Retrieved March 18, 2012, from biology-online.org website: http://www.biology-online.org/dictionary/Negative_feedback
Homeostasis is the concept that a system has the ability to maintain its internal structure and environmental including factors such as temperature and hormone levels. This is achieved by external stimulus acting upon a receptor which then sends a signal to the control center usually the brain. The control center then sends a signal to effectors, which would be a muscle, organ or structure. The effectors then correct the difference, as defined by the control center, by the use of positive feedback that boosts or enhances the output or negative feedback that depresses it.
Heart rate, as controlled by the autonomic nervous system and endocrine system, is affected by both positive and negative feedback through the sympathetic and parasympathetic envious system respectively. The sympathetic system is active during exercise, times of stress and fear. This system causes an increase in heart beat strength and frequency. This system is also affected by the hormone adrenaline which the body uses in times of “Fight, Flight and Fright.” The parasympathetic system on the other hand is active during resting periods and times of peace. The Sino-Atrial node, a small cluster of excitable cells located in the top part of the right atrium, generally referred to as the “pacemaker” sends impulses to the muscles fibers to cause a contraction. The control center for the cardio-vascular system is the medulla which is the lowest part of the brain which regulates the heart rate and modifies it as to reflect responses to the sympathetic and parasympathetic nervous systems.
Respiration, also known as the breathing rate, is controlled by the respiratory center in the medulla and is responsible for the rate, depth and rhythm of each breath. This system can be voluntary overridden by cerebral cortex. This happens when a person holds their breath, speaks or takes a deep breath. This system reacts when chemo-receptors, that measure the H+ ion levels and send this information to the medulla, detects a change to the level of carbon dioxide circulating in the blood. When these levels are elevated such as during exercise messages are sent to the brain to increase the breathing rate in order to expel the carbon dioxide and increase the intake of oxygen. This is controlled by nerve impulses which are sent to the intercostals muscles that then contract to form inspiration this stops when the stretch receptors send signals to the respiration center to confirm the lungs are full. The muscles then contract so expiration can occur.
Thermoregulation, also known as body temperature, is controlled by the hypothalamus which uses temperature detectors in the skin and other internal components such as organs to monitor the temperature levels. Heat is either generated by the body as part of a metabolic process or gained from external mediums such as radiation conduction and convection. Heat is also lost via conduction and convection.
Blood sugar, which is under the control of the pancreas, is the concentration of glucose in the bloodstream. The pancreas also produces hormones which are responsible for the control of insulin which lowers the blood sugar and glucagon which raises the blood sugar. Because of shortly following meals it is possible to have an inaccurate reading.
Homeostasis is important in maintaining the healthy functioning of the body as without these systems the body would be unable to support a constant stable environment. Without the cardio-vascular system the body would not be able to transmit nutrients, hormones and gasses necessary to sustain life also the body would be unable to dispose of waste materials. Without Respiration the body would be unable to perform gaseous exchanges in the blood so the body would be unable to dump carbon dioxide and other waste gasses and be unable to obtain oxygen. Without Thermoregulation the body would be unable to maintain a constant internal temperature which could lead elements such as water to freeze or enzymes to die or become denatured. Without Blood sugar controls the body would be unable to host a continuous and stable level of energy for metabolic reactions and thus cause biochemical disturbances.
The exercise session I participated was unplanned and could have been improved and made more reliable if I had a verifier to check my breathing rate. I am unable to provide a blood sugar level reading as I did not have the required equipment. The normal resting breathing rate is 16-20 times a minute. The normal resting core temperature is 36-37 degrees centigrade. The normal resting heart rate is 60-80 bpm. To ensure the validity of this test I should have repeated the exercise a few hours or days later to identify abnormalities.
