An overview of the nervous system

ТЕКСТ ПЕРЕВОДА

A doctor should always remember a basic anatomical data for a better absorption of topical diagnosis of diseases of the nervous system, i.e. a neurologist needs to have anatomophysiological vision. So the next chapter will contain information about the neural structure of the brain and its functions.

However it is reasonable to inform you that the neuron should be accurately localized in macroanatomical structure of the brain or the spinal cord.

The brain has a shape of the cranial cavity and fits the individual configuration of the skull, i.e. it can be spherical and elliptical. On the average the length of the brain is 160 - 180 mm, the largest cross-section is 140 mm. On the average the female brain is slightly shorter than the male brain. On the average the weight of the man's brain is 1400 g, the women brain is 1200. People aged from 20 to 25 have the largest weight of the brain. Brachycephalic brain is usually heavier than dolichocephalic brain.

There is no direct dependence between brain weight and intellectual capacities. For example, the weight of a writer A.N. Turgenev's brain is 2012, of a poet Byron- 1807, of a philosopher Immanuel Kant - 1600, of a poet Friedrich Schiller – 1580, of a physician Brock - 1484, of a physician G. Dupuytren - 1437, of a poet A. Dante - 1420, of a painter A. Tiedemann – 1254. It is known that other people with an outstanding mind have the brain with a relatively low weight. The idiot's brain has particularly low weight; sometimes it does not even reach 300g. The experience shows that more spiritually developed people often have greater brain weight. However in any case a high weight of the brain is not a mark of higher spiritual development. However the weight of the brain must be a bit bigger than some minimum standards for performing properly mental functions. A minimum standard brain weight for men is considered to be 1000 g, for women - 900, the spinal cord is about 2% of brain weight and it is equal to 34-38g.

The overall diagram of the structure and location of the nervous system are shown on the picture 5. If one examine the brain from above and from the side (Pic. 6), one can see a deep vertical slot which divides the brain into two symmetrical halves - the two hemispheres of the endbrain. In the depths of this gap there is a corpus callosum connecting two hemispheres (Pic. 7). Ahead of the corpus callosum this gap gets into the ventral surface of the brain; from behind of the corpus callosum it also deeply penetrates down and goes to a large transverse slot which separates two hemispheres of the brain from a the cerebellum, which lies below. The surface of the hemispheres is cut up by more or less deeply penetrating slots and fissures. There is a gyrus between them.

The ventral surface of the brain called the base of the brain (Pic. 8) is structured more difficultly. Here one can see how the brain passes to its base. In the midline in the front part of the base the median gap passes to the visual nerve. If this cross is turned a little aback, then you'll see a thin gray easily torn terminal plate going from the front border of the chiasm in the depth of the longitudinal slot of the brain. There are optic nerves forward from the chiasm, and optic tracts go back and aside from chiasm. On both sides of them there is a gray field dotted with small and medium holes. The front boundary of the field is the olfactory triangle from the front corner of which a narrow white band extends forward. It is an olfactory tract ending with the broadened olfactory bulb. The olfactory filaments go off from the ventral surface of the soft white bulbs. They break when the brain is being removed from the skull.

A gray bump rises behind the chiasm of the optic nerve. It extends into bone resembling a funnel with a bean-shaped body, the hypophysis, it lies in deepening of the sellar sphenoid bone. The gray bump is limited in the sides by the optic tract which further stretches through going from back to front and outward cerebral peduncle and then plunge deeper. Two white pear-shaped formation rise behind the gray bump. They are mamillary bodies. Below them there is an interpeduncular fossa which passes into recessus anterior in front, and into recessus posterior behind. The bottom of fossa is formed by a gray dotted surface with numerous holes divided into two parts by the mid-reaching fissure. It is also limited from the side of the cerebral peduncle by fissure. Fibres of the oculomotorius nerve go from it.

Behind them in depths of formations there is a whitish wide cross lying splenium - the bridge of the brain (Pons varolii) sharply limited in front and behind. The bridge narrows and plunges into the cerebellum outwards. From behind of the bridge there is a cone-shaped formation - the medulla oblongata which goes to the spinal cord. In the midline of the medulla oblongata there is a fissure which is bounded on each side of the white splenium - a pyramid. Outwards from the pyramid there is less deep fissure exterior. There is an olive. The medulla oblongata covers the middle part of the cerebellum and it lies here in a wide slot called the vallecula cerebelli. The ventral surface of the cerebellum is sharply arched. Posterior medial deep slot separates cerebellar hemispheres from each other which are covered by numerous narrow convolutions.

With the sagittal section of the brain at the midline one can see the corpus callosum above which there are convultions and fissures of hemisphere of the brain (frontal, parietal and occipital lobes). The middle part of the corpus callosum is called the stem - truncus corporis callosi. Posterior corpus callosum thickens forming splenium (splenium corporis callosi). It bends down in front and forms a genu knee of the corpus callosum which narrows and turns into a rostrum (rostrum corporis callosi), turning into the thin plate lamina (lamina rosralis) which as a finite plate is sent to the front surface of the optic chiasm. Behind the corpus callosum there is a cerebellum covered by the back area of ​​the hemispheres.

From the bottom surface of the corpus callosum on the border with its splenium and the brain stem, a white cerebral plate moves forward which in the form of the arc deeply penetrates into the brain substance and is a part of a set of fornix. There is a transparent wall (septum pellucidum) between the fornix and the brain stem, knee, rostrum and plate. Under the fornix and the back of the corpus callosum there is a thalamus. Between its front part and the fornix there is an interventricular Monro's foramen sinking deeply into the brain substance. At the rear end of the thalamus under the splenium there is a pineal body under which the anterior transverse section of epithalamic commissure (commissura posterior cerebri), and behind it quadrigeminal plate (lamina quadrgemina), medullary velum and the cerebellum adjoin.On the medial surface of the thalamus behind the Monro's foramen there is a cross section of intermediate mass (massa intermedia), connecting both the thalamus. From the Monro's foramen under the intermediate mass, the hypothalamic (Monro's) sulcus goes to the epithalamic comissure and it separates the thalamus from the hypothalamus. Further it adjoins to the brain stem, to the bridge of the brain, the cerebellum and the medulla oblongata. The hypothalamic (Monro's) sulcus runs into the aqueduct of cerebrum located under quadrigeminal plate. The aqueduct of cerebrum ends in the fourth ventricle of cerebrum located under the cerebellum.

CHAPTER 2

Date: 2015-12-11; view: 1184