Olfactory BrainThe olfactory brain develops from the ventral part of the terminal brain and consists of two parts - peripheral and central.
The peripheral department consists of the formations located on the base of the brain - the olfactory bulb, the olfactory tract, the olfactory triangle and the anterior perforated substance (Figure 3.31).
Fig. 3.31. The ventral surface (base) of the brain. Places of exit of cranial nerves:
I - the location of the olfactory nerves; II - optic nerve; III - the oculomotor nerve; IV - the block nerve; V - the trigeminal nerve; VI - the abducent nerve; VII - the facial nerve; VIII - anterior-cochlear nerve; IX - glossopharyngeal nerve; X - the vagus nerve; XI - additional nerve; XII - hyoid nerve; 1 - olfactory bulb; 2 - eyeball; 3 - optic nerve; 4 - visual crossover; 5 - visual tract; 6 - pituitary gland; 7 - the leg of the brain; 8 - the bridge; 9 - the pyramid; 10 - olive; 11 - cerebellum; 12 - the first cerebrospinal nerve; 13 - spinal cord; 14 - olfactory triangle; 15 - olfactory tract
The central part includes the vaulted gyrus, which ends near the temporal pole by a crochet; hippocampus (the foot of a sea horse, or Ammon horn) - a special form of formation located in the cavity of the lower horn of the lateral ventricle; dentate gyrus, detectable in the form of a narrow strip in the depth of the furrow of the hippocampus, under the foot of the sea horse (Figure 3.32).
Basal nuclei are a group of nuclei located at the base of the hemisphere (Figures 3.33, 3.34). Because they lie deep in the hemisphere, they are also called nodes of the base of the brain. This group of nuclei consists of caudate and lenticular nuclei, a fence and an amygdala.
Fig. 3.32. The anterior surface of the corpus callosum, arch, the formation of the posterior and lower horn of the lateral ventricle:
1 - mastoid body; 2 - coracoid plate; 3 - pillars of the arch; 4 - knee of the corpus callosum; 5, 11 - fimbria of the hippocampus; 6 - the body of the arch; 7 - bulb of the rear horn; 8 - bird's spur; 9 - collateral triangle; 10 - dentate gyrus; 12 - hippocampal foot
The horsetail nucleus has the form of a comma located in the sagittal plane. The anterior end of the caudate nucleus - its head - is thickened. Gradually decreasing in volume, the head of the nucleus continues into the body, the free surface of which protrudes into the cavity of the lateral ventricle. The body of the caudate nucleus, gradually becoming thinner and bending downwards, continues into the tail. The horsetail nucleus, with its bend, covers the fibers of a white substance, partially extending from the legs of the brain. It is located laterally and above the thalamus.
Fig. 3.33. Horizontal section of the brain through the lateral ventricles:
1 - frontal forceps; 2 - transparent partition; 3 - the body of the arch; 4 - the lower horn of the lateral ventricle; 5 - hippocampus; 6 - vascular plexus of the lateral ventricle; 7 - occipital forceps; 8 - posterior horn of lateral ventricle; 9 - the papillae of the cerebellum; 10 - superior sagittal sinus; 11 - straight sine; 12 - bulb of the rear horn; 13 - bird's spur; 14 - collateral triangle; 15 - spike of the arch; 16 - fimbria of the hippocampus; 17 - terminal strip; 18 - head of caudate nucleus
Fig. 3.34. The back surface of the brainstem. Horizontal section at basal nucleus level:
1 - the cerebellum; 2 - auditory striae; 3 - facial mound; 4 - upper cerebral sail; 5 - the nerve block; 6 - thalamus; 7 - red core; 8 - terminal strip; 9 - the body of the caudate nucleus; 10 - transparent partition; 11 - anterior horn of lateral ventricle; 12 - head of caudate nucleus; 13 - outer capsule; 14 - the most external capsule; 15 - shell; 16 - islet; 17 - pale balloon; 18 - a fence; 19 - upper mound; 20 - the lower mound; 21 - middle cerebellar pedicle; 22 - upper cerebellar pedicle; 23 - lower cerebellar pedicle; 24 - triangle of the hyoid nerve; 25 - triangle of the vagus nerve; 26 - wedge shaped tubercle; 27 - thin tubercle; 28 - wedge-shaped beam; 29 - thin beam
The free surface of the head of the caudate nucleus forms the lateral wall of the anterior horn of the lateral ventricle. The front surface of the head is fused with the white matter of the frontal lobe. With its free surfaces (upper and medial), the body of the caudate nucleus forms in the parietal lobe the bottom of the central part of the lateral ventricle. The tail is sent to the temporal part of the hemisphere. Ahead he reaches the amygdala.
