Motor Systems I Pyramidal Primary Motor System

The motor function is mainly supported by the corticospinal (or pyramidal) tract. The majority of fibers of the pyramidal tract take origin from the precentral gyrus (primary motor area - area 4), and caudal premotor cortex (area 6). The largest amount comes from the axons of the giant pyramidal (or Betz's) neurons located in the V and VI layers of the posterior fifth of the motor cortex. The motor cortex is somatotopically organized, and movements of the hind limb are located in the medial motor cortex (lobulus paracentral, with the foot located caudally, and the hip at the vertex). The trunk is in the upper part of the prerolandic gyrus, followed by the forelimb and the hand. The motor area for the contralateral hand is thicker than the rest of the primary motor cortex and folded; therefore it is well recognizable ("omega" or"epsilon" sign). Movements of the face are located successively, closer to the sylvian fissure. During their course, the axons pass through the centrum semiovale, the corona radiata, the genu and posterior limb of the internal capsule, the cerebral peduncle, the pons and the medulla. Here, approximately at the foramen magnum level, 80-90% of fibers cross the midline (pyramidal decussation) continuing their course in the anterolateral spinal column (tractus pyramidalis lateralis). The remaining fibers, whose role is still controversial, remain homolateral (tractus pyramidalis anterior). The fibers are somatotopically organized in their entire course: in the internal capsule, head and neck fibers are located in the genu, while in the spinal cord the more distal fibers are the more peripheral. The main terminations of the corticofugal system are: thalamus, striatum, brainstem and spinal cord. In the brainstem, the most important terminations are the tectum, the basal pontine nuclei, and the reticular formation; in the spinal cord, fibers terminate in the anterior horn, in correspondence with the motor nuclei.

Postcentral gyrus (area 2,1,3)

Central sulcus

Motor cortex (area 4]

Parietopontine tract Occipitopontine tract

Temporopontine tract

Pyramidal tract

Frontopontine tract

Pyramidal tract

Pyramidal decussation

Motor Systems - (I) Pyramids) System

Postcentral gyrus (area 2,1,3)

Parietopontine tract Occipitopontine tract

Temporopontine tract

Pyramidal tract

Pyramidal decussation

Central sulcus

Pyramidal tract

Frontopontine tract

Motor cortex (area 4]

Pre mo tor cortex (area 6) Premotor cortex (area 8)

Meniscus Tear Mri Images
Corticospinal tract
Frontopontine TractAnterior Limb The Internal Capsule

Corticospinal tract, posterior limb of the internal capsule

Corticospinal tract, posterior limb of the internal capsule

Corticospinal tract, corona radiata

Corticospinal tract, corona radiata

Primary motor cortex (area 4) Areas 2,1,3 Pre mot or area 8 Premotor area 6

Superior frontal gyrus (F1 )

Middle frontal gyrus (F2)

P recentra I gyrus ~ Postcentral gyrus -

Superior frontal gyrus (F1 )

Middle frontal gyrus (F2)

P recentra I gyrus ~ Postcentral gyrus -

Precentral Gyrus Mri

Primary motor cortex (area 4) Areas 2.1,3

Superior frontal gyrus (Fl)

Middle frontal gyrus (F2)

Precentral gyrus

Postcentral gyrus

Superior frontal gyrus (Fl)

Middle frontal gyrus (F2)

Precentral gyrus

Postcentral gyrus

Premotorarea 8 Prem oto r area 6

Superior frontal gyrus (Fl J

Middle frontal gyrus (F2)

Precentral gyrus (Fa, ascending frontal gyrus)

Postcentral gyrus (Pa, ascending parietal gyrus)

Superior frontal gyrus (Fl J

Middle frontal gyrus (F2)

Precentral gyrus (Fa, ascending frontal gyrus)

Postcentral gyrus (Pa, ascending parietal gyrus)

Primary motor cortex (area 4) Areas 2,1,3

Superior frontal gyrus (Fl)

Middle frontal gyrus (F2)

Precentral gyrus

Postcentral gyrus

Superior frontal gyrus (Fl)

Middle frontal gyrus (F2)

Precentral gyrus

Postcentral gyrus

Premotor area 8

] Premotor area 6

Superior frontal gyrus (Fl)

Middle frontal gyrus (F2)

Precentral gyrus

Postcentral gyrus

Paracentral lobule

Superior frontal gyrus (Fl)

Middle frontal gyrus (F2)

Precentral gyrus

Postcentral gyrus

Paracentral lobule

Precentral Gyrus

Region of activation obtained during a right finger tapping task.The hand motor area: middle genu of precentral gyrus (preCC). Courtesy of Massimo Caulo, MD, PhD, ITAB, Chieti, Italy

Visual Task Head Fixed Mice

Region of activation obtained during right toe flexion task. Courtesy of Massimo Caulo, MD. PhD, ITAB. Chieti, Italy

Reverse Testicular Atrophy

Scheme: Sensory and Motor Pathways

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