When we exercise, our muscle cells are more active and require more energy and oxygen to move and so we need to breathe more air. In order for this to happen, the air travels down the trachea, through the bronchi and bronchioles and finally into air sacs called alveoli where the oxygen is diffused through the thin walls into the blood vessels called capillaries. At the same time, carbon dioxide is diffused through the wall from the blood vessel to the air sac and back out the same way the oxygen came in. The oxygen is then transported around the body through the blood vessels and into the muscles. At this stage, the deoxygenated blood goes to the heart and lungs to become oxygenated. This supplies oxygen to all the body tissues. As more energy is needed in the muscles more oxygen is needed in the blood and as a result, respiration increases. Basically when we exercise, our muscles need more oxygen and fuel to continue working. To allow continuation, our heart rate increases to get more fuel and oxygen to the muscles more quickly. Our breathing rate increases to increase the supply of air to the lungs, so that more oxygen can be absorbed and supplied to the muscles. Depending on how hard we exercise, our heart will speed up accordingly to give the muscles the power it needs to keep going. Changes in heartbeat occur mainly because of the adrenaline we get from exercising. Adrenaline is a hormone which causes the heart rate to quicken. The Autonomic Nervous System (ANS) plays a major role in regulating the rate of heart contraction as well as the force of these contractions. The ANS is composed of the sympathetic and parasympathetic systems. The sympathetic nervous system acts by increasing heart rate and contraction force through the release of norepinephrine (neurotransmitter). In contrast, the parasympathetic nervous system acts to decrease heart rate and the force of contraction force through the release of acetylcholine (neurotransmitter).
So when we exercise, due to the adrenaline we get, our body is called into action, using energy it requires. This is what is referred to as the ‘fight or flight’ response, in the division of the sympathetic nervous system. In such circumstances, the body experiences changes with increasing temperature, pulse and respirations. Whilst this is happening, in an attempt to maintain homeostasis, the parasympathetic nervous system kicks in, otherwise called the ‘rest and digest’ response. This system works to save energy and to get temperature, pulse and respirations back within a normal range. “When you’re exercising, your sympathetic nervous system will be on, increasing your heart rate, respiration and temperature. Once you stop, your body always tries to get back to homeostasis, so the parasympathetic nervous system kicks in to get everything back down to baseline levels.” (Victoria J. Vieira, a predoctoral fellow in kinesiology, Journal of the American Geriatrics Society, 2007)
The autonomic nervous system therefore plays a vital role in the maintenance of normal internal functions.
Following exercise, temperature also rises considerably. “More than 70 percent of the energy that powers the muscles is lost as heat, causing body temperature to rise during exercise.” (Hay, G.J et al...