Question

Why do you shiver and why do your teeth chatter when it is very cold in winter?

Answer 1

Hint: Humans are warm blooded organisms which means that they can maintain a constant core temperature of the body irrespective of the temperature conditions of the surroundings.

Complete answer:
We will first learn the basics of thermoregulation.
The literal meaning of “thermoregulation” is “temperature” + “regulation”. It represents the ability of humans to maintain constant body temperature. Our body temperature is kept near the setpoint.
We can feel the deviation during a fever when the body temperature is elevated above the setpoint.
To maintain the temperature near the setpoint, our body has certain mechanisms. When the body temperature falls below the normal, as it occurs during winters, the processes that conserve the body heat are stimulated so that the body does not lose heat to the surroundings.
Additionally, the processes that produce the internal body heat are also triggered to maintain the core temperature near the setpoint. One such mechanism is the involuntary contraction of skeletal muscles.
We know that skeletal muscles are voluntary, meaning that their contraction is regulated by the person’s will. However, when we feel cold, the hypothalamus triggers the involuntary contraction of skeletal muscles. This contraction does not produce any movement and the heat generated is used to raise the body temperature to the normal range. The rapid and involuntary contraction of skeletal muscles generates shivering. Jaw muscles are also skeletal muscles. Therefore, their involuntary contraction to generate heat causes the chattering of teeth.

Note: Hypothalamus is the thermostat of the body. The sensory receptors that detect the deviation of the body temperature from the normal point send the information to the hypothalamus. Hypothalamus commands the skeletal muscles to contract involuntarily.