Bridges Descending Motor Flashcards
positive signs of lesion of corticospinal tract
Babinski sign, hyperreflexia
negative signs for lesion of corticospinal tract
Loss independent movements, hemiparesis, decreased superficial reflexes
Brodmann areas for premotor cortex
6/8
Brodmann area for primary motor cortex
4
Brodmann area for somatosensory cortex
3/1/2
Brodmann area for posterior parietal cortex
5/7
primary motor cortex sends projections to this major structure in brainstem via corticospinal tract
red nucleus
pyramidal cells of cortical layer V; UMN of primary motor cortex
Betz cells
areas involved in planning and programming movement
supplementary motor cortex, premotor cortex, posterior parietal cortex
lesions of supplementary motor cortex will cause what?
difficult in reaching and bimanual coordination
primary input for premotor cortex; provides info on orientation of the body in space
posterior parietal cortex
plays role in controlling proximal and axial muscles, orienting body and arms to target
premotor cortex
neuron types in premotor cortex
context-dependent, mirror, canonical, set-related
neurons in premotor cortex that depends on type of movement and the context (reach to grasp, but not reach to push away)
context-dependent
neurons in premotor cortex that fire when you perform a task and also when you see someone else perform it
mirror
neurons in premotor cortex that are activated when you see object that can be grasped (brain foreseeing possible interaction w/ object and preparing itself)
canonical
neurons in premotor cortex that create internal representation of an action
mirror and canonical
neurons in premotor cortex that activate when preparing to make a particular movement (preparatory)
set-related
projections of posterior parietal cortex
premotor area, supplementary; motor area, cerebellum
encodes spatial coordinates for coordinated movements (w/in spatio-temporal domain); identifies target in space an in relation to body
posterior parietal cortex
sensory inputs to posterior parietal cortex
visual and proprioceptive pathways
in lesion of PPC…will have hemineglect of ipsilateral or contralateral body/field?
contralateral
compares central commands from primary motor cortex to actual movements that result (then makes the necessary corrections)
cerebellum
required for adapting predictive/feedforward control programs from one movement to next
cerebellum
allows cerebellum to undergo feedforward control programs from one movement to next
error-dependent learning mechanism
functional cerebellum involved in execution, feedback adjustments
spinocerebellum
three functional divisions of cerebellum
vestibulocerebellum, spinocerebellum, cerebrocerebellum
functional division of cerebellum involved in motor learning, planning movement, evaluating sensory info for action (*lateral parts cerebellar hemispheres*)
cerebrocerebellum
ipsilateral or contralateral cerebral cortex has input into cerebrocerebellum?
contralateral
where does the output of cerebrocerebellum go? this output travels via what?
contralateral motor/premotor areas, parietal lobe; dentate nucleus and thalamus
dentate nucleus and premotor cortex project here; how does this structure/layer project back to the cerebellum?
parvocellular of red nucleus; inferior olive
5 types of neurons in cerebellum; which one is excitatory?
stellate, basket, purkinje, golgi, granule; granule
represent output of cerebellum; where does this input travel to initially?
purkinje cell axons; deep nuclei, lateral vestibular nuclei
fibers that provide most input to cerebellar cortex; what do these fibers activate?
mossy; granule cell interneurons
stimulation of these will cause single spikes spikes in the Purkinje cell response
mossy fibers
where do climbing fibers originate (second group of input fibers to cerebellar cortex); do these fibers make excitatory or inhibitory synapse with Purkinje cell?
contralateral inferior olivary nucleus; excitatory
give rise to parallel fibers in cerebellar cortex
granule cells
if this is damaged, learning motor skills will be impaired
inferior olivary nucleus
these may create “error signal” that modulates responsiveness of Purkinje cells to input from mossy fibers (in motor learning)
climbing fibers
inputs of inferior olivary nucleus
proprioceptors, motor cortex, motor center brainstem, RNp
ataxia caused by antibodies developed against a tumor that also attack cells in the brain (*specifically the cerebellum*); what is an example of an antibody that can cause this?
paraneoplastic syndrome; Yo antibody
additional symptoms of paraneoplastic syndrome (in addition to ataxia affecting trunk and limbs)
dysarthria, oculomotor nystagmus
loss of muscle coordination; broad, irregular, staggering gait; intention tremor, nystagmus, irregular speech
cerebellar ataxia
sensory ataxia can occur in this condition (loss of afferent proprioceptive input)
Tabes dorsalis
cerebellar hemisphere involved in ipsilateral or contralateral half of body?
ipsilateral
most common cause of damage to flocculonodular lobe of cerebellum
medulloblastoma (in roof 4th ventricle)
damage of this part of cerebellum will cause vestibulocerebellar impairment
flocculonodular lobe
what is damaged?….loss control stable eye/trunk position, falling over while standing, staggering gait (drunken sailor’s gait), normal movement when trunk supported, nystagmus
vestibulocerebellar system
projects via fastigial nuclei to brain areas giving rise to medial reticulospinal and vestibulospinal tracts
vermis
alcohol-induced cerebellar degeneration is usually limited to this area; what area of the body is mostly affected?
