Patho: Socrative Chapter 17

4. Preload represents the volume work of the heart and is largely determined by: a. Venous blood return b. Vascular resistance c. Force of contraction d. Ventricular emptying

a. Venous blood return Rationale: Preload represents the amount of blood the heart must pump with each beat and represents the volume of blood stretching the ventricular muscle fibers at the end of diastole. Pressure (resistance), contraction, and ventricular emptying relate to afterload.

3. A client with a history of heart failure has been referred for an echocardiogram. Results of this diagnostic test reveal the following findings: heart rate 80 beats/minute; end-diastolic volume 120 mL; and end-systolic volume 60 mL. What is this client's ejection fraction? a. 200 mL b. 50% c. 0.80 d. 66%

b. 50% Rationale: Ejection fraction = stroke volume ÷ end-diastolic volume, whereas stroke volume equals the difference between end-diastolic and end-systolic volume. Therefore, EF = 60 ÷ 120, or 50%.

2. Heart muscle differs from skeletal muscle tissue by being able to generate: a. Contractions b. Calcium influx c. Action potentials d. Sacromere binding

c. Action potentials Rationale: Heart muscle, or the myocardium, is unique among other muscles in that it is capable of generating and rapidly conducting its own electrical impulses or action potentials. These action potentials result in excitation of muscle fibers throughout the myocardium. Similarities to skeletal muscle include contractility, calcium influx, and actin-myosin (sarcomeres) binding.

1. A patient diagnosed with left sided heart failure is confused as to why his heart is causing him to be short of breath. How would the nurse best explain the pumping of blood through the left side of the heart? a. Blood is pumped from the lungs through the right side of the heart and directly into the left atrium b. Blood is pumped from the left side of the heart into the lungs via the pulmonary artery c. Blood is pumped from the lungs through the pulmonary vein into the left atrium d. Blood is pumped from the lungs through the pulmonary artery into the left ventricle

c. Blood is pumped from the lungs through the pulmonary vein into the left atrium Rationale: blood flows through the right side of the heart, into the lungs via pulmonary artery, out of the lungs through the pulmonary vein and into the left atrium through mitral valve into the left ventricle and out to the body through the aorta

5. A large increase in heart rate can cause: a. Increased blood viscosity b. Loss of action potential c. Decreased stroke volume d. Reduced cardiac contractility

c. Decreased stroke volume Rationale: The time spent in diastole and filling of the ventricles becomes shorter as the heart rate increases. This leads to a decrease in stroke volume and, at high heart rates, may produce a decrease in cardiac output. Increased heart rate does not typically cause increased blood viscosity, a loss of action potential, or reduced cardiac contractility.