(8) Coryza (common cold) and Influenza (flu). Common colds are caused
by viruses and typical symptoms include sneezing, excessive nasal secretion, and
congestion. (A fever is not usually one of the symptoms.) A virus also causes influenza
(flu) with accompanying symptoms of chills, fever (usually higher than 101F),
headache, and muscular aches. As the fever subsides, cold-like symptoms appear.
1-16. RESPIRATORY CYCLE
a. A respiratory cycle (figure 1-11) consists of one inspiration, one rest period,
and one expiration--in that order.
Figure 1-11. Respiratory cycle.
b. Air is made up of several gases, the most important being oxygen. Carbon
dioxide and nitrogen are also present along with some other gases in small amounts.
The air we breathe in is not the same as the air we breathe out. Look at the gases in
the air in figure 1-12 below.
Figure 1-12. Gases in the air.
c. You can see that air breathed out has less oxygen than air breathed in. The
body has used some of the oxygen. Air breathed out has more carbon dioxide than air
breathed in. The body is expelling carbon dioxide that has been formed as body cells
work and use up oxygen.