MOTOR PARALYSIS Flashcards
Reason behind muscle irritability
the axon is unstable and capable of spontaneous
impulse generation, and all the muscle fibers that it controls
may discharge sporadically; in isolation from other
units.
____________appears in the EMG as a large spontaneous
muscle action potential
Fasciculation
spontaneous contractions of multiple motor units cause
a rippling of muscle
Myokimia
The _____ and ______ set the pattern and timing of the
muscle action in any projected motor performance.
basal ganglia
cerebellum
Suprasegmental control
of the axial and proximal limb musculature (antigravity
postural mechanisms) is mediated primarily by the
________ and ________
reticulospinal and vestibulospinal tracts
A tap on a tendon stretches or perhaps causes vibration
of the spindle and activates its _____________.
Afferent projections from these fibers synapse directly
with ________ in the same and adjacent
spinal segments; these neurons, in turn, send impulses
to the skeletal muscle fibers, resulting in the familiar
_____________ or monophasic
nuclear bag fibers
alpha motor neurons
monosynaptic muscle contraction
The _________ are simultaneously inhibited
but through disynaptic rather than monosynaptic
connections.
alpha
neurons of antagonist muscles
_________ also
participate by providing negative feedback through
inhibitory synapses of alpha motor neurons (recurren t
inhibition)
Renshaw cells
___________
are silent in relaxed muscle and during passive stretch;
they serve, together with muscle spindles, to monitor or
calibrate the length and force of muscle contraction under
different conditions
Golgi tendon receptors
The alpha motor neurons of the_______ of the
anterior horn supply trunk or axial muscles, and neurons
of the ______supply the appendicular muscles
medial parts
lateral parts
The large neurons of the anterior horns of the spinal cord contain high concentrations of _________ as
their transmitter at the neuromuscular junction
choline acetyltransferase and use acetylcholine
The main
neurotransmitters of the descending corticospinal tract,
in so far as can be determined in humans, are ____
and _______
aspartate
glutamate.
_______ is the neurotransmitter released
by Renshaw cells, which are responsible for recurrent
inhibition, and by interneurons that mediate reciprocal
inhibition during reflex action.
Glycine
_______ serves as the inhibitory neurotransmitter
of interneurons in the posterior horn.
Gamma-aminobutyric
acid (GABA)
________ are released by primary afferent terminals
and interneurons and act specifically on excitatory amino
acid receptors.
L-glutamate and
L-aspartate
In LMN lesions,
The denervated muscle undergoes extreme atrophy,
being reduced to _________of its original bulk
within _________
20 or 30 percent
3 to 4 months.
This is caused by the interruption
of descending tonic excitatory impulses, which normally
maintain a sufficient level of excitation in spinal motor
neurons to permit the peripheral activation of segmental
reflexes.
spinal shock
what attenuates spinal shock
naloxone
This is
the only direct long-fiber connection between the cerebral
cortex and the spinal cord
CST
Indirect pathways
rubrospinal, reticulospinal, vestibulospinal, and
tectospinal
______percent of the descending axons arose in
the parietal lobe, _______ percent in motor area 4, and the remaining _____percent in premotor area 6
40
31
29
About ______ of the
fibers cross and the remaining fibers descend ipsilaterally,
mostly in the uncrossed ventral corticospinal tract
75 to 80 percent
_______in the corticospinal
tract account for mirror movements that are seen during
efforts at fine motor tasks, particularly in children,
Uncrossed fibers
Beyond their decussation, the corticospinal pathways
descend as well-defined bundles in the ___________ of the spinal cord
anterior and
posterolateral columns of white matter (funiculi)
The l___________ tract lies at the periphery of the cord, where it occupies
the most anterolateral portion of the anterior funiculus
ateral vestibulospinal
_________ is also electrically excitable
but requires more intense stimuli than area 4 to evoke
movements
Area 6, the premotor area,
Stimulation of the _________ elicits more general movement patterns, predominantly of proximal limb musculature.
rostral premotor area (area 6a)
Stimulation of this area
may induce relatively gross ipsilateral or contralateral
movements, bilateral tonic contractions of the limbs,
contraversive movements of the head and eyes with
tonic contraction of the contralateral arm, and sometimes
inhibition of voluntary motor activity and vocal arrest
SMA
The corticospinal and corticobulbar
tracts, which project to all levels of the spinal cord and
brainstem, terminating diffusely throughout the _______ and _________
nucleus
proprius of the dorsal hom and the intermediate zone
A _______, which arises
in the tectum (tectospinal tract), vestibular nuclei (vestibulospinal tract), and pontine and medullary reticular cells (reticulospinal tract) and terminates principally on the internuncial cells of the ventromedial part of the spinal
gray matter.
ventromedial pathway
function of the VM pathway
This system is mainly concerned with axial
movements-the maintenance of posture, integrated
movements of body and limbs, and total limb movements.
(
from
the magnocellular part of the red nucleus and terminates in the dorsal and lateral parts of the internuncial zone
A lateral pathway
function of the lateral pathway
This pathway adds to the capacity for independent use
of the extremities, especially of the hands
their fibers are
arranged somatotopically and influence stretch reflexes
corticoreticulospinal pathways
results of UMN lesion
decreased voluntary drive on spinal motor neurons
(fewer motor units are recruitable and their firing rates
are slower), resulting in a slowness of movement
increased degree of co-contraction of antagonistic
muscles, reflected in a decreased rate of rapid alternating
movements
activation of paralyzed
muscles as parts of certain automatisms called __________
(synkinesias).
If the upper motor neurons are interrupted above
the level of the facial nucleus in the pons, hand and arm
muscles are affected __________and the leg muscles to a ________
most severely
lesser extent
it is referred
to as “Broadbent’s law.”
distribution of facial paralysis
that relatively spares the forehead muscles,
fibers that descend to the upper medulla and then ascend recurrently to the pons
Pick’s bundle
the selective blocking of _________neurons abolishes spasticity as well as hyperactive segmental tendon reflexes but to leave power unchanged.
small gamma
___________ phenomenon-the result
of interruption of descending inhibitory pathways
release
the medial
reticulospinal and vestibulospinal tracts, which together
_________
facilitate extensor tone.
the_____________, which has
inhibitory effects on stretch reflexes
dorsal reticulospinal tract
primary involvement of
the _________ and thalamus
is the feature that determines the persistence of flaccidity
after stroke
lenticular nucleus of the basal ganglia