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Homeostasis - Biology
By the end of this section, you will be able to:
- Define homeostasis
- Discuss positive and negative feedback mechanisms used in homeostasis
- Describe thermoregulation of endothermic and ectothermic animals
Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis (“steady state”). Homeostasis means to maintain dynamic equilibrium in the body. It is dynamic because it is constantly adjusting to the changes that the body’s systems encounter. It is equilibrium because body functions are kept within specific ranges. Even an animal that is apparently inactive is maintaining this homeostatic equilibrium.
The goal of homeostasis is the maintenance of equilibrium around a point or value called a set point . While there are normal fluctuations from the set point, the body’s systems will usually attempt to go back to this point. A change in the internal or external environment is called a stimulus and is detected by a receptor the response of the system is to adjust the deviation parameter toward the set point. For instance, if the body becomes too warm, adjustments are made to cool the animal. If the blood’s glucose rises after a meal, adjustments are made to lower the blood glucose level by getting the nutrient into tissues that need it or to store it for later use.
Bio-systems such as those in the body are constantly separated from their points in equilibrium. When you exercise, for example, your muscles boost your heat production and boost your body temperature.
Likewise, blood glucose increases as you drink a glass of fruit juice. The ability of the body to identify and resist these changes depends on the homeostasis.
In order to maintain homeostasis, negative feedback loops usually occur. These loops work against the signal or sign that activates it.
If the body temperature is too high, for example, a negative feedback loop would reverse it to the fixed point or target value of 98.6, ^circ ext F98.6.
F, end text/37.0.0, ^circ ext C37.0 [C37], point, 0, degrees, start text, C, end letter. C38, point, 6, degrees, start word/38.0.
How do you do that? First, sensors — mainly nerve cells with endings in your skin and brain — and relay them to a temperature control center in your brain will detect high temperatures.
Obviously, body temperature is not only higher than the intrinsic value — it can even be lower than that. Homeostatic circuits generally involve two or more negative feedback loops:
One is activated when a parameter — like the temperature of the body — is over the setpoint and is designed to lower it.
When the parameter is under the specified point and is intended to bring it back up, one is activated.
Let us look closely at the opposing feedback loops that regulate the body temperature to make this theory more concrete.
Read also: A level Biology (9700)
Homeostasis Responses in Temperature Regulation:
Blood flow to your skin increases to accelerate heat loss in your environment and you may also start to sweat to cool off your skin.
⦁ The blood vessels constrain as the body temperature drops, sweat glands do not produce sweat, and temblor generates heat to heat the body.
⦁ This brings the heat back to normal at body temperature.
⦁ If the body temperature is too high, the veins of the blood dilate and sweat glands secrete fluid and the body loses heat.
⦁ The temperature of the body returns to normal as heat is lost to the environment.