Unit 4 : Homeostasis
Is the tendency of a system, especially the physiological system of higher animals, to maintain internal stability, owing to the coordinated response of its parts to any situation or stimulus that would tend to disturb its normal condition or function.
Here are some homeostasis examples that occur in the human body:
- Humans’ internal body temperature is a great example of homeostasis. When an individual is healthy, his or her body temperature retains a temperature 98.6 degrees Fahrenheit. The body can control temperature by making or releasing heat.
- Glucose is a type of sugar that is found in the bloodstream, but the body must maintain proper glucose levels to ensure that a person remains healthy. When glucose levels get too high, the pancreas releases a hormone known as insulin. If blood glucose levels happen to drop too low, the liver converts glycogen in the blood to glucose again, raising the levels.
- When bacteria or viruses that can make you ill get into your body, your lymphatic system kicks in to help maintain homeostasis. It works to fight the infection before it has the opportunity to make you sick, ensuring that you remain healthy.
- The maintenance of healthy blood pressure is an example of homeostasis. The heart can sense changes in the blood pressure, causing it to send signals to the brain, which then sends back signals telling the heart how to respond. If blood pressure is too high, naturally the heart should slow down; while if it is too low, the heart wants to speed up.
- A human’s body contains chemicals known as acids and bases, and a proper balance of these is required for the body to function optimally. Lungs and kidneys are two of the organ systems that regulate acids and bases within the body.
- More than half of a human’s body weight percentage is water, and maintaining the correct balance of water is an example of homeostasis. Cells that have too much water in them bloat and can even blow up. Cells with too little water can end up shrinking. Your body maintains a proper water balance so that neither of these situations occurs.
- Calcium levels in the blood must be maintained at proper levels. The body regulates those levels in an example of homeostasis. When levels decrease, the parathyroid releases hormones. If calcium levels become too high, the thyroid helps out by fixing calcium in the bones and lowering blood calcium levels.
- Exercising causes the body to maintain homeostasis by sending lactate to the muscles to give them energy. Over time, this also signals to the brain that it is time to stop exercising, so that the muscles can get the oxygen they need.
- The nervous system helps keep homeostasis in breathing patterns. Because breathing is involuntary, the nervous system ensures that the body is getting much needed oxygen through breathing the appropriate amount of oxygen.
- When toxins get into your blood, they disrupt your body’s homeostasis. The human body, however, responds by getting rid of these toxins by use of the urinary system. An individual simply urinates the toxins and other nasty things from the blood, restoring homeostasis to the human body.
Negative feedback mechanisms - Almost all homeostatic control mechanisms are negative feedback mechanisms. These mechanisms change the variable back to its original state or “ideal value”.
A good example of a negative feedback mechanism is a home thermostat (heating system). The thermostat contains the receptor (thermometer) and control center. If the heating system is set at 70 degrees Fahrenheit, the heat (effector) is turned on if the temperature drops below 70 degrees Fahrenheit. After the heater heats the house to 70 degrees Fahrenheit, it shuts off effectively maintaining the ideal temperature.
The control of blood sugar (glucose) by insulin is another good example of a negative feedback mechanism. When blood sugar rises, receptors in the body sense a change . In turn, the control center (pancreas) secretes insulin into the blood effectively lowering blood sugar levels. Once blood sugar levels reach homeostasis, the pancreas stops releasing insulin.
A good example of a negative feedback mechanism is a home thermostat (heating system). The thermostat contains the receptor (thermometer) and control center. If the heating system is set at 70 degrees Fahrenheit, the heat (effector) is turned on if the temperature drops below 70 degrees Fahrenheit. After the heater heats the house to 70 degrees Fahrenheit, it shuts off effectively maintaining the ideal temperature.
The control of blood sugar (glucose) by insulin is another good example of a negative feedback mechanism. When blood sugar rises, receptors in the body sense a change . In turn, the control center (pancreas) secretes insulin into the blood effectively lowering blood sugar levels. Once blood sugar levels reach homeostasis, the pancreas stops releasing insulin.
Positive feedback mechanisms
A positive feedback mechanism is the exact opposite of a negative feedback mechanism. With negative feedback, the output reduces the original effect of the stimulus. In a positive feedback system, the output enhances the original stimulus. A good example of a positive feedback system is child birth. During labor, a hormone called Oxycontin is released that intensifies and speeds up contractions. The increase in contractions causes more Oxycontin to be released and the cycle goes on until the baby is born. The birth ends the release of Oxycontin and ends the positive feedback mechanism.
Another good example of a positive feedback mechanism is blood clotting. Once a vessel is damaged, platelets start to cling to the injured site and release chemicals that attract more platelets. The platelets continue to pile up and release chemicals until a clot is formed.
Just remember that positive feedback mechanisms enhance the original stimulus and negative feedback mechanisms inhibit it.
A positive feedback mechanism is the exact opposite of a negative feedback mechanism. With negative feedback, the output reduces the original effect of the stimulus. In a positive feedback system, the output enhances the original stimulus. A good example of a positive feedback system is child birth. During labor, a hormone called Oxycontin is released that intensifies and speeds up contractions. The increase in contractions causes more Oxycontin to be released and the cycle goes on until the baby is born. The birth ends the release of Oxycontin and ends the positive feedback mechanism.
Another good example of a positive feedback mechanism is blood clotting. Once a vessel is damaged, platelets start to cling to the injured site and release chemicals that attract more platelets. The platelets continue to pile up and release chemicals until a clot is formed.
Just remember that positive feedback mechanisms enhance the original stimulus and negative feedback mechanisms inhibit it.
Homeostasis is regulated by two hormones, insulin and glucagon which are both secreted by the endocrine pancreas. The production of insulin and glucagon by these pancreatic cells ultimately determines if a patient has diabetes or another related problem.
Thermoregulation is an important aspect of human homeostasis. Heat is mainly produced by the liver and muscle contractions. Humans have been able to adapt to a great diversity of climates, including hot humid and hot arid. High temperatures pose serious stresses for the human body, placing it in great danger of injury or even death. In order to deal with these climatic conditions, humans have developed physiologic and cultural modes of adaptation. Temperature may enter a circle of positive feedback, when temperature reaches extremes of 45°C (113°F), at which cellular proteins denature, causing the active site in proteins to change, therefore causing metabolism stop and ultimately death.