Ch. 18 Heart (Homework)
end diastolic volume and the first heart sound are observed during the __________ phase of the cardiac cycle
isovolumetric contraction
Arrange elements of the intrinsic conduction system in the order that a depolarizing impulse travels during a normal heartbeat
-SA node -Internodal pathways -AV node -AV bundle -bundle branches -Purkinje fibers
Calculate the stroke volume if the end diastolic volume (EDV) is 135 mL/beat and the end systolic volume (ESV) is 60 mL/beat.
75 ml/ beat The SV is calculated by subtracting the ESV from the EDV. You are comparing the volume of the ventricle at its fullest to its emptiest.
Calculate the cardiac output if heart rate (HR) is 90 beats per minute, stroke volume (SV) is 110 ml/beatml/beat, end diastolic volume (EDV) is 140 mlml, and end systolic volume (ESV) is 30 mlml.
9.9 L/min Cardiac output is the product of heart rate times stroke volume. Cardiac output increases to meet increased metabolic demand, often by increasing both heart rate and stroke volume at the same time. This occurs, for example, during maximal exercise, when cardiac output may increase to four or five times the resting level.
_______ is the electrical link between atria and ventricles
AV bundle
delays occur here while atria contract
AV node
Which of these structures conduct(s) action potentials the slowest?
AV node Action potentials slow down as they pass through the AV node. This gives the atria time to finish contracting before the ventricles are depolarized.
Which part of the intrinsic conduction system delays the impulse briefly before it moves on to the ventricles?
AV node the AV node slows down the impulse giving the atria time to contract before the ventricles contract.
Increased pressure in the ventricles would close what valve(s)?
Yes, increased pressure in the ventricles would close the AV valves
These activities change heart rate by changing the balance of parasympathetic and sympathetic stimulation of the heart. Sort each of the activities according to whether it decreases or increases heart rate. -digesting a meal -lying down -fright or anger -standing up
Decrease= digesting meal, lying down Increase=fright or anger, standing up, exercise The balance between parasympathetic and sympathetic stimulation to the heart controls heart rate. Increased parasympathetic activity decreases heart rate, and sympathetic activity increases heart rate.
True or false: The base of the heart is located at the bottom of the heart.
False Explanation: The base is located at the top of the heart. It is unusual to see the largest portion of an organ at the top. Typically, the base is at the bottom of an organ, as in the lungs.
Which statement regarding cardiac muscle structure is accurate? -Myofibrils of cardiac muscle tissue vary in diameter and branch extensively -Cardiac cells are long, cylindrical, and multinucleate. -Cardiac muscle cells are independent of one another both structurally and functionally -Cardiac cells possess fewer mitochondria than other types of muscle cells
Myofibrils of cardiac muscle tissue vary in diameter and branch extensively The myofibrils of cardiac muscle have various diameters; they also branch in order to maintain connections, via intercalated discs, with other muscle cells.
Contraction of the atria results from which wave of depolarization on the ECG tracing?
P wave the P wave represents atrial depolarization, which leads to atrial contraction.
_______ convey the impulse throughout the ventricular walls
Purkinje fibers
_________ sets the pace for the entire heart
SA node
A person notices his or her heart beat because he or she senses blood being pumped by the heart. Excessive caffeine intake can lead to irregular heart rhythms (arrhythmias) that patients perceive as "skipped beats." Given that caffeine is a stimulant, which of the following mechanisms best explains the reason for the feeling that the heart skipped a beat?
Purkinje fibers initiate spontaneous action potentials, which cause the ventricles to contract early. Action potentials normally originate in the SA node because the pacemaker cells there depolarize faster than pacemaker cells located elsewhere in the heart. However, certain drugs, such as caffeine, nicotine, or cocaine, can stimulate other pacemaker cells to speed up and temporarily "escape" the SA node rhythm. If this ectopic focus consists of Purkinje fibers, then ventricular contraction will occur prematurely, prior to ventricular filling. Without proper filling, this abnormal contraction pumps little blood and is not sensed. However, the following normal beat generated from the SA node has augmented filling and is sensed, resulting in the missed beat sensation.
Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat?
SA node Like the rest of the intrinsic conduction system, the SA node contains pacemaker cells that spontaneously depolarize. The cells within the SA node, however, depolarize faster than the other cells within the system. This causes action potentials to initiate in the SA node rather than in any of the other structures.
Which part of the conduction system initiates the depolarizing impulse, which spreads throughout the heart?
SA node the SA Node spontaneously depolarizes, causing the wave of depolarization that spreads through the rest of the conduction system and heart.
After you note a murmur in a newborn, the pediatric cardiology consultant diagnoses a patent ductus arteriosus. Why is this a cause for concern?
The higher pressure in the aorta will push extra blood through the ductus arteriosus into the child's pulmonary circulation. Normally, the ductus arteriosus serves as a shunt or "detour" to bypass the uninflated lungs during fetal life. This works because pressure is higher in the pulmonary trunk than the aorta. After the lungs inflate at birth, the pressure in the aorta exceeds that in the pulmonary circulation, and the ductus should close. If it does not, the pulmonary vessels are subjected to systemic pressure.
What is the ligament arteriosum?
a remnant of the ductus arteriosus Explanation: The ligamentum arteriosum is a remnant of the ductus arteriosus. The ductus arteriosus is a fetal shunt that connects the pulmonary trunk to the aorta.
the vessel that carries oxygen-rich blood to tissues is the _________
aorta
the structure that is located anatomically between the aorta and the left ventricle Is the ______________
aortic semilunar valve
________ control blood flow into the ventricles
atrioventricular valves
Identify the ear like flaps that are attached to the top chambers of the heart.
auricle
Identify the valve found between the left atrium and left ventricle.
bicuspid (mitral) valve
_______ convey the impulse down the inter ventricular septum
bundle branches
volume of blood per min. pumped out by one ventricle
cardiac output (CO)
What fibrous structure functions to anchor the atrioventricular valves in a closed position?
chordae tendineae Explanation: Chordae tendineae are the fibrous cords that attach the atrioventricular valves to papillary muscles. They help anchor the atrioventricular valves in a closed position during ventricular contraction.
An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________.
contractility Increased sympathetic activity increases heart contractility. This causes cardiac fibers to contract more forcefully at all levels of preload. Regardless of end diastolic volume, this mechanism increases stroke volume by reducing end systolic volume.
the _______ carries oxygen-poor venous blood of the coronary circulation into the right atrium
coronary sinus
Describe the path of blood flow from the coronary sinus to the capillaries of the lungs
coronary sinus, R atrium, tricuspid valve, R ventricle, pulmonary semilunar valve, pulmonary trunk, pulmonary arteries, capillaries of lungs
What does the ECG wave tracing represent?
electrical activity of the heart the ECG waves show the depolarization and repolarization in various areas of the heart
a test that records the electrical activity of the heart is an __________
electrocardiogram
volume of blood in one ventricle before contraction
end diastolic volume (EDV)
volume of blood in one ventricle after contraction
end systolic volume (ESV)
Name the inner lining of the heart.
endocardium Explanation: The endocardium is the smooth, slick lining of the chambers of the heart. Endocardium is a continuation of endothelium that lines blood vessels. Both endocardium and endothelium are composed of simple squamous epithelial tissue, which minimizes friction between the wall of the chamber/vessel and the blood.
Which of the following would increase cardiac output? - epinephrine -parasympathetic stimulation -decreased cytoplasmic calcium concentration during contraction -high blood pressure
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.
True or false: Oxygenated blood flows through the right side of the heart.
false Explanation: Oxygenated blood returning from the lungs is received by the left atrium, then to the left ventricle before being pumped out to the body. This pathway of blood flow is known as the systemic circulation.
True or false: The moderator band is found on both the right and left side of the heart.
false Explanation: The moderator band is a cord like structure found in the right ventricle. It contains portions of the cardiac conduction system that help convey the electrical message for the ventricles to contract. It works as a shortcut within the cardiac conduction system.
When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane?
fast calcium unlike nerve cells or cardiac muscle cells, fast calcium channels are responsible for the depolarization phase of the autorhythmic cell action potential. When the fast calcium channels open, calcium rushes into the cell making it less negative (or more positive).
