A natural body defense that plays an active role in preventing infection is:
A. Yawning
B. Body hair
C. Hiccupping
D. Rapid eye movements
Correct Answer: B. Body hair
Hair on or within body areas, such as the nose, traps and holds particles that contain microorganisms. One of the body’s most important physical barriers is the skin barrier, which is composed of three layers of closely packed cells. The thin upper layer is called the epidermis. A second, thicker layer, called the dermis, contains hair follicles, sweat glands, nerves, and blood vessels. A layer of fatty tissue called the hypodermis lies beneath the dermis and contains blood and lymph vessels
Option A: Evidence suggests that drowsiness is the most common stimulus of yawn. Boredom occurs when the main source of stimulation in a person’s environment is no longer able to sustain their attention. This induces drowsiness by stimulating the sleep generating system. At this moment, the mind has to make an effort to maintain contact with the external environment.
Option C: Hiccupping does not prevent microorganisms from entering or leaving the body. As they breathe out, the diaphragm pushes up to expel the air. When a person has hiccups, the diaphragm contracts and pulls down, drawing in air between breaths. Immediately after this, the windpipe closes for a moment to prevent more air from entering the lungs. Hiccups often come after eating or drinking too much or too quickly.
Option D: Rapid eye movement marks the stage of sleep during which dreaming occurs. Rapid eye movement (REM) is the stage of sleep characterized by rapid saccadic movements of the eyes. During this stage, the activity of the brain’s neurons is quite similar to that during waking hours. Most of the vividly recalled dreams occur during REM sleep.