Neurology (01/26) Descending Motor Systems Flashcards
primary muscle disease
myopathies (occur in the muscle fibers)
innervates striated muscle, directly signals muscle to contract, only way movement can be initiated
is the LAST NEURON in chain of neurons
lower motor neuron
motor neurons that deal with extrafusal muscle fibers
alpha motor neurons
motor neurons that deal with intrafusal muscle fibers
gamma motor neurons
five types of lower motor neuron lesions
- atonia
- areflexia
- flaccid paralysis
- fasciculations
- atrophy
lower motor neuron lesion that is a loss of muscle tone
atonia
lower motor neuron lesion that is a loss of myotatic (knee jerk) reflex
areflexia
lower motor neuron lesion where the muscle becomes limp and just “sits” there
flaccid paralysis
lower motor neuron lesion that causes spontaneous muscle contractions (you can see them, they look like twitches)
fasciculations
lower motor neuron lesion that is a loss of muscle tissue
atrophy
neurons whose axons descend from cortex and end on or near lower motor neurons
Upper motor neurons
what are the 4 types of upper motor neuron lesions?
spastic paralysis
- hypertonia
- hyperreflexia
- pathologic reflexes
- big toe dorsoflexion
upper motor neuron lesion that causes increased resting tension and makes it difficult for patients to move arms and legs
hypertonia
upper motor neuron lesion that deals with the fanning of toes when the side of the heal is stroked
big toe dorsiflexion
in upper motor neurons, is atrophy severe or mild?
mild
in lower motor neurons, is atrophy severe or mild?
severe
during a routine exam you note that the patient has tongue fasciculations. this raises concern for?
lower motor neuron injury
in lower motor neurons, the cell bodies are in the _____ horn
anterior
in lower motor neurons, the axons in ______ root divide into terminal branches widely distributed in target muscle
ventral
in lower motor neurons, each branch ends at one _______ ______
neuromuscular junction
in lower motor neurons arrangement in the spinal cord, the neurons controlling axial muscles are _____ to those controlling distal muscles
medial
in lower motor neurons arrangement in the spinal cord, neurons controlling flexors are located _____ to the extensor group
posterior
1 motor neuron + all myofibers it innervates
motor unit
T/F all motor units are similar in size
false
in motor units, does the motor nerve actually innervate every myofiber?
no, it is scattered throughout
what are the three types of muscle fibers
- standing
- running
- jump
type of muscle fiber that contracts weakly for long periods
standing
type of muscle fiber that contracts strongly for short/long periods
running
type of muscle fiber that contract very strongly for very short periods
jump
each muscle fiber type populates one _____ ____. aka no mixing
motor unit
which type (1 or 2) of muscle fiber is used for sustained force weight bearing?
1
which type (1 or 2) of muscle fiber is used for sudden movements in purposeful motion
2
which type (1 or 2) of muscle fiber has an abundant amount of lipids?
1
which type (1 or 2) of muscle fiber has a scant amount of lipids
2
which type (1 or 2) of muscle fiber has a scant amount of glycogen
1
which type (1 or 2) of muscle fiber has an abundant amount of glycogen?
2
which type (1 or 2) of muscle fiber has many mitochondria?
1
which type (1 or 2) of muscle fiber has very few mitochondria
2
which type (1 or 2) of muscle fiber is involved with slow twitch
1
which type (1 or 2) of muscle fiber is involved with fast twitch
2
which type (1 or 2) of muscle fiber did the teacher say has a “duck breast muscle”
1
which type (1 or 2) of muscle fiber did the teacher say has a “turkey breast muscle”
2
_____ _____ and ______ influence cerebral cortical output to cord and brainstem but everything must first go through the _____
- basal ganglia
- cerebellum
- thalamus
basal ganglia, cerebellum, and associated cortex are vital in design, choice, and monitoring of movement, but note they have NO direct effect on ______ ______ ______
lower motor neurons
does damage to the basal ganglia or cerebellum areas cause weakness?
no, but there may be involuntary movements, incoordination, and difficulty initiating movements
as far as deciding what movement should occur, the _______ cortex plans and tells the ______ cortex what to do which is then relayed to the _____ _____ _____
- premotor
- motor
- lower motor neurons
basal ganglia and cerebellum are involved in planning and monitoring movements by effecting the ____ and _______ cortexes
- motor
- premotor
where are the two places that most descending motor pathways terminate on?
