CHYS 2P10- Lecture 4: Chapter 6
Physical Development: Brain, Body, Motor Skill
October 2 2012
Rapid growth in first 2 years:
- The brain is growing the fastest between birth and the age two. If we grew
at this rate forever we would be 4 meters tall and 3 tons by the age of 18.
General Growth Trends:
- Changes in Body proportions- Cephalocaudal – physical development.
From head to tail, hence the reproductive system grows last.
- What parts of the body are the first to reach true adult size? – Hands and
feet are the first things to finish fully growing.
- In the last few years we have seen how much environment affects brain
development. After 40 days the spinal chord starts to develop and the
brain and the spinal chord make up the human nervous system
Human Nervous System
- Nervous system = more than a trillion specialized cells
o Cells that work together to transmit electrical and chemical signal
throughout the body
- Neurons = specialized cells that transmit electrical signals/ impulses
throughout the body – example when you touch a hot stove the signal sent
to your brain to tell it to take your hand off/ its hot is extremely quick
- Proceeds in overlapping steps:
o 1.Make brain cells via cell division (mitosis)
o 2.Get the cells to where they need to be (migration)
Info from genes
according to function they will serve (memory, attention,
o 3.Grow axons, dendrites – the connection between each cell where
the messengers communicate.
(connectors to other nerve cells)
o 4.Develop synapses/synaptogenesis (points of communication
with other cells)-
o 5.Refine synapses (maturation, pruning)- enhancing the
communication among the nerve cells
o 6.Form supportive tissue/myelination (supports effective
communication among nerve cells) – experience dependent.
Complex environment is extremely important for young children.
This is why full day kindergarten is being enforced. - A basic neuron is made of a cell body (which contains the nucleus),
dendrites and a long axon. Myelin sheaths wrap around the axon
Two neurons forming a synapse:
- Transmit information via synapses- connections
- Called: synaptogenesis
- Axons, dendrites form connections or synapses
- Connections allow nerve cells to communicate with each other
- Starts prenatally and extends well into childhood years
- Stability, strength of synapses depend on effective communication of
- Effectiveness determined by speed that neurons conduct nerve impulses
- Speed is determined by amount of myelin
o A fatty substance that wraps itself around nerve axons
o Insulates axon and increases conduction velocity- just like an
electrical wire. Speed makes a connection more effective
- Amount of myelin determined by environment and experience