anterior vermis; legs
lack of coordination/ataxia of leg movements…even when trunk is supported
anterior lobe syndrome
damage to nucleus interpositus causes what?
dysmetria, intention tremor, poor coordination, pendular reflexes
limb oscillates at end of a tendon reflex
pendular reflex
what part of red nucleus does the rubrospinal tract originate?
magnocellular
integrates info from vestibular nuclei and cerebral cortex (important in maintenance of posture)
reticulospinal tract
originates in SC…coordinates head and neck movements (reflex or turning head in response to visual and other stimuli)
tectospinal tract
ways motor cortex can act on motor neurons *indirectly* (via these structures)
SC, red nucleus, RF
where do 60% of LCS fibers originate? where do the remainder come from?
precentral cortex (areas 4 and 6); parietal lobe (3, 1, 2 and somatosensory)
the majority of LCS fibers terminate directly on what? where do the remainder terminate?
alpha motor neurons; interneurons (that relay sensory to motor)
is major descending pathway from brain stem UMN medial or lateral?
medial (for axial and proximal muscles)
is major descending pathway from cerebral cortex UMN medial or lateral?
lateral (for distal muscles/digits)
what are UMN of primary motor cortex (pyramidal cells)?
Betz cells (layer V)
what makes up supplementary motor cortex?
medial area 6, area 8, FEF
what makes up premotor cortex?
lateral area 6
what areas are associated with posterior parietal cortex?
5 and 7
this model allows your to combine sensory inputs with past experiences to predict an appropriate output; what two major structures/areas are involved in this?
feed forward; PPC and cerebellum
what is involved in movement preparation (feeling of an urge to move)? what is involved in motor prediction/selection (conscious intentions to move)?
SMA; PPC
divides flocculonodular lobe from corpus cerebelli
posterolateral fissure
divides the corpus cerebelli into anterior and posterior lobes
primary fissure
this regulates balance and eye movements…covers same region as anatomical flocculonodular lobe
vestibulocerebellum
what is output of vestibulocerebellum?
medial systems (via lat vestibular nucleus and vestibulospinal tract)
this regulates body and limb movements…includes vermis and paravermis regions of cerebellum (*concerned with execution of movements and feedback adjustments*)
spinocerebellum
what are two major inputs to spinocerebellum?
spinal cord and V
what is output of vermis (spinocerebellum)? occurs via what?
medial system; fastigial nucleus
what is output of paravermis (spinocerebellum)? this occurs via what cerebellar structure?
lateral systems (magnocellular red nucleus and motor cortex); interposed nucleus
what part of red nucleus does dentate project to? how does this then feedback to cerebellum?
parvocellular; ipsilateral inferior olivary nucleus
what does fastigial nucleus project to axial body regions via?
vestibular nuclei and pontine RF
what makes up interposed nucleus?
Globose and emboliform
this projects via thalamus to motor, premotor cerebral cortex, and parvocellular red nucleus
dentate
medial systems that spinocerebellum (via vermis/fastigial) projects to
vestibulospinal, reticulospinal, ventral corticospinal
what lateral systems does spinocerebellum (via paravermis/interposed nucleus) project to?
rubrospinal and corticospinal
what makes up outermost, molecular layer of cerebellar cortex?
axons granule cells (parallel fibers)
what makes up middle cell layer of cerebellar cortex?
Purkinje cells (GABA-ergic)
bulbous terminal expansions of afferent mossy fibers
cerebellar glomeruli
make up inner granular layer of cerebellar cortex
granule cells and cerebellar glomeruli
what is NT for granule cells?
glutamate
inhibitory output within cortex to granule cells (GABA transmitter)
golgi cells
where does monoaminergic input to cerebellar cortex originate (regulate excitability of cerebellar cortical neurons)?
locus ceruleus and raphe nuclei
modifies response of Purkinje cell to mossy fiber input (learning)…*error signal*
climbing fiber
what are inputs to inferior olivary nucleus?
proprioceptors, motor cortex, motor centers in brain stem
lesions of this cause minor motor deficits (unless wide spread)…have to think about all the motions
cerebrocerebellum
widespread damage to cerebrocerebellum (ipsilateral decomposition of movement, dysmetria, delays in initiation, intention tremor, dysdiadochokinesia, dysarthria, hypotonia)
neocerebellar syndrome
major sign of neocerebellar syndrome…disturbance of synergy, temporal coordination, and spatial coordination (muscles are used one at a time)
decomposition of movement
inability to stop a movement at the appropriate time or to direct it in the appropriate direction (over or undershoot)
dysmetria
seen at end of movement (in neocerebellar syndrome)…entire movement carried out by sequence of motor commands, each directing movement closer to target
intention tremor
irregular pattern of movement seen when performing rapid, alternating movements
dysdiadochokinesia
