Biology behind parachuting

Adrenaline / Epinephrine
When parachuting, the skydiver may have the feeling of being extremely alert, energetic and responsive. This happens when humans and animals are faced with stressful, life-threatening situations. The reason is the secretion of adrenaline or epinephrine by the body as a response to stress and danger. The 'flight or fight' response of the body to threatening situations is aided internally by this hormone. It activates all the basic instincts of survival in humans.

Epinephrine enhances production of energy in the body, activates all the sensory processes to full alert as a priority and shuts down less important processes in that moment, like digestion. It leads to increase in blood sugar levels, higher heart rate and increase in blood pressure. It also starts energy production driving the body to the best possible levels of energy and concentration in order to achieve survival.

Effects of Epinephrine

Epinephrine is like the key or trigger for the activation of the survival instinct in the body. Once epinephrine is secreted by the body in the endocrine glands, it flows in the blood stream reaching various organ centers. It starts by activating some strategically placed receptors in the body. One by one, it activates these receptors which trigger the initiating of many chain reaction processes.

When epinephrine reaches the liver cells, it activates a receptor there which initializes a chain reaction that culminates into breaking down of glycogen, releasing glucose, an energy source in our body, into the blood stream. Simultaneously, it also activates the other liver receptors which again accelerates glucose production.

Receptors are also present in the muscles. When they are activated by epinephrine, they cause the widening of blood vessels so that more blood can reach the muscles for efficient operation, increasing the heart pumping rate.

On the other hand, when other receptors in muscles, when switched on by epinephrine, cause the narrowing or constriction of smooth muscles, resulting in decreased blood supply in some parts and increases resistance to blood flow in the arteries. This makes the skin pale, as less and less blood reaches it. This measure achieves conservation of body warmth.