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Nervous System
True/False: Motor control
True/False | Answer |
---|---|
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. |