Detailed Notes on Biology

Detailed Notes on Biology

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The term homeostasis appears early on in biology texts and seems to be something important to know. What is it?

Homeostasis is a balancing act. It's the process and ability of an organism to maintain equilibrium or balance within itself. You experience homeostasis in your daily activities such as drinking, eating, and dressing.

Now, there are two different ways homeostasis is maintained. One is called a negative feedback loop and the other is called a positive feedback loop.

Negative feedback loop

Your body most frequently uses a negative feedback loop. Your body experiences a change and it does something to neutralize that change. Basically, something is broken and your body tries to fix it. Please note that the examples below are simplified, as they talk about systems independently of each other, but biological systems work together.

Body temperature

Your body wants to stay in its optimal temperature range. If you're too hot, your body sweats. You seek shade. If you're too cold, you shiver to burn more energy to heat yourself up, put on warmer clothes, as seek out a warm space. Once you do whatever it is you need to, you end up back at a good temperature, and you don't feel too cold or warm. You achieved your temperature homeostasis.


Your body needs a lot of water to carry on its processes. If your body is low on water, it signals you to drink by giving you a thirst sensation and making your lips dry and chapped. When you've had enough water and your water is in balance, your thirst dissipates. Proper hydration requires enough water, and not too much water.


Your body needs food to burn to maintain processes such as body temperature. When low on food, your body gives a hunger signal. Sometimes your body needs something specific, like salt, so your body creates a craving. Homeostasis returns after you eat.

Sugar Levels

As you eat, the levels of glucose in your blood increase. Your pancreas secretes more insulin to get your body to absorb the glucose.

Positive feedback loop

The positive feedback loop isn't as common., and it might be a bit more difficult to understand. The body detects a change, and instead of neutralizing the change, the body works to increase the change. Sometimes a positive feedback loop helps maintain homeostasis.

Blood clotting

If you have an injury and start to bleed, your body starts to build a clot. Once your body notices it's building a clot, it works faster and faster until the bleeding stops. The clotting process, which is the reaction to the change in the body, accelerates.


Another popular example for a positive feedback loop is childbirth. Once labor starts, your body accelerates the labor. Contractions come closer together in the goal of pushing the child out.


Once you start to eat, if your food contains any protein, the body will detect that partially digested food. You stomach produces more acid. It also produces more of the enzyme that this site digests the protein.

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