Notes – Body Systems and Cells:
Temperature Regulation
I. How do living things stay alive in extreme temperatures?
 One of the characteristics of living things is that they can maintain stable internal
conditions. This is called _____________________________.
 One type of balance that organisms must maintain is temperature balance.
Why do you think organisms would want to maintain stable temperatures? Why not just let your body be any
temperature?
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Some organisms are ectotherms – they get heat from their external environment.
ECTO = outside
THERM = heat
Some organisms are endotherms – they make their own heat through metabolism (chemical reactions) and
other ways such as shivering.
ENDO = inside
THERM = HEAT
Some ways that living things carry out thermoregulation:
Dogs – panting
Squirrels – laying on cool surfaces
Cows – finding shade
Kangaroos – licking arms
Lizards – sitting in the sun
Humans – sweating and vasodilation
II. How do humans maintain homeostasis in extreme temperatures?
 Two body systems that are involved in thermoregulation are the ________________________________ and the
_________________________________.
Heart, veins, arteries, capillaries
CIRCULATORY SYSTEM:
 The circulatory system includes the heart, veins, arteries, and capillaries. These last three
are called blood vessels. The specialized function of this body system is to pump blood to
cells in the body. Blood carries oxygen, carbon dioxide, and nutrients to and from cells.
 Red blood cells are specialized cells that have iron atoms in them. Oxygen diffuses through
lung tissues into blood vessels and binds to (sticks to) the iron in the red blood cell. Then
when the red blood cell reaches an area that has a low amount of oxygen, the oxygen
diffuses into the cells that need it.

How does the structure (shape and make-up) of a red blood cell
match its function (its job)?
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Brain, spinal cord, nerves
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NERVOUS SYSTEM:
The nervous system includes the brain, spinal cord, and nerves. The specialized function of
this body system is to send and receive messages through the body with electrical currents
and chemical signals.
Nerves are specialized cells that have many protein pumps. The pumps can pump + or - ions
into our out of the cell. When these ions flow back to equilibrium, they create an electric
current.
Nerves also have dendrites and axon terminals, extensions that let them communicate with
many other nerve cells to create complex thoughts.
How does the structure of a nerve cell match its function?
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III. So what do these systems have to do with temperature regulation?

A part of the brain called the hypothalamus is constantly monitoring body temperature. (For humans, it should
be 98.6°F) If the body is too hot or too cold, the brain sends an electrochemical signal to other parts of the body.
TOO HOT  Brain sends a signal telling veins to dilate (get larger). This allows heat to leave the blood more quickly.
TOO HOT  Brain sends a signal telling skin to start sweating. This allows hot water molecules to leave the skin, making
the skin cooler.
TOO COLD  Brain sends a signal telling veins to constrict (get smaller). This allows the body to conserve (save) heat.
TOO COLD  Brain sends a signal telling muscles to shiver (shake). This creates heat, raising the internal temperature.
Temperature Regulation Homework/Practice:
Due Date____________________________
1. Why do organisms maintain stable temperatures in their bodies?
2. Circle one for each: The structure of a cell is its: (shape or job?) The function of a cell is its: (shape or job?)
3. This cell is specialized to be able to move. How does its structure match its function? (How does its shape match its
job?)
4. Describe one way that the nervous system works with the circulatory system to regulate body temperature.