Cardiac Glycoside or Digitalis Glycoside Digoxin (Lanoxin)
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RESPIRATIONS Respiration is the act of breathing. Inhalation or inspiration refers to the intake of air into the lungs. Exhalation or expiration refers to breathing out or the movement of gases from the lungs to the atmosphere. Ventilation is also used to refer to the movement of air in and out of the lungs.
There are basically two types of breathing: costal (thoracic) breathing and diaphragmatic (abdominal) breathing . Costal breathing involves the external intercostal muscles and other ac- cessory muscles, such as the sternocleidomastoid muscles. It can be observed by the movement of the chest upward and outward. By contrast, diaphragmatic breathing involves the contraction and re- laxation of the diaphragm, and it is observed by the movement of the abdomen, which occurs as a result of the diaphragm’s contraction and downward movement.
Mechanics and Regulation of Breathing During inhalation, the following processes normally occur ( Figure 29–16 ■ ): The diaphragm contracts (flattens), the ribs move upward and outward, and the sternum moves outward, thus enlarg- ing the thorax and permitting the lungs to expand. During exhalation ( Figure 29–17 ■ ), the diaphragm relaxes, the ribs move downward and inward, and the sternum moves inward, thus decreasing the size of the thorax as the lungs are compressed. Normal breathing is auto- matic and effortless. A normal adult inspiration lasts 1 to 1.5 seconds, and an expiration lasts 2 to 3 seconds.
Respiration is controlled by (a) respiratory centers in the me- dulla oblongata and the pons of the brain and (b) chemoreceptors located centrally in the medulla and peripherally in the carotid and aortic bodies. These centers and receptors respond to changes in the concentrations of oxygen (O 2 ), carbon dioxide (CO 2 ), and hydrogen (H + ) in the arterial blood. See Chapter 50 for details.
Sternum moves outward