L11 Motor Cortex Flashcards
(30 cards)
Motor cortex site
(posterior 1/3 of frontal lobes):
– Anterior to central cortical sulcus
– Motor cortex is divided into three subareas
(1) primary motor cortex
(2) premotor area
(3) supplementary motor area
-primary motor cortex site
anterior to central sulcus ( pre central gyrus )
-area 4 in Brodmann’s classification?
PRIMARY MOTOR CORTEX
-Body representation in PRIMARY MOTOR CORTEX
Upside down
crossed, inverted, with head in correct position
• Face and mouth → near the sylvian fissure
• Arm and hand → midportion of the primary motor cortex
• Trunk → near the apex of the brain
• Leg and foot → in the part of that dips into the longitudinal fissure.
……………….……… have wide area of representation in area 4
Muscles of Hand , Muscles of mouth ( speech )
-Most of the body muscles represented ………………….in area 4
Unilateral
-Respiratory muscle represented …………in area 4
bilaterally
-Excitation of a single motor cortex neuron usually excites a ……,,,,,,,,,,
specific movement ( group of muscles ) rather than one specific muscle
PREMOTOR AREA site
anterior to the primary motor cortex.
Topographical representation of pre motor area ( responsible for ) ?
More complex “PATTERNS” of movement
**Example:
the pattern may be to position the shoulders and arms so that the
hands are properly oriented to perform specific tasks ( writing )
-Anterior part of the premotor area first develops a …………………….
“ MOTOR IMAGE” of the (total) muscle movement that is to be performed.
الحركة كلها بشكل عام
-posterior premotor cortex function?
image that have taken in the Ant. Part, excites each successive pattern of muscle activity required to achieve the image.
تحدد صورة للعضلات انه من يتحرك اول وترسله ل 4
posterior part of the premotor cortex sends its signals either :
1-directly to the primary motor cortex to excite specific muscles
2-by way of the basal ganglia and thalamus back to the primary motor cortex.
-SUPPLEMENTARY MOTOR AREA site
in the longitudinal fissure and ( superior frontal cortex)
-SUPPLEMENTARY MOTOR AREA properties?
1-Contractions elicited by stimulating this area BILATERAL rather than unilateral.
2-functions in concert with the premotor area to provide
A.attitudinal movements
B. fixation movements of the different segments of the body
C. positional movements of the head and eyes
D. background for the finer motor control of the arms and hands by the premotor area and primary motor cortex.
E.g bilateral grasping movements of both hands simultaneously ( hand functions required for climbing)
SPECIALIZED AREAS IN MOTOR CORTEX
-Broca’s area 44, 45
-Voluntary eye movement 8
-Head rotation area
-Area for hand skills
-Broca’s area 44, 45 ?
Word formation (Motor Speech Area)
Damage to it (does not prevent a person from vocalizing)
but makes it impossible to speak whole words
closely associated area also causes appropriate activation of vocal cord simultaneously with movements of mouth and tongue during speech
-Voluntary eye movement 8 damage
*prevents a person from voluntarily moving the eyes toward different objects
Loss of blinking
-Head rotation area?
It directs the head toward different objects (head rotation )
It is closely associated with the eye movement field
-Area for Hand Skills Destruction ?
hand movements become uncoordinated and non-purposeful, a condition called motor ((apraxia))
-MIRROR NEURONS
performs a specific motor task or when the person observes the same task performed by others
transform SENSORY representations of acts that are heard or seen into MOTOR representations of these acts ( connection )
LEARNING new skills by imitation.
-Motor signals are transmitted from the cortex to the spinal cord through :
Direct via:
1- corticospinal (Pyramidal) tract This pathway is mono-neuronal
2- cortico-bulbar or nuclear
(concerned more with discrete and detailed movements, distal segments of the limbs, hands and fingers)
Indirectly via:
the extrapyarmidal tracts
accessory pathways that involve the basal
ganglia, cerebellum, and various nuclei of the brain stem
Not fine skilled movement as ( hand hanging during walking )
PYRAMIDAL TRACT
Origin:
– 30 % from the primary motor cortex
– 30 % from the premotor and supplementary motor areas
– 40 % from the somatosensory areas posterior to the central sulcus
