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NAUI Master Scuba Diver 106 Diving Physiology LEARNING GOALS In this chapter, you will: 1. Be introduced to terms presented in bold letters. 2. Explore the processes of human respiration and circulation. 3. See ways diving can affect respiration and circulation. 4. Learn the causes, effects, general first aid, and prevention for: - Excess breathing resistance - Carbon dioxide toxicity - Carbon monoxide toxicity - Oxygen toxicity - Drowning and near drowning - Nitrogen narcosis - Decompression sickness - Cramps - Carotid sinus reflex - Hypothermia - Hyperthermia - Seasickness - Disorientation - Vertigo - Dehydration - Things that go bump - Barotrauma of the lung, ear, sinuses, teeth, and gastrointestinal tract 5. Read about medical problems believed to increase health risk while diving. 6. Learn the rationale for fitness requirements for diving, and list at least five ways to achieve and maintain physical fitness for diving. You have many body processes. Two most noticeably affected during diving are respiration and circulation. RESPIRATION Respiration is the process of getting oxygen (O2) and carbon dioxide (CO2) into and out of you (figure 4-1). You breathe voluntarily and automatically. Your brain’s automatic center breathes for you all the time when you are not thinking about it. If you had to think about it, you would never have time to do other things like scuba dive or read this chapter, and you could never sleep or you would suffocate. You can voluntarily increase and decrease your inhaled and exhaled volumes, change your breathing rate, even stop breathing entirely for short periods, for example, to go breath-hold diving. Voluntarily changing your breathing can have several effects in diving, as you will see. Air that you breathe in passes through your nose and mouth down to a junction of two tubes - your stiff trachea, where air continues down to your lungs, and right behind it, your muscular esophagus, which pushes and squeezes food down to your stomach. Your trachea has strong cartilage rings to hold it open, almost like the hose of an old double-hose scuba regulator, except that most of the rings of the trachea are “C” shaped and don’t continue all the way to the back of your trachea. The “C” shape gives your trachea sturdiness to remain open and a bit of flexibility to expand and compress as needed. You can feel the front of the rings in front of your throat. Your trachea continues through your cartilaginous voice box or larynx (pronounced LAR’ inks). Inside your larynx are your vocal folds (or vocal cords). When you pull your vocal cords together and vibrate them, you make noise like a reed instrument. The rest of the time you keep your vocal cords apart so you can breathe. Your vocal cords, their associated muscles and other structures, and the space between them is called your glottis. A flappy cartilage sits over your glottis, so is called the epiglottis (the prefix epi- means “over”). Your epiglottis opens when you breathe to allow air to pass and closes when you swallow to keep food and liquid out. That’s why you can’t breathe when you swallow. When things manage to get past your epiglottis into your trachea (down the wrong tube), your larynx and vocal cords are your next defense to catch them, because your body does not like foreign things such as food, water, or marbles in your lungs. The problem with foreign matter in your larynx is that your larynx hates that, and will put you into spasms of coughing to get those things back out. In severe cases, your glottis closes off entirely, choking


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