Select the correct statement about cardiac output.

• Decreased venous return will result in increased end diastolic volume.
• If a semilunar valve were partially obstructed, the end systolic volume in the affected ventricle would be decreased.
• Stroke volume increases if end diastolic volume decreases.
• A slow heart rate increases end diastolic volume, stroke volume, and force of contraction.

A slow heart rate increases end diastolic volume, stroke volume, and force of contraction.

Which of the following terms is correctly matched to its description?

• atrial systole: period of atrial relaxation
• stroke volume: amount of blood pumped out by each ventricle in one minute
• quiescent period: period of total heart relaxation
• ventricular diastole: period of ventricular contraction

quiescent period: period of total heart relaxation

Ex.

During each cardiac cycle there is a period of time in which both the atria and ventricles are relaxed (in diastole) at the same time; this is called the quiescent period.

The atrioventricular (AV) valves are closed ________.

• while the atria are contracting
• when the ventricles are in diastole
• by the movement of blood from atria to ventricles
• when the ventricles are in systole

when the ventricles are in systole

Total peripheral resistance ________.

• increases as blood vessel diameter increases
• is not a major factor in blood pressure in healthy individuals
• increases as blood viscosity increases
• decreases with increasing length of the blood vessel

increases as blood viscosity increases

Which of the following hormones will lower blood pressure?

• antidiuretic hormone (ADH)
• angiotensin II (Ang II)
• aldosterone
• atrial natriuretic peptide (ANP)

atrial natriuretic peptide (ANP)

Ex.

Atrial natriuretic peptide (ANP) is a hormone released by the atria of the heart. It stimulates the kidney to excrete more sodium and water in the urine, which decreases blood volume, leading to a reduction in blood pressure. It also causes generalized vasodilation.

Which of the following is involved in long-term regulation of blood pressure?

• chemoreceptor reflexes
• renin-angiotensin-aldosterone mechanism
• adrenal medulla hormones
• baroreceptor reflexes

renin-angiotensin-aldosterone mechanism

Ex.

Long-term control of blood pressure is achieved through direct and indirect renal mechanisms. The kidneys regulate blood pressure indirectly via the renin-angiotensin-aldosterone mechanism, which also involves ADH. In response to low blood pressure, increased release of renin results in increased synthesis of angiotensin II (Ang II). Ang II stimulates secretion of ADH and aldosterone, which work together to promote increased salt and water reabsorption by the kidneys. This in turn decreases urine output and gradually increases blood volume and pressure (assuming the individual is also consuming fluid). The increased thirst that accompanies the fall in blood pressure is due in part to the stimulation of the hypothalamic thirst center by Ang II.

Which of the following would decrease total peripheral resistance to blood flow?

• decreasing the hematocrit
• vasoconstriction
• increasing blood vessel length
• atherosclerosis

decreasing the hematocrit

Ex.

Decreasing the hematocrit (fraction of whole blood consisting of blood cells) would lead to decreased blood viscosity, and thus would decrease resistance.

As your skeletal muscles contract during physical activity, more blood is returned to the heart. Which variable would be affected and what would be the outcome of this action?

• End-systolic volume would be increased, which would increase cardiac output.
• Afterload would increase, which would increase cardiac output.
• Preload would be increased, which would result in a larger cardiac output.
• Contractility would be increased, which would result in a larger cardiac output.

Preload would be increased, which would result in a larger cardiac output.

Ex.

More blood returning to the heart would increase the volume of blood in the ventricles at the end of their filling phase (called end diastolic volume, or EDV). A larger EDV results in greater stretching of the myocardium, or a greater preload. Stretching (lengthening) the contractile cells brings them closer to their optimal length, allowing them to produce more force when stimulated to contract. The stronger contraction results in a larger stroke volume, and therefore a larger cardiac output.

As pressure in the aorta rises due to atherosclerosis, more ventricular pressure is required to open the aortic valve. True or False.

True

Which of the following events best describes when the pulmonary and aortic valves open?

• At the beginning of diastole
• At the end of diastole
• At the beginning of systole
• At the end of systole

At the beginning of systole

Ex.

During phase 2b the pressure in the ventricles exceeds that of the aorta and pulmonary trunk, so their valves open and allow blood to be ejected.

Increasing end-diastolic volume (EDV) and end-systolic volume (ESV) will increase stroke volume. True or False.

False

Ex.

Stroke volume (the volume of blood ejected from the ventricle during systole) is equal to the difference between EDV (the volume of blood in the ventricle before it contracts) and ESV (the volume of blood remaining in the ventricle after it contracts). Increasing EDV will result in a larger stroke volume; however, increasing ESV will result in a smaller stroke volume.