Download UNIT II: THE HUMAN BRAIN

UNIT II: THE HUMAN BRAIN
How many cells are
in the human brain?
• 1 trillion!
• Two categories:
– Glial Cells
– Neurons
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Glial Cells
• Three Functions:
– Provide scaffolding to support
both developing and mature
neurons.
– Wrap around neurons to form
insulation from electrical signals
– Releasing chemicals that influence
neuron growth
• Make up 90% of cells in brain!
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Neurons
• 100 billion cells - both sends and receives messages and
signals (up to 268 mph!)
• Allows us to:
– Receive sensory information
– Control muscle movement
– Regulate digestion
– Release hormones
– Complete mental processes (thinking, etc.)
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Neurons (cont)
• Each neuron has hundreds of connections
– Approximately 100 trillion neural connections in
the brain
• Which is more: the world’s communications,
or the brain’s?
• 0.00005%
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Neuron Growth
• Humans born with all our neurons that
slowly die over our lifetime.
• What two areas of the brain does new
research suggest can regrow?
– Hippocampus and olfactory bulb
• Humans do have the ability to rewire our
brains -> recover from traumatic event
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Alzheimer’s Disease
• Excessive buildup of protein amyloid destroys
neurons faster than body can repair them.
• All people produce amyloid, Alzheimer’s patients
cannot get rid of it
– Teeth plaque
• Only “cure” right now is to
slow or stop amyloid buildup
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Neurons – Structure and Function
1. Cell body – egg-shaped structure that
provides fuel, manufactures chemicals,
maintains working order in the neuron,
contains neurons DNA
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Neurons – Structure and Function
2. Dendrites – Branchlike extensions; receive
signals from cells or other neurons and pass
them to the cell body.
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Neurons – Structure and Function
3. Axon – single threadlike structure, carries
messages to other neurons, organs, or
muscles. Can be the length of the width of a
human hair, or over 3 feet!
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Neurons – Structure and Function
4. Myelin Sheath – looks like separate tube-like
segments composed of fatty tissue. Prevents
interference from other electrical signals and
helps signals travel faster.
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Neurons – Structure and Function
5. Terminal bulbs – look like tiny bubbles at the end of
axon’s branches. Acts like a tiny container that
stores neurotransmitters. Do not actually touch any
neighboring organs, muscles, or cells.
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Neurons – Structure and Function
6. Synapse – Infinitely small gap between
terminal bulb and its neighboring organ,
muscle, or other neural cells. Terminal bulbs
eject neurotransmitters into the synapse to
send messages.
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What’s Wrong Here?
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Reattaching Limbs
• Limbs can be reattached because of
something we call nerves.
• In whole body except brain/spinal cord
• String-like bundles of axons and dendrites
• Carry messages from senses, skin, muscles,
and organs
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Reattaching Limbs
• Nerves (but not neurons) have the ability to regrow
• Gives us the ability to reattach limbs
• Difference between nerve and neuron:
– Neuron is individual cell
– Nerve is a group of neurons
• Think of nerves as the superfast lane of highway
neurons use to get signals to your brain
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