Neurons are specific, unique kinds of cells in our bodies that carry information through electrical and chemical signals. Neurons are a core component of our nervous system, which includes both the brain and the spinal cord.
The neuron hypothesis was a major influence on modern neuropsychology.
The neuron hypothesis has three key aspects:
- Neurons are discrete, autonomous cells that interact but are not physically connected.
- They send electrical signals that have a chemical basis.
- They communicate with one another by using chemical signals.
Want to learn more about the amazing neuron? Read on…
Discovering the Neuron
Descartes described neurons as hollow filled tubes. However, when Anton van Leeuwenhoek examined nerves with a microscope, this is not what he found (Kolb, Whishaw, 2009).
As microscopes became more powerful, the neuron and its various parts became more visible. Eventually this led Theodor Schwann to suggest that cells are the basic structural units of the nervous system (neurons and glial cells).
An important development in the visualizing of cells was the introduction of staining, which permits us to differentiate among various parts of the nervous system. Anatomist Camillo Golgi used a silver-staining technique to become the first to visualize an entire neuron and all of its processes.
Electrical Activity and Behavior
Italian physicist Luigi Galvani found that wires used to electrically stimulate a frog’s nerve causes muscle contractions. Galvani got the idea that electrical stimulation may cause movement after observing that frog legs hanging from a metal wire twitched during an electrical storm.
Fritsch and Hitzig demonstrated that stimulating the cortex electrically produced movement. The technique of stimulating the cortex consisted of placing a thin uninsulated wire onto or into the cortex and sending a small electrical current through the uninsulated tip of the wire. Today researchers use transcranial magnetic stimulation (TMS) to induce electrical activity into the brain. This technique allows researchers to study how the brain produces behavior and which parts of the brain participate in specific actions.
Neurons as Basis of Learning
British psychologist Charles Scott Sherrington investigated how nerves connect to muscles. He suggested there is no continuous connection. He theorized that junctions connect neurons and that additional time is required to cross the junction. He referred to these junctions or gaps as synapses.
Otto Loewi found that chemicals carry messages across the synapse. Loewi’s discovery prompted a further discovery, that a synapse releases chemicals to influence the adjacent cell. Neuropsychologist Donald Hebb proposed a learning theory: individual cells, activated at the same time, form connecting synapses or strengthen existing ones and become a functional unit. He proposed that the new or strengthening units are the basis of memory.
Acceptance of the idea that the brain is plastic and is constantly changing at each of its billions of synapses revolutionizes our view of the brain from one that represents “self” by a static structure to one that represents self by dynamic, ongoing reorganization. (Kolb & Whishaw, 2009, p.23)
In Part 2 of The Amazing Neuron, we’ll see specifically how neurons communicate with one another and explore more about their functioning.
Kolb, B., & Whishaw, IQ. (2009). Fundamentals of Human Neuropsychology 6th Ed . New York, NY: Worth.
Photo credit: HENNING DALHOFF / SCIENCE PHOTO LIBRARY