Organization of motor pathways

Question 1

Overview of the motor organization

Answer 1

signal originates in the prefrontal cortex, goes to the premotor cortex and then finally reaches the Primary motor cortex. Motor signals from here are coarse and require modulation by the basal ganglia, cerebellum and sensory systems.

Question 2

Rubrospinal tract and reticulospinal tracts connection with main pathways

Answer 2

Primary motor cortex sends message to red nucleus and then to the spinal cord

Reticulo spinal system receives input from ALS and the primary motor cortex and sends it to the muscles.

Question 3

Vestibulospinal tract

Answer 3

Vestibulospinal tract receives sensory from vestibular nuclei but are influenced weakly by the cerebral cortex and are largely involuntary. They also receive feedback from muscle spindles, DCML pathways, ALS pathways,

Question 4

Lower motor neurons

Answer 4

transmit signals from teh central nervous system directly to muscle cells.

Question 5

Upper motor neurons

Answer 5

originate in brain and regulate lower motor neurons

undergo decussation to exert either bilateral or contralateral control

Question 6

Pontine and Medullary reticulo spinal pathway

Answer 6

Pontine- oral and caudal reticular nuclei in pons

Medullary- Gigantocellular reticular nucleus in medulla

Question 7

Lateral and Medial Vestibulo spinal

Answer 7

lateral- lateral vestibular nucleus(largely pontine)

Medial- medial vestibular nucleus in pons and medulla

Question 8

the descending motor tracts are subdivided into

Answer 8

ventromedialpathways(BIAS for EXTENSION)- pontine reticulospinal, lateral vestibulospinal, medial vestibulospinal

lateral pathways(BIAS for FLEXION)- Lateral corticospinal, rubrospinal, medullary reticulospinal

Question 9

Rubrospinal tract

Answer 9

Red nucleus (midbrain)

Question 10

corticobulbar

Answer 10

pyramidal cells Layer 5 of brodmann’s area 4

Question 11

Lateral Corticospinal

Answer 11

Pyramidal cells in layer 5 of broadmann’s area 4

Question 12

Lateral pathway images

Answer 12

Question 13

Medial pathways image

Answer 13

Question 14

in the ventral horn of the spina cord, flexor and adductor neurons lie

Answer 14

dorsal to the extensor and abductor neurons

Question 15

Cells for distal muscles lie

Answer 15

laterally to those for truncal structures

Question 16

Location of motor neuorns, flexor biased white matter and extensor biased white matter

Answer 16

Question 17

lateral motor pathways strongly influence

Answer 17

Flexor muscles whose spinal motor neurons dewll in the distal portion of the ventral horn

Question 18

medial motor pathways more strongly influence

Answer 18

extensory muscles with spinal motor neurons that dwell in the ventral portion of the ventral horn.

Question 19

Amyotropic Lateral Sclerosis (Lou Gehrig’s disease)

Answer 19

initially destroys lower motor neurons and eventually parts of the corticospinal/bulbar tracts and the primary motor cortex (precentral gyrus and anterior paracentral lobule

symptoms-

1. weakness or difficulty swallowing
2. require ventilation and gastrostomy
3. atrophy
4. fasciculations
5. spasms,
6. cramping,
7. loss of thenar, hypothenar, interossei, arm and sholder muscles
8. reduction of cough reflex- leads to pneumonia
9. bulbar motor nuclei deficits- difficulty swallowing, coughing, speaking
10. weak pharyngeal and laryngeal muscles
11. death occurs from respiratory insufficiency and aspiration pneumonia

Question 20

Anterior Spinal Artery Syndrome

Answer 20

Anterior spinal aretery supplies two thirds of the spinal cord.

lesions of- anterior horn cells, lateral and anterior corticospinal tract, anterolateral system

Symptoms

1. spastic paraparesis
2. bilateral extensor plantar response
3. bilateral loss of pain and temperature below lesion
4. touch vibration, propriocepion intact
5. retention of urine
6. sexual functions impaired.

Question 21

central medullary synrome

Answer 21

syringomyelia is a longitudinal cysts that develops along the central canal. it usually expands ventrally to compress the ventral horn and ventral white commissure

usual symptoms

1. muscular atrophy(hand most often due to cervical involvement)
2. loss of pain and temperature at the level of the lesion.
3. can also be caused by tumors or hemorrhages.
4. may produce pain and weakness with stiffness in the back, shoulders, arms, and legs.
5. can also disturb sweating, sexual functions, bladder, and bowel controls.