Muscles in the body produce body heat through a mechanism Australian researchers have uncovered in a study.
Muscles in the body produce body heat through a mechanism that Australian researchers have uncovered in the Proceedings of the American Academy of Sciences (Pnas).
A specific channel that does not exist in amphibians and reptiles
To contract, muscle cells pump all the calcium from their inner environment into a specific membrane compartment, the sarcoplasmic reticulum. The nerve signal causes all that calcium to be released into the cell, which sets in motion the contractile proteins in the muscle fibers. But the sarcoplasmic reticulum leaks slightly, shows the team of Bradley S. Launikonis. This leak requires its calcium pump to always remain active, at the cost of a permanent energy expenditure which is met by the cell’s power stations, the mitochondria. It is the activity of the latter which provides at the same time a source of heat to the organism.
In amphibians and reptiles, this permanent loss of calcium does not exist and therefore their body temperature cannot remain constant. The researchers identified the specific mammalian calcium channel causing the leak, called the ryanodine receptor. He was already suspected for this role, a mutation in his gene having been implicated in cases of malignant hyperthermia, a disease which is revealed under the effect of halogenated anesthetics and characterized by generalized muscle contraction but also a strong elevation of body temperature.
A muscular mechanism linked to maintaining our temperature at 37°C
In addition, our nervous system can accentuate the leakage of this calcium channel into muscle cells when we feel cold, which increases the intensity of warming before the more drastic stage of shivering. This mechanism allows the body temperature of mammals to be maintained at 37°C regardless of the external temperature, and probably that at 40[…]
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