ABSTRACT
The presence of stretch receptors in the muscles of Raja and Scylliwn has been physiologically demonstrated. Their morphology is unknown.
The behaviour of a single end-organ in the radial muscles of the pelvic fin of Raja clavata has been examined in detail.
The adaptation curve and the tension-frequency relationship have been determined.
Under constant tension a single end-organ has continued to function rhythmically for over 1 hour.
When tension is suddenly reduced, there follows a silent period before the frequency of discharge corresponding to the reduced tension appears.
The quantitative aspects of the behaviour of the stretch receptor of Raja bear a closer resemblance to those of the receptors of the carotid sinus than to those of mammalian and amphibian limb muscles.
The response of muscle receptors during a passive undulatory movement of the pectoral fin has been recorded, and their role in the swimming rhythm is discussed.
This statement is quoted from Kappers, Huber & Crosby’s The Comparative Anatomy of the Nervous System in Vertebrates, including Man, p. 35. We have been unable to obtain the original paper.
The terni “silent period” was applied originally to the interval during which action currents cease in a muscle that is executing a myotatic reflex. Denny-Brown (1928) advanced the explanation that this was due to inhibitory impulses set up in muscle spindles. Matthews (1931 b), however, suggested that the pause in the discharge from stretch receptors during contraction could account for a reflex pause in the motor discharge to the muscle, but his later work on mammals (1933) led him to modify this conception, and to advance the view that “the silent period appears to be due both to the absence of excitatory impulses from A1 endings, and to the inhibitory impulses set up by B endings”. Lindsley’s (1934) reflex studies confirm the intervention of inhibition in the causation of the silent period in muscle. Nevertheless, there appears to us to be no danger of confusion if the same term is applied to the pause in activity of muscle fibres during a tendon-jerk, and of stretch receptors after a reduction in tension. Phenomenally, the two events are identical. Bronk & Stella (1935) have already employed the term “silent period” with reference to the receptors of the carotid sinus, and we see no objection to following their example.
