Motor and premotor Cortex Flashcards
what can the motor cortex be divided into?
primary motor cortex (M1)
Premotor cortex
supplementary area
True or false: there is more surface area of the motor cortex specific for fine motor movements
True, it is soma topically organized
what areas of the motor cortex would be larger?
Hands and face
what does the motor cortex encode?
movements not individual muscles
what is the main function of the primary motor cortex?
the execution of voluntary movement
is movement contralateral or ipsilateral to the motor cortex?
contralateral
what components of movement does the primary motor cortex encode?
force
direction
distance
speed
what is alien hand syndrome?
Involuntary, uncontrollable
movement of the upper extremity
what part of the brain is activated when you have alien hand syndrome?
contralateral primary motor cortex
what lobe is the premotor cortex in?
frontal lobe
what are the main functions of the premotor cortex?
motor planning
it selects the appropriate movements to perform
what part of the motor cortex are mirror neutrons in?
premotor cortex
how does the premotor cortex influence motor behaviour?
primarily via connections with the primary motor cortex
less commonly via axons projecting through the pyramidal tracts
what impairments may we se if there is a lesion to the premotor cortex?
speed and automaticity of reaching/grasping
sequential movements
gait and posture
what are the main functions of the supplementary motor area?
Programming complex sequences of
movements and coordinating bilateral movements
Selects movements based on previous experience
if you were learning how to play tennis and imagines yourself serving like Serena Williams, what part of the brain does this motor imagery?
supplementary motor area
what happens if there is a unilateral lesion of the SMA?
complete lack of contralateral movement and impaired ipsilateral movement
anti phase movement can be affected
what are anti phase movements?
Typing and playing the piano
tapping your head and rubbing your belly
where does intention of movement occur?
prefrontal cortex
where does motor planning occur?
premotor cortex
where does the execution of movement occur?
primary motor cortex
what is the somatotropin organization of the anterior horn of the spinal cord?
medial= proximal muscles
lateral= distal muscles
what is an interneuron/ local circuit neuron/
the “middle-man” that branches locally to innervate other neurons
are interneurons primarily inhibitory or excitatory?
inhibitory
do interneurons project ipsilaterally or contralaterally?
both!
what are the two types of interneurons?
long circuit
short circuit
what is the function of long circuit interneurons?
innervates proximal muscles for balance and postural control
what is the function of short circuit interneurons?
innervates distal muscles for fine motor control
how many levels do long circuit interneurons span?
multiple levels
can long circuit interneurons cross sides of the spinal cord?
yes it can cross bilaterally
what part of the spinal cord can long circuit interneurons activate?
medial aspect of the anterior horn of spinal cord
what is the functional relationship of long circuit interneurons?
bilateral control of postural muscles
balance
how many levels does the short circuit interneurons span?
a few spinal levels (2-3)
does the short circuit cross the midline of the spinal cord?
it is almost exclusively ipsilateral
what part of the spinal cord does the short circuit interneurons activate?
lateral aspect of the anterior horn of the spinal cord
what is the functional relationship of the short circuit interneurons?
allows for fine motor control
where are the cell bodies of upper motor neurons located?
in supraspinal areas
what two tracts can the descending motor pathway be divided into?
pyramidal and extrapyramidal tracts
where does the pyramidal tract originate?
cerebral cortex
what is the pyramidal tract responsible for?
skilled, voluntary movements of the limbs
where does the extrapyramidal tract originate?
in the brainstem
what is the extrapyramidal tract responsible for?
posture balance and gait
where does the lateral corticospinal tract originate?
motor cortex, mostly M1
where does 85% of the lateral corticospinal tract cross?
at the pyramidal decussation
what is the destination of the lateral corticospinal tract?
lateral LMN of spinal cord
local short distance interneuron networks
What is the function of the lateral corticospinal tract?
skilled, voluntary movement of the limbs
If there is a lesion to the lateral corticospinal tract what side would be impaired?
contralateral side
what is the origin of the anterior corticospinal tract?
motor cortex, mostly M1
where does the remaining 15% of the corticospianl tract cross over?
in the spinal cord
what is the destination of the anterior corticospinal tract?
it terminates bilaterally in the spinal cord
via long distance interneuron networks
what is the function of the anterior corticospinal tract?
gross control of proximal postural muscles
what are the impairments if there is a lesion to the anterior corticospinal tract?
minimal clinical effect
what do most corticospinal fibres synapse directly with?
spinal interneurons that in turn synapse with LMNs
what is the origin of the corticobulbar tract?
motor cortex
what is the destination of the corticobulbar tract?
Most terminate bilaterally on local
circuit neurons in brainstem
LMN nuclei of cranial nerves
what is the function of the corticobulbar tract?
Controls efferent activation of cranial
nerves
if there is an injury to the corticobulbar tract (UMN) what would be the impairment?
Weakness in contralateral inferior facial muscles (left side of face) (Stroke)
if there is an injury to the facial nerve (LMN) what would be the impairment?
Weakness in ipsilateral superior and
inferior facial muscles (entire left side of face)
what is the origin of the extrapyramidal pathways?
various nuclei in the brainstem
what is the destination of the extrapyramidal pathways?
Cross in antero-medial white matter of spinal cord
Innervates bilateral local long interneuron circuits
what are the main functions of the extrapyramidal pathways?
- Proximal muscles
- Gait and postural stability
- Recruits LMNs for sophisticated reflexes
- Largely automatic control of movement
is there function if the extrapyramidal pathways are damaged?
you can maintain some function
what are the names of the extrapyramidal tracts?
rubrospinal
vestibulospinal
reticulospinal
tectospinal
what is the function of the rubrospinal tracts?
flexor muscle tone and arm swinging
what is the function of the vestibulospinal tract?
posture and balance
what is the function of the reticulospinal tract?
Influence voluntary movements, gait, posture, reflexes, and excites/inhibits
muscle tone, sympathetic nervous system functions
what is the function of the tectospinal tract?
eye/head motion
are Parkinson’s and Huntington’s disease pyramidal or extrapyramidal?
extrapyramidal
what are the clinical presentations of extrapyramidal tract disorders?
Slowing or loss of voluntary and automatic movements
Postural instability
Abnormal movement
are extrapyramidal disorders typically bilateral or ipsilateral?
typically bilateral effects
is the extrapyramidal tract movement volitional or automatic?
automatic
is the pyramidal tract movement volitional or automatic?
volitional
what distance local circuit neurons are with the extrapyramidal tract?
long distance local circuit neurons
what distance local circuit neurons are with the pyramidal tract?
short distance local circuit neurons
