Cortical Motor Connections Flashcards
- received sensory input from the sensory relay nuclei of the thalamus
- afferent information from the contralateral side of the body, face and head
primary somatosensory cortex/post central gyrus
- gives rise to descending corticospinal tract (pyramidal tract)
- controls movement of contralateral side of the body
primary motor cortex/pre central gyrus
- contains interneurons that receive afferent and efferent from a variety of areas
- involved in analysis of sensory information
- integration of sensory information into perception and motor planning
association areas
large apical dendrite with up to 20,000 dendritic spines; large axon with many collateral branches that extend through the cortex into the spinal cord
pyramidal cells
what is the name for the largest pyramidal cells and where are they the most dense
- betz cells
- motor cortices
- also known as granular cells
- interneurons
- smaller, star-shaped with numerous short dendrites in many directions
stellate cells
do stellate cells leave the cortex
no
how many cell layers compose the cortex and how are they arranged
- 6 layers
- laminar columns
input layers of the cortex that receive input from many areas within the cortex, thalamus, subcortical regions
layer I-IV
this cortical layer is the thickest in the motor areas because this layer is the primary motor output for efferent axons (Betz cells and cells for all the extrapyramidal pathways)
layer V
cortical layer that lies adjacent to the internal capsule and corona radiata and consists mostly of association and commissural fibers
layer VI
ultimate command center for motor control; plans and executes complex voluntary motor activity; receives information from the basal ganglia, cerebellum and thalamus
cerebral cortex
initiation and motivation to move, control of muscle tone, quality and quantity of movement
basal ganglia
integrates visual, auditory, vestibular and somatosensory information to modify movement
cerebellum
what does the cerebellum do to help with overall movement
smooth, orderly, sequenced, and coordinated (SOSC)
- timing, speed, direction and precision
what is involved in direct regulation of motor activity
primary motor cortex and secondary motor cortices
the direct regulation of motor activity will directly influence voluntary motor activity via direct projections from the corticospinal tracts to:
- brainstem cranial nerve nuclei (via corticobulbar tract)
- reticular formation (autonomic system)
- anterior horn cells in spinal cord
what structures are involved in indirect regulation of motor activity by sending and receiving information about movement commands from primary and secondary motor cortices via the motor nuclei of the thalamus
basal ganglia and cerebellum
basal ganglia and cerebellum exert their influence on the brainstem and spinal cord by way of
extrapyramidal pathways
neurotransmitter for pyramidal cells and is excitatory
glutamate
too much of this neurotransmitter thought to contribute to aging of the nervous system and degenerative pathologies
glutamate
inhibitory neurotransmitter utilized by non-pyramidal neurons
GABA
where does the primary motor cortex receive input from
primary somatosensory, supplementary motor, cerebellum, basal ganglia, cingulate motor
emotions and memory components of movement
cingulate motor area
controls movement to the contralateral side of the body and continues to receive ongoing information as long as movement is taking place
primary motor cortex (M1)
what does the primary motor cortex directly influence
manual dexterity, speech, proximal and distal muscle control
are organized in functional groups with the number of cells in each being proportional to the complexity of the movement produced by that region (motor homunculus)
upper motor neurons
lesions to the primary motor cortex can produce
hemiplegia, hemiparesis, and all UMN lesions
primary motor cortex is somatotropically organized
motor homonculus
motor homonculus LE
medial
motor homonculus trunk
superior
motor homonculus UE
superiolateral
motor homonculus face and tongue
inferiolateral
where does 1/2 of motor homonculus is associated with what suggesting emphasis on human functions of manual dexterity and speech
hands, tongue, lips and larynx
what are the 5 secondary motor areas and what are the brodmann’s areas
- supplementary motor 6
- premotor cortex 6
- frontal eye field 8
- posterior parietal motor area 5, 7
- cingulate motor area 23, 24
motor planning areas where sensory input is incorporated to create a motor plan and then relays the motor plan to the primary motor cortex for future planning and execution
secondary motor cortices
