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Endocrine System: Feedback Loops
The human body is made up of an incredible number and variety of subsystems-each monitored and
controlled by feedback loops. The negative feedback loop tends to slow down a process, while the
positive feedback loop tends to speed it up (positive feedback loop example: contractions in
childbirth-when a contraction occurs, the hormone oxytocin is released into the body, which
stimulates further contractions).
How does a negative feedback loop work?
1. Balance a hardcover book on your head
2. Walk about 3 meters forward and backward- once with eyes
open, then with eyes closed
Analysis Questions (write the Q & A or just a complete sentence)
1. Describe the negative feedback loop that helped keep the book balanced on your head. How
did closing your eyes affect your ability to balance the book?
2. Think of another example of a negative feedback loop that you might observe in your everyday
life (you may use one of the examples below). Explain how the loop works.
Examples to choose from (or think of your own)
The respiratory system takes in the air needed to ensure that the cells of our
body receive an adequate supply of oxygen. When that supply starts to run low, a
negative feedback loop triggers faster, deeper breathing. But if we breathe too
hard or too fast for too longs, when our body doesn’t need so much oxygen, we get
light-headed…another negative feedback loop that causes our breathing to slow to
Our digestive system contains similar feedback loops. When the
concentration of sugars, proteins, and other nutrients in our blood dips
below the level our cells require, we feel hunger. This sensation
encourages us to seek food and to eat. But when we have taken in
enough food, we start to feel full; this in turn encourages us to stop
eating before we’ve consumed enough to make us sluggish.
Our circulatory system gets oxygen and vital nutrients to our cells when they
need them, in the quantities in which they need them. During periods of exertion,
these needs mount-and the circulatory system rises to the occasion! Our heart
beats faster, pumping fresh, oxygenated, nutrient-laden blood to our organs as
quickly as they can use its precious cargo-carting away carbon dioxide and other
metabolic waste products before they can build to dangerous levels.