motor intro kjg
TRANSCRIPT
Dr.K.Jaiganesh, MD
Professor of Physiology,
MGMC & RI
Cerebral cortex
Ascending tracts- Sensory
Carrying up sensationsDescending tracts-Motor
Carrying down orders
Motor System
Cerebral cortex
30%
40%
30%
Cerebral cortex
30%30% 40%
Motor Homonculus
Left Right
UMN & LMN Lesion
Motor neuron
UMN & LMN paralysis
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
Stretch Reflex
Muscle
Spinalcord
Dorsal rootganglion
BASIS-
REFLEX ARC
Muscle
spindle
Sensory nerve
Motor nerve
I
a
α Motor neuron
CS
T
Stretch reflex
G
Cortex
1 a
Role of Higher centers
PF
+
MI
-
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.
Cortex
Voluntary movement
by cortex
G