How Does the Brain How Does the Brain Develop?Develop?

Everything we do, feel and Everything we do, feel and say from infancy to the end say from infancy to the end of life reflect the functioning of life reflect the functioning

of our brainof our brain

How is the brain organized?

The NeuronThe 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 neuron4 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 NeuronThe Neuron2. The Cell body

contains the cell nucleus

The cell body relays the information down to the axon

The structure of a neuronThe structure of a neuron3. 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 Once the information hits the the Terminal buttonTerminal button, it is , it is

transmitted outside the cell transmitted outside the cell by by neurotransmittersneurotransmitters, which , which reside in the axon terminal.reside in the axon terminal.

The NeuronThe Neuron

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

How do neurons communicate?

Electrical CommunicationElectrical 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 transmissionSynaptic 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

NeurotransmittersNeurotransmitters

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 What observations can you make about the brain?make about the brain?

Brain Brain DevelopmentDevelopment

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.

Looking at the BrainLooking at the BrainThe 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 The Corpus CallosumCorpus Callosum connects these hemispheres connects these hemispheres and allows communication and allows communication

from one side of the brain to from one side of the brain to the other.the other.

Corpus CallosumCorpus Callosum

The beginning of the brain The beginning of the brain can be traced to the can be traced to the period of the zygoteperiod of the zygote

Approximately 3 weeks after conception a groups of cells form a flat structure called the neural plate

The The neural plateneural plate folds to folds to form a tube that ultimately form a tube that ultimately

becomes the brain and becomes the brain and spinal cordspinal cord

3 week old

zygote

Early Brain DevelopmentEarly Brain DevelopmentIn 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 developmentBrain growth and developmentThere 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 If cells are unused they atrophyatrophy and are and are rededicatedrededicated to other senses. Underused to other senses. Underused neurons, like synapses are neurons, like synapses are

inactivated by inactivated by pruningpruning process process

When children suffer brain When children suffer brain damage, cognitive processes damage, cognitive processes are usually impaired; these are usually impaired; these

processes often improve processes often improve gradually showing the brain’s gradually showing the brain’s

plasticityplasticity

The brain’s organization is somewhat flexible and if damaged the brain can

make new connections