Your body’s reaction to heat loss is involuntary and driven by the hypothalamus, the tiny gland in the brain acting as a thermostat. The hypothalamus is very sensitive to any temperature variation in your body. Even a small drop brings the temperature regulation mechanisms into action: blood vessels in the skin constrict to prevent excessive heat loss and muscles shiver to create heat.
The hypothalamus is a cruel gland, though. Its only concern is to keep the vital organs at an acceptable temperature, and couldn’t care less if your toes or fingers became icicles. All of the thermoregulation mechanisms are designed to protect the core.
To guarantee wellbeing, the body’s core temperature needs to be maintained at around 36.9°C. What comprises the core? It includes all the vital organs such as heart, lungs, liver and kidneys central to your body. Because the brain is also important for your survival, it is part of the core despite being nowhere near the centre.
Surrounding the core is the periphery. It includes the skin, the muscles, arms and legs. Shake the hands of someone on a cold day and you’ll find out that the temperature of the periphery can be well below the core temperature icy-cold hands. However, a cold periphery is quite natural and, to a degree, an advantage. You constantly lose heat to a cooler environment until the periphery reaches the same temperature, and then the heat flow stops and you preserve heat.
This has its limits. The problems begin when the surroundings have a very low temperature. In this case, the temperature exchange between your body and the environment doesn’t stop and your core temperature starts to drop. Women have an advantage over men in that respect because their skin generally reaches a slightly lower temperature, so they have less heat to lose.
Every person reacts differently to thermal stress. Age, fitness level and underlying diseases play a major part in someones reaction. In addition, cold reactions are not Your teeth chatter, your body shivers and despite all efforts, you can’t prevent it. The tiny hairs on your body stand upright and try desperately to function as an insulating fur. Your skin looks bloodless and feels cold. All these reactions are an attempt by your body to preserve heat, although not a very successful one. Humans are well equipped to lose heat, but are less efficient in retaining it.
Necessarily associated with wintry conditions, as a sharp temperature drop in summer may have similar effects. Cold snaps bring relief from stifling heatwaves, but the cardiovascular system has not much time to adjust to the rapid temperature change and is, therefore, subjected to immense stress.
What are the effects on our cardiovascular system?
When blood vessels constrict to preserve heat, the heart has to work harder to squeeze blood through the narrow vessels. This may be too much for a sick heart. Surveys of blood donors revealed that blood pressure rose markedly after temperature drops. Published figures showed increases of between 12 and 18mmHg. While such an increase is not significant for a healthy person, it is sometimes a deciding factor for a person suffering already from high blood pressure.
Further, a heart under strain needs a high volume of oxygen-rich blood. However, narrow vessels do restrict the supply and symptoms of angina could develop. The British Heart Foundation defines angina as: