Brain Development

The valet brain is considered as the almost authorized and complex part of the dead body consisting of about 180 gazillion cells (Kolb and Whishaw 84). Of those 180 billion cells, 60 billion neurons atomic number 18 actively involved in thought processing, and from each one of these may synapses with as many as 15,000 neighboring neurons. Because of this complexity, for many years researchers in neuroscience have been hesitant to take on the difficult task of explaining the intricacies of the world brain. Prenatal Development The brain is among the first body parts to specialize and function in the embryo.It originates as a flat sheet of cells on the stop number locate, c completelyed the neural plate. The brain begins to develop between the second and third calendar week after fertilization and anticipate to develop rapidly throughout gestation (Spear 406-407). At 3 weeks of embryonic training, a tube appears on the back of the embryo. This is the neural tube, from wh ich the entire nervous system develops. At the top of the tube, three bulges develop to grad the three main divisions of the brain- the forebrain, the midbrain, and the hindbrain, and, behind them, the spinal cord.By the time the embryo is 13 mm (y in) in distance the three swellings have scram five, as the forebrain itself separates into the region to become the cerebral hemispheres and below this the diencephalons. The swellings argon so large that to accommodate them the tube must begin to kink. At 7 weeks, the parts of the development neural tube initially form a straight line, but the tube soon change shape so that the forebrain and hindbrain are at right angles to each other.The hindbrain develops rapidly at this stage and begins to sprout a series of nerves (cranial nerves). The forebrain also begins to enlarge, forming two bulges. These will become the large, folded cerebrum and underlying structures, such as the thalamus. At 11 weeks, most features of the adult brain appear in rudimentary form. The hindbrain differentiates into the cerebellum (largely concerned with balance and coordination) and the pons and medulla (which control vital functions such as breathing and heartbeat).Meanwhile, the forebrain continues to grow, and the bulk of it the cerebrum begins to overlap the underlying structures. By the fifth month, the wrinkles on the cortical scrape of the cerebrum have appeared, and simple but recognizable EEG patterns have developed. Once the tube has been closed off, the cells inside it divide, going through a number of precursor stages before their daughters eventually differentiate to give dress up to the populations of neurons and glia that will form the adult brain.The rate of cell proliferation is extraordinary an average of more than 250,000 neurons per dainty must be formed during the nine months of pregnancya rate dramatically surpassed by that of synapse governing body More than 30,000 synapses must be formed per second unde r every square centimeters of cortex to engender the complement insert in the early post-natal period. During pregnancy the fetal brain grows dramatically in size of it and complexity, and the neurons and glia which constitute it must find their appropriate positions and make their ordered connections, for instance within the half a dozen layers of the cerebral cortex.Because the cells are generated from a single initial sheet, it is necessary for them to migrate considerable distances to their final location. The cerebral hemispheres develop from the front portion of the neural tube, and, as their progenitor cells are formed, by the fifth week of pregnancy, the wall of the tube bulges to form the cerebral vesicles. Over the next hundred days, cells close to the ventricle are destined to give rise to the neurons which will form the cortex, while the glia are born in a second layer slightly further from the ventricles.The newborn neurons migrate from the ventricular zone towards the surface of the cerebral vesicles, where they meet axons growing in from the region of the developing brainstem, through which the later-born neurons must migrate. Before birth, grand enlargement of the cerebrum continues. Its most impressive development occurs in the cerebral cortex (the outer layers of the cerebrum) the site of all higher conscious activity. At birth, the cerebrum makes up the bulk of the brain (The American Medical Association 12-13).Hence, by the time of birth, virtually all of the approximately 100 billion neurons in the human brain already are present (Cowan 113-115). early childhood But even this phenomenal rate of development may be an understatement (Clarke 345). Further Myers stated that in humans, though the brain tissue from the cerebral cortex has increased in complexity of the neural networks, the number of nerve cells dont increase, but their interconnections do (63) Research in animals indicates that early in development, about twice as many ne urons are produced than will be present in the adult brain.In addition, many neurons initially grow axons that connect to the wrong targets. During the normal course of development, the redundance neurons die and the inappropriate connections degenerate, leaving the appropriate connections in place (Cowan, Fawcett, OLeary, and Stanfield 1258-1260). Scientists believe that this overproduction and, later, death of neurons and their connections is an important mechanism for forming and fine-tuning the developing nervous system. The brain is non completely developed even in full-term newborn infants.A great deal of brain development takes place in the first few months of postpartum life and, in fact, brain growth continues at least until adolescence (Benjamin, Hopkins, and Nation 313). They further added at birth, the human brain is immature The neural networks that enable infants to walk, talk, and remember are still forming. This helps explain why infants memories do not predate du ring their third or fourth birthdays. In infancy, the brain also grows rapidly specifically during the first two years after birth (Spear 170).Unlike all other cells in the body, however, the neurons are not usually replaced when they die, and from early infancy onwards there is indeed a small but looker loss of neurons. The growth is accounted for by increases in the number of glial cells, but above all in the massive development of dendritic processes and synaptic connections, as the brain wires itself up in a dramatic interplay of epigenetic specificity and experience-dependent plasticitythat is, the way that neural pathways are modified as a result of experience and most notably, learning and memory.Although all of a persons neurons are present at birth, the number and complexity of the connections among neurons increase substantially after birth (Parmelee and Sigman 295-98), and this increase is partly responsible for the growth in brain size. Thus, both the increased neural connections and the development of myelin after birth make viable more and more complex behavior and thought as the child grows. In some areas of the brain, these developmental changes continue until adolescence (Yakovieve & Lecours 5-7).The human brain, and its functions, thus develop at first rapidly and then more steady over the first few years of infancy, across puberty, and even into late adolescence. Works Cited Benjamin, Ludy, Hopkins, Roy, and Jack Nation. Psychology. second ed. New York Macmillan Publishing Company, 1997. Clarke, P. G. H. Neuronal Death in the development of the vertebrate nervous system. Trends in Neuroscience. Cambridge Harvard University Press, 1995. Cowan,W. M. The development of the brain. Scientific America,241(1989)113-120. Cown,W. M. ,Fawcett,. j. w. , OLeary,. D.D. M. ,& Stanfield,B. B. Regressive Events in Neurogenesis. Science,225(1991)1258-1260. Clayman,C. B. ,M. D. The Brain and Nervous System. The American Medical Association. second ed. 199 7. Kolb,B. , AND Whishaw,I. O. Fundamentals of human neuropsychology. New York Freeman,1995. Parmelee,A. H. , and Sigman,M. D. Prenatal brain development and behavior. In P. H. Mussen (Ed). Handbook of Child Psychology,Vol II. Infancy and development psychology. New York John Wiley &Sons, 1984. Spear, Peter D. Psychology perspective on behavior, New York John Wiley &Sons, 1998.