areas of ____ in the frontal lobe receive information from associations areas in parieoccipital regions (___)
- 6 and 8
- 5, 7
superior portion of Brodmann’s 6
supplementary motor area (SMA) (M2)
programs patterns and sequences of elaborate movements prior to the actual occurrence of motion - cells in this area are goal-oriented
supplementary motor area
where does the primary input come from to the supplementary motor area that is associated with intended movements
auditory and visual cues
what does supplementary motor area coordinate
bimanual movement and movements occurring on two sides of the body at the same time
associated with contractions of the trunk and proximal limb musculature
supplementary motor area
what will lesions of the supplementary motor area result in
difficulty with bilateral hand tasks, diminished ability to self-initiate a task
motor planning for control of axial and proximal limb muscle contractions and for sequencing a series of movement together
premotor cortex (PM)
guides or turns the limbs or trunk in the desired direction of a target as when reaching for food and bringing to the mouth
premotor cortex
when is PM active and when does it decrease
- PM activity decreases once the activity has begun
- PM is active only when movements are occurring in sequence rather than isolated movement patterns
lesions to premotor cortex
motor apraxia, perserveration, loss of rhythmic movement, inability to produce complex or sequential motor tasks
located rostral and anterior to premotor/supplemental motor areas
frontal eye field (FEF)
information from association areas needed for coordination and tracking of eye movements (saccades and smooth pursuit)
frontal eye fields
what are frontal eye fields important for to help maintain the image being observed on the fovea via VOR and optokinetic reflexes (fixation)
establishing voluntary gaze
where do motor neurons in frontal eye fields send axons to
superior colliculi, pre-tectal nuclei, and nuclei associated with eye movement via MLF
T/F: posterior parietal cortex is both sensory and motor
T
coordination of visual and tactile information used by the motor areas to produce goal-directed movement
posterior parietal cortex
area that receives discriminative tactile information (stereognosis) and then transmits it to PMC/SMA/FEF
5
area that receives visual information then to PMC/SMA/FEF to assist in visually guided motor activities like reaching for an object and helps with orientation of the body in relation to the object
7
where is the cingulate motor areas located
base and banks of the cingulate sulcus on medial hemisphere
where does cingulate motor areas receive inputs from about motivational state, internal status of the individual and environmental conditions
prefrontal cortex and other limbic areas
projections from cingulate motor areas to primary and supplementary motor areas guide
motivation and desire to move
projections from cingulate motor areas directly onto ________ of spinal cord and influence LMN’s via interneurons (cingulospinal pathway)
intermediate zone
primary relay center for modifying information coming into and out the motor cortices from the basal ganglia, cerebellum, brainstem and spinal cord
thalamus
is the known as the motor thalamus and is connected to the primary motor cortex
ventrolateral nucleus
where do the primary efferent pathways of the corticospinal tract go
to LMN in lamina 9 of the spinal cord
what are the two bundles of the corticospinal tract
anterior and lateral funiculi
what does the corticospinal tract travel through
internal capsule to medulla
where does 90% of the corticospinal tract decussate and which division and will synapse on interneurons that influence alpha motor neurons in lamina 9
- at pyramids
- lateral funniculus
where does the lateral funniculus terminate in the spinal cord
cervical spinal cord, thoracic cord, and lumbosacral cord segments
where does 10% of the the corticospinal tract cross and what division is it apart of
- cross in the cord before synapsing on lamina 9
- anterior funniculus
extend only to upper thoracic levels and contribute to regulation of neck, upper trunk, and proximal UE
anterior funniculus
where do axons of corticobulbar tract from UMN arise from
primary motor cortex and premotor cortex
where does the corticobulbar tract terminate
nuclei of cranial nerves
what does the corticobulbar travel in parallel with
corticospinal tract
corticospinal affects motor branches of CN
3, 4, 5, 6, 7, 9, 11, 12
where are cell bodies of extrapyramidal tracts located
- in other motor areas of cortex and brainstem
- DO NOT arise from primary motor cortex
what are the names of the extrapyramidal tracts
- tectospinal
- rubrospinal
