How Does the Brain Develop?
Everything we do, feel and say from
infancy to the end of life reflect the
functioning of our brain
How is the brain organized?
The Neuron
The neuron is the basic building block of
the nervous system
‐ They are often grouped in bundles called
nerves.
There are billions and billions of
neurons throughout the body
4 parts of the neuron
1.
Dendrites are specialized to receive signals
from neighboring neurons and carry them
back to the cell body
Thin, bushy-like structures that receive
information from outside the neuron
Relays the information into the cell body
The Neuron
2.
The Cell body
contains the cell
nucleus
The cell body
relays the
information
down to the
axon
The structure of a neuron
3.
Axon: A thin, long structure that transmits
signals from the cell body to the terminal
buttons.
‐
The axon is wrapped in myelin, a fatty sheath
that allows it to transmit information more
rapidly.
Once the information hits the
Terminal button, it is transmitted
outside the cell by neurotransmitters,
which reside in the axon terminal.
The Neuron
Fun Facts
Average number of neurons in the human
brain
‐ 100 billion
Average number of neurons in an octopus
brain
‐ 300 million
Rate of neuron growth during development
of a fetus (while in the womb)
‐ 250,000 neurons per minute
The information shoots from one
end of the neuron to the other.
How do neurons communicate?
Electrical Communication
Action potential is an electrical current sent
down the axon initiates the release of
neurotransmitter.
The activity within the neurons is electrical.
This current causes the neuron to “fire”
When an action potential moves down the
axon, it causes the release of neurotransmitters
Synaptic transmission
The neurons don’t actually touch each
other, there is a gap between one neuron
and the next called Synapses.
‐ The space between neurons
Information must be transmitted across the
synapse to other neurons via the
neurotransmitters.
Presynaptic Neuron
Postsynaptic Neuron
Neurotransmitters
Neurotransmitters are chemical substances that
reside in the axon terminals
They communicate to other neurons by
binding to receptors on neighboring neurons
What observations can you make
about the brain?
The wrinkled outer
area of the brain is
called the Cerebral
CortexThe cortex regulates
many of our functions
that we think of
distinctly human.
Your personality,
ability to carry out
plans, certain types of
thinking, memory,
sensory activity.
Brain
Development
Looking at the Brain
The exterior covering (cortex) of the brain is
wrinkled which increases the surface area of
the brain
The brain is divided into 2 hemispheres
‐ Right and left hemispheres
The Corpus Callosum connects these
hemispheres and allows
communication from one side of the
brain to the other.
Corpus Callosum
The beginning of the brain can be
traced to the period of the zygote
Approximately 3 weeks after conception a
groups of cells form a flat structure called the
neural plate
The neural plate folds to form a tube
that ultimately becomes the brain
and spinal cord
3 week old
zygote
Early Brain Development
In the months after birth the brain grows rapidly,
producing billions of neurons, dendrites and axons, as
well as synapses reaching its peak around the infant’s
first birthday.
-In the first 2 years the brain increases in size from 25% to
75% of its adult weight
Soon after synapses soon to gradually disappear a
phenomenon known as synaptic pruning.
-This process is the brain’s way of “weeding out” the
unnecessary connections between neurons.
Brain growth and development
There is a fivefold increase in the number of
dendrites in cortex from birth to age 2 years, as a
result approximately 15,000 new connections may
be established per neuron.
‐ This is called “Transient exuberance”
These connections are necessary because thinking
and learning require many connections between
many parts of the brain
Experience is vital for brain formation
If cells are unused they atrophy and
are rededicated to other senses.
Underused neurons, like synapses
are inactivated by pruning process
When children suffer brain damage,
cognitive processes are usually
impaired; these processes often improve
gradually showing the brain’s plasticity
The brain’s organization is somewhat flexible and
if damaged the brain can make new connections