BIO 132

1. BIO 132 Neurophysiology

2. Lecture Goals: • Course overview - syllabus & tentative schedule • How to succeed in Bio 132 • Historical perspective of Neuroscience

3. Course Overview

4. 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?

5. -500 1000 0 500 1500 2000 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. • 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.

6. -500 1000 0 500 1500 2000 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. • Aristotle’s view one out over Hippocrates’ view, which was held for about 500 years.

7. -500 1000 0 500 1500 2000 Ancient Romans (~150 ad.) • Galen was a writer and physician to the gladiators. • 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.

8. -500 1000 0 500 1500 2000 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 • Claimed the soul communicated with the body through the pineal gland in the brain.

9. -500 1000 0 500 1500 1750 2000 1700-1750 • Scientists took a closer look at the brain doing careful dissections. • 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.

10. Fissure (sulcus) Bump (gyrus) Central NS Peripheral NS

11. -500 1000 0 500 1500 1751 2000 1751 • Ben Franklin publishes paper on electricity which gives scientist a new tool. • 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.

12. -500 1000 0 500 1500 1810 2000 1810 • Two scientist in different labs showed that neurons carry sensory or motor information, but not both. • 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.

13. -500 1000 0 500 1500 1810 2000 1810 • Gall, an Austrian, developed “phrenology” which correlates skull bumps with personality traits. • 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.

14. -500 1000 0 500 1500 1820 2000 1820 • 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. • 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. • Recognized that perceived sensations depend on the sensory organ type.

15. -500 1000 0 500 1500 1859 2000 1859 • Charles Darwin publishes On the Origin of Species • 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.

16. -500 1000 0 500 1500 1860 2000 1860s • Broca, a neurologist, had a patient who could understand speech but couldn’t speak. • 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.

17. -500 1000 0 500 1500 1870 2000 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.

18. -500 1000 0 500 1500 1870 2000 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.

19. -500 1000 0 500 1500 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. • 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.