Developmental Timeline The development of an individual is the result of maturation of the nervous system and psychological reactions, which in turn is determined through genetics and environmental factors. The study of an individual and his environment is summarized under the biopsychosocial model. A better understanding of human psychological, cognitive and moral development is largely dedicated to the efforts of Erik Erikson, Jean Piaget, and Lawrence Kohlberg.

Brain and Nervous System Development

Neurologic development begins in the third week of intrauterine life, marked by the development of a neural plate on the ectodermal surface. In folding of this plate produces a neural tube, which is destined to be the future Central Nervous System, and a neural crest, which forms the peripheral nervous system. Neuroectodermal cells differentiate into neurons. The forebrain, midbrain and hindbrain are evident by the fifth week, during which, the dorsal and ventral horns of the spinal cord have also begun to form, along with their motor and sensory nerves. Myelination of these nerves begins by mid-gestation...

(Kliegman, Behrman, Jenson & Stanton, 2009)
Axons and dendrites develop most rapidly during the first trimester. DNA replication, which is a marker of brain growth, is greatest before mid-gestation and in the first few months of life. By the fortieth week of gestation, the structure of brain development is complete. Synapses are pruned back considerably and new connections continue to form after birth. (Kliegman et al., 2009)

Lifespan Development

The developmental milestones are divided into gross motor, fine motor, and communication and cognitive. In the neonatal period, the newborn lies in a flexed attitude, and displays Moro's and doll's eye reflex. By the third month, the infant can lift head and displays a social smile. By seven months of age, an infant babbles monosyllables, can sit with support and may show signs of displeasure when social contact is broken. By ten months, an infant can sit up without support, responds to its name and can play 'peek-a-boo'. By one year, a child can walk with one hand held and can say a few words.…