13. Motor Tracts Flashcards
For motor tracts, instead of there being 3 neurons, there are only 2. What are they?
upper motor neuron (UMN)
lower motor neuron (LMN)
What are two examples of both UMN and LMN?
UMN: Corticospinal and corticobulbar (corticonuclear) tracts
LMN: Peripheral and Cranial Ns
What is the difference between direct and indirect somatic motor pathways?
direct from cerebral cortex to spinal cord to muscles
indirect includes synapses in BS, basal gang, thalamus, reticular formation and cerebellum
The corticospinal tract is a direct pathway which controls voluntary motion. UMN arise from cortex and synapse in SC on LMN. What are the two paths?
Medial corticospinal tract (postural)
MAIN: lateral corticospinal tract (90%) - muscles/fine movement
What is the general overview/pathway of the corticospinal pathway? 8
- Cell bodies in cortex
- Descends through posterior limb of internal capsule
- Continues as lateral corticospinal tract
- Passes through midbrain at cerebral peduncles
- Through anterior pons
- Through pyramids of medulla
- Fibers cross in LOWER medulla pyramids
- Descend in lateral column of spinal cord and synapase with LMNS
The primary motor cortex (brodmanns area 4) is in the precentral gyrus. The right side motor strip usually controls?
left side of body and vice versa
Muscles in the homunculus are represented unequally according to the number of motor units in a muscle. What are examples of areas with more motor units? (5)
vocal cords tongue lips fingers thumb
What is the difference between corticospinal and bulbar tracts? Where are they located in the internal capsule?
Corticobulbar is face motor and located in GENU of internal capsule
Corticospinal is arms thorax and legs and located in posterior limb of internal capsule
When the lateral corticospinal tract descends and crosses at the lower medulla, not all cross. What are the two different tracts called?
medial corticospinal tract (not many-dont cross)
lateral corticospinal tract (cross)
The lateral corticospinal tract after crossing in lower medulla will descend in the lateral column of the spinal cord and synapse where?
Synapses on LMNs in the VENTRAL horn of spinal cord
What are the two main blood supplies to the corticospinal tract in the internal capsule?
lenticulostriate A
anterior choroidal A
What is the main blood supplies to the corticospinal tract in the midbrain?
posterior cerebral A
What are the two main blood supplies to the corticospinal tract in the medulla?
anterior spinal A via sulcal A
What are the main blood supply to the corticospinal tract in the pons?
paramedian branches of basilar A
What are the two main blood supplies to the corticospinal tract in the spinal cord?
Anterior and posterior spinal A
The 10% of the corticospinal tract that does not cross becomes the medial corticospinal tract and has no clinical significance. What does it control?
postural and proxiaml movements (neck shoulders trunk)
The corticobulbar/nuclear tract arises from the lateral precentral gyrus, descends and influences muscles innervated by CNs. Which ones? (6) (axons cross)
5,7,8,10,11,12
The corticobulbar tract follows the same path as the lateral corticospinal tract except for what region?
in cortex, corticobulbar tract descends through the genu of the internal capsule
In the mid pons, what does the corticobulbar tract give off?
bilateral fibers to trigeminal motor nucleus
In the lower pons, what does the corticobulbar tract give off?
Bilateral facial forehead, only one side innervates mouth