Exam 2 Flashcards
(260 cards)
where are the cell bodies of LMNs located?
in the ventral horn of the SC
are LMN peripheral neurons?
yes!
what are the signs of a LMN lesion?
hypotonicity
hyporeflexia/areflexia
neurogenic atrophy
fasciculation/fibrillation
paralysis and paresis
do UMNs or LMNs lesions result in neurogenic atrophy?
LMN lesions
do UMN or LMN lesions result in disuse atrophy?
UMN lesions
what is hypotonicity?
low muscle tone (abnormally low resistance to passive motion)
what is muscle tone?
resistance to muscle stretch in resting muscle
what is flacidity?
more severe where there is an absence of resistance to passive movement
do UMN or LMN lesions result in resting tension close to none?
LMN lesions
why can hypotonicity lead to injury?
there is ligament laxity and hypermobility of the jts
lack of voluntary muscle control
what is the importance of the phasic stretch reflex/DTR?
it determines the integrity of the monosynaptic reflex and SC at different segmental levels
it determines the excitability of the alpha motor pool
is phasic stretch reflex the same thing as tonic stretch reflex?
no! tonic stretch reflex is abnormal
what does diminished input from motor neurons to skeletal muscles lead to?
hyporeflexia
what is neurogenic muscle atrophy?
rapid loss of muscles bulk due to denervation of skeletal muscle associated with LMN lesions
what chain of events lead to neurogenic atrophy?
lack of neural stimulation and contraction–>lack of gene expression–> changed protein production–>rapid atrophy
what is this describing?: a ground motor neuron is trying to innervate a lot of motor fibers but can’t support them so they die
neurogenic atrophy
what is fasciculation?
spontaneous quick twitch of a single motor unit (one motor neuron and all its fibers it innervates) that can be seen
not always pathological like an eyelid twitch
is a fasciculation pathological?
not always
when is fasciculation pathological?
with atrophy
what are some common causes of fasciculation?
too much caffeine
fatigue
what is fibrillation?
spontaneous contraction of muscle fibers that can’t be observed with the eye
pathological sign of denervation/electrolyte imbalance
what is fibrillation a sign of?
denervation
electrolyte imbalance
is fibrillation pathological?
yes!
what causes fibrillation?
muscles not getting enough ACh, so the receptors get dispersed and become hypersensitive to ACh