11,12 Flashcards
(11 cards)
Primary Motor Cortex lies in
frontal lobes anterior to the central sulcus.
Excitation of a single motor cortex neuron usually excites a specific movement rather than one specific muscle
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Premotor Area lies
1 - 3 centimeters anterior to the primary
motor cortex
The premotor area cause much more complex
Supplementary Motor Area
lies in
Mainly in the longitudinal Fissure but extend a few centimeter into the superior frontal cortex
Contractions elicited by stimulating this area are
often bilateral rather than unilateral
this area functions in concert with the premotor
area to provide body-wide attitudinal movements
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Some Speci alized Areas of Motor Control Found in the Human Motor Cortex
broca’s Area and Speech
Voluntary eye movement field
Corticospinal (Pyramidal) Tract
Origin:
- 30 % from the primary motor cortex
- 30 % from the premotor and
supplementary areas - 40 % from the somatosensory areas
The most impressive fibers in the pyramidal tract are
large myelinated fibers that originate from giant pyramidal cells , called Betz cells.
Corticospinal (Pyramidal) Tract
Pathway
- Fibers Leave the cortex to passes through the
posterior limb of the internal capsule - downward through the brain stem, forming the
pyramids of the medulla. - Most fibers cross in the lower medulla to the opposite side and descend into the lateral corticospinal tracts
- A few of the fibers do not cross to the opposite side in the Medulla but pass ipsilateral down the cord
in the ventral corticospinal tracts.
Effects of unilateral pyramidal tract lesion
Paralysis or paresis
Hypotonia, flaccidity pure pyramidal tract lesion
Babiniski sign
Paralysis or paresis:
Level of lesion
1- Cortex or corona radiata: Opposite side monoplegia.
2-Internal capsule: Opposite side hemiplegia.
3-brain stem: Opposite side hemiplegia.
+ same side cranial nerve lesion
4- Spinal cord: Same side
Above the brachial : hemiplegia
Below brachial, above lumber plexus: monoplegia
OTHER CORTICAL AND BRAIN STEM Paralysis).
PATHWAYS INVOLVED IN POSTURE AND VOLUNTARY MOVEMENT
1-The axons from the giant Betz cells send short collaterals back to the cortex itself (Sharpening effect)
2-•A large number of fibers → caudate nucleus and putamen. → Basal ganglia
3-•A moderate number of fibers → red nuclei. → Rubro spinal tract
4-•A moderate No. of fibers → Riticular formation (RF) & Vestibular Nuclei
→ 1- Spinal cord ( Reticulo & Vestibulo Spinal Tracts)
→ 2- Cerebellum (Reticulo & Vestibulo Cerebellar T.)
5-•A tremendous No. of fibers → Pontine Nuclei
→ Pontocerebellar fibers
6-•Collaterals → inferior olivary nuclei → olivocerebellar fibers
Upper motor and lower motor neuron lesion (UMNL&LMNL)
Upper motor neurons:Fibers from cortex to
AHC in the spinal cord or motor cranial nerve nuclei in the brain stem. UMN
