Descending Pyramidal Motor Pathway Flashcards
Describe the basic structure of the descending pathway
What are the 2 functions of the descending motor pathway
Motor cortex =(UMN)=< o=(LMN)=
Modulate reflexes responses
Voluntary movement
What are the 3 fibre types
Name some examples
What do they do
Projection
- join cortex with other areas of the CNS
- corticopetal (afferent)
- corticofugal (efferent)
- CS, CT, CP
Association
- intrahemisphere connections
- short (within grey)
- long (between grey via white)
Commissural
- interhemisphere connections
- corpus callosum
- massa intermedialis
What is the function of the CBT
- describe the innervation
- what are the exceptions to this
Motor cranial nerve innervation
-BILATERAL for head and neck
CONTRALATERAL only in
- VII lower face
- XII
What is the function of the CST
- what are the 2 branches
- what do they innervate
- where do they decussate and synapse
how are the neurons organized in the SC
Lateral (limbs, trunk)
- medulla decussation
- synapse onto LMN, interneurons
Neurons organized by limb part
- lateral neurons => distal limbs
- medial neurons => proximal limbs
Anterior (neck, axial)
- BILATERAL
- SC decussation
- synapse onto LMN, interneurons
Where do the CST, CBT start
What cells make up the UMN of this tract
What NT is released
What is the blood supply
Premotor
Supplementary motor
Primary motor
Betz cells release glutamate
ACA, MCA
What structure do the fibres form
What structure do they pass through
-how does this structure relate to the motor homunculus
-describe the blood supply of this structure
-which fibres pass through each section
Which arteries are vulnerable to stroke/aneurysm and why
Corona radiata, pass through int capsule
Post limb (peripheral limbs, CS) MCA + AchA Genu (face, CB) MCA Ant limb (CP) MCA + ACA
Lenticulostriate at right angles to MCA
What structure in the midbrain get branches from the tract
-what are their functions
What is the blood supply of this region
Red nucleus - locomotion
Sup coll - head mv from visual stimuli
III, IV - BILATERAL eye mv
Substancia nigra - BG, mv
Basilar
SC
PIC
What structures in the pons get branches from the tract
-what are their functions
What is the blood supply of this region
Pontine nucleus
V-VII - BILATERAL except VII lower (contralateral)
Reticular formation
Basilar
SC
AIC
What structures in the medullae get branches from the tract
What is the blood supply of this region
IX-XII
Vertebral
Basilar
PIC
AS
What is the blood supply of the lateral CST, anterior CST
Lateral CST
-PS
Anterior CST
-AS