Motor pathways Flashcards
What is the general hierarchy of movement?
Movement is hierchical-higher levels are involved in complex parts-program and decide on movement, coordinate them
Lower-just execute (move the limbs)
1ary motor complex is the in the primary gyrus, but helped by Basal ganglia, thalamus, cerebellum, brain stem etc
What is the role of cerebellum for movement? And basal ganglia?
Usually movements pass by it, leading to refining-smaller motor movements. Basal ganglia has a similar role “modulatory”W
What is the role of the brain stem and spinal cord for movement?
lower tier-just exercuting the orders. Brain stem-Head and face, spinal-rest of the body
Where and what is the primary motor cortex? How is it organised?
Precentral gyrus, anterior to central sulcus
Control fin, discrete and VOLUNTARY movement
Neurons can be huge and extend down into the spinal cord
Somatotopic organisation (motor humonculus)-lower limbs are higher up the brain (matters in stroke-anterior cerebral artery)-and not all areas are the same size (hands are massive)
What is the wiring of the 2 descending motor pathway?
Most are lateral-cortical tract:
Motor area-pass by basal ganglia internal capsule, via cerebral peduncle of midbrain (mickeymouse ears), then pons (not visible, but where cerebellum links), then pyramidals in the medulla. END OF MEDULLA PASS OVER
(Still no synpase)-then down via lateral corticalspinal tract to the appropriate level, where synapse with lower motor neuron (in ventral horn)-and to the muscle
Other pathway doesnt cross over (ipsilateral)-descend in anterior cortical spinal tract till the right level WHERE IT THEN CROSSES OVER (usually do the intercostal and similar)
What is the cortical bulbar pathway?
It refers to the motor neurons that go the brainstem-and act in cranial nerves
Like hypoglossal nucleus, in the medulla (near center because motor), then to tongue. do cross over
What is the pre-motor cortex? What is its role?
Anterior and down from primary motor cortex
Role in planning of movement and regulate externally cued movement (how you interact with the environement
What is the Supplementary motor cortex
Also anterior to motor, but more medial than pre-motor
Role in planning complex movements, and programming spequencing of movement (Like talking and stuff)
The area thatll actvate when thinking of movement
What is the association cortex?
Not stricktly motor but have a role
Posterior parietal cortex: Ensure movements are targeted accuratly in space (like picking an apple-not missing it)
Prefrontal cortex: Selection of appropriate movement-personality involvment in action (like picking up a hot plate
Define upper motor neuron, lower motor neurons, pyramidal and extrapyramidal
Lower-those in the ventral horn, and the bulbar ones in the brain stem
Upper-corticospinal and corticobulbar (the ones in the brain)
Pyramidal-exactly the lateral corticospinal tract (so pyramidal problem are there)
Extrapyramidal-basal ganglia, cerebellum (so extrapyramidal problems are there)
What are the main problems with upper motor lesions
Loss of function: (negative signs)
Paresis-graded weakness of movement, Paralysis (plegia)-complete loss
abnormal function (positive sign-loss of inhibitory)
Spasticity-increased muscle tone
Hyper-reflexia-
Clonus-Abonrmal repeated muscle contraction
(Babinski’s sign-movement of toes after stimulating bottom of foot)
What is Apraxia?
Damage to the inferiot parietal lobe/frontal lobe (premotor/supplementary)
Not weak or aything, but loss of organising of skilled movement
eg: lose ability to put buttons together, etc
Any disease can cause it, but more commonly stroke and dementia
What are consequences of lower motor lesions?
Weakness, hypotonia, hyporeflexia, (over time-muscle atrophy), fasciculations (damaged units create spontanous AP-twitch), fibrillations-twitching of individual muscle fibre (seen with EMG)
What is motor neuron disease?
Rare, but progessive neurodegenerative disorder of motor system (both upper and lower motor neurons)
Most common one is Amyotrophic lateral sclerosis (ALS)
Varied phenotype and cause (but signs are what are expected-tones increase-rigid tongue, hands, etc)
Usually distal to proximal, until respiratory
What are the different parts of the basal ganglia?
Caudate nucleus-the higher part (head and tail) and Lentiform neucleus (putament and external globus pallidus (internal also there)) Caudate, Putamen and external-striatum Subthalamis nucleus, substantia nigra (in midbrain, but project to ganglia) Ventral pallidum (dopagenic), claustrum grey matter), nucleus accumbens (reward system-bottom of lentiform) , nucleus basalis of Meynert (cholinergic to forebrain-memory)
