Neurobio N110 Midterm Exam 1

Galvani

- Went to roof during thunderstorms..table with lower part of frog and nerves exposed & metal hook attached to nerve & on other side of roof: pole - As moved preparation further and further away from lightning rod, electrical field got weaker & so probability of generating contraction decreased..but when did generate contraction, force was same - Realized that electricity from electromagnetic field was not directly stimulating muscle..only triggering - Hypothesized that nerves have endogenous "animal electricity" (INTRINSIC) - to discount volta's counterargument, EXPERIMENT: laid exposed nerve on cut muscle & as soon as nerve touched cut muscle, leg contracted (NO METAL INVOLVED)

Volta

-NOTHING INTRINSIC TO MUSCLE BEING TRIGGERED..JUST GENERATING ELECTRICAL STIMULATON BY USING 2 DIFF METALS - made "voltaic pile" with alternating metals with nonconducting material in between, generating large voltage (battery) & directly stimulating muscles - argued Galvani's experiment was just working bc using battery & activating nerve muscle prep directly

Golgi

1800s, reticular theory & staining cells technique

Cajal

1900s, Spanish physician used microscope & Golgi's technique of cell staining; Neuron doctrine

Charles Sherrington

1900s; English physiologist who studied REFLEXES; said that circuits were made of connected individual neurons that Cajal had hypothesized; coined the term SYNAPSE

doctor who believed in right to die: anesthetic & then KCl (if injected in veins, more KCl outside so would flow inside cell so Veq goes from -70 to 0 mV)

Doctor Kevorkian

Nernst equation

Ek = RT/Fz*ln[Kout/Kin]

Understanding the neural code via monkey-robotic arm experiment

Electrodes attached to motor cortex to see activity as monkey is playing game In other room, brain connected to computer is attached to robot arm playing same game..computer is getting impulses from monkey brain..use pattern recognition software Showed that language of brain can be read Monkey can control robotic arm by brain only

reticular theory

NS = one continuous web of material allowing entire web to be instaneously conscious of that touch..thought of this bc was so fast

Galvani & Volta similarities & differences (1800)

both agreed that electricity contracts muscles disagreed whether body generates naturally (Galvani) or something we impose on body (Volta)

passive response

cell is ONLY responding to charge injected by electrode

cochlear implant

device attached to skull with magnet..ray of electrodes placed in inner ear to stimualte neurons even tho hair cells are dead & connected to stimulator..external part attached to scalp with magnet with microphone & speech processer (divides sound into relative freq) & that's transferred to stimulator that stimulates the ear

1939 Hodgkin & Huxley

first recording of AP measured transmembrane potential vs time instead of conductance like with Cole & Curtis & found that membrane potential went from rest to tens of mV past zero..disproving bernstein's 2nd hypothesis.. HODGKIN suggested quickly went from being permeable to one ion (potassium) to permeable to something else (sodium) & then permeable to potassium again (potassium permeability doesn't change much, just sodium changes alot)

Bernstein's second hypothesis (1902)

general increase in membrane permeability for all ions could underlie AP; tested by Cole & Curtis

1888 Nernst chemist

if have membrane and diff concentrations of ions on either side..produces potential

Bernstein's first hypothesis

if have membrane only permeable to one ion & differential distribution of that ion across membrane, the resting potential = equilibrium potential

neuron doctrine

like any other tissue, NS is composed of individual cells/neurons that come together to form NS

conductance units

mS/cm^2

Cole & Curtis (1939)

measured membrane conductance during AP to test Bernstein's second hypothesis but results didn't prove anything...there was a small increase in conductance but not as much as expected if general increase in membrane permeability for all ions

most important ion in creating resting membrane potential

potassium

Hodgkin & Katz's test of Bernstein's hypothesis

squid giant axon; tried to prove Bernstein's first hypothesis; increased EC [K+] and calculated equilib potentials & see if resting membrane potentials moved & ya saw it but then plotted RMP vs [K+] out and saw it was exponential, at low concentrations, also largely permeable to sodium..CONFIRMED BERNSTEIN'S FIRST HYPOTHESIS THAT RESTING POTENTIAL IS LARGELY DETERMINED BY K+'S EQUILIB POTENTIAL

what did Cole and Curtis invent?

voltage clamp amplifier

equilibrium potential

when chemical & electrical forces are balanced even though [ions] not balanced