21 Neuroanatomy: Motor Tracts

Question 1

Lower and Upper Motor Neurons

• Lower
  
  • Are these neurons afferent or efferent?
  • What connection are these nerves important for?
  • Where are they located in the
    
    • spinal cord?
    • brainstem?
• Upper
  
  • What is the general role of these neurons?
  • What are the two general locations that hey are located in?

Answer 1

Question 2

Complexity of Motor Functions

• Where is the reflex motor center?
• What structure is the most important source of upper neurons?
• What structure modulates the neurons f located in the motor regions of the cerebral cortex?
• What structure is the major integrator of motor function?
• What structure houses the major tracts from upper motor neurons that influence spinal motor neurons?
• What structure is the “relay” station?

Answer 2

Question 3

Descending Tracts

• These are typical motor pathways. What are the two other kinds of pathways that can be descending tracts?
• What are the 2 main tracts located in the cerebral cortex?
• What are the 4 main tracts that originate in the brain stem?
  
  • Which ones originate in the pons?
  • Which ones originate in the Midbrain?

Answer 3

Question 4

Lateral and Medial Motor Systems

• Medial Motor System
  
  • What spinal cord column is associated with this system?
  • What part of the ventral horn do they synapse with?
• Lateral Motor System?
  
  • What spinal cord column is associated with this system?
  • What part of the ventral horn do they synapse with?

Answer 4

Question 5

Corticospinal Tract aka Pyramidal Tract

• What side of the body does this track control the movement of?
• Pathway
  
  • Where in the brain does it arise from?
  • What are the 3 places in the CNS that this tract descends in?
  • Where do 90% of the fibers cross, creating the lateral corticospinal tract?
  • What tract is made up of the 10% of fibers that do not cross over into the lateral corticospinal tract? Do these fibers ever cross over?

Answer 5

Question 6

Primary Motor Cortex

• On what gyrus is this located?
• What are the two components of the motor association cortex?
  
  • Where do they lie in relation to the primary motor cortex?
  • What component of movement do they have a role in?
  • What condition arises from lesions in this area?
    
    • Do these patients have any deficits in muscle strength?

Answer 6

Question 7

Corticospinal Tract Origin

• What area do over 50% of corticospinal fibers arise from?
  
  • What are the 3 areas the remaining corticospinal fibers arise from?
• Axons from the cortex enter the upper portions of the cerebral white matter?
  
  • What is this area of white matter called?
  • What structure do these axons descend to?

Answer 7

Question 8

Internal Capsule

• What are the 3 components of the internal capsule?
  
  • Where do the corticobulbar fibers reside?
  • Where do the corticospinal fibers reside?
• What are the 3 major components of the corticofugal fibers?

Answer 8

Question 9

Somatotopic Organization

• In the internal capsule, motor fibers from most anterior and medial to progressively posterior and lateral supply the following structures
  
  • Trunk
  • Face
  • Leg
  • Arm

1. Assign each of the above structures to one of the colored areas
2. What midbrain structure has the same configuration (medial to lateral)?

Answer 9

Question 10

Pathway through brainstem

• Where are the corticospinal fibers in the following parts of the brain stem?
  
  • Midbrain
  • Basilar Ppns
  • Medulla
• When the corticospinal fibers are in the pyramids, which of the following types of fiber is most medial?
  
  • Cervical region terminating
  • Lumbo/Sacral region terminating

Answer 10

Question 11

Corticospinal Tracts

• Label the following as being either Lateral Corticospinal Fibers or Anterior Corticospinal Fibers
  
  1. Innervate Medial Aspect of Ventral Horn
  2. Control Movements of Extremities
  3. Regulate Postural Mechanisms
  4. Innervate Lateral Aspect of Ventral Horn

Answer 11

Question 12

Cortiocofugal Fibers

• Give a name to each of the following fibers

Answer 12

Question 13

Descending Tracts: Midbrain Originating Tracts

• Rubrospinal Tract
  
  • Location of cell bodies?
  • After decussation in the midbrain, where does it fibers descend to?
  • What are the two main functions
• Tectospinal Tract
  
  • Location of cell bodies?
  • After decussation in the midbrain, where does it fibers descend to?
  • What function does this tract have?

Answer 13

Question 14

Descending Tracts: Rostral Medulla-Originating Tracts

• Lateral Vestibulospinal Tract
  
  • Pathway
    
    • Does this track ever cross the spinal cord?
    • Where does it terminate?
  • What kind of neurons does it innervate, and what do these neurons control?
  • What is the main function of this tract?
• Medial Vestibulospinal Tract
  
  • Pathway
    
    • Does this track ever cross the spinal cord?
    • Where does it terminate?
  • What is the main function of this tract?

Answer 14

Question 15

Descending Tracts: Reticular Formation

• Where is this located in the brainstem?
• What are the general roles of this?
• 1. Reticulospinal Projections
  
  • These projections control posture and the antigravity muscles? Where do they synapse in order to this?
  • 2. Medial Retocularpsinal Tract
    
    • What brainstem structure do these come from, and what fasciculus are they apart of?
  • 3. Lateral Retocularpsinal Tract
    
    • What part of the Reticular Formation has projections in this tract?

Answer 15

Question 16

Label the following

1. Rubrospinal Tract
2. Lateral Reticulospinal Tract
3. Ventral Corticospinal Tract
4. Tectospinal Tract
5. Ventral White Commissure
6. Lateral Corticospinal Tract
7. Medial Reticulospinal Tract
8. Vestibulospinal Tract

Answer 16

Label the following

1. Rubrospinal Tract
   
   • D
2. Lateral Reticulospinal Tract
   
   • B
3. Ventral Corticospinal Tract
   
   • F
4. Tectospinal Tract
   
   • H
5. Ventral White Commissure
   
   • A
6. Lateral Corticospinal Tract
   
   • C
7. Medial Reticulospinal Tract
   
   • E
8. Vestibulospinal Tract
   
   • G

Question 17

Decorticate and Decerebrate Posturing

• Fill in the blocked out words

Answer 17

Question 18

Decorticate and Decerebrate Posturing

• Which figure shows Decorticate Posturing and which shows Decerebrate Posturing?
• Which is more severe?
  
  • In the less severe one:
    
    • What tract has EXCESSIVE action?
    • What does the excessive aciton in the above tract cause in the upper limbs?
  • In the more severe one:
    
    • What structure has pathology moved through?
    • What two tracts/systems are lost in this?
    • What happens to all 4 limbs?

Answer 18

Question 19

Lower and Upper Motor Neurons

• Lower Motor Neurons
  
  • What are the 4 main signs of lesions that affect these neurons?
• Upper Motor Neurons
  
  • What are the 5 main signs of lesions that affect these neurons?

Answer 19

Question 20

Lower and Upper Motor Neurons

• Label each of the following as upper motor neurons (UMN), lower motor neuron (LMN) lesions, or both
  
  • Weakness
  • Atrophy
  • Fasculations
  • Spasms
  • Increased Reflexes
  • Decreased Reflexes
  • Increased muscle tone
  • Decreased muscle tone

Answer 20