Which of the following descriptions does not describe atrioventricular (AV) valves? -flap-like -formed from pocket-like cusps -anchored inferiorly by specialized connective tissue -open based on pressure changes in the atria versus the ventricles
formed from pocket-like cusps "Pocket-like" is a description that better fits the crescent moon shaped cusps that form semilunar valves.
Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane?
gap junctions action potentials generated by the autorhythmic cells spread waves of depolarization to contractile cells through gap junctions. If the depolarization causes the contractile cells to reach threshold, they will in turn generate an action potential.
What causes the aortic semilunar valve to close?
greater pressure in the aorta than in the left ventricle backflow of blood in the aorta (towards the left ventricle) closes the aortic semilunar valve
# of heartbeats per min
heart rate (HR)
Which of the following would decrease stroke volume? -increasing contractility -increasing afterload -increasing sympathetic stimulation -increasing preload
increasing afterload
the ________ carries oxygen-poor venous blood from below the diaphragm from the areas of the lower body and extremities into the right atrium
inferior vena cava
the structure dividing the two atria of the heart is called the _________
interatrial septum
________ link between the SA node and AV node
internodal pathways
Put the phases of the cardiac cycle in the correct order, starting after ventricular filling.
isovolumetric contraction, ventricular ejection, isovolumetric relaxation the ventricles must contract and eject blood before they relax and fill again.
The dicrotic notch occurs during the ______________ phase of the cardiac cycle.
isovolumetric relaxation
What heart chamber pushes blood through the aortic semilunar valve?
left ventricle Explanation: The aortic valve is located between the left ventricle and the aorta. The left ventricle pumps oxygenated blood out of the heart through the aortic valve to the body.
Identify the most muscular chamber
left ventricle Explanation: The left ventricle is responsible for pumping blood out to the body. This requires a lot of force. The left ventricle is the most muscular in order to pump the blood with adequate force.
Describe the path of oxygen-rich blood flow from the lungs returning to the heart
lung capillaries, pulmonary veins, left atrium, mitral/bicuspid valve, left ventricle, aortic/semilunar valve
The structure that prevents back flow of blood in the left atrium is the ___________
mitral (bicuspid) valve
Which of the following is correct about the filling of the ventricles? -The majority of ventricular filling is caused by contraction of the atria. -Most blood flows passively into the ventricles through open AV valves.
most of the ventricular filling is passive; atrial contraction adds just a little more blood.
As part of a blood drive on campus for the American Red Cross, you and your friends have just donated 500 mlml of blood. You are now relaxing at the student lounge, waiting for A&P lab to begin. Unfortunately, even though you are thirsty, you haven't bothered to buy yourself a drink. Other than a little soreness of the skin and tissue around your median cubital vein, you feel fine. How has your 500 mlml decrease in blood volume most likely affected your cardiac output, heart rate, and stroke volume?
no change in cardiac output, increased heart rate, decreased stroke volume Donating blood does not alter resting cardiac output. However, the decreased blood volume does decrease venous return and end diastolic volume. This decreases preload, thereby lowering stroke volume. By itself, decreased stroke volume would decrease cardiac output. But remember, the body still requires a resting blood flow of around 5 L/minL/min. To meet this demand, homeostatic mechanisms quickly restore cardiac output to resting levels. For example, heart rate is increased as parasympathetic influence is removed and sympathetic activity is increased. Even though your blood volume is a bit low, your body has no problem compensating to meet your resting metabolic needs. Running away from a tiger? Now that might be a different story.
Name the ridged bundles of muscle found projecting inside the right atrium.
pectinate muscles Explanation: The pectinate muscles are ridge like elevations of muscle. They are parallel to each other and resemble teeth of a comb. They are easily observed inside the right atrium.
One of the changes that occurs in the pacemaker potential (unstable resting membrane potential) in the SA node (an autorhythmic cell) is a decreased efflux of what ion?
potassium if there is a decreased efflux of potassium while there is a normal influx of sodium, the inside of the cell would become less negative. Thus, threshold would be reached. The ability of these autorhythmic cells to spontaneously depolarize is what results in the pacemaker potential.
