Motor intro kjg

1. Dr.K.Jaiganesh, MD
Professor of Physiology,
MGMC & RI

2. Cerebral cortex
Ascending tracts- Sensory
Carrying up sensationsDescending tracts-Motor
Carrying down orders

3. Motor System

4. Cerebral cortex
30%
40%
30%

5. Cerebral cortex
30%30% 40%

6. Motor Homonculus
Left Right

8. UMN & LMN Lesion
Motor neuron

9. UMN & LMN paralysis

10. UMN Lesion LMN Lesion
Muscle bulk Disuse atrophy Wasting
Muscle tone (spasticity) (flaccidity)
Superficial
reflexes
Lost Lost
Deep reflexes Exaggerated Lost
Plantar reflex Babinski’s sign Normal
Clonus Present Absent
Cause Damage to motor
tracts above the
anterior horn cell
Damage to the
anterior horn
cells and below
UMN & LMN Lesion

11. Stretch Reflex

12. Muscle
Spinal
cord
Dorsal root
ganglion
BASIS-
REFLEX ARC
Muscle
spindle
Sensory nerve
Motor nerve
I
a
α Motor neuron
CS
T

14. Stretch reflex

15. G
Cortex
1 a
Role of Higher centers
PF
+
MI
-

16. ά- γ linkage
γ (Gamma) motor neuron discharge by HC influence
contraction of the ends of the intra fusal fibers
stretching of the intra fusal fibers
Ia afferent impulses to the spinal cord
reflex firing of ά (alpha) motor neuron)
contraction of extra fusal fibers
in muscle tone.

17. Cortex
Voluntary movement
by cortex
G