Historical Milestones in Neuroscience

A set of question-and-answer flashcards covering key historical discoveries, experiments, and concepts in neuronal signaling, membrane potentials, synaptic transmission, and sensory transduction.

What principle did Santiago Ramón y Cajal propose to explain the one-way flow of information within a neuron?

The Principle of Dynamic Polarization.

How did Cajal’s Golgi-stain drawings support the Neuron Doctrine?

They showed that neurons are separate, individual cells rather than parts of a continuous syncytium.

Which technique invented by Sakmann & Neher in 1976 enabled the direct recording of currents through single ion channels?

The patch-clamp method.

For which methodological breakthrough did Sakmann & Neher receive the 1991 Nobel Prize?

Their invention and development of the patch-clamp technique.

What key structural feature of K⁺ channels did Roderick MacKinnon reveal in 2001?

The selectivity filter that allows K⁺ ions to pass while excluding other ions.

Why was J. Z. Young’s discovery of the squid giant axon pivotal for neurophysiology?

Its large diameter allowed electrodes to be inserted, enabling direct recording of neuronal electrical activity.

What experimental advantage did Baker, Hodgkin & Shaw gain by perfusing the squid giant axon in 1962?

They could precisely control intra- and extracellular ion concentrations while monitoring membrane potential.

According to Julius Bernstein’s 1902 membrane hypothesis, which ion’s selective permeability explains the resting membrane potential?

Potassium (K⁺).

What incorrect prediction did Bernstein make about the membrane potential during an action potential?

He predicted it would rise only to 0 mV, not overshoot due to Na⁺ influx.

Which instrument did K. S. Cole invent in 1949 to hold membrane voltage constant while measuring ionic currents?

The voltage clamp.

What central finding did Hodgkin & Huxley report in 1952 about action potentials in the squid giant axon?

Voltage-dependent Na⁺ and K⁺ conductances generate the action potential, captured in the Hodgkin-Huxley model.

Whose work on trans-Atlantic telegraph cables provided the mathematical basis for passive ‘cable properties’ of neurons?

William Thomson (Lord Kelvin).

Which electrical characteristics of long cables modeled by Lord Kelvin are also critical for dendrites and axons?

Resistance, capacitance, and voltage decay over distance.

What did Furshpan & Potter discover in 1959 about the crayfish lateral giant synapse?

It is a rectifying electrical synapse that passes depolarizing current preferentially in one direction.

Which classic 1921 experiment by Otto Loewi demonstrated chemical neurotransmission?

Stimulation of one frog heart’s vagus nerve slowed a second, connected heart via a released chemical (later identified as acetylcholine).

What intracellular recording evidence convinced John Eccles that inhibition is chemical?

Excitatory inputs depolarized, whereas inhibitory inputs hyperpolarized, cat spinal motor neurons recorded with microelectrodes.

What spontaneous events did Fatt & Katz identify at the neuromuscular junction that suggested quantal release?

Miniature end-plate potentials (MEPPs) of ~1 mV caused by single quanta of acetylcholine.

How did lowering extracellular Ca²⁺ help Fatt & Katz show that transmitter release is quantal?

Evoked end-plate potentials became all-or-none steps equal to 1, 2, 3… MEPP amplitudes, indicating integer numbers of quanta.

What did Rodolfo Llinás demonstrate about Ca²⁺ influx at presynaptic terminals?

Calcium enters in tight microdomains near release sites and precisely triggers vesicle exocytosis.

Which imaging technique did Heuser et al. use in 1979 to capture vesicles fusing with the presynaptic membrane?

Freeze-fracture electron microscopy.

What structural factor did Lowenstein & Mendelson show was responsible for the rapid adaptation of Pacinian corpuscles?

The layered mechanical capsule surrounding the nerve ending.

Why did Lowenstein & Mendelson apply the local anesthetic procaine during Pacinian corpuscle experiments?

To block action potentials and isolate the receptor potential.

Who coined the term “synapse” in 1897 to describe specialized junctions between neurons?

Charles Sherrington.

According to Georg von Békésy’s work, where along the cochlea do high-frequency sounds cause maximum vibration?

Near the base of the cochlea; low frequencies peak at the apex.

What photochemical event in visual pigments did George Wald discover in the 1950s?

Light induces the isomerization of retinal from 11-cis to all-trans form.

What key capability did the patch-clamp technique introduce to electrophysiology?

Recording real-time currents from individual ion channels.

What is the structural basis for K⁺ selectivity revealed by MacKinnon’s 2001 X-ray structure?

A narrow pore whose carbonyl oxygens form a selectivity filter precisely matching dehydrated K⁺ ions.

How did perfusing the squid axoplasm assist Baker, Hodgkin & Shaw in studying the resting potential?

It allowed controlled substitution of internal ions while monitoring voltage changes.

What does the Hodgkin-Huxley model mathematically describe?

Time- and voltage-dependent Na⁺ and K⁺ conductances that generate the action-potential waveform.

In the crayfish electrical synapse found by Furshpan & Potter, what does ‘rectification’ mean?

Current flows more readily in one direction than the other across the gap junction.