Lecture 1, 3 семестр.pptx the process, Salon or four brain
- 1. Lecture: The Prosencephalon or Forebrain Principal parts Neocortex
- 2. Position of CNS in the body
- 3. Brain
- 4. General Anatomy (ontogenesis) • The cranial part of the neural tube at the end of 3 weeks of gestation is divided into three primary cerebral vesicles: anterior ( the prosencephalon), middle (the mesencephalon) and posterior or hindbrain (the rhombencephalon).
- 5. Development of the brain • The differentiation of the prosencephalon are more marked. It is subdivided into the telencephalon and diencephalon. • The rhombencephalon also subdivided into two secondary vesicles: the metencephalon and the myelencephalon. • The middle primary vesicle is not divided.
- 6. Development of the brain • From five secondary vesicles (5 weeks of gestation) are formed all parts of the brain. • With the development and growth of the vesicles, its residual internal cavity and white matter form the internal structures of the brain. • The human brain grows intensively in the embryonic period and during the first years of life.
- 7. The telencephalon or ‘endbrain’ • The telencephalon includes: 1/ the cerebral hemispheres, the comissures which connect them, and the cavities which they contain; 2/ the anterior parts of the third ventricle, including the preoptic regions in the telencephalon impar.
- 8. The cerebral Hemispheres • Each cerebral hemisphere consist of an outer layer of grey matter, termed the cortex, an inner mass of white fibres, the deeply situated basal nuclei and a cavity, the lateral ventricle.
- 9. The cerebral hemispheres • A hemispheres are incompletely separated by a deep median fissure (the longitudinal cerebral fissure), and each possesses a central cavity or lateral ventricle. • The median fissure contains a falx cerebri and the anterior cerebral blood vessels. Behind this part of brain meninges locate a great central white commissure (the corpus callosum), which connects the hemispheres across the median plane. • Each cerebral hemisphere presents three surfaces: superiolateral, medial and inferior.
- 10. Surfaces of the Cerebrum • The surfaces are formed into a number of irregular eminences, named gyri or convolutions, and separated by furrows termed sulci or fissures. • Anatomically, all sulci are classified on primary, secondary and other ranges (3, 4 and more).
- 11. The lateral surface of hemisphere
- 12. The Surfaces of the Cerebrum • The sulci develop along lines separating areas which differ from one another in the details of their microscopic structure and in the functions which they predominantly observe. • Such fissures may therefore be termed primary (limiting) sulci, since they establish the limits of lobes. The secondary sulci are located into the lobes of hemisphere cerebri. • These types of sulci and gyri are fairly constant in arrangement; at the same time they vary within certain limits, not only in different individuals, but in the two hemispheres of the same brain.
- 13. Cerebral Cortex • According to C. von Economo (1931), the cerebral cortex divides on six laminae or layers: I/ plexiform, molecular; II/ external granular; III/ pyramidal, small cells; IV/ internal granular; V/ ganglionic, large pyramidal cells; VI/ multiform lamina or polymorphic cells.
- 14. Quantitative Aspects • The total surface area of the cerebral cortex as 285000 mm^2, with a volume of 300 cm^3. • The total number of cortical nerve cells as more than 15,000 million. • The column of cells 1 mm square and 2,5 mm deep may contain as many as 60,000 neurons.
- 15. Quantitative Aspects • Each neuron from precentral gyrus to take part in about as many synapses and to connect with some 600 other nerve cells. • The density of packing of nerve cells in different areas and their laminae shows much variation. Anatomically, the cerebral cortex is divides on 52 cytoarchitectonic areas. • The cerebral cortex forms a complete mantle or pallum covering the hemisphere and obviously variable in thickness (1,5 – 4,5 mm). • The larger part of the cortex (in average 75%) is hidden from surface view, and locate into the gyri.
- 16. Laminar Pattern of the Cerebral Cortex • The cortex or pallium of the cerebrum may be conveniently divided into an older (2%) and original part (98%). The older part consist of the archiocortex and paleocortex. • The neocortex may be equated with those system of sensory and motor activity.
- 17. Representative Variants of Cortical Structure • Two of them are known as heterotypical (granular and agranular types), and the homotypical variance (frontal or premotor, parietal or postcentral, and polar or visuopsychic. • The granular type of cortex accompanied with poorly development of laminae III and V. • To the other hand, in the agranular areas (motor cortex) are predominate the pyramidal neurones.
- 18. Representative Variants of Cortical Structure
- 19. Clinical Anatomy
- 20. The Main Cortical Areas • Even the simpler differentiation of the cortex into sensory areas receiving afferent projection, fibres and motor areas projecting efferents – the remainder being regarded as ’silent’ or associational.
- 21. The Frontal Lobe • The cortex of the frontal lobe may be divided for two main regions, precentral and prefrontal. The former is largely sensorimotor, the latter ‘association’ cortex. • The precentral area includes the whole of the precentral gyrus and the posterior parts of the frontal gyri.