- dorsal horn neuons
- interneurons on the dorsal horn
tract that goes from cortex to spinal cord and is considered a classic upper motor neuron. some fibers to hand region of cord terminate on primary motor neurons in anterior horn
corticospinal tract (pyramidal tract)
tract that goes from cortex to brainstem
corticobulbar (corticoneuclear) tract
tract that goes from cortex to basilar pons
corticopontine tract
what are the 5 origins of the corticospinal tract?
- primary motor area (40%)
- somatic sensory area (25%)
- premotor area (20%)
- supplementory motor area (10%)
- superior parietal lobe (5%)
what numbers are included in brodmann area?
312
area 4 on the medial and lateral aspect, its functions are the execution of contralateral voluntary movements (crosses the medulla) and control of fine digital movements.
primary motor area
the primary motor area projects to what two places?
- brainstem
- spinal cord
a lesion of the primary motor cortex causes what?
paralysis of contralateral musculature
what are the three functions of the premotor area?
- plan movements (response to external cues)
- control of proximal and axial musculature (trunk, shoulder, hip)
- assembles empathetic facial movements
the premotor area projects to where?
primary motor area and reticular formation
a lesion of the premotor area causes what two things?
- moderate weakness of contralateral proximal muscles
- loss of ability to associate learned hand movements to verbal or visual cues
what is the function of the supplementary motor area? (medial aspect of area 6)
plans movements while thinking
(assembles new sequence)
(assembles previously learned sequence)
(“imagines” movements)
what two places does the supplementary motor area project to?
- premotor area
- primary motor area
the division of the parietal lobe that projects to the primary motor area is responsible for what?
directing motor patterns in response to sensory input
the division of the parietal lobe that projects to the sensory areas of the brainstem and spinal cord is responsible for what?
modulate sensory signals
if the corticospinal tract is cut in monkeys, after a period of _____ _____, they move again, but fine ______ movement is lost permanently
- flaccid paralysis
- finger
are all movement dependent on the corticospinal tract?
no (remember the monkeys) other paths can become active and take over the functions
what two places does the corticospinal tract originate from?
- precentral gyrus
- cerebral cortex
where does the corticospinal tract decussate?
spinomedullary junction
in the corticospinal tract, 85% of the fibers cross in decussation in medulla and descend in _____ _____
lateral funiculus
in the corticospinal tract, 15% of fibers remain uncrossed and descend in _____ _____
anterior funiculus
in the corticospinal tract, some of the fibers regarding ____ muscle activity cross in the anterior _______ prior to synapsing
- axial
- commissure
what are the 4 less important pathways that the professor just wants us to know exist
- rubospinal tract
- reticulospinal tract
- vestibulospinal tract
- tectospinal tract
less important tract that is in control of shoulder and proximal arm
rubospinal tract
less important tract that is in control of axial musculature - walking
reticulospinal tract
less important tract that is in control of axial musculature - balance
vestibulospinal tract
less important tract that is believed to be important in head turning reflexes in response to visual stimuli, has an unclear function in humans
tectospinal tract
where is the origin of the corticobulbar pathway?
face/mouth portion of motor cortex and other nearby areas
the corticobulbar pathway descends with the corticospinal tract to the level of the target nucleus, then splits off so no ______ _______ exists
corticobulbar decussation
in the corticobulbar pathway, the _____ face is bilateral, and the _____ face is ipsilateral.
- upper
- lower
unilateral damage to the corticobulbar pathway results in what?
inability to smile or show teeth symmetrically
the ability to wrinkle forehead is unaffected
