How Does the Brain Develop?

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How Does the Brain Develop?
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Everything we do, feel and say from infancy to
the end of life reflect the functioning of our
brain

• How is the brain organized?

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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

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4 parts of the neuron

• 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

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The Neuron

• The Cell body contains the cell nucleus
• The cell body relays the information down to the
  axon

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The structure of a neuron

• 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.

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Once the information hits the Terminal button, it
is transmitted outside the cell by
neurotransmitters, which reside in the axon
terminal.
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The Neuron
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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

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The information shoots from one end of the neuron
to the other.

• How do neurons communicate?

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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

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Synaptic transmission

• The neurons dont 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.

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Presynaptic Neuron
Postsynaptic Neuron
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Neurotransmitters

• Neurotransmitters are chemical substances that
  reside in the axon terminals
• They communicate to other neurons by binding to
  receptors on neighboring neurons

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What observations can you make about the brain?
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Brain Development

• The wrinkled outer area of the brain is called
  the Cerebral Cortex-
• The 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.

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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

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The Corpus Callosum connects these hemispheres
and allows communication from one side of the
brain to the other.
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Corpus Callosum
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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

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The neural plate folds to form a tube that
ultimately becomes the brain and spinal cord

• 3 week old zygote

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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 infants 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 brains way of weeding out
  the unnecessary connections between neurons.

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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

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If cells are unused they atrophy and are
rededicated to other senses. Underused neurons,
like synapses are inactivated by pruning process
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When children suffer brain damage, cognitive
processes are usually impaired these processes
often improve gradually showing the brains
plasticity

• The brains organization is somewhat flexible and
  if damaged the brain can make new connections