control of mastication Flashcards
muscle of mastication UMN location
motor cortex (precentral gyrus)
muscle of mastication LMN location
trigeminal motor nucleus in the pons
______ projection of UMN –> LMN receives _______ innervation
bilateral
bilateral
jaw-jerk reflex
tapping chin with percussion hammer –> stretch of mm. mastication –> stretch of muscle spindles –> sensory root of V3 –> mesencephalic nucleus of V –> trigeminal motor nucleus –> motor root of V3 –> muscle of mastication contraction
jaw-jerk reflex location of proprioceptor cell bodies
mesencephalic nucleus
jaw-jerk reflex location of motorneuron cell bodies
trigeminal motor nucleus
the jaw-jerk reflex is _______ under physiological conditions but is exaggerated in ____________ of the innervation to the trigeminal motor nucleus
weak or absent
upper motor neuron lesions
jaw-jerk reflex:
___________ innervating muscle spindles set reflex sensitivity and _________, and keep _______ in sensitive range during muscle contraction (jaw closing)
gamma-motorneurons
muscle tone
afferents
lesions of motor component of trigeminal nerve:
UMN unilateral lesion
very little effect (because of bilateral projections)
lesions of motor component of trigeminal nerve:
UMN bilateral lesion
impairment of jaw movement, increased jaw-jerk reflex
lesions of motor component of trigeminal nerve:
LMN lesion
- paralysis of muscles of mastication ipsilaterally
- muscle atrophy (temporalis atrophy detectable on palpation)
- on opening, deviation of the jaw to the side of the lesion
- diminished jaw jerk reflex
initiation of chewing is _______ and ________
unconscious and automatic
*triggered by food placed in the mouth
chewing is controlled by…
brainstem central rhythm & pattern generator circuitries
direction of mandibular movements with chewing
vertical, lateral, and anterior/posterior
