PSYC 2450- CH 6: Physical Development of the Brain, Body, Motor Skills
& Sexual Development
An Overview of Maturation & Growth
Changes in Height & Weight
• Height & weight increase rapidly in the first two years- but it is very uneven.
• By age 2 toddlers are half their eventual height & have quadrupled their birth
• Age 2 until puberty, children gain 5-8 cm in height & 3kg in weight every year
• Two to 3 year growth spurt at adolescence.
Changes in Body Proportions
• Anewborn’s head is 70% of it’s eventual adult size & makes up ¼ of their total
Cephalocaudal Development- a sequence of physical maturation and growth that
proceeds from the head (cephalic region) to the tail (caudal region).
Proximodistal Development- a sequence of physical maturation and growth that
proceeds from the centre of the body (the proximal region) to the extremities (distal
• Pattern reverse before puberty- hands & feet are first to adult size, followed by
limbs & then the trunk.
• At birth an infant’s bones are soft & nearly all the bones are a source of blood
cells- reason why they can’t sit up
• Skeletal & muscular development parallel the changes occurring in height &
• The skull is separated by six soft spots (fontanelles) which are filled in by
minerals to form single skull by 2
SkeletalAge- a measure of physical maturation based on the child’s level of skeletal
• Skeletal development is done by 18, but the thickness increases slightly
• Born with all the muscles we will ever have
• At birth it is 35% water but grows as the cellular fluid in muscle tissues is
bolstered by protein & salt
• Grows slowly in childhood & accelerates in adolescence
• By Mid 20’s skeletal muscle accounts for 40% of boys’body weight & only 24%
Variations in Physical Development
• Physical growth is uneven (asynchronous) o Brain, reproductive system & lymph tissues mature at diff rates.
o Sizeable individual & cultural differences in development.
Development of the Brain
• Increases from 25% of eventual weight toth5% of eventual weight by 2.
Brain Growth Spurt- the period between the 7 prenatal month and 2 years of age
where more than half of the child’s eventual brain weight is added.
Neural Development & Plasticity
Synapses- the connective space between one nerve cell (neuron) and another.
Neurons- nerve cells that receive and transmit neural impulses
• Produced in the neural tube of developing embryos & migrate along pathways
laid out by guiding cells to form major parts of the brain.
• Formation of new neurons in the hippocampus occurs throughout life
Glia- nerve cells that nourish neurons and encase them in insulating sheaths of myelin
• Major contributor to brain development
• Many more neurons & synapses are created than are ever needed- those that are
unused disappear (pruning) and those that are used are strengthened.
• Individual neurons have the potential to serve any function, but it depends where
they end up.
Synaptogenesis- formation of connections (synapses) among neurons.
Plasticity- capacity for change; a developmental state that has the potential to be shaped
• Brain shows a lot of this up until puberty
• Highest brain centre (cerebellum) consists of two hemispheres separated by the
Myenilization- the process by which neurons are enclosed in waxy myelin sheaths that
facilitate the transmission of neural impulses.
Cerebrum- the highest brain centre; includes both hemispheres of the brain and the
fibres that connect them.
Corpus Callosum- the bundle of neural fibres that connect the two hemispheres of the
brain and transmit information from one hemisphere to the other.
Cerebral Cortex- the outer layer of the brain’s cerebrum, which is involved in voluntary
body movements, perception & higher intellectual functions such as learning, thinking
Cerebral Lateralization- the specia