has flexed arms and extended legs).
Upper motor neuron lesions produce fasciculations. False, fasciculations are not seen with upper motor neuron lesions.
Upper motor neuron lesions produce increased spinal reflexes. True, there is reduced supraspinal inhibition of the reflexes.
Upper motor neuron lesions produce spasticity. True, the muscles become hypertonic because of an increase in motor neuron activity.
Upper motor neuron lesions produce wasting. False, wasting is not a feature of upper motor neuron lesions.
Lower motor neuron lesions produce weakness. True, these produce weakness in the muscles supplied by that nerve.
Lower motor neuron lesions produce fasciculations. True, this represents partial re-innervation by the remaining nerves.
Lower motor neuron lesions produce increased spinal reflexes. False, the spinal arc is disrupted therefore cannot be activated.
Lower motor neuron lesions produce spasticity. False, there is reduced output from the motor neuron so the muscle loses its natural tone.
Lower motor neuron lesions produce wasting. True, spontaneous nerve firing produces trophic changes in muscle fibres. If they are lesioned, the muscles lose this input and atrophy.
Upper motor neurons innervate skeletal muscle. False, these neurons originate from the primary motor cortex and synapse with the lower motor neurons in the spinal cord.
Lower motor neurons originate from the dorsal horn of the spinal cord. False, lower motor neurons originate from the ventral horn.
Alpha motor neurons produce forceful contractions of skeletal muscle. True, they synapse with muscle fibres at the neuromuscular junction.
Alpha motor neurons contain motor and sensory fibres. True
Gamma motor neurons cause the contraction of intrafusal fibres. True
Large innervation ratios give fine control over movement. False, if one neuron innervates many muscle fibres then coarse control of movement is produced.
Smaller motor neurons are recruited before larger ones. True, true for both reflex and voluntary movements.
Muscle fibre type is determined by the firing properties of the nerve innervating it. True
Fast fibres contain many mitochondria, high levels of glycolytic enzymes and high levels of myosin ATPase. True, these features are determined by the firing patterns of the fast fibre nerve.
Spontaneous muscle activity can occur in a motor neuron disease. True, fasciculations and fibrillations are a feature of several degenerative motor neuron diseases.
Created by: sallyelphick