Descending Pyramidal Motor Pathway Flashcards

1
Q

Describe the basic structure of the descending pathway

What are the 2 functions of the descending motor pathway

A

Motor cortex =(UMN)=< o=(LMN)=

Modulate reflexes responses
Voluntary movement

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2
Q

What are the 3 fibre types
Name some examples
What do they do

A

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
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3
Q

What is the function of the CBT

  • describe the innervation
  • what are the exceptions to this
A

Motor cranial nerve innervation
-BILATERAL for head and neck

CONTRALATERAL only in

  • VII lower face
  • XII
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4
Q

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

A

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
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5
Q

Where do the CST, CBT start
What cells make up the UMN of this tract
What NT is released
What is the blood supply

A

Premotor
Supplementary motor
Primary motor

Betz cells release glutamate

ACA, MCA

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6
Q

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

A

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

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7
Q

What structure in the midbrain get branches from the tract
-what are their functions

What is the blood supply of this region

A

Red nucleus - locomotion
Sup coll - head mv from visual stimuli
III, IV - BILATERAL eye mv
Substancia nigra - BG, mv

Basilar
SC
PIC

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8
Q

What structures in the pons get branches from the tract
-what are their functions

What is the blood supply of this region

A

Pontine nucleus
V-VII - BILATERAL except VII lower (contralateral)
Reticular formation

Basilar
SC
AIC

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9
Q

What structures in the medullae get branches from the tract

What is the blood supply of this region

A

IX-XII

Vertebral
Basilar
PIC
AS

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10
Q

What is the blood supply of the lateral CST, anterior CST

A

Lateral CST
-PS

Anterior CST
-AS

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