it is all about motar system and its function

1. MOTOR FUNCTIONS
PRESETED BY
SRILOY MOHANTY
B.N.Y.S

2. MOTOR CORTEX
• Primary motor cortex ( M1)
• Premotor area (PMA)
• Supplementary motor area (SMA)
Note: All the three projects directly to the spinal cord via
corticospinal tract.
• Premotor and supplementary motor cortex also project to
primary motor cortex and is involved in coordinating &
planning complex sequences of movement (motor learning).

3. PRIMARY MOTOR CORTEX (M-I)
Location :-
Immediately anterior to the central sulcus and
extends to the medial surface of hemisphere
also known as Broadmann’s area 4 is a
motor homunculus.
Description: Body is represented as up side
down and stretched on the medial surface
where pelvic and leg muscles are
represented.
Hand and mouth has a greater area of

4. - It controls the musculature of the opposite side of
the body.
-Face area is bilaterally represented.
Functions:-
Is used in execution of skilled movements also in
codes the direction, force and velocity of
movements.
Lesions:-
Pure M-I lesions are rare. May have contra lateral
weakness in distal muscle (fingers).
Ability to control fine movements is gone.
Ablation of M-I alone cause hypotonia not Spasticity.

5. SUPPLEMENTARY MOTOR AREA (M-II)
Location:
Found on both in lateral and medial aspect of the frontal
lobe. It extends from cingulate sulcus on the medial side
to reach premotor cortex on the lateral surface of the
brain.
Function:
It works together with premotor cortex.
Involved in programming of motor sequences.
Lesions:
Produces awkwardness in performing complex activity like
bimanual coordinated activity.

6. It function in mental rehearsal of movements before
performing a complex motor functions.
With premotor cortex it translates the desire to
perform a motor task into a series of motor
command that will do the task.

7. PREMOTOR CORTEX (PMC)
Location:
Broadmann’s area 6. It lies immediately anterior to primary
motor cortex. It is more extensive than primary motor
cortex (about 6 times)
Functions:
It works with the help of basal ganglia, thalamus, primary
motor cortex, posterior parietal cortex. It plays role in
planning and anticipation of a specific motor act.

8. Premotor cortex – Two-hand
Coordination
THE MONKEY HAS LEARNED THE TASK
PUSH THE OBJECT THROUGH THE HOLE AND CATCH IT WITH THE OTHER HAND; With
damage to premotor cortex, cannot coordinate two hands to do the task

9. Lesion:
It results in re-emergence of suckling and grasp
reflex in adults.
Its lesion do not case paralysis but only slowing of
the complex limb movement.
Lesion may result in loss of short-term or working
memory.
When damaged with supplementary cortex it may
result in APRAXIA.

11. VOLUNTARY MOVEMENT: INSTRUCTIONS
FROM CEREBRAL CORTEX
• Dorsolateral Prefrontal Cortex: directs movement of
our limbs (as in reaching) and movements of our
fingers.
• Actual signal for movement must go through pre-motor
cortex, then motor cortex.
• From motor cortex, signal travels down spinal cord
eventually reaching the alpha motor neuron.
• BUT, the instructions for this movement ultimately
comes from our Parietal lobe, which receives sensory
input.

20. CEREBELLUM
• Vermis
• Intermediate zone
• Lateral zone
• Within are deep
cerebellar nuclei:
• Fastigial nucleus
• Interpositus
nucleus
• Dentate nucleus

21. VERMIS
Kinesthetic and
somatosensory inputs
from the spinal cord
projections to fastigial
nucleus
• Damage interrupts
posture and walking
• In monkeys, unilateral
lesions of the fastigial
nucleus cause the
monkeys to fall
(ipsilateral side)

22. INTERMEDIATE ZONE
• Inputs from red nucleus
(brain stem & motor cortex)
and somatosensory info
from the spinal cord
• Projects to interpositus
nucleus  red nucleus (loop)
• Damage produces rigidity
and difficulty in moving
limbs
• Action tremor or intention
tremor – a tremor causing
movement to occur in a
staggered manner during
motor act.

23. LATERAL ZONE
• Inputs from motor and
association cortices
(through pons)
• Projections to dentate
nucleus  primary
motor and premotor
cortex
1. Balistic movement –
movement that occurs
so quickly that it can
not be modified by
feedback
• E.g., swinging of a
batter trying to hit a
ball moving 140 km/h

24. LATERAL ZONE
2. Multijoint movements
3. Learning of new movements
4. Timing of motor movements (and
cognitive functions)

25. BASAL GANGLIA
• Unlike the cerebellum, which
plays a role in rapid balistic
movements, the basal ganglia
are more important for the
accomplishment of
movements that may take
some time to initiate or stop
• Important for internal guiding
(rather then external) of
movement
• Dopamine – nigrostriatal
pathway

26. BASAL GANGLIA
Damage to the basal ganglia:
• Produces either too much
activation (hyperkinetic)
responses= twitches, movements
bursts, jarring, etc.
• Huntington’s Chorea-dominant
gene based, increases glutamate in
striatum which destroys GABA
neurons in BG and loss of
inhibition
• No cure
• Tourette’s
OR
• Produces too little force
(hypokinetic)=rigidity
• Parkinson’s disease
Pink=inhibition
Blue=excitation

27. BRAIN STEM MOTOR CENTERS
• Pontine reticular nuclei – excite antigravity
muscles (muscles of the vertebral column and
limb extensor muscles) – pontine reticulospinal
tract.
• Medullary reticular nuclei – inhibit antigravity
muscles – medullary reticulospinal tract.
Pontine & medullary systems balance each other.
• Vestibular nuclei – supplement the excitatory
function of the pontine system by integrating
vestibular information – lateral and medial
vestibulospinal tracts.

29. Summary of the
major descending
spinal tracts and
their points of
origin corticospinal tract
rubrospinal
tract
reticulospinal tracts
tectospinal,
vestibulospinal
tracts

30. Corticospinal Tract
Origin – Sensory cortex, primary Motor Cortex, premotor & supplementary cortex
(40%) (30%) (30%)
Internal Capsule
Cerebral Peduncle (midbarain)
Pons
Medullary Pyramid
Pyramidal Decussation
Lat.Cross & Vent. Uncross White matter in spinal cord
Ant. Horn of spinal cord through a interconnection
α motor neuron of opposite side

31. MOTOR UNIT…

32. •Every striated
muscle has
encapsulated
muscle fibers
scattered
throughout the
muscle called
muscle
spindles.
•Extrafusal and
intrafusal
fibers

33. organization of motor subsystems

34. Overview - organization of
motor systems
Motor Cortex
Brain Stem
Spinal Cord
Skeletal muscle
-motor
neuron
Final common
pathway

35. Steps in Motor Action

36. THANK YOU…