Do Now:

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Do Now
Using the clock on the wall, time how long you
can hold your breath.
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Breathing
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Aim How does air enter and leave the human body?
I. Breathing to inhale and exhale air.
Fran, did you remember to breathe before you went
to sleep last night?
NO? Its a miracle that you are alive today!!!
A. Breathing is an involuntary (automatic)
activity that is controlled by your brain.
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B. It is the contracting and relaxing of the
diaphragm (muscle) that forces air in and out of
the lungs.
C. Breathing is broken into two parts, inhaling
and exhaling.
Bell Jar Model
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1. Inhaling
a. Diaphragm contracts (pulls down).
b. Volume inside the chest cavity increases.
c. Pressure inside chest cavity decreases.
d. Air rushes into the lungs.
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2. Exhaling
a. Diaphragm relaxes (goes up).
b. Volume inside the chest cavity decreases.
c. Pressure inside chest cavity increases.
d. Air rushes out of the lungs.