Scientists: Sir Charles Sherrington
Towards the end of the 19th century, neurologists were split between two schools of thought about how the brain worked and what it is made up of. Some believed in 'reticular theory', and some believed in the 'neuron doctrine'.
'Reticular theory' was championed by scientists such as Golgi (read more on Golgi). It explained the brain and nervous system as one directly connected mass, in which information was freely exchanged throughout. The 'neuron doctrine', believed by scientists such as Cajal (read more on Cajal), said the nervous system is made up of discrete individual brain cells (neurons), which we now know to be true.
This might seem obvious now, but it was being debated at a time when cell theory had only been introduced a few decades previously. Sir Charles Sherrington, an English neuroscientist, defended the neuron doctrine theory and carried out a great deal of research to provide evidence for it.
A kneejerk reaction
During his earlier years of research, Sherrington concentrated his studies on reflex arcs - the neural pathway that controls a reflex such as a knee jerk. He discovered the main principal of a reflex, which was then named after him: Sherrington's Law states that when one set of muscles is stimulated, muscles opposing the action are simultaneously inhibited.
For example, when the tendon just below the knee (the patellar tendon) is tapped, an action potential (nerve impulse) is sent through the central nervous system and stimulates the thigh muscles (quadriceps) to contract and straighten the leg. At the same time, the action potential stimulates the hamstrings to relax and allows the leg to straighten.
What is a synapse?
In 1906 Sherrington presented a series of ten lectures describing his research on neurons, helping to solidify the neuron doctrine theory. Notably, he was the first person to describe the minute gap between neurons connecting the different cells, the 'synapse' (from the Greek 'syn', meaning together, and 'haptein', meaning to clasp).
The synapse contains a presynaptic neuron (containing the neurotransmitter, mitochondria and other organelles), a postsynaptic neuron (containing the receptors for the neurotransmitter) and a synaptic cleft (the gap itself). An action potential (electrical impulse) reaches the presynaptic neuron and cannot pass across to the next neuron cell, so the impulse is transported across the synaptic cleft by the neurotransmitter.
During World War I Sherrington had to pause his research, as did many other scientists at the time. He worked at a shell factory in Birmingham owing to his role as Chairman of the Industrial Fatigue Board, set up to look into the connection between workers' fatigue and performance.
Sherrington also had many hobbies, including philosophy and writing; he published a book of war poems in 1925. The poems were very well received and even prompted one reviewer to hope "Miss Sherrington" would publish more verse! He clearly had more talents than just neuroscience.
After years of extensive research into many aspects of neuroscience, both before and after the war, he was able to summarise his findings in a theory of the entire nervous system. He stated that the nervous system acts as a coordinator of various parts of the body and that reflexes are the simplest expressions of the interactive action of it.
Sherrington received the Nobel Prize for Physiology or Medicine in 1932, and many of his ideas are still in use today. His work shaped neurology for the future and made him one of the most prominent names in the field.
Questions for discussion
- Can you think of any other examples of reflex arcs within the body?
- Using Sherrington's Law, decide which muscles play which part in that reflex arc.
This article is part of the online content for ‘Big Picture: Inside the Brain’.
Image: Sir Charles Sherrington. Credit: Wellcome Library, London.