Download Brain`s Building Blocks

Brain’s Building Blocks
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fact that your brain does not develop into a
nose is because of instructions contained in
your genes
Genes
◦ chains of chemicals that are arranged like rungs on
a twisting ladder
◦ there are about 20,000-25,000 genes that contain
chemical instructions that equal about 300,000
pages of written instructions
◦ genes program the development of individual parts
into a complex body & brain
Six week old brain
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Human brain:
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is shaped like a small wrinkled melon
1,350 grams (less than 3 pounds)
pinkish-white color
consistency of firm Jell-O
Fueled by sugar (glucose)
1 trillion cells divided into
 glial cells
 neurons
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Glial cells
3 Functions:
◦ guide the growth of developing neurons
◦ wrap around neurons and form an insulation to
prevent interference from other electrical signals
◦ release chemicals that influence a neuron’s growth
and function
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Neuron
◦ a brain cell with 2 specialized extensions
◦ one extension is for receiving electrical signals
◦ the other extension is for transmitting electrical
signals
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http://www.dnatube.com/video/1301/Neuro
ns-and-Neuro-transmitters
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Can a brain grow new neurons?
◦ canary brain
 can grow about 20,000 neurons a day during the
spring (learns new breeding song)
◦ primate and human brain
 researchers conclude that adult monkey and human
brains are capable of growing relatively limited
numbers of neurons throughout adulthood
 Some new neurons play important role in continuing to
learn and remember new things (hippocampus)
 http://www.youtube.com/watch?v=FZ3401XVYww
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Repairing the Brain
◦ advances in stem research suggest the human brain
may be able to grow more neurons
◦ repair damages:
 accident
 disease
 Alzheimer’s
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Mind-body Question
◦ how complex mental activities such as
 feeling
 thinking
 learning
◦ can be explained by the
 physical
 chemical
 electrical activities
◦ of the brain
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Cell Body
◦ large egg-shaped structure that provides fuel,
manufactures chemicals, and maintains the entire
neuron in working order
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Dendrite
◦ branchlike extensions that arise from the cell body
◦ receive signals from other neurons, muscles, or
sense organs
◦ pass these signals onto the cell body
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Axon
◦ a single threadlike structure that extends from and
carries signals away from the cell body to
neighboring neurons, organs, or muscles
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Myelin Sheath
◦ looks like separate tubelike segments composed of
fatty material that wraps around and insulates an
axon
◦ prevents interference from electrical signals
generated in adjacent axons
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End bulbs or Terminal bulbs
◦ located at extreme ends of the axon’s branches
◦ miniature container that stores chemicals called
neurotransmitters (used to communicate with
neighboring cells)
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Synapse
◦ infinitely small space (20-30 billionths of a meter)
◦ exists between and end bulb and its adjacent body
organ, heart, muscles, or cell body
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Alzheimer’s disease
◦ excessive buildup of gluelike substances
◦ gradually destroy neurons
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Researchers recently discovered an
experimental vaccine that may help stop the
buildup of these gluelike, killer substances
and they continue to search for other
interventions
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Reattaching Limbs
◦ John Thomas
 lost arms in farming accident
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Transplanting a Face
◦ Isabelle
 face severely disfigured by a dog
 received
 new nose
 lips
 chin
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Peripheral Nervous System
◦ made up of nerves that are located throughout the
body, except in the brain & spinal cord
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Central Nervous System
◦ made up of neurons located in the brain & spinal
cord
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Nerves
◦ stringlike bundles of axons and dendrites that
come from the spinal cord and are held together by
connective tissue
◦ carry information from the senses, skin, muscles,
and the body’s organs to and from the spinal cord
◦ nerves in the peripheral nervous system have the
ability to grow or reattach if severed or damaged
◦ axon membrane has chemical gates that can open
to allow electrically charged particles to enter or
can close to keep out these particles
◦ ions are chemical particles that have electrical
charges
◦ opposite charges attract and like charges repel
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Resting state
◦ the axon has a charge
◦ the charge results from the axon membrane
