Neuroanatomy Lecture #38: Organization Of Motor Pathways

Front 1

Def of Lower Motor Neuron

Back 1

Motor neurons that communicate directly with the somatic muscle

Front 2

Def of Upper Motor Neuron

Back 2

Motor neurons arising from motor centers in the brain that communicate w/ lower motor neurons
- directly or
- indirecty via interneurons

Front 3

Def Pyramidal Motor System

Back 3

Tracts formed by corticospinal and coricobulcar fibers that form the pyramids of the ventral medulla

Front 4

Def of Plegia

Back 4

Paralysis

Front 5

Def of Paresis

Back 5

Slight or incomplete paralysis; muscle weakness

Front 6

Def of Hemiparesis

Back 6

Partial paralysis on one side of the body

Front 7

Name the Starting location of the following Motor Pathways:
1. Lateral Corticalspinal
2. Corticobulbar
3. Rubrospinal
4. Lateral Vestibulospinal
5. Medial Vestibulospinal
6. Pontine (Medial) Reticulospinal
7. Medullary (Lateral) Reticulospinal

Back 7

The Starting location of the the Motor Pathways:
1. Pyramidal cells (layer 5) of area 4
2. Pyramidal cells (layer 5) of area 4
3. Red Nucleus in the midbrain
4. Lateral Vestibular nucleus (mostly pontine)
5. Medial Vestibular nucleus in the pons and medulla
6. Oral and Caudal reticular nuclei in the pons
7. Gigantocellular reticular nucleus in the medulla

Front 8

Descending motor tracts
• Two subdivisions and the actions associated with each
• The 3 tracts within each subdivision and whether they participate in voluntary/involuntary movement
• The general location of the spinal motor neurons each subdivision iNN

Back 8

Descending motor tracts
• Two subdivisions
- Ventromedial: Extension
1) Pontine/Medial Reticulospinal (Voluntary)
2) Lateral Vestibulospinal (Involuntary)
3) Medial Vestibulospinal (Involuntary)

Location of spinal motor neurons: Ventral portion of the ventral horn

- Lateral: Flexion
1) Lateral Corticalspinal (Voluntary)
2) Rubrospinal (Voluntary)
3) Medullary/Lateral Reticulospinal (Voluntary)

Location of spinal motor neurons: Dorsal portion of the ventral horn

Front 9

In the ventral horn of the spinal cord, describe how the following neurons are arranged relative to one another:
Flexor/ADductor, Extensor/ABuctor

Back 9

Flexor/ADductor neurons lie dorsal to the Extensor/ABductor neurons

Front 10

In the ventral horn of the spinal cord, describe how neurons iNN distal and proximal structures are arranged relative to one another

Back 10

Neurons iNN distal structures are more lateral to those iNN proximal/truncal structures

Front 11

ALS
• General description
• Cell types and regions of the CNS it affects
• Some sx
• NOT commonly affected fxns

Back 11

ALS
• Progressive neuromuscular disease
• affects/destroys lower motor neurons, parts of the pyrimidal tract, precentral gyrus and paracentral lobule

• Paresis (often beginning in the hands), difficulty speaking and/or swallowing and often loss of respiratory fxn

• Sensory loss, sphincter control, intellectual ability, skin integrity

Front 12

Anterior Spinal Artery Syndrome
• Etiology (most and least common)
• Lesioned structures (4)
• Sx
• Parts of sensory system left intact

Back 12

Anterior Spinal Artery Syndrome
• Most common - infarction
Least common - tumors, epidural spinal abscess

• Lesioned structures
- 2nd order motor neurons in the anterior horn
- Lateral corticospinal tract
- Anterior corticospinal tract
- Anterolateral system

• Sx
- Spastic parapesis
- Bilateral extensor plantar response
- Bilateral loss of pain and temperature below the lesion
- Urine retension
- Impaired sexual fxns

• TVP intact

Front 13

Central Medullary Syndrome
• Most common disease state
• Etiology (3 possible)
• Sx

Back 13

Central Medullary Syndrome
• Syringomyelia
• A cyst that develops along the central canal, tumors or hemmorrhages
- any abnormality that develops ventrally and applies pressure on the ventral horns and anterior white commissure
• Sx
- segmental muscle atrophy, loss of pain and temperature due to the anterior white commissure being destroyed