Which Of The Following Would Increase Cardiac Output

Question: At what rate does the sinoatrial (SA) node depolarize?

30 times per minute

40 times per minute

50 times per minute

75 times per minute

Answer: 75 times per minute

The sinoatrial node typically depolarizes spontaneously about 75 times per minute, although this can vary in different individuals. This rate is directly modulated by the autonomic nervous system.

Question: Which of the following increases stroke volume?

decrease in end diastolic volume (EDV)

severe blood loss

decrease in preload

exercise

Answer: exercise

Exercise increases venous return, which would in turn increase the amount of blood in the presystolic ventricle (preload).

Question: Which of the following would cause a DECREASE in cardiac output (CO)?

decreasing thyroid function (thyroxine)

suddenly standing up from a supine position

an increase in adrenal medulla output (epinephrine)

heightened use of skeletal muscle

Answer: decreasing thyroid function (thyroxine)

Thyroxine increases basal metabolic rate, respiratory rate, and both heart rate and contractility.

Question: The __________ valve is located between the right atrium and the right ventricle.

mitral

aortic semilunar

pulmonary semilunar

tricuspid

Answer: tricuspid

The tricuspid valve is located between the right atrium and right ventricle.

Question: What structures connect the individual heart muscle cells?

intercalated discs

trabaculae carneae

chordae tendineae

anastomoses

Answer: intercalated discs

Intercalated discs connect the heart muscle cells. They include desmosomes (anchoring junctions) and gap junctions (communicating junctions).

Question: Which portion of the electrocardiogram represents the depolarization wave received by the atria from the sinoatrial (SA) node?

S-T segment

P wave

QRS complex

T wave

Answer: P wave

The P wave represents the depolarization of the left and right atria and the beginning of atrial systole.

Question: The first heart sound (the “lub” of the “lub-dup”) is caused by __________.

atrial contraction

closure of the semilunar valves

closure of the atrioventricular valves

ventricular contraction

Answer: closure of the atrioventricular valves

The first heart sound (the “lub” of the “lub-dup”) is generated by the closure of the atrioventricular valves

Question:

Answer: Gap junctions allow action potentials to spread to

connected cells.

Gap junctions are a form of electrical synapse that allow action potentials to spread to connected cells. This property allows the signal to spread efficiently through the heart.

Question: Which of the following would increase cardiac output?

parasympathetic stimulation

decreased calcium during contraction

high blood pressure

epinephrine

Answer: epinephrine

Sympathetic stimulation leads to the release of epinephrine and norepinephrine, both of which increase heart rate and increase contractility, which increases stroke volume. Increasing heart rate and stroke volume increases cardiac output.

Question: Which of the following does NOT deliver deoxygenated blood to the heart?

coronary sinus

pulmonary veins

superior vena cava

inferior vena cava

Answer: inferior vena cava

The pulmonary veins deliver oxygenated blood to the left atrium.