Homeostasis is a state of balance
inside the body, where the body systems work
together to keep it functioning normally. The
endocrine system keeps this internal balancing
act going by releasing chemicals called hormones.
The release of the hormones is controlled by
negative feedback mechanisms. A negative feedback
mechanism works something like a thermostat in
your home.
A thermostat helps maintain a constant
temperature, called the normal range. When the
temperature rises beyond the normal range, the
thermostat turns on the air conditioner. Eventually
the air conditioner restores the temperature
to the normal range. This process is called negative
feedback. It starts with a normal range, goes
beyond the normal range, and then back to normal
again. An example of how negative feedback works
in the body can be demonstrated by the endocrine
system's controls over the amount of sugar
in the bloodstream.
Insulin is a hormone secreted
by the pancreas that maintains a normal amount
of sugar in the bloodstream. Shortly after
eating a candy bar, tiny sugar molecules enter
the bloodstream raising the blood sugar levels.
In response, the pancreas secretes the insulin
into the bloodstream. Now, the sugar molecules
move out of the bloodstream and into the cells
of the skeletal muscles, fat and liver. In turn,
the blood sugar levels return to normal.
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