24: Motor Tracts Flashcards
Primary motor cortex
Precise and individual movements of digits and extremities
Premotor cortex
Ideation and programming of movement patterns
Supplementary motor cortex
Influences limb musculature and movement
UMNs vs LMNs
UMNs: terminate on another neuron
LMNs: terminate on a muscle cell
UMN paralysis
Spastic paralysis, hypertonia, hyperreflexia, Babinski sign, clonus, rigidity
LMN lesion
Flaccid paralysis, areflexia, atonia, atrophy, fasciculations
Two types of LMNs and what they innervate
Alpha MNs: innervate extrafusal skeletal muscle
Gamma MNs: innervate intrafusal fibers
LMN pools
Group of highly inter connected interneurons in intermediate gray matter
Lesion of the CST
Contralateral spastic hemiplegia or hemiparalysis
Lesion of the LCST
Ipsilateral paralysis or paresis of distal limb musculature below level of lesion
Lesion of ACST
Minimal clinical effect
Blood supply to the CST
Parmedian branches of the basilar A
Lesion above and below decussation in the corticobulbar tract
Above decussation: contralateral CN palsies (ex: supranuclear facial palsy)
Below decussation: ipsilateral CN palsies
How to generally test to see if the corticobulbar tract is intact?
Performing a typical neuro exam of the CNs
If multiple abnormal CN findings on exam…
Lesion most likely at superior CN on side of deficits
What causes acute anterior poliomyelitis?
Inflammation of MNs in anterior horn, neuron death, astrocytic gliomas form
S/S of acute anterior poliomyelitis
fever, HA, N/V, neck stiffness, pain in back and limbs (like any other acute viral meningitis)
What does ALS stand for?
Amyotropic lateral sclerosis
ALS: structures involved
LMNs and UMNs
S/S ALS
Paresis and atrophy of hands -> arms -> shoulders; dysarthria, dysphagia, paresis of tongue, spastic paralysis, hyperreflexia, Babinski sign
What causes supranuclear facial paralysis?
Unilateral lesion of corticobulbar fibers above level of facial nucleus
Two parts of the facial motor nucleus and what they receive fibers from
Anterior part: receives corticobulbar fibers
Posterior part: receives fibers from both hemispheres
What is innervated by the anterior and posterior parts of the facial motor nucleus?
Anterior part: muscles of lower quadrant of face
Posterior part: muscles of upper quadrant of face
S/S supranuclear facial paralysis
Palsy of contralateral mimetic muscles on lower quadrant of face
Bell’s palsy
Ipsilateral paralysis of mimetic muscles
What cases Bell’s palsy
Central lesion of facial nerve
What causes a Lenticulostriate infarct?
Ischemia in territory of ICA or MCA
S/S Lenticulostriate infarct
Motor and/or sensory deficits, cognitive dysfunction
CN 3 motor component
Extrinsic eye muscles (besides SO, LR), levator palpebrae superioris, constrictor pupillae, ciliary muscles of lens
CN 4 motor component
SO
CN 5 motor component
Muscles of mastication, tensor tympani, tensor veli palatini, mylohyoid, anterior belly digastric
CN 6 motor component
LR
CN 7 motor component
Mimetics, stapedius
CN 9 motor component
Stylopharyngeus
CN 10 motor component
Striated and smooth muscles of pharynx/larynx, smooth muscles in thorax and abdomen
CN 11 motor component
SCM, trapezius
CN 12 motor component
Intrinsic and extrinsic tongue musculature
Apraxia
Inability to properly perform complex learned motor acts
Agnosia
E: right-left disorientation
Areflexia
Loss of efferent component of reflex arc
Atonia
Absence of muscle tone
Fasciculations
Twitching
Dystonia
Uncontrolled muscle contractions - repetitive movements
