The role of the cortex in the regulation of motor functions

Motor zone to about ry in primates and humans predtsentralnoy located in the area, ie.   e.   in front of the central gyrus and the posterior portions of the upper and middle lo b GOVERNMENTAL convolutions. Besides these, an additional motor area is located on the medial surface of the cortex. Electrical stimulation of the motor cortex different portions causes a clear, coordinated motor s nye reaction, and (if a weak stimulation) reducing individual muscles opposite body halves.

In humans and primates different muscle groups represented by groups of neurons of the motor cortex, located in a certain sequence of STI, ie.   e.   zones of the motor cortex are organized strictly according to the somatotopic principle – each muscle has its own part of the cortex area. Thus, the representation of the lower limb muscles are located in the medial part of the ascending frontal convolution near the longitudinal slot, and the representative s GUSTs muscles of the head and neck – in the dorsolateral areas. N muscles of the left of the body than half are represented in the right hemisphere, and vice versa.

Neuronal groups of the motor cortex, associated with the movement of Dr. of muscle activation, occupy different sized squares and distributed inequality in uniformly. A disproportionately large areas associated with the movement of the fingers, hands, tongue, face muscles and much less – with great and the muscle of the back and lower limbs. The card of representation of the muscles of the motor cortex has the appearance of a “homunculus” – a little man with a huge head, tongue, hand and very small body and legs. Nera in the number distribution is due to the fact that axons of the pyramidal neurons of the motor cortex give the greatest number of synaptic contacts on those motor neurons of the spinal cord that innervate the muscles of the fingers, hand, tongue, face. Such an organization provides the most subtle and precise control of the movement of precisely these muscles. The removal of areas of the mantle cortex causes a disturbance of the corresponding movement.

In humans and primates giant pyramidal Betz cells and other neurons in the motor cortex are grouped into vertically oriented column ( “elementary functional units”) that control the slave of that small groups of muscle fibers. Such columns of nerve cells include all six layers of the cortex. It is believed that motor speakers are able to excite or inhibit a group of functionally homogeneous motoneurons. At the same time it revealed that cortical neurons that regulate the activity of a muscle, not concentrated within only about Dr. Noah column. It is shown that the speaker is characterized by a thin functional s specialty. For example, there are separate columns of the motor cortex associated with fast (phase, or phase) and slow (tonic) movements. Each column is believed to control a su with a tav, t.   e.   from the column there are commands to different muscles, the activity of which is related to this joint. It was found that the vertical s nye speakers and specialize in relation to the joint position – in of excitation of one column causes a corresponding bending of the joint, and other excitement – the fixation of this joint. In other words, the motor column in large part is a functional of Z unity of neurons that regulate the activity of several muscles, and dis t vuyuschih on a particular joint. Thus, in the columns of pyramidal neurons in the motor cortex represented not so much muscle as DV and zheniya.

The efferent exits of the columns are giant pyramidal neurons (Betz cells) located in the layer of the motor cortex. These are not the first of the Rhone have a background activity, a change which precedes the appearance of voluntary movements. Axons of giant pyramidal neurons form a pyramidal path, ending with excitatory synapses on alpha motoneurons (in part, on intercalated neurons and on gamma motoneurons) of different levels of the spinal cord and brainstem of the opposite side. The axons of pyramidal paths have largest body excitation transfer rate and serve to call produ of freestyle movements. In addition, the descending signal in the pyramidal hairs to nach affects the neurons of ascending afferent pathways, modes have lating in their transmission pulses, which apparently is also assembles n that the cortical organization of motor acts. Along with the pyramidal system in the motor cortex begins extrapyramidal system. This si a topic is different in that it axons of cortical cells go to the basal ganglia, cerebellum, red nucleus, the vestibular nuclei, reticular formation and other structures of the brain stem, which in descending item in Cham effect on spinal neurons. In general pyramidal and extrapyramidal the way – is a single mechanism by which to s is satisfied complex purposeful movement, while maintaining equal to f This and orientation in space.

The motor cortex afferentation comes from tactile, proprior e tseptivnyh, vestibular, visceral, visual and auditory retse n tori, either directly from the corresponding projection, and from association areas of the cortex. It is important to emphasize that through the system and with associativity fibers motor area of the cortex is associated with a number of a contact in the opposite hemisphere, which is important for e f ficiency control voluntary movements.

Of particular importance for the activity of the motor cortex is afferentation, which enters it from the receptors of muscles, tendons and joints. The entrance to the motor cortex from the proprioceptors of the muscles is topically specific. This ensures the implementation of reflexes, which are closed through pyramidal cells directly on the alpha-motoneurons of the spinal cord. Such an organization is the basis of a high degree of self-organization and owl p -improvement movement by correcting for motion control of a Nove feedback signals.

It is the primary somatosensory zone localized at the back tse n tral gyrus, is a leading signal when analyzing the skin, m s antiplaque and visceral sensitivity, which arrive here with uch as pation relay cell axons of ventral posterior thalamic nucleus. Ra s private parts of the body have in this area a clear spatial Representat and ernment (Vol.   e.   there is a somatotopic principle of organization). For example, the projection of the lower extremities is in the upper portions of the postcentral gyrus, and the projection of the head and upper half of the body is in its lower portions. The area of representation depends on the importance of the site – it is much higher for the hands, face and voice Appar and that compared to the trunk and lower limbs. Second COMAT about sensorkaya zone located in the lateral (sylvian) sulcus floor at chaet sensory axons relay information from cell adjustable central nucleus of the thalamus. This zone also plays a role in de I telnosti motor centers of the cortex, although it is smaller than the first zone.

The structures of the cortex responsible for the design and the organization of movement are the main associative zones of the cortex: the frontal associative region and the parietal associative region. Frontal association area, participating in the implementation of mental processes, is also a place of organisms and tion of purposeful activity, including through the adoption of decisions and the formation of the program. This area of the person is also called e mediocre attitude to the formation of oral (motor or rechedv and gatelny, Broca’s area) and writing. Information about the plan of the motion is transmitted to relevant centers of the motor cortex that n and p layers control the motor commands to the alpha motor neurons of the spinal cord (at feasts etc. Nome way), as well as the basal ganglia, cerebellum, red nucleus, vestib in polar nuclei and the reticular formation of the brain stem (in ekstrap and ramidnomu way). Arhiopaleokorteks structure includes old and old bark bol s Shih hemispheres – and olfactory tubercle surrounding cortex, anterior socketed space, hippocampus, dentate gyrus, transparent partitions kernel and vaulted gyrus comprising cingulate gyrus, isthmus, parahippocampal gyrus and hook. As you know, he Representat to wish to set up one of the important integrative brain systems and is nespets and graphically activator all types of cortical activity. Among other functions (smell, attention, emotion, autonomic regulation, etc. of processes), arhiopaleokorteks ensure the implementation of biologically important BPO Well dennyh reflexes (eg, search, food, sex, oboronitel s ny) and motor components. It is obvious that the indicated structures of the archiopaleocortex contain innate motor programs, the real and implementation of which ensures the manifestation of the indicated reflexes.

local_offerevent_note May 11, 2019

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