Julius Bernstein
Encyclopedia
Julius Bernstein was a German physiologist who was born in Berlin
. He studied medicine at the University of Breslau under Rudolf Heidenhain
, and at the University of Berlin under Emil Du Bois-Reymond
. He received his medical degree at Berlin in 1862, and began his career at the Physiological Institute of the University of Heidelberg as an assistant to Hermann von Helmholtz
. In 1872 he succeeded Friedrich Goltz
as professor of physiology at the University of Halle. Bernstein remained in Halle for the remainder of his career.
Bernstein's work was concentrated in the fields of neurobiology and biophysics
. He is remembered for his explanation regarding the origin of the "resting potential" and "action potential" of nerves and muscles. In 1902 he developed the "membrane theory" of electrical potential in biological cells and tissues, which provided the first practical physico-chemical
explanation of bioelectric events. This hypothesis is considered the first actual quantitative theory in electrophysiology
.
Bernstein (1902, 1912) correctly proposed that excitable cells are surrounded by a membrane selectively permeable to K+ ion
s at rest and that during excitation the membrane permeability to other ions increases. His "membrane hypothesis" explained the resting potential of nerve and muscle as a diffusion potential set up by the tendency of positively charged ions to diffuse from their high concentration in cytoplasm
to their low concentration in the extracellular solution while other ions are held back. During excitation, the internal negativity would be lost transiently as other ions are allowed to diffuse across the membrane, effectively short-circuiting the K+ diffusion potential. In the English-language literature, the words "membrane breakdown" were used to describe Bernstein's view of excitation. (From Ion Channels of Excitable Membranes, Third Edition, by Bertil Hille).
His pioneering research laid the groundwork for experimentation on the conduction of the nerve impulse, and the transmission of information in the nervous system
. Bernstein also invented a "differential rheotome", a device used to measure the velocity
of bio-electric impulses.
Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...
. He studied medicine at the University of Breslau under Rudolf Heidenhain
Rudolf Heidenhain
Rudolf Peter Heinrich Heidenhain was a German physiologist who was born in Marienwerder, East Prussia . He studied medicine at the Universities of Halle and Berlin. After receiving his doctorate, he remained in Berlin as an assistant to Emil du Bois-Reymond...
, and at the University of Berlin under Emil Du Bois-Reymond
Emil du Bois-Reymond
Emil du Bois-Reymond was a German physician and physiologist, the discoverer of nerve action potential, and the father of experimental electrophysiology.-Life:...
. He received his medical degree at Berlin in 1862, and began his career at the Physiological Institute of the University of Heidelberg as an assistant to Hermann von Helmholtz
Hermann von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions to several widely varied areas of modern science...
. In 1872 he succeeded Friedrich Goltz
Friedrich Goltz
Friedrich Leopold Goltz was a German physiologist and nephew of the writer Bogumil Goltz.Goltz held various university positions in Königsberg, Halle and Strasbourg, Germany...
as professor of physiology at the University of Halle. Bernstein remained in Halle for the remainder of his career.
Bernstein's work was concentrated in the fields of neurobiology and biophysics
Biophysics
Biophysics is an interdisciplinary science that uses the methods of physical science to study biological systems. Studies included under the branches of biophysics span all levels of biological organization, from the molecular scale to whole organisms and ecosystems...
. He is remembered for his explanation regarding the origin of the "resting potential" and "action potential" of nerves and muscles. In 1902 he developed the "membrane theory" of electrical potential in biological cells and tissues, which provided the first practical physico-chemical
Physical chemistry
Physical chemistry is the study of macroscopic, atomic, subatomic, and particulate phenomena in chemical systems in terms of physical laws and concepts...
explanation of bioelectric events. This hypothesis is considered the first actual quantitative theory in electrophysiology
Electrophysiology
Electrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart...
.
Bernstein (1902, 1912) correctly proposed that excitable cells are surrounded by a membrane selectively permeable to K+ ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s at rest and that during excitation the membrane permeability to other ions increases. His "membrane hypothesis" explained the resting potential of nerve and muscle as a diffusion potential set up by the tendency of positively charged ions to diffuse from their high concentration in cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
to their low concentration in the extracellular solution while other ions are held back. During excitation, the internal negativity would be lost transiently as other ions are allowed to diffuse across the membrane, effectively short-circuiting the K+ diffusion potential. In the English-language literature, the words "membrane breakdown" were used to describe Bernstein's view of excitation. (From Ion Channels of Excitable Membranes, Third Edition, by Bertil Hille).
His pioneering research laid the groundwork for experimentation on the conduction of the nerve impulse, and the transmission of information in the nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
. Bernstein also invented a "differential rheotome", a device used to measure the velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
of bio-electric impulses.
Written works
- Untersuchungen über den Erregungsvorgang im Nerven- und Muskelsysteme, Heidelberg: Winter, 1871 (Experiments of the excitation procedure in nerve and muscle systems)
- Die fünf Sinne des Menschen. (The five senses of humans) Leipzig: Brockhaus, 1875
- Die mechanische Theorie des Lebens, ihre Grundlagen und ihre Erfolge. Braunschweig: Vieweg, 1890
- Lehrbuch der Physiologie des thierischen Organismus, im speciellen des Menschen. Stuttgart: F. Enke, 1894
- Elektrobiologie: Die Lehre von den elektrischen Vorgängen im Organismus auf moderner Grundlage dargestellt. Braunschweig: Vieweg, 1912