18. The Heart

A birth defect called transposition of great vessels results in the pulmonary trunk emanating from the left ventricle and the aorta stemming from the right ventricle.

Which ventricle is thicker-walled, and why?

As Cara worked at her dissection, she became frustrated that several of the structures she had to learn about had more than one common name. Provide another name for each of these structures:

a. Atrioventricular groove

b. Tricuspid valve

c. Bicuspid valve (give two synonyms)

d. Atrioventricular bundle

The chordae tendineae:

a. The atrioventricular valves

b. Prevent the AV valve flaps from everting

c. Contract the papillary muscles

d. Open the semilunar valves

The fact that the left ventricular wall is thicker than the right reveals that it:

a. Pumps a greater volume of blood

b. Pumps blood against greater resistance

c. Expands the thoracic cage

d. Pumps blood through a smaller valve

More than one choice may apply.

Which heart chamber pumps blood with the greatest amount of force?

a. Right atrium

b. Right ventricle

c. Left atrium

d. Left ventricle

More than one choice may apply.

How many cusps does the right atrioventricular valve have?

a. Two

b. Three

c. Four

d. Six

More than one choice may apply.

During atrial systole,

a. The atrial pressure exceeds ventricular pressure.

b. 70 percent of ventricular filling occurs.

c. The AV valves are open.

d. Valves prevent backflow into the great veins.

Discuss how the Frank-Starling law of the heart helps to explain the influence of venous return on stroke volume.

Cardiac output is equal to the:

(a) Difference between the end-diastolic volume and the end-systolic volume

(b) Product of heart rate and stroke volume

(c) Difference between the stroke volume at rest and the stroke volume during exercise

(d) Stroke volume less the end-systolic volume

(e) Product of heart rate and blood pressure

What three factors regulate stroke volume to ensure that the left and right ventricles pump equal volumes of blood?

Cardiac output cannot increase indefinitely because:

(a) The available filling time decreases as heart rate increases

(b) The heart becomes unable to contract at faster rates

(c) Stroke volume increases too much, leading to overfilling

(d) The heart’s muscle fibers lose their ability to stretch

(e) None of these reasons

Differentiate between stroke volume and cardiac output. How is cardiac output calculated?

What factors influence cardiac output?

The following measurements were made on two individuals (the values recorded remained stable for 1 hour):

Person 1: heart rate, 75 bpm; stroke volume, 60 mL

Person 2: heart rate, 90 bpm; stroke volume, 95 mL

Which person has the greater venous return?

Which person has the longer ventricular filling time?

Karen is taking the medication verapamil, a drug that blocks the calcium channels in cardiac muscle cells. What effect should this medication have on Karen's stroke volume?