The body shivers are a way for the body to regulate its temperature. They may also occur when the person experiences an intense emotion such as fear, happiness, excitement, etc.
The most common response to when you ask someone about body shivers or the reason for the body shivers is that someone walked over your grave. Well that is a superstition, a reason that the ancients came up with to explain this bodily phenomenon.
The real reason that the body shivers is that it is cold. Shivering is an evolutionary response that the body has developed to allow it to survive. The body maintains an internal body temperature of 98.6 deg Fahrenheit. If and when that temperature falls, the body must regulate the temperature in order to maintain homeostasis. In order to do this, the brain must tell the body to warm itself back up.
The body’s temperature usually falls either due to a lower external temperature, such as a cold day or after taking a swim, or due to internal changes that may be caused by an infection or fever. However, either way the body has the task of raising the temperature back to the normal of 98.6 deg Fahrenheit.
In order to do this, the brain sends a signal throughout the nervous system warning it that the body temperature is falling. The nervous system in turn sends a signal to all the muscles to start tightening and loosening very fast, i.e. what we know as shivering. This fast tightening and loosening of muscles serves a special purpose; it actually burns up energy and creates heat. This heat basically raises the temperature of the body back to normal, and when the body temperature becomes normal, we stop shivering.
However, our body does suffer from involuntary shivers that run up and down our spice even when we are not really cold. These occur for a completely different reason. They also may or may not be accompanied by goosebumps. When we are feeling an intense emotion or stressed out, it is our bodies’ reflex to send a shudder down the spine. This reflex could be brought on by a sudden change in weather, listening to a favorite song, being startled by someone or something, or watching a scary movie.
This reflex is actually an evolutionary response that we continue to have from our ancestors. When we are feeling cold or threatened or extremely intense, the hairs on our bodies stand up in order to provide us with another layer of insulation. This also makes us appear to be bigger hence scaring off any possible predators. This response is controlled by the hypothalamus and is often combined with a shuddering. The hypothalamus is also linked with our emotions, hence when we are feeling a strong emotion, such as particularly happy, sad, exited, or experiencing love or fear, it triggers our hypothalamus which sends a signal to our body to produce adrenaline and trigger this response. The sudden adrenaline rush causes shivers and goosebumps, as well as sweaty palms, tears, or increased blood pressure.