Introduction: Our bodies need to be in balance in order to function properly, and there are many ways the body maintains balance, or homeostasis. Homeostasis is the maintenance of nearly constant conditions in the internal environment. Our normal heart rate is an example of our body in homeostasis and any sort of change, or stimulus, can alter it. Exercise, adrenaline in the blood, and a low blood pH are all stimuli that increase the heart rate. Exercise, for example, stimulates stretch receptors in the muscles. These receptors then send a signal to a part of the brain called the medulla oblongata that receives the sensory input. It then in turn sends nerve impulses to the sinoatrial node in the heart. This node generates an impulse and initiates contraction of the heart at a quicker pace. Thus, the heart beats faster, which equals an increased heart rate. This is an example of a homeostasis imbalance. The heart reaches homeostasis again when exercise ceases and the heart rate drops down to its basal rate, or its rate at rest. This whole process is an example of a negative feedback cycle: a stimulus (increased heart rate) sends receptors to the control center (medulla oblongata), which then sends effectors (impulses by the vagus nerve, or the efferent pathway) to the heart to slow the heart contractions, thus reducing the heart rate and bringing it back to its basal rate. In our experiment we studied heart rate before and after a brief exercise session. Our hypothesis is exercise will increase the heart rate, and a negative feedback mechanism will occur to restore the heart rate back to its normal basal rate.
Materials: Stop watch, metronome, stairs
• Eight subjects took their own resting, or basal, heart rate for 15 seconds while standing up. Some subjects chose to take their heart rate at their carotid artery, and some took their pulse using their radial artery. This number was multiplied
Citations: Heart Rate Regulation in Humans. (2010, January 23). The Student Room. Retrieved August 24, 2013, from http://www.thestudentroom.co.uk/showthread.php%3Ft%3D1059551%26page%3D45&q=&esrc=s&ei=EEIuUtiHKMKUiQL86YDQDQ&usg=AFQjCNGj9jN4mV3pDlB7dF1yuUm0gn81gA