Nerve-muscle threshold, anesthesia and fatigue
The threshold of stimulation is the weakest stimulus that still produces a response. Early physiologists used it to compare organisms, tissues and states. Verworn reported Pfeffer's work on thresholds in the chemotaxis of microorganisms1. Loeb used it to ask whether the central nervous system matters for a reflex2. Cannon measured it in nerve-muscle before and after fatigue, in decerebrate and urethane-anesthetized animals467.
- Earliest held
- 1899, Verworn, M.
- Most discussed in
- The Integrative Action of the Nervous System, 1906
- In the library
- 26 passages in 8 works
- Rewritten
- 2026-11-03
Threshold as a comparison
Verworn (1899) reported Pfeffer's work on bacteria and flagellates. The threshold concentration at which a substance just begins to exert its chemotactic effect differed between substances and between organisms1. Loeb (1900) turned the idea to reflexes. He dropped water from a pipette and took the minimum fall height as a measure of irritability, the reciprocal of the threshold. He found the threshold higher in operated animals than in normal ones2. He also noted that dogs studied by Goltz and Ewald showed a raised threshold and probably slower conduction3.
Cannon's measurements
Cannon (1915) determined the threshold of the peroneus communis nerve with an inductorium. In decerebrate animals it ranged from 0.319 to 2.96 units, averaging 1.179 over sixteen experiments4. Cannon noted that this average matched one found by E. L. Porter for the radial nerve in the spinal cat4. Animals under urethane anesthesia gave a higher average. It ranged from.644 to 7.05 and averaged 3.081 over ten experiments5.
Effect of fatigue
Cannon cites an earlier observation, confirmed by Gruber, that the threshold stays constant for hours. Any change after fatigue must therefore come from alterations the fatigue process sets up in the nerve-muscle or muscle6. In sixteen decerebrate animals the threshold rose from 1.179 to 3.34, an increase of 183 per cent6. In ten urethane animals it rose from 3.08 to 9.408, an increase of 208 per cent7.
Specific and general thresholds
Lillie (1923) described receptor specialization as a lowered threshold for one agent. It need not alter the general sensitivity to mechanical and electrical stimulation, so a specific irritability is superposed on a general one9. Bayliss (1915) cited Sherrington's description of plastic tonus of skeletal muscle in the decerebrate animal. In that state the vasto-crureus can be held at different lengths with the same load8.
The threshold of stimulation, i.e., that degree of concentration at which the substances just begin to exert their chemotactic effect, is very different for different substances and different organisms.
Verworn, M., 1899 · General Physiology: An Outline of the Science of Life · open at passage 1100The threshold of stimulation for producing this reflex is higher in animals which have been operated upon than in normal animals.
Loeb, J., 1900 · Comparative Physiology of the Brain and Comparative Psychology · open at passage 57The threshold of stimulation was raised and probably the rapidity of the conduction decreased.
Loeb, J., 1900 · Comparative Physiology of the Brain and Comparative Psychology · open at passage 68The threshold for the peroneus communis nerve in decerebrate animals varied from 0.319 to 2.96 units, with an average in sixteen experiments of 1.179.
Cannon, W. B., 1915 · Bodily Changes in Pain, Hunger, Fear and Rage · open at passage 165For animals under urethane anesthesia a higher average was obtained. In these it varied from .644 to 7.05, or an average in ten experiments of 3.081.
Cannon, W. B., 1915 · Bodily Changes in Pain, Hunger, Fear and Rage · open at passage 165After fatigue the threshold of the nerve-muscle, in sixteen decerebrate animals, increased from an average of 1.179 to 3.34
Cannon, W. B., 1915 · Bodily Changes in Pain, Hunger, Fear and Rage · open at passage 167In ten animals under urethane anesthesia the threshold after fatigue increased from a nor- mal average of 3.08 to 9.408
Cannon, W. B., 1915 · Bodily Changes in Pain, Hunger, Fear and Rage · open at passage 167In this state the vasto-crureus, for example, may be maintained at different lengths with the same load, or at the same length with different loads.
Bayliss, W. M., 1915 · Principles of General Physiology · open at passage 2348Such special sensitivity may be described as consisting in a lowering of the threshold of stimulation for a particular agent, and need not affect the general sensitivity to mechanical and electrical stimulation.
Lillie, R. S., 1923 · Protoplasmic Action and Nervous Action · open at passage 449
| 1906 | The Integrative Action of the Nervous System · Sherrington, C. S. | 9 |
| 1915 | Bodily Changes in Pain, Hunger, Fear and Rage · Cannon, W. B. | 6 |
| 1899 | General Physiology: An Outline of the Science of Life · Verworn, M. | 3 |
| 1900 | Comparative Physiology of the Brain and Comparative Psychology · Loeb, J. | 3 |
| 1912 | The Mechanistic Conception of Life · Loeb, J. | 2 |
| 1923 | Protoplasmic Action and Nervous Action · Lillie, R. S. | 1 |
| 1906 | Behavior of the Lower Organisms · Jennings, H. S. | 1 |
| 1915 | Principles of General Physiology · Bayliss, W. M. | 1 |