Describe the pressures in the atria and ventricles that would cause the opening of the AV valves.
pressure in the atria would be greater than pressure in the ventricles higher pressure in the atria than in the ventricles forces the AV valves to open and blood moves into the ventricles.
What is the function of the coronary circulation?
provide blood supply to the heart Explanation: The coronary circulation provides oxygenated blood to the heart through coronary arteries. Coronary veins return the deoxygenated from the heart to the coronary sinus on the posterior surface of the heart. The coronary sinus empties the deoxygenated blood directly into the right atrium where it joins deoxygenated from the body.
Your patient has been diagnosed with right ventricular failure. Which of the following abnormalities is not a direct result of this problem?
pulmonary edema (fluid in the alveoli) Left ventricular failure directly causes blood to "back up" into the pulmonary veins, increasing pressure in the pulmonary capillaries and causing fluid to be pushed from the blood to the alveoli.
Identfiy the valve located at the exit of the right ventricle.
pulmonary semilunar valve Explanation: The pulmonary valve is the semilunar valve found between the right ventricle and the pulmonary trunk. Deoxygenated blood travels through the pulmonary valve as it exits the right side of the heart on its way to the lungs.
Which chamber of the heart exits into the pulmonary trunk?
right ventricle Explanation: The right ventricle pumps deoxygenated blood through the pulmonary semilunar valve into the pulmonary trunk to be distributed to the lungs.
The anatomy of the intrinsic conduction system causes contraction of the ventricles to begin at the apex and move superiorly. Why is this important?
so blood is forced upward, toward the semilunar valves Beginning contraction at the apex causes blood to be forced upward, through the semilunar valves, and into the aorta and pulmonary trunk. This makes ventricular ejection more efficient, much like squeezing a tube of toothpaste up from the bottom is more efficient at dispensing the toothpaste than is squeezing from the top.
volume of blood per heart beat pumped out by one ventricle
stroke volume (SV)
The ______ carries oxygen-poor venous blood from above the diaphragm areas of the upper body and extremities into the right atrium
superior vena cava
the capillaries receiving blood flow from the left side of the heart are the ______________
systemic capillaries
_______ is a faster than normal heart rate
tachycardia
In order to cause cardiac muscle contraction, the contractile cells must also depolarize. What causes the depolarization of the contractile cells?
the flow of positive ions from adjacent cells the flow of positive ions from the autorhythmic cells (or adjacent cells) brings the membrane to threshold initiating depolarization of the contractile cell.
Name the irregular ridges of muscle lining the ventricles.
trabeculae carneae Explanation: Trabeculae carneae are the small elevated ridges of muscle arranged in a web type fashion found in both the right and left ventricles.
Identify the right atrioventricular valve.
tricuspid valve
True or false: The first branch off the arch of the aorta is the brachiocephalic artery in both the sheep and the human.
true Explanation: In both the sheep and human, the brachiocephalic artery is the first major vessel to exit the arch of the aorta. Further branching of the brachiocephalic artery and the arch of the aorta differs between a sheep and a human.
True or false: Blood on the right never mixes with blood on the left, once the heart is fully developed.
true Explanation: Once fetal modifications (i.e. foramen ovale, ductus arteriosus) close following delivery of the infant, blood on the right side of the heart should not mix with blood on the left side of the heart.
______ is the volume of blood per minute flowing into one atrium
venous return (VR)
What does the QRS complex represent in the ECG wave tracing?
ventricular depolarization the QRS complex represents depolarization in the ventricles, which have greater mass than the atria
Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.
ventricular diastole both occur during ventricular diastole when the ventricles are not actively contracting and ejecting blood.
The semilunar valves open during the ______________ phase of the cardiac cycle, allowing blood to exit the ventricles.
ventricular ejection
The P wave and subsequent atrial contraction are evident during the _______________ phase of the cardiac cycle.
ventricular filling
Repolarization of an autorhythmic cell is due to the opening of which channels?
voltage-gated potassium channels opening of voltage-gated potassium channels causes positive potassium ions to move out of the cell. This efflux of potassium causes the cell to become more negative inside thus, repolarizing the cell.