- 22. The precentral area (‘the motor homunculus’ by W. Penfield) • A feature of the area is the prominence of pyramidal nerve cells of all sizes. The largest of these, the giant pyramidal cells of Betz. • The number of these cells in the human motor cortex has been estimated as between 25,000 – 30,000. • This is the first or leading somatomotor area.
- 23. The Parietal Lobe • Immediately posterior to the central sulcus, occupying most of the postcentral gyrus. It is the primary or first somatosensory area. • Posterior to it is the large ‘silent’ area of the parietal lobe (second speech area). • Inferiorly, in the lowest part is the second somatosensory area.
- 24. The primary or first somatosensory area.
- 25. The Occipital Lobe • Almost the whole of this lobe is occupied by the striate or visuosensory cortex. • The striate cortex, or first visual area occupies the cortex near the calcarine sulcus. • Histologically the area is of the granular type, with stria and thinness of the cortex.
- 26. The Striate Cortex • The status of area as the primary visual centre has been established both electrical stimulation in man and by connections with other parts of organum visus. • The retinotopical organization which exists in the lower parts of the visual pathway have also been shown to be carried through to the cortical level. • Each striate area receives impulses from the two ipsilateral half retinae, representing the contralateral half of the binocular visual field.
- 27. The Temporal Lobe • The lobe is regarded as highly evolved in man and of relatively recent phylogenetic development. In a general way it may be regarded as a particularly involved in hearing, language and perception. • The first acoustic area is occupied the superior temporal gyrus. Area is histologically a variant of the granular type.
- 28. The Temporal Lobe • The dorsal parts of temporal lobe is perhaps more concerned with somatic activities, and especially with linguistic communication in its auditory and visual forms. • The anterior parts of temporal lobe are linked to the limbic system. Effects on blood pressure, respiration, and gastric motility – usually depression – have been elicited by stimulation of this part of the anterior temporal lobe. • In recent years the temporal lobe has been loosely associated with the activities of memory (‘short term’ memory).
- 29. The Insula • Part of the temporal lobe is rolled into the posterior limb of the lateral fissure . • The insula has been regarded as a gustatory area. Stimulation in man excites visceral motor and sensory effects, such as gastric movement e.a.
- 30. The Olfactory (limbic) Lobe • Traditionally, all brain structures associated with olfaction are named rhinencephalon. • The structures which are included in the limbic system are: 1/ the olfactory nerves, bulb and tract; 2/ the anterior olfactory nucleus; 3/ cingulum and other parts of brain.
- 31. The role of the limbic system • Many of the structures such as amygdaloid and septal complexes and the hippocampal formation were for long regarded as primarily olfactory integration centers. • An intact limbic system, hypothalamus and brainstem are necessary for fully integrated and effective homeostatic responses to occur under a wide range of environmental conditions. • Stimulation or ablation of different regions such as amygdala, septal area and hippocampus, lead to a variety of complex changes in behaviour involving locomotor, autonomic and endocrine effects.
- 32. The Hippocampal Formation • The hippocampal formation develops in the medial palial fringe of the cerebral hemisphere. • These structures included the indusium griseum, the gyrus fasciolaris, the dentate gyrus, cornu ammonis, parts of the uncus.
- 33. The Hippocampus • The hippocampus consist of the complex interfolded layers of dentate gyrus and cornu ammonii, latter being continuous with the cortex of the parahippocampal gyrus. • Afferent pathways to the hippocampus arise in 1/ parts of the cinglate gyrus; 2/ the septal nuclei; 3/ the entorhinal cortex; 4/ comissural fibres from the opposite hippocampal formation.
- 34. Cerebral Dimensions • The human brain has been weighed and measured by many observers. • An average human male brain is said to weight about 1,450 gm and that of his female counterpart about 100 gm less. • Prior to maturity, the human brain varies markedly and in ratio to total body weight.
- 35. Cerebral Dimensions • Unlike some other mammals, the maximum growth rate may be pre- or postnatal, the cerebral growth spurt in mankind and primates in general is perinatal – in late fetal development and the first year of extrauterine life. • During this first year the brain at least doubles in weight and reaches about 90 per cent of its final weight by the six year.
- 36. Cerebral Dimensions • The human brain is obviously large, both absolutely and relatively. • Dolphins, elephants (4,000 – 5,000 gm) and wholes (6,800 gm) have heavier brains than man, although this is offset by brain: body weight ratios of about 1:600 in elephants. In dolphins the ratio approximately 1:40, which is some ‘better’ than the human average of about 1:50. • In absolute size of brain, the human brain (1100 -1800 gm) much surpasses any other primates (e.g. largest gorilloid brain recorded weighed 750 gm).
- 37. Cerebral Dimensions • Measurements of brain size and brain: body weight ratio afford no indication of organization within the brain. • The cubic mm of cortex has been estimated to contain as many as 142,000 cells in the mouse, 21,500 in the macaque, and merely 10,500 cells in man. • However, the area of the human cerebral cortex is at least twelve times greater than that of the macaque, which may nevertheless have a brain: body weight ratio similar to man’s.
- 38. Clinical Anatomy