chapter 23 respiratory

Question 1

what are the advantages of air as a respiratory medium & what is the advantage of water as a respiratory medium

Answer 1

**—amount of oxygen varies— air is a better source of oxygen than water

**—air weighs less than water— therefore, less energy is used in ventilation by air breathers

**—oxygen diffuse more rapidly in the air than in water—therefore, it is replenished more quickly in air respiratory surface must be kept moist for oxygen uptake

–»this is the only factor that favors aquatic animals better

Question 2

why do smaller homeotherms have higher metabolic rates than larger homeotherms

Answer 2

smaller homeotherms have a greater surface area to volume ratio and thus lose relatively more body heat than larger homeotherms. [they have higher metabolic rates which compensate for this problem of greater heat loss]

Question 3

trace the pathway of air into the human lungs

Answer 3

**Air inhaled into nostrils, nasal cavity where it is warmed and humidified and filtered, pharynx, larynx (upper part of trachea, contains vocal cords), trachea (walls reinforced with rings of cartilage), bronchi, bronchioles, alveoli (300 million per pair of human lungs, giving a respiratory surface of approximately 750 square feet, about 40x (times) the surface area of the skin).

Question 4

what are the air sacs in the human lungs where exchange of gases occurs

Answer 4

alveoli

Question 5

what muscles are contracting during inhalation (and relaxing during exhalation) in humans

Answer 5

rib muscles

Question 6

what is the main regulatory factor affecting the breathing rate in humans

Answer 6

the concentration carbon dioxide in blood [respiratory neurons in the brain] respond more quickly to increased carbon dioxide levels in blood than to decreased oxygen levels in blood