Lateral to caudate nucleus and visual hillock is a well-defined strip of white matter-an inner capsule that separates the caudate nucleus from the lenticular nucleus.
The lenticular nucleus is surrounded on all sides by a white substance and has a wedge shape in all planes. The lenticular nucleus is distinguished by two parts - lateral and medial. The lateral part, large in size, is called the shell, the medial part is a pale sphere.
The shell, like the caudate nucleus, has a gray-pink coloration. The pale ball on a fresh preparation differs yellowish color. A thin plate of white matter - a cerebral stripe - separates the shell from the pale sphere.
Fence is lateral to the shell and separated from it by a layer of white matter representing the outer capsule. Another lateral is a strip of white matter - the most external capsule separating the fence from the bark of the islet. Its outer surface has dentate contours corresponding to the bends of the island's crust. In the direction upward and downward, the fence becomes thinner and closer to the amygdala. In the three-dimensional image, the fence has the form of a disk located in the sagittal plane.
Almond-shaped body in shape and size resembles a bone of almonds. It is located in the thickness of the white matter of the temporal pole. The amygdala with its upper surface acts as an elevation in the anterior part of the lower horn of the lateral ventricle. Thin plaques of white matter, it is divided into a number of secondary nuclei. In addition to communication with the fence, the amygdala has a connection with the olfactory area, in particular with the anterior perforated substance.
The horsetail nucleus and the shell are united by the name of the striatum (striatum), and together with the pallid sphere (pallidum) they constitute the so-called striopallidal system. Such a combination of striatum and pallidum is due to a functional relationship.
These structures mutually balance each other and, therefore, have an optimal effect on motor acts. Being the highest department of the extrapyramidal system, they provide the performance of various involuntary (automated) movements, regulate the state of the muscle tone, and consequently, affect the nature of voluntary movements. Moreover, in a single functional system, the pallidum exerts an activating effect on the subcortical formations of the extrapyramidal system, and the striatum - inhibitory.
The stryopallidar system receives afferent information from the neurons of the medial thalamus nuclei. In addition, the striatal system has connections with the cortex of the cerebral hemispheres, in particular the bark of the frontal, temporal and occipital lobes - the efferent cortico-striatal path terminates in the striatum body. In turn, the striatal system sends inhibitory efferent impulses to the neurons of the pale sphere. From the latter, the efferent impulses reach the neurons of motor nuclei of the spinal cord and cranial nerves.
Basal nuclei of the right and left cerebral hemispheres of the large brain are connected by commissural fibers that pass as part of the posterior spike of the brain. This provides their combined work on performing automated, usually stereotyped, but rather complex reflex motor acts (walking, swimming, eating, etc.) that a person does "without thinking". The close connection of the striopallidar system with the nuclei of the hypothalamus (posterior group of the hypothalamus nuclei) explains the possibility of its influence on the emotional reactions of the organism.
When a striopallidal system is affected, clinical manifestations are determined by the dominance of functional disorders in the striatal or pallidarnom departments. With excessive inhibitory effect of the striatal system, hypokinesia develops-poverty of movements, poverty of mimicry (hypomia). Hypo-function of the striatal system, on the contrary, leads to the appearance of excessive involuntary movements - hyperkinesis, since there is no inhibitory effect on the pallidar system.
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