Topic 1.2
How does the body maintain homeostasis and stay healthy?
Homeostasis is the state in which the internal conditions of living organisms remain stable (within a normal range), regardless of the external environment. These internal conditions include body temperature, pH, and glucose level. It is the optimal internal state at which the body operates best.
Homeostasis
Suppose it’s really cold outside and you run out to your letterbox in a T-shirt. While you’re out there, a neighbour stops by to chat. Your skin senses the cold conditions outside, and nerve impulses are sent from receptors in your skin to your brain that say, “Hey! It’s cold out here!!” In an attempt to stay around 37°C, your body makes some changes
Firstly, goose pimples form. These are from your body, making your hair stand up higher to help insulate your body. Next, if that doesn’t help to maintain the normal temperature, you start to shiver. Shivering is an attempt by your body to create heat by making your muscles move.
Finally, if shivering doesn’t help keep you warm, your body’s “thermostat” will begin to drop. Your internal “furnace” will kick in to create heat internally so that homeostasis — maintaining relatively normal values — occurs.
Homeostasis and body temperature
The control of body temperature in humans is an example of homeostasis. Normal body temperature can be affected by outside temperatures, hormones, metabolic rate, and disease, which can make the body too hot or too cold.
The body’s temperature is controlled by a part of the brain called the hypothalamus. Feedback about body temperature is sent through the nervous system and the bloodstream to the brain. The brain can change things like breathing, blood sugar, and metabolic rates.
The body can eliminate heat by being less active and perspiring (sweating), allowing more blood to circulate near the skin’s surface.
The body can keep more heat by reducing blood flow to the skin. The use of clothing, shelter and external heat sources also helps. These activities help keep temperatures in the ‘normal’ range that sustains life (homeostatic plateau).
Diabetes
When the body can’t regulate blood sugar levels, it leads to diabetes. In this condition, insulin, a hormone needed to keep glucose in check, is either not produced or not used properly, disrupting homeostasis.
Dehydration
When you’re dehydrated, your body loses more fluids than it can take in. This leads to a failure in maintaining water balance, which can cause headaches, dizziness, or even kidney damage.
Heatstroke
In extreme heat, if the body can’t cool itself down through sweating, the internal temperature rises uncontrollably. This is known as heatstroke, a serious condition where homeostasis is overwhelmed.
Hypothermia
When the body gets too cold and can’t generate enough heat, hypothermia sets in. This is an example of homeostasis failure as the body struggles to maintain its normal temperature.
Discussion Prompts
- What do you think defines a ‘normal’ or ‘healthy’ body?
- How can we tell what is normal in the human body?
- What are some markers that give us hints about health?
Lab: Body temperature as a marker of health
- Everyone in class takes their temperature and plots it on a graph. (Use Excel or a website like Geogebra, https://www.geogebra.org/graphing)
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- What do you notice?
- Web search: what is the ‘normal’ body temperature?
- Did you find an absolute number or a range?
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- Predict what you would expect to happen to body temperature if you hold icepacks for 2-3 minutes.
- Try doing this and get class members to take their temperature again
- Plot the new results on a graph
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- What did you notice?
- Why do you think this is?
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Now that you’ve explored how the body maintains balance, watch the following video to see how water content, temperature, and blood glucose levels are regulated. As you watch, think about how feedback systems help your body respond to changes. This will set you up for the next page: negative feedback loops.