Download A Brief History of the Discovery of the Neuron Based on the History

A Brief History of
the Discovery of
the Neuron
Cell Theory
 1838 – Matthias Schleiden and Theodore Schwann
proposed the cell was the basic functional unit of all
living things
 BUT it was widely believed this did not apply to the nervous system
Development of the
Achromatic Lens
 1820’s
Johannes Purkinje
 1832 – Purkinje began examining thin sections of
nervous tissue
 First neurons to be identified: Purkinje cells found
in the cerebellum
Otto Friedrich Carl Dieters
 1863 - Further improvements in microscopy enabled Dieters to
produce the most accurate description yet of a nerve cell
 Referred to the axon as the “axis cylinder” and the dendrites as
“protoplasmic processes”
The Great Debate
 Debate among researchers raged on about the
organization of the nervous system
 Reticularists believed the nervous system consisted of
a large network of tissue or (anastomoses) formed by
the fused processes of nerve cells
 Neuronists argued that the nervous system consisted
of distinct cells
Joseph von Gerlach
 A reticularist
 1871 - Used gold chloride or carmine to stain nerve
tissue
 Concluded:
“the finest divisions of the protoplasmic processes
ultimately take part in the formation of the fine nerve
fibre network which I consider to be an essential
constituent of the gray matter of the spinal cord.”
Camillo Golgi
 1873 - Developed a new staining technique which
involves hardening of tissue in potassium bichromate
and ammonia, followed by immersion in silver nitrate
 Still thought his observations confirmed the “nerve
network” organization of the nervous system
Wilhelm His, Sr.
 1880’s studied embryological development of the central
nervous system
 “I consider as a definitive principle the theorem that every
nerve fiber originates as the outgrowth of a single cell.”
His micrograph of the
neuroblastic cells
with processes
growing toward the
surface (human
embryo at four
weeks)
Santiago Ramon Cajal
 1887 used Gogi’s method of staining nervous tissue with the
addition of immersing the tissues in fixative and silver nitrate
a second time
 Observation of the basket cells of the cerebellar cortex:
“The special character of these cells is the striking
arrangement of their nerve filament (axon), which arises from
the cell body but also very often from any thick, protoplasmic
expansion (dendrite).”
The Big Breakthrough!
 The twentieth century invention of the
electron microscope allowed
researchers to examine nervous tissue
in greater detail.
 Electron micrograph (right) shows
clusters of vesicles docked at the
presynaptic membrane.
 Scanning electron micrograph (below)
shows vesicles in the process of fusing
with the presynaptic membrane
The Neuron Doctrine
 The neuron is the fundamental structural and
functional unit of the nervous system.
 Neurons are discrete cells which are not continuous
with other cells.
 The neuron is composed of 3 parts – the dendrites,
axon and cell body.
 Information flows along the neuron in one direction
(from the dendrites to the axon, via the cell body).
Current Vocabulary
 The term “neuron” was introduced in 1891 by Heinrich
Wilhelm Gottfried von Waldeyer-Hartz (A)
 “Axis cylinder” was named “axon” by Rudolph Albert
von Kolliker (B)
 “Protoplasmic processes” were called “dendrites” by
Wilhelm His Sr. (C)
 And finally, “synapse” was coined by Sir Charles
Sherrington in 1897 (D)
A
B
C
D