Functions Of Descending Motor Tract

Question 1

GR: The name of the pyramidal tract

Answer 1

Because some fibers arise from the pyramidal (Betz) cells present in motor area 4

Question 2

Functions if pyramidal tract

Answer 2

1. Controls fine skilled motor movements especially in the distal joints
2. Shares with extrapyramidal tract in gross movements and postural adustment as background for fine movements
3. Facilitatory to superficial & deep reflexes
4. Inhibits primitive withdrawal reflex
5. Conrticobulbar tract controls lateral eye movemts

Question 3

Mention parts of medial brain stem

Answer 3

Work via vertical corticospinal tract
PRS & MRS, vestibulospinal, tectospinal tracts

Question 4

Describe termination of medial brain stem pathways

Answer 4

-Terminate on interneurons in ant horn of spinal cord to control axial & proximal muscles
-Some terminate directly on motor neurons to control axial muscles

Question 5

Describe lateral brain stem pathway

Answer 5

Arise from red nucleus of midbrain which has a somatotopic representation like area 4 but less fine, terminate on interneurons in ventral horn of spinal cord controlling distal muscles, it excited flexor & inhibits extensor muscle, may be a weak alternative in fine skilled movement in case of pyramidal lesion

Question 6

Enumerate functions of extrapyramidal tract

Answer 6

1. Control gross movements if axial & proximal muscles.
2. Provide postural background for performance of fine skilled movements
3. Associated with basal ganglia in semiautomatic movements
4. In selective corticospinal tract lesion, rubrospinal tract can control fine movements of hand & wrist but not fingers.
5. Regulation of muscle tone
6. Med tectospinal —reflex head turning in response to sound, lateral tectospinal —protective eye reflexes, head turning in response to visual stimuli.
7. Vestibulospinal tract activate antigravity muscles.
8. Autonomic functions

Question 7

Describe autonomic functions of extrapyramidal tract

Answer 7

1. Respiratory center to AHCs of respiratory muscles
2. Vasomotor tract to LHCs in thoraco-Lumbar region
3. Sweat secretion (from heat regulating center in hypothalamus)

Question 8

Compare pyramidal to extrapyramidal with respect to termination & when function starts

Answer 8

Pyramidal, terminate on cranial nerve nuclei & alpha & gamma (AHCs) , begins one year after birth
Extrapyramidal, terminate on alpha & gamma neurons, during first year

Question 9

Mention site of termination of medial & lateral motor systems

Answer 9

M, medial or ventral portion of anterior horn
L, lateral portion of anterior horn