EAR-20 Lecture 14: EAR-20 - Day 14
Keenan Lieu
Spring 2020
Child Growth and Development
The Developing Brain
● Even before birth, the brain growth is rapid
● Size of the brain swiftly increases from about 4 percent of its adult weight at 5 months
after conception to about 25 percent at birth
● By the age of 4, the size of the brain is about 80 percent of its adult weight
● Brainstem and midbrain are involved in basic reflexes and sensory processing as well
as essential biological functions like digestion, elimination and respiration – these are
established at birth
● Neural changes in the cortex, part of the brain most closely linked to sensation, motor
response, thinking, planning and problem solving, continue to take place well after birth
● Within the cortex, regions associated with sensory and motor functions tend to be
among the earliest to mature
● Frontal cortex is the region of the brain most directly involved in higher levels of
cognition and tends to be among the latest
● At cellular level, several important changes occur early in development in the neurons –
these neuronal changes are proliferation, migration and differentiation
● Neurons: nerve cell within the central nervous system that is electrochemically designed
to transmit messages between cells within various regions of the brain
1. Neuron Proliferation
● Neuron Proliferation: is the production of new nerve cells
● Neuron production in humans beings near the end of the first month of prenatal
development, shortly after the neural tube closes, and much of it, at least in the
cerebral cortex is completed by the 6th month of prenatal development
● During period of peak neuron proliferation, 20,000 neurons are generated every
minute
● At a very early age, an extremely large number of young neurons (over 100 billion)
have formed
2. Neuron Migration
● Shortly after neurons form they move or migrate from the neural tube where they
were produced to other locations
● In some regions of the brain, this movement occurs passively, so that, as
additional neurons are born, older ones are pushed farther to the outside of that
portion of the brain
● This type of growth takes place in the hypothalamus, the brainstem and the
cerebellum
● In the cerebral cortex the neurons may migrate a great distance, passing through
levels of older neurons that already have reached their final destination
● Inside out pattern of development in the brain is when layers of nerve cells nearer
the outer surface are younger than layers deeper in the cortex
● Both neurochemical and mechanical information plays a role in telling where
neurons to migrate to and when to stop migrating
Document Summary
Even before birth, the brain growth is rapid. Size of the brain swiftly increases from about 4 percent of its adult weight at 5 months after conception to about 25 percent at birth. By the age of 4, the size of the brain is about 80 percent of its adult weight. Brainstem and midbrain are involved in basic reflexes and sensory processing as well as essential biological functions like digestion, elimination and respiration these are established at birth. Neural changes in the cortex, part of the brain most closely linked to sensation, motor response, thinking, planning and problem solving, continue to take place well after birth. Within the cortex, regions associated with sensory and motor functions tend to be among the earliest to mature. Frontal cortex is the region of the brain most directly involved in higher levels of cognition and tends to be among the latest.
