How Do We Shiver?

No, you are not afraid of cold. Like any mammal, you are programmed to shiver when body temperature drops below a threshold, an automatic and subconscious function. The involuntary contractions of the muscles produce warmth, rising the body temperature. A new research, published in the journal Nature Neuroscience, has assessed how we do it: the brain's wiring system constantly supervises the temperature of the skin and establishes when the shivering should start.

Shivering is a homeostatic function (that keeps balance in the body), just like the adjustment of breathing rates, blood pressure, heart rate and weight control, being the body's last resort to maintain a constant temperature.

"Shivering, which is actually heat production in skeletal muscles, requires quite a bit of energy and is usually the last strategy the body uses to maintain its internal temperature to survive in a severe cold environment", said co-author Kazuhiro Nakamura, of Oregon Health & Science University.

The research team made the study on rats, figuring out the shivering sensory pathway from their skin to specialized neurons, in a brain area named the lateral parabrachial nucleus. The neurons of the lateral parabrachial nucleus can send data to another brain part, the preoptic area, which controls the moment when the body must begin shivering.

This pathway must be the same in humans, as there are many similarities in how the two species detect environmental temperature and control body temperature. In fact, this research links conscious and subconscious cold-sensing pathways.

"One fascinating aspect of this study is that it shows the sensory pathway for shivering, which can be thought of as brain wiring, is parallel but not the same as the sensory pathway for conscious cold detection. In other words, your body is both consciously and subconsciously detecting the cold at the same time using two different but related sensory systems. The sensory system the researchers found in the brain also seems to operate other cold-control mechanisms, such as the restriction of blood flow to the skin", said Nakamura.