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Gas Exchange Review Unit 4.doc

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Department
Biology
Course
BLG 411
Professor
Mc Grey
Semester
Summer

Description
Gas Exchange Review Unit#4 Lesson 1 Questions 1. What purpose is served by the respiratory system? The main function of therespiratory system is gas exchange. This refers to the process of Oxygen and Carbon Dioxide moving between the lungs and blood . The respiratory system brings oxygen into the blood so the blood can distribute to all of the body’s cells. It also turns oxygen into nutrients and removes carbon dioxide from the body. The respiratory system also regulates the body’s pH balance. 2. Why is the respiratory surface for terrestrial organisms inside rather than outside the body? Amphibians, frogs, and fish all use their skin as a respiratory surface to obtain oxygen and eliminate carbon dioxide. Humans cannot diffuse oxygen through their skin. They can only exchange about 1% of their carbon dioxide through there skin. The same goes for terrestrial animals; they are only able to exchange a very small amount of gases through their skin. As a result, they must develop more efficient lungs in order for their bodies to obtain an efficient amount of oxygen for bodily functions. Thus, their respiratory systems are inside their bodies. Also, respiration must take place in a moist environment. Aquatic animals live in water, so they can exchange gas outside of their bodies seeing that a moist environment is provided to them. The same cannot be said for terrestrial animals since they live on land, and therefore since all of the fluid is inside their bodies, respiration must take place inside. 3. How does the human respiratory system achieve a large surface area? The human respiratory system achieves a large surface area through bronchioles and alveoli. Each bronchiole ends in a grape-like cluster of tiny sacs called alveoli. If all of the alveoli in an average human lung were spread out on a smooth surface, they cover bout 70 -90 meters squared. As you can see, these structures greatly increase the surface area of the lungs, which helps to maximize the volume of oxygen and carbon dioxide that diffuses to and from the lungs. 4. Explain the process of breathing. 1. Inhalation beings with the intercostal muscles contracting. The muscles associated with the ventral surface of the rib cage lift the rib cage up and out, allowing the diaphragm to contract and move downwards at the same time. 2. This increases the volume of the thoracic activity inside our chests. The increased volume creates a decrease in pressure in the lungs. Air moves from concentrations of high pressure to concentrations of low pressure. As the pressure in the lungs decreases, air flows in. 3. During exhalation the intercostal muscles relax, which returns the rib cage back down to its normal position. The diaphragm then also moves up, resuming its previous position. 4. This decreases the volume in the chest, and increases the pressure concentration inside the lungs. As result, air flows out. 5. How does the brain monitor the need for oxygen? The brain monitors the need for oxygen by special cells inside the aorta and carotid artery called chemo-receptors. When breathing stops, the carbon dioxide increases and this is detected by the cells. When the oxygen content in the blood drops below a certain level, the chemo- receptors send stimuli to the medulla oblongata (which is a part of the brain responsible for controlling some of the body's flexes), and the medulla oblongata increases the breathing rate to increase the amount of oxygen being taken in. 6. How is breathing rate set? An increase in the concentration of carbon dioxide in the body leads
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