- reticulospinal
- vestibulospinal
visual association areas (17, 18) to superior colliculi in midbrain
tectospinal tract
what is the track of the tectospinal tract
originates from superior colliculi, decussates in midbrain, travels in MLF through anterior funiculus
where does the tectospinal tract synapse
cervical and thoracic LMN
what does tectospinal tract
reflexive control of neck mm in response to visual, auditory and vestibular information
where are cell bodies for the rubrospinal tract found
in the ipsilateral motor cortex and cerebellum
where does the rubrospinal tract send axons to
red nucleus in brainstem
red nucleus axons form 2 tracts
rubrobulbar and rubrospinal
terminates on CN nuclei to influence facial movements
rubrobulbar
descends in the lateral funniculus of the spinal cord
rubrospinal
where does the rubrospinal tracts synapse
with anterior horn cells (alpha and gamma)
what do the rubrospinal tracts influence
hand control, facilitates flexor tone and inhibits extensor tone of UE’s
from UMN axons travel to several nuclei in the reticular formation of pons and medulla
reticulospinal tract
travels in anteriomedial funniculus of the cord
pontine reticulospinal tract
what does the pontine reticulospinal tract excite and inhibit
excites extensor muscles and inhibits flexor muscles
travels in anterolateral funniculus of the cord
medullary reticulospinal tract
what does medullary reticulospinal tract excite and inhibit
inhibits extensor muscles and excites flexors
also carries ANS information about pupillary dilation, heart rate and sweating
medullary reticulospinal tract
these tracts influence axial and proximal limb muscles to maintain posture and orient limbs in an intended direction
reticulospinal tracts
how many vestibular nuclei are located in the brainstem and receive information from the vestibular branch of CN 8
4
medial and lateral vestibular nuclei send axons to the spinal cord and synapse where
on alpha and gamma motor neurons
descends only to cervical/high thoracic cord levels
medial vestibulospinal tract
what does the medial vesibulospinal tract influence
head movement while maintaining fixed gaze
descends to all levels of the spinal cord
lateral vestibulospinal tract
what does the lateral vestibulopspinal tract influence
extensor activity in antigravity muscles to assist in maintaining posture and balance
what are the 2 functional groups for the arrangement of descending pathways
ventromedial and lateral groups
what does the ventromedial descending tracts consist of
- anterior corticospinal tract
- medial and lateral vestibulospinal and reticulospinal tracts
- tectospinal tract
what does the ventromedial descending group travel in and where does it synapse
- anterior funiculus
- medial aspect of anterior horn
what are the functions of the ventromedial descending group
- control axial and b/l proximal limb musculature
- balance and postural adjustments
what does the lateral descending group consist of
lateral corticospinal and rubrospinal tracts
what does the lateral descending group travel in and where does it synapse
- lateral funniculus
- lateral aspect of anterior horn
fibers that are anteriorly placed in the anterior horn of the lateral group innervate
extensors
fibers that are posteriorly placed in the anterior horn of the lateral group innervate
flexors
what are the functions of the lateral descending group
- fractionated movement
- directly innervates limb muscles, intrinsics of the hands involved in fractionated movements of the digits, and some proximal extremity muscles
signs of UMN lesions
- paresis/paralysis
- abnormal reflexes (babinski, hyperreflexive)
- abnormal muscle tone (flaccidity, hypotonicity, hypertonicity)
- loss of fractionated movement (abnormal muscle synergies)
- loss of postural control (gait and balance deficits, motor apraxia, temporal deficits)
clinical diagnoses associated with UMN lesions
stroke, CP, spinal cord injury, TBI, PD, MS, amyotrophic lateral schlerosis (ALS), huntington’s disease, multiple system atrophy, brain tumors
in the motor cortex with long apical dendrites for processing sensory information from multiple cortical and thalamic inputs
pyramidal cells
______ from motor cortex through corona radiata and internal capsule to brainstem and through the ant/lat funiculi of spinal cord carrying motor messages
projection fibers (axonal tracts)
primary descending motor tracts to lower motor neurons in ventral horn of SC
corticospinal tract
descend to motor nuclei for cranial nerves
corticobulbar tracts
from brainstem nuclei to interneurons and motor neurons in spinal cord influencing postural control, eye-head-hand control, and reflexes
extrapyramidal tracts