separating positive ions on the outside from
negative ions on the inside
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Action potential
◦ tiny electric current that is generated when the
positive sodium ions rush inside the axon
◦ enormous increase of sodium ions inside the axon
causes the inside of the axon to reverse its charge
◦ inside becomes positive and outside becomes
negative
PLAY
VIDEO
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Sending information
◦ action potential is a tiny electrical current that is
generated when the positive sodium ions rush
inside the axon
◦ the enormous increase of Na ions inside the axon
causes the inside to reverse its charge
◦ the inside becomes positive & the outside becomes
negative
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All-or-None law
◦ if an action potential starts at the beginning of the
axon, the action potential will continue at the same
speed segment to segment to the very end of the
axon
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Nerve impulse
◦ nerve impulse is made up of 6 action potentials,
with the first occurring at the beginning of the axon
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A transmitter is a chemical messenger that
transmits information between nerves and
body organs, such as muscles and heart
Excitatory and Inhibitory
◦ excitatory transmitters
 open chemical locks and turn on neurons
◦ inhibitory transmitters
 block chemical locks and turn off neurons
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Neurotransmitters
◦ dozens of different chemicals that are made by
neurons and then used for communication between
neurons during the performance of mental or
physical activities
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Alcohol (ethyl alcohol)
◦ A psychoactive drug that is classified as a
depressant, which means that it depresses the
activity of the central nervous system
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Alcohol affects the brain by imitating a
naturally occurring neurotransmitter, GABA
GABA Neurons
◦ GABA neurons have chemical locks that can be
opened by chemical keys in the form of the
neurotransmitter GABA
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GABA Keys
◦ alcohol molecules so closely resemble those of the
GABA neurotransmitter that alcohol can function
like GABA keys and open GABA receptors
◦ when GABA neurons are excited, they decrease
neural activity
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many people drink alcohol to feel less
anxious and more relaxed
appears to be a biological link between
alcohol and anxiety
deficiency in a specific brain protein is
associated with high anxiety and excessive
alcohol use
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Number of well-known neurotransmitters,
such as
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Acetylcholine
GABA
Norepinephrine
Epinephrine
Dopamine
Serotonin
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New
◦ Endorphins (1970’s)
 painkiller similar to morphine
 decreases effects of pain during great bodily stress
◦ Anandamide (1990’s)
 similar to THC (active ingredient in marijuana)
 involved with
 memory
 motorcoordination
 emotions
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Anandamide may help people regulate
emotions, which would help them to better
deal with anxiety and stress
◦ Nitric oxide (mid-1990’s)
 may be involved in regulating aggressive and
impulsive behaviors
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Reflex
◦ unlearned, involuntary reaction to some stimulus
◦ neural connections underlying a reflex are prewired
by genetic instructions
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Reflex sequence
◦ sensors
 sensors trigger neurons that start the withdrawal effect
◦ afferent neurons
 carry information from the senses to the spinal cord
◦ Interneuron
 relatively short neuron whose primary
task is making connections between
other neurons
◦ Efferent neuron
 carry information away from the spinal
cord to produce responses in various
muscles and organs throughout the body
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Parkinson’s Disease
◦ includes symptoms of tremors and shakes in the
limbs, a slowing of voluntary movements, muscle
stiffness, problems with balance and coordination
and feelings of depression
◦ as the disease progresses, patients develop a
shuffling walk and may suddenly freeze in space for
minutes or hours at a time
◦ Michael J. Fox
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Parkinson’s Disease
◦ it is caused by destruction of neurons that produce
dopamine
◦ L-dopa is a medication that boosts the levels of
dopamine in the brain
◦ eventually the drug causes involuntary jerky
movements
◦ after prolonged use, L-dopa’s beneficial effect may
be replaced by unwanted jerky movements
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Sterotaxic procedure
◦ fixing a patient’s head in a holder and drilling a
small hole through the skull
◦ the holder has a syringe that can be precisely
guided into a predetermined location in the brain
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Removing part of the brain
◦ Thalamotomy (Michael J. Fox)
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Brain Stimulation
◦ electrodes placed into thalamus
◦ patient controls amount of stimulus
◦ helps reduce tremors