Somatic motor system

1. Introduction to
somatic motor
system and motor
areas.
Name- Suhani Chhabra
Roll No.- 160
Batch -2019
GDMC

2. Index
 Introduction
 Connections of motor cortex
 Motor areas of cerebral cortex
 Motor homunculus
 References

3. Introduction
 The word motor means
“MOVEMENT”.
 Motor system – central structures (
cerebral cortex, brain stem) +
peripheral structures ( skeletal
muscles)
 Motor system deals with the study of
physiology of movements.
 Motor physiology involves initiation ,
execution and control of movements.

4. MOTOR SYSTEM

5. Connections of motor cortex

6. MOTOR AREAS
Korbinian Brodmann
•(1868-1918) German Neurologist.
•Became famous for his definition of
the cerebral cortex into 52 distinct
regions from their histological
characteristics , known as
“BRODMANNS FUNCTIONAL
AREAS OF CEREBRAL CORTEX”.

7. MOTOR CORTEX
•Anterior to the central cortical sulcus ,occupying approx
the posterior 1/3rd of the frontal lobes is the motor cortex.
•The motor cortex itself is divided into three sub areas each
of which has its own topographical representation of
muscle groups and specific motor functions.
• These areas are :-
•PRIMARY MOTOR CORTEX
•PREMOTOR AREA
•SUPPLEMENTARY MOTOR AREA

8. Motor areas

9. PRIMARY MOTOR CORTEX / AREA 4
•It lies in front of pre central gyrus or central sulcus.
•It begins – laterally : in the sylvian fissure
of the brain and dips deep into
superiorly : uppermost portion
longitudinal fissure.
•Corticospinal and corticobulbar tracts originates from
this area.
•This area is involved in planning and initiation of
voluntary movements.

10. Connections of primary motor
cortex

11. Pre motor cortex / lateral
area 6
• It lies anterior to the primary motor
cortex.
• It extents inferiorly into the sylvian
fissure and superiorly into the
longitudinal fissure.
• Fibres to the pyramidal tract also arise
in this region.
• It sets posture at the beginning of
planned movement, thus helps to
prepare for execution of movements.

12. Connections of pre motor cortex

13. Supplementary motor area/
medial area 6
• It lies in longitudinal fissure and extends to the
superior frontal cortex.
• It is involved in higher motor functions like
planning and programming the motor sequences
and it controls bimanual tasks.
• It co-ordinates activities of other motor areas like
:
AREA 8/FRONTAL EYE FIELD AREA:-
• It helps in involuntary and conjugate movement
of the eye.
• It also controls the movement of eyelids, size of
pupils and lacrimation.

14. AREA 44/BROCA SPEECH AREA:-
• It is present in dominant hemisphere anterior to
the primary motor cortex just above the sylvian
fissure.
• It helps in vocalisation by controlling the
movement of tongue, lips, larynx and respiratory

15. CONNECTIONS OF
SUPPLEMENTARY MOTOR
AREA

16. CONNECTIONS OF FRONTAL
EYE FIELD

17. MOTOR
HOMUNCULUS
• A topographical arrangement of different parts of the
body in the pre central gyrus (motor cortex) is termed
as motor homunculus.
• The body is represented upside down in the motor
cortex except for the face which is not inverted.
• The representation of body parts is contralateral but
the face has ipsilateral representation (the areas of
face represented bilaterally and rest of the body is
unilateral).
•to be continued........

18. • The area of representation is proportional
to the functional importance and activity of
the area (skill with which the body part is
involved in voluntary activities).
• As human beings are specialised in
speech, the lips, jaw and tongue occupy
significantly large area in the cortex. This
is called the VOCALISATION OF THE
CORTEX.

19. continued :
•The arm and hands are represented in the
mid portion of primary cortex.
• The regions of face and mouth are located
near the sylvian fissure.
• The trunk corresponds to the area near the
apex of brain.
• The leg and foot areas in the primary
cortex dipping into longitudinal fissure.
• Stimulation of medial part causes
movement of toes and lower limbs.
• Stimulation of lateral part causes
movement of tongue.

20. Motor homunculus

21. References
• Dr A .K Jain (textbook of physiology )
• G.K Pal
• Guyton
• Wikipedia

22. THANK
YOU