Human Anatomy and Physiology : Help with Heart Physiology

Study concepts, example questions & explanations for Human Anatomy and Physiology

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Example Questions

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Example Question #1 : Circulatory And Lymphatic Physiology

Which blood vessel directly feeds blood to the left ventricle before it is pumped out to the rest of the body?

Possible Answers:

Superior vena cava

Aorta

No blood vessel directly feeds the left ventricle

Inferior vena cava

Pulmonary vein

Correct answer:

No blood vessel directly feeds the left ventricle

Explanation:

Blood enters the left ventricle from the left atrium through the mitral valve; no blood vessel directly feeds blood to the left ventricle to be distributed to the rest of the body. The left atrium is directly fed by the pulmonary vein, and the left ventricle empties into the aorta.

Example Question #2 : Circulatory And Lymphatic Physiology

Which of the following cellular junctions allows for the spreading of an action potential throughout the heart muscle?

Possible Answers:

Tight junctions

Chemical synapses

Desmosomes

Gap junctions

Correct answer:

Gap junctions

Explanation:

Cardiac muscle cells are connected to one another by intercalated discs. These discs are composed of gap junctions, which allow for communication between the neighboring cells. These gap junctions allow for an action potential to spread throughout the entire muscle by electrical synapses, and result in a unified contraction.

Example Question #3 : Circulatory And Lymphatic Physiology

Which structure contains autorhythmic cells that spontaneously conduct action potentials?

Possible Answers:

Vagus nerve

Atrioventricular node

Bundle of His

Sinoatrial node

Correct answer:

Sinoatrial node

Explanation:

In order to beat, the heart has a conduction system that works independently of the nervous system. The sinoatrial node, found in the right atrium, is composed of autorhythmic cells that can spontaneously depolarize. This results in an action potential that then spreads throughout the entire heart.

From the sinoatrial node, this action potential spreads through gap junctions to the atria to cause atrial systole, and to the atrioventricular node. The action potential is delayed at the atrioventricular node before being distributed to the bundle of His and Purkinje fibers to cause coordinated ventricular systole. The vagus nerve sends parasympathetic signals to the sinoatrial node to decrease heart rate. The natural rhythm of the heart is roughly 80-100 beats per minute, but the vagus nerve reduces resting heart rate to around 60 beats per minute.

Example Question #4 : Circulatory And Lymphatic Physiology

How does the systemic circuit of the heart get blood to farther sections of the body compared to the pulmonary circuit, which only needs to pump blood to the nearby lungs?

Possible Answers:

The left ventricle has a larger stroke volume than the right ventricle

The left ventricle pumps more frequently than the right ventricle

The left ventricle pumps with more force

The left ventricle does not need to push blood through a valve

Correct answer:

The left ventricle pumps with more force

Explanation:

The left ventricle needs to pump blood to all areas of the body. As a result, the left ventricle has a very powerful muscle wall, which allows for the blood to be pumped with a great deal of force throughout the body. The left ventricle typically has a muscle wall three times as thick as the right ventricle, but both ventricles have the same stroke volume. Otherwise, there would eventually be a backup of blood on one side of the heart. Both ventricles also contract with the same frequency, coordinated by the purkinje fibers.

Example Question #5 : Circulatory And Lymphatic Physiology

How is cardiac output calculated in the body?

Possible Answers:

Systolic blood pressure minus diastolic blood pressure

Heart rate plus systolic blood pressure

Heart rate multiplied by contractile force

Heart rate multiplied by stroke volume

Correct answer:

Heart rate multiplied by stroke volume

Explanation:

Cardiac output tells us the volume of blood pumped by each ventricle every minute. As a result, the two factors that we need to consider are the number of times that the heart beats every minute (heart rate), and the amount of blood pumped by each ventricle every beat (stroke volume). These two factors are multiplied in order to determine the cardiac output of the heart.

Example Question #6 : Circulatory And Lymphatic Physiology

What would happen if the vagus nerve was detached from the heart?

Possible Answers:

The heart's contractions would not be affected

The heart would not beat in a steady rhythm

The heart rate would increase

The heart would stop beating

Only one side of the heart would beat

Correct answer:

The heart rate would increase

Explanation:

The vagus nerve is a parasympathetic nerve. The parasympathetic nervous system is responsible for "rest and digest" functions in the body, and helps slow down the heart rate. When the vagus nerve is detached from the heart, the heart will still beat, but the loss of parasympathetic innervation will result in an increased heart rate.

Autorhythmic contraction of the heart begins in the sinoatrial node with spontaneous depolarization. The sinoatrial node will generate an action potential roughly 80-100 times per minute. Innervation by the vagus nerve mediates these depolarizations to reduce resting heart rate to around 60 beats per minute.

Example Question #7 : Circulatory And Lymphatic Physiology

If an individual has a stroke volume of 65mL and a heart rate of 80 beats per minute, then what is this indiviudal's cardiac output?

Possible Answers:

Correct answer:

Explanation:

Cardiac output is the volume of blood that the heart pumps out per minute. The equation for cardiac output is:

Stroke volume (blood pumped out in one beat) x Heart rate = Cardiac output

We are given the stroke volume and beats per minute; it is simply a matter of multiplying our values.

Example Question #1 : Help With Heart Physiology

An individual has an end diastolic volume of 120mL, an end systolic volume of 50mL, and a stroke volume of 70mL. He also has a heart rate of 60 beats per minute. What is his ejection fraction?

Possible Answers:

Correct answer:

Explanation:

Ejection fraction is the percentage of blood pumped out of the left ventricle, in comparison to its volume when completely filled. Ejection fraction can be found by dividing stroke volume by end distolic volume. The other information given is excess and unnecessary.

Example Question #2 : Help With Heart Physiology

The primary pacemaker cells are found in the __________.

Possible Answers:

bundle branches

atrioventricular node

Purkinje fibers

bundle of His

sinoatrial node

Correct answer:

sinoatrial node

Explanation:

In a normal, healthy heart, electrical conduction begins in the pacemaker cells of the sinoatrial node. This signal first spreads across the left and right atria before being directed to the atrioventricular node. The signal slows for an instant to allow the ventricles to fill with blood. This signal is then released and moves along the bundle of His, located within the interventricular septum. From here, the signal divides into the left and right bundle branches, and terminates in the Purkinje fibers on the ventricles. 

Example Question #2 : Help With Heart Physiology

Joe has a cardiac output of  and a heart rate of . What total volume of blood does his heart pump during each cardiac cycle?

Possible Answers:

Correct answer:

Explanation:

In order to determine the total volume of blood the heart pumps out during each cycle, we must first determine Joe's stroke volume, given his cardiac output and heart rate. Rearrange the cardiac output formula, to solve for stroke volume. 

The question is asking us for the total volume that the heart pumps out per cycle. Stroke volume is defined as the amount of blood pumped out of the left ventricle per heart beat, so we must multiply our answer by 2 in order to determine the total volume of blood pumped during each cardiac cycle. 

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