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27 Cards in this Set

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what is the term for the alpha motor neuron and all the muscle fibers it innervates?
motor unit
the final common pathway for movement is what?
the alpha motor neuron
muscle tone is regulated by what?
CNS centers especially through the gamma motor neurons
axial muscles are innervated by alpha motor neuron nuclei from where?
the medial nucleus of the anterior horn
limb muscles are innervated by alpha motor neuron nuclei from where? At what spinal levels are these nuclei found?
the lateral nuclei of the limb muscles. C5 to T1 and L1 to S4.
the spinal accessory nucleus is found where?
in the cord at levels C1 to C6
all motor activities exhibit reciprocal innervation via interneurons found where?
the intermediate zone of the cord
what cells make recurrent inhibition of motor neurons possible? Where is recurrent inhibition found in the CNS?
the inhibitory interneurons called renshaw cells. Throughout the CNS
describe the path (including nuclei) of the gag reflex.
The pharynx or palate stimulates the glossopharyngeal which synapses on the Nu solitarius and then sends an interneuron which forks to go to both Nu ambiguuses to stimulate the vagus to contract the pharyngeal and palatal muscles.
distinguish between an indirect (consensual) reflex and direct reflex.
direct is muscle action on the same side of the body that initially sensed to do the reflex while consensual is the contralateral muscle action (ex. is with corneal and gag reflexes)
describe the path (including nuclei) of the corneal reflex.
the opthalmic nerve senses croneal touching and synapses in the spinal nu of trigem and then sends an interneuron that forks to both motor nuclei of the facial and the alpha motor neurons signal for the orbicularis oculi to contract
what are the spinal levels and names of the nerves containing the alpha motor neurons stimulated for the following reflexes: biceps, brachioradialis, triceps, patellar, achilles, and the jaw jerk?
C5, musculoskeletal
C6 radial
C7 radial
L4 femoral
S1 achilles
trigeminal
distinguish between fasciculations and fibrillations.
fasciculations are spontaneous contractions involving one or more motor units that can be seen through the skin. Fibrillations are spontaneous contractions of individual muscle fibers that can only be detected through elctromyography
lower motor lesions are located where in relationship to the deficit observed?
on the same side and same level
what disease leads to loss of voluntary muscle control by causing lesions on the lower and upper motor neurons?
amyotrophic lateral sclerosis
A tibial nerve lesion would cause what? where on the cord (if on the cord) would the lesion be located?
flaccid paralysis and atrophy of gastroc and soleus, dorsiflexion of foot, shortening of extensor tendons, arthritic changes with pain, and impaired plantar flexion. Level of the sacral enlargement
a lesion of the median nerve would cause what? If on the cord, where would this lesion be located?
flaccid paralysis and atrophy of thenar emminence, wrist and finger flexors of digits 1 to 3. wrist and finger flexion impaired as well as thumb movement. Extension of digits 1through 3 and shortening of extensor tendons. Level of cervical enlargement.
a lesion to the spinal accessory nerve would do what? where in the CNS would this lesion be located (if in CNS)?
Flaccid paralysis and atrophy of sternocleidomastoid and trapezius resulting in impaired shoulder rising and turning head to contralateral side. Level of rostral cord to caudal medulla.
what would a lesion to the hypoglossal do? Where in the CNS would this lesion be located?
flaccid paralysis and atrophy of ipsilateral tongue musculature resulting in dysarthria and deviation of tongue ipsilaterally. Found at mid medulla.
what would a lesion to the vagus nerve do? where in the CNS would this lesion be located?
flaccid paralysis of the pharynx, larynx, and palate musculature ipsilaterally resulting in dysphonia (weak voice), dysphagia (impaired swallowing), contralateral deviation of the uvula, and impaired gag reflex. Level of mid medulla
what would a lesion of the facial nerve do? where would this be located in the CNS?
flaccid paralysis and atrophy of the muscles of facial expression, stylohyoid, posterior belly of digastric, and stapedius muscles resulting in facial paralysis (Bell's palsy), facial drooping, widening of palprebal fissure, hyperacusis (increased sensitivity to loud sounds), and impaired corneal reflex. located in the caudal pons.
what pathogen can cause bell's palsy?
herpes simplex virus
what would a lesion to the trigeminal nerve do? where in the CNS would this lesion be located?
flaccid paralysis and atrophy of muscles of mastication and MATT muscles thus impaired chewing, deviation of jaw ipsilaterally, impaired jaw jerk reflex and possible impairment of corneal reflex. located at the mid pons
opthalmoplegia and diplopia are consistant with what cranial nerve lesions?
abducens, trochlear, and occulomotor
what would a lesion to the abducens nerve do? what level of the CNS would the lesion be located?
flaccid paralysis and atrophy of the lateral rectus muscle, thus internal strabismus (medial deviation of ipsilateral eye). Located in the caudal pons.
what would a lesion to the trochlear nerve do? where in the CNS would this be located?
flaccid paralysis and atrophy of superior oblique nerve thus impaired ipsilateral downward gaze and eyeball slightly extorted. Note the trochlear nerve is weird bc it exits the brainstem posteriorly and the must cross to the contralateral side to reach its nucleus. Location is on the midbrain (inferior colliculi).
what would a lesion to the occulomotor nerve do? where would this lesion in the CNS be located?
flacid paralysis and atrophy of all the eye muscles this guy innervates. Thus external strabismus (lateral deviation of the left eye) and ptosis of eyelid. Note that parasympathetic defects may also be present. This lesion is in the midbrain (superior colliculus).