TIMELINE OF GENERAL REFLEX CONTRIBUTIONS
The general scientific timeline shows many independent neurophysiologist scientific contributions made between the mid-1600s and the 1800s. With this knowledge, scientists in the latter half of the 1800s were able to begin building the foundation for our modern understanding of reflexes and their important structures.
1649 – René Descartes, French philosopher, and scientist:
Proposes his first mechanical understanding of what would later be called the reflex arc. According to Descartes, the actions of the body are reflexive, but the actions of the mind are meaningful, conscious, and voluntary. Descartes' proposal was based on a basic model of sensory input and motor output controlled by the brain. Although the basic concept he proposed was correct, neural activity was not yet understood enough to leave him to explain neural activity through "animal spirits."
1664 - Thomas Willis, English professor at Oxford:
Proposes that nerve impulses involving animal spirits produce one of three different types of reflex movements toward and from the brain, depending on the strength of the incoming stimulus. Weak, continuous stimulus-evoked reflexes are necessary for survival (e.g., heartbeat); A more intense sensory stimulus evokes involuntary movements such as walking, and very intense stimuli evoke voluntary actions.
1664 - John Swimmer den, a Danish biologist:
Shows that movement was caused by external stimulation ("irritation") of nerves. The swimmer was unable to determine, however, what energy was causing the action. This fundamental discovery scientifically demonstrated the stimulus-response relationship involved in the activity.
1751 - Albrecht Van Haller, Swiss biologist:
Expands on Swammerdam work and shows that stimulation of a nerve causes contraction of the muscles attached to it - or muscle activity. This led to the scientific conclusion that nerves carry impulses that produce sensation. Like Swammerdam, van Haller was unable to determine the energy content of combustion.
1791 - Luigi Galvani, Italian biologist:
While dissecting a frog on the same bench as the "electric machine," he accidentally discovered that the frog's muscles responded with movement to external electrical stimuli. Galvani proposed that the internal element responsible for the motion was electrical. This was the first scientific evidence that nerve activity (burning that could not previously be explained) was electrical.
1802 - Marie-François-Xavier Brecht, French anatomist, and physiologist:
Proposes that life is regulated by the system DES ganglion (ganglionic nervous system). Piaget's "ganglionic nervous system" along with Bell's description of "vegetative functions" in 1811 were precursors to the more formal autonomic nervous system proposed by Langley in 1898.
1811 - Charles Bell, English surgeon, and experimental physiologist:
Shows that spinal nerves serve no single purpose, but instead carry both motor and sensory impulses to and from the brain. That same year, he published his book Idea of a New Anatomy of the Brain, which some have called the "Magna Carta of Neurology". In this book, he discussed the functions of the brain, the cerebellum, the double roots of the spinal nerves, and his experimental investigation of their function. He hypothesized that the ventral roots connected the peripheral nervous system to the cerebrum, which was then considered the center of "sensation and movement," while the dorsal roots connected the kidneys to the cerebellum, the center of which he called "the body." Bell's description of the "vegetative functions" of the body, along with Beget's 1802 "ganglionic nervous system," were precursors to the more formal autonomic nervous system first proposed by Langley in 1898.
1820 - Francois Magenta, French physiologist:
Building, Bell's work shows that the ventral roots of spinal nerves are motor and the dorsal roots are sensory. This discovery became known as Bell-Magenta's law and was considered the first important step toward the investigation of nerves, which became the starting point for much of Charles Herrington's later work.
1836 - 1903, Bernard Perez, French physician (spinal Perez reflex)
837 - Marshall Hall, English physiologist:
Discovers that the headless newt moves when its skin is pricked. This work led Hall to propose his theory of reflex action, "which stated that the spinal cord consisted of a chain of units and that each of these units acted as an independent reflex arc." And the motor nerves and the part of the spinal cord are where these nerves originate; and the arcs are interconnected, communicating with each other and with the brain to produce coordinated movement.
1850 - Gustav Theodor Fischer, germ
nice work
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