Learning Objectives By the end of this section, you will be able to: The autorhythmicity inherent in cardiac cells keeps the heart beating at a regular pace; however, the heart is regulated by and responds to outside influences as well.…
Learning Objectives By the end of this section, you will be able to: The period of time that begins with contraction of the atria and ends with ventricular relaxation is known as the cardiac cycle (Figure 19.27). The period of contraction that…
Learning Objectives By the end of this section, you will be able to: Recall that cardiac muscle shares a few characteristics with both skeletal muscle and smooth muscle, but it has some unique properties of its own. Not the least…
Learning Objectives By the end of this section, you will be able to: The vital importance of the heart is obvious. If one assumes an average rate of contraction of 75 contractions per minute, a human heart would contract approximately…
Figure 19.1 Human Heart This artist’s conception of the human heart suggests a powerful engine—not inappropriate for a muscular pump that keeps the body continually supplied with blood. (credit: Patrick J. Lynch) CHAPTER OBJECTIVES After studying this chapter, you will be able to: In…
An Overview of Blood Blood is a fluid connective tissue critical to the transportation of nutrients, gases, and wastes throughout the body; to defend the body against infection and other threats; and to the homeostatic regulation of pH, temperature, and…
Learning Objectives By the end of this section, you will be able to: Platelets are key players in hemostasis, the process by which the body seals a ruptured blood vessel and prevents further loss of blood. Although rupture of larger vessels…
Learning Objectives By the end of this section, you will be able to: The leukocyte, commonly known as a white blood cell (or WBC), is a major component of the body’s defenses against disease. Leukocytes protect the body against invading microorganisms…
Learning Objectives By the end of this section, you will be able to: The erythrocyte, commonly known as a red blood cell (or RBC), is by far the most common formed element: A single drop of blood contains millions of erythrocytes…
Learning Objectives By the end of this section, you will be able to: The lifespan of the formed elements is very brief. Although one type of leukocyte called memory cells can survive for years, most erythrocytes, leukocytes, and platelets normally…