Transcript Lecture 1

BIO 132
Neurophysiology
Lecture Goals:
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Course overview - syllabus & tentative schedule
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How to succeed in Bio 132
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Historical perspective of Neuroscience
Course Overview
History of Neuroscience: A
Perspective
Where in the body are memories stored; do
commands to move come from; is sensory
information processed; do consciousness, logic
and emotion stem from?
What evidence do you have to support your
answer?
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The Ancient Egyptians
 Greatly interested in physiology and how the body and
mind worked.
 Thought the heart was seat of consciousness, and the
brain did nothing important.
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When embalming the dead they would take great care to
preserve the heart but the brain was pulled out through the
nose and thrown out.
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The Ancient Greeks (~400b.c.)
 Hippocrates claims that the brain is the center of
sensation and movement.
Why would he come to this conclusion? He had no
scientific tools like microscopes or MRI machines.
 Aristotle claimed that the heart “seethed” with emotion
and that the brain was just a radiator to cool the body.
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Aristotle’s view one out over Hippocrates’ view, which
was held for about 500 years.
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Ancient Romans (~150 ad.)
 Galen was a writer and physician to the gladiators.
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He saw the effects of brain and spinal injuries.
By poking on the brain he noticed that the front was soft and
back was hard, and concluded that the front dealt with
memories and back dealt with movement.
He dissected sheep brains and noted they had hollow cavities
filled with fluid.
He proposed that information was sent via the fluid traveling
through nerves, which he considered just hollow tubes.
This view was held for about 1,500 years.
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Renaissance (1500-1600)
 Galen’s views were strengthened by invention of
hydraulics.
 Philosopher Rene Descartes ("I think therefore I am.“)
developed a dualistic view of the human mind: soul and
body were separate entities
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Claimed the soul communicated with the body through the
pineal gland in the brain.
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1700-1750
 Scientists took a closer look at the brain doing careful
dissections.
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Grey and white matter found.
White matter continuous with nerves of the body so assumed
that it carried information.
Found that there was a central nervous system and peripheral
nervous system.
Found that bumps (gyri) and fissures (sulci) on the brain are
universal among people.
Central NS
Bump
(gyrus)
Peripheral NS
Fissure
(sulcus)
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1751
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1751
 Ben Franklin publishes paper on electricity which gives
scientist a new tool.
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Others found that shocking muscle causes twitches.
Shocking limbs elicits sensation.
Galen’s “fluid theory” replaced with one stating nerves use
electrical pulses to carry info.
It wasn’t known if the same nerve carried both sensory and
motor information.
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1810
 Two scientist in different labs showed that neurons
carry sensory or motor information, but not both.
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Nerves branch at the spinal cord, connecting with the front
and back.
If front branch is cut, movement is lost; if back branch is cut,
sensation is lost.
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1810
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Gall, an Austrian, developed
“phrenology” which
correlates skull bumps with
personality traits.
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Scientists didn’t believe Gall’s
theory since skull bumps don’t
follow brain bumps (gyri).
Mainstream public bought
100,000 copies of Gall’s book.
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1820
1820
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Scientists look to see if different brain areas have specific
functions using “experimental ablation method” which
destroys a brain area to see what function is lost.
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Only large crude destruction was possible.
Found that cerebrum is for sensation and perception, cerebellum is
for movement coordination.
Johannes Muller realizes that sensory systems and not the
stimuli themselves produce sensations.
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Recognized that perceived sensations depend on the sensory organ
type.
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1859
1859
 Charles Darwin publishes On the Origin of Species
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Darwin includes behavior among heritable traits.
He observed that many mammals show similar behavior
when frightened.
Concluded animal nervous system probably share
common wiring and underlying mechanisms.
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1860
1860s
 Broca, a neurologist, had a patient who could
understand speech but couldn’t speak.
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The patient’s words were jumbled together and didn’t
make sense.
After patient died, Broca examined his brain and saw a
lesion in a brain area.
Today the area is called Broca’s area and it is responsible
for communication.
This was the first evidence that a specific brain area had a
specific function.
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1870
1870s
 Scientists could apply a small shock to the brain and
elicit movement.
 Destruction of the same brain area caused paralysis.
 Mapping of the brain’s functions begins.
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1870
1870s
 Nissl invents the Nissl stain and is able to see cell
bodies under the microscope.
 Golgi invents the Golgi stain which shows the
outline of neurons.
He proposes the "Reticular Theory" - all neurons are one
big net.
Cajal uses Golgi stain to advance histology of brain to
unprecedented heights and proposes "Neuron Doctrine" each neuron is separate.
Golgi and Cajal, bitter rivals, must share the Nobel Prize (1st
time ever) in 1906.
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1950 2000
1950s
 Electron microscope invented and shows that Cajal
was correct (*usually).
 Hodgkin and Huxley use giant squid axon to test
action and membrane potentials.
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They pioneered the use of the voltage clamp technique to
change and measure the potential (charge) inside a
neuron.
They developed a model for activation and threshold
energies.
They shared the Nobel Prize in 1952.