Anatomy and Physiology of the heart

Question 1

Where do coronary arteries originate anatomically?

Answer 1

Originate just above the aortic valve where the aorta exits the heart

Question 2

What does the left main coronary artery subdivides into?

Answer 2

The left main coronary artery subdivides into the left anterior descending and circumflex arteries

Question 3

What part of the myocardium does the LAD artery supply?

Answer 3

Left anterior descending (LAD) supplies the anterior wall of the more muscular left ventricle and the interventricular septum

Question 4

What part of the myocardium does the cirumlfex artery supply?

Answer 4

Circumflex feeds the lateral and posterior portions of the left ventricle and part of the right ventricle

Question 5

What part of the myocardium does the right coronary artery and the left anterior descening artery supply?

Answer 5

The right coronary artery and the left anterior descending artery supply most of the right atrium and ventricle and the inferior aspect of the left ventricle

Question 6

What is the function of anastomoses?

Answer 6

• Provide collateral circulation
• Play an important role in providing alternative routes of blood flow if there is blockage in one or more of the coronary vessels

Question 7

What is the function of coronary capillaries?

Answer 7

Permit the exchange of nutrients and metabolic wastes

Question 8

What valves does the contraction of the right ventricle push blood against?

Answer 8

Contraction of the right ventricle pushes blood against the tricuspid valve (forcing it closed), and through the pulmonic valve (forcing it open), allowing blood to enter the lungs via the pulmonary arteries

Question 9

Which blood vessels carry blood from the lungs to the left atrium?

Answer 9

From the lungs, the blood travels through four pulmonary veins back to the left atrium

Question 10

Which valve allows blood flow into the left ventricle?

Answer 10

Mitral valve

Question 11

What valve does the blood passing from left atrium into the left ventricle open?

Answer 11

The blood passing from the left atrium to the left ventricle opens the bicuspid valve when the ventricle relaxes to complete left-ventricular filling

Question 12

Can ventricles under normal conditions pump sufficient amounts of blood to maintain homeostasis without the help of the atria?

Answer 12

Yes, under most conditions, the ventricles can pump sufficient amounts of blood to maintain homeostasis without the help of the atria

Question 13

When does the “priming pump action” of the atria become important to maintain pumping efficiency?

Answer 13

Under conditions of stress, when the heart may pump 300% to 400% more blood than during rest, the priming pump action of the atria becomes important in maintaining pumping efficiency.

Question 14

What is a cardiac cycle

Answer 14

The cycle of rhythmic, alternate contraction (systole) and relaxation (diastole) of the atria and ventricles

Question 15

What is the main factor responsible for blood movement within the heart chambers?

Answer 15

Pressure changes produced within the heart chambers by contraction are responsible for blood movement, as blood moves from areas of high pressure to areas of low pressure

Question 16

What happens to pressure inside the heart chambers during ventricular systole?

Answer 16

During ventricular systole, ventricular pressure exceeds atrial pressure, causing the atrioventricular (AV) valves to close

Question 17

What happens in the heart as the contraction proceeds, and ventricular pressure continues to rise until it exceeds that in the pulmonary artery on the right side and in the aorta on the left side of the heart?

Answer 17

The pulmonary and aortic valves open, and blood flows from the ventricles into those arteries (ejection)

Question 18

What happens after ventricular contraction, when ventricular relaxation begins, and ventricular pressure falls rapidly?

Answer 18

When the pressure falls below the pressure in the aorta or the pulmonary trunk, blood is forced back toward the ventricles, closing the pulmonary and aortic valves

Question 19

What happens in the heart chambers as ventricular pressure drops below atrial pressure?

Answer 19

As ventricular pressure drops below atrial pressure, the tricuspid and mitral valves open, and blood flows from the atria into the ventricles

Question 20

When does teh atrial systole occur in relation to the ventricular cardiac cycle?

Answer 20

Atrial systole occurs during ventricular diastole

Question 21

What is a stroke volume?

Answer 21

The amount of blood ejected from each ventricle with one contraction

Question 22

What does stroke volume depend on?

Answer 22

a. Preload (the volume of blood returning to the heart)
b. Afterload
c. Myocardial contractility

Question 23

What concept explains the heart’s ability to pump more strongly when it has larger preload?

Answer 23

Starling’s law of the heart.

Question 24

What is Starling’s law?

Answer 24

Myocardial fibers contract more forcefully when stretched

When the ventricles are filled with larger-than-normal volumes of blood (increased preload), they contract with greater-than-normal force to deliver their entire contents to the systemic circulation

Question 25

What is the most important feature of the heart’s ability to adapt itself to changing volumes in venous return?

Answer 25

The most important feature of the heart’s ability to adapt itself to changing volumes in venous return is that, within reasonable limits, changes in arterial pressure have minimal effect on cardiac output.

In other words, the heart can pump either a small amount of blood or a large amount, depending on the amount of venous return.

Question 26

What is the most important factor for SV?

Answer 26

Venous return is the most important factor in SV

Question 27

Is there any limitation to the theory of Starling’s law and its effect on stroke volume?

Answer 27

Yes, the theory of Starling’s law and its effect on SV can be applied only up to a certain limit of muscle fiber stretching.

Beyond that limit, muscle fiber stretch actually diminishes the strength of contraction, and the heart begins to fail.

Question 28

What is afterload?

Answer 28

A result of peripheral vascular resistance—the total resistance against which blood must be pumped

Question 29

What is the effect of increased peripheral vascular resistance on stroke volume?

Answer 29

An increase in peripheral vascular resistance decreases SV because of the increased pressure in the aorta that the ventricular muscle must overcome to open the aortic valve and push blood through

Question 30

What is the effect of decreased peripheral vascular resistance on stroke volume? (if there is sufficinet volume of fluid in the system)

Answer 30

A decrease in peripheral vascular resistance increases SV if there is sufficient volume of fluid in the system

Question 31

What factor is more important in maintaing cardiac output?

Preload or afterload?

Answer 31

Preload

Question 32

Define cardiac output

Answer 32

Cardiac output is the amount of blood pumped by the ventricles per minute

Question 33

What factors that make up CO can increase it?

Answer 33

Cardiac output can increase by increasing the heart rate, SV, or both

Question 34

Which nerve provides parasympathetic stimulation of the heart?

Answer 34

Vagus nerve

Question 35

Name four ways that the vagus nerve can be stimulated

Answer 35

1) Valsalva maneuver
2) Carotid sinus massage
3) Pain
4) Distention of the urinary bladder

Question 36

What is the chemical mediator of the parasympathetic nervous system?

Answer 36

Acetylcholine

Question 37

Can SV actualy increase with decreased heart rare and why or why not?

Answer 37

SV may increase with a decreased heart rate because the

longer time interval between heart beats allows the heart

to fill with a volume of blood, and thus contract more

forcefully (Starling’s law)