Mastering A&P HW CH 18

What causes the aortic semilunar valve to close?

greater pressure in the aorta than in the left ventricle Yes, backflow of blood in the aorta (towards the left ventricle) closes the aortic semilunar valve.

Name the needle like ridges of muscle lining the ventricles.

Trabeculae carneae; Correct. Trabeculae carneae are the small elevated ridges of muscle arranged in a web type fashion found in both the right and left ventricles.

What does the ECG wave tracing represent?

electrical activity in the heart Yes, the ECG waves show the depolarization and repolarization in various areas of the heart.

Calculate the stroke volume if the end diastolic volume (EDV) is 135 mL and the end systolic volume (ESV) is 60 mL.

75 mL 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.

What heart chamber pushes blood through the aortic semilunar valve?

Left ventricle; 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.

Select the correct partial path. This path is part of the complete blood flow pathway. You should be able to trace flow starting in any location.

aorta to smaller systemic arteries to systemic capillaries to systemic veins to right atrium through the tricuspid valve All systemic veins return oxygen-poor venous flow to the right atrium, through the tricuspid to the right ventricle, and up and out the pulmonary semilunar valve to the pulmonary trunk and pulmonary arteries to the capillaries of the lungs. Returning oxygen-rich blood flowing through pulmonary veins enters the left atrium, passes through the mitral valve to the left ventricle, and flows out through the aortic semilunar valve into the aorta and on to systemic capillaries. Congratulations on completing blood flow through the two-sided heart, identifying oxygen-rich and oxygen-poor locations, and preparing yourself for knowledge you will use again and again!

carries oxygen-poor venous blood of the coronary circulation into the right atrium.

coronary sinus

When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane?

fast calcium Yes, 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).

Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane?

gap junctions Yes, 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.

Which of the following is NOT a factor that increases stroke volume?

increasing afterload Increasing afterload decreases stroke volume.

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

Put the phases of the cardiac cycle in the correct order, starting after ventricular filling.

isovolumetric contraction, ventricular ejection, isovolumetric relaxation Yes, the ventricles must contract and eject blood before they relax and fill again.

Identify the most muscular chamber.

left ventricle; 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

Blood on the right never mixes with blood on the left, once the heart is fully developed.

true; Correct. 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.

The first branch off the arch of the aorta is the brachiocephalic artery in both the sheep and the human.

true; 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.

Name the ridged bundles of muscle found projecting inside the right atrium.

Pectinate muscles Correct. 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.

Which of the following is correct about the filling of the ventricles?

Most blood flows passively into the ventricles through open AV valves. Yes, most of the ventricular filling is passive; atrial contraction adds just a little more blood.

Which statement regarding cardiac muscle structure is accurate?

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 Yes, the P wave represents atrial depolarization, which leads to atrial contraction.

Which part of the conduction system initiates the depolarizing impulse, which spreads throughout the heart?

SA node Yes, the SA Node spontaneously depolarizes, causing the wave of depolarization that spreads through the rest of the conduction system and heart.

The structure that is located anatomically between the aorta and the left ventricle is the

aortic semilunar valve

Identify the ear like flaps that are attached to the top chambers of the heart.

auricles; The auricles are flap like extensions of the atria that are observed on the external surface of the heart

What structures connect the individual heart muscle cells?

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

Which of the following would increase cardiac output?

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.

The base of the heart is located at the bottom of the heart.

false; 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.

What does the QRS complex represent in the ECG wave tracing?

ventricular depolarization Yes, 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 Yes, both occur during ventricular diastole when the ventricles are not actively contracting and ejecting blood.

Repolarization of an autorhythmic cell is due to the opening of which channels?

voltage-gated potassium channels Yes, 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.

______ carries oxygen-poor venous blood from above the diaphragm from areas of the upper body and extremities into the right atrium

superior vena cava

oxygen-poor

superior vena cava, right ventricle, pulmonary arteries, right atrium

structure that prevents backflow of blood into the left atrium is the

mitral (bicuspid) valve

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 Yes, 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.

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 Yes, the flow of positive ions from the autorhythmic cells (or adjacent cells) brings the membrane to threshold initiating depolarization of the contractile cell.

oxygen-rich

pulmonary veins, left ventricle, aorta, left atrium

What fibrous structure functions to anchor the atrioventricular valves in a closed position?

Chordae tendineae; Correct. 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.

Identify the right atrioventricular valve.

Tricuspid valve Correct. The tricuspid valve is the atrioventricular valve located on the right side of the heart. It separates the right atrium from the right ventricle.

vessel that carries oxygen-rich blood to tissues is the

aorta

What is the ligamentum arteriosum?

A remnant of the ductus arteriosus; 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.

Which part of the intrinsic conduction system delays the impulse briefly before it moves on to the ventricles?

AV node Yes, 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)?

AV valves only Yes, increased pressure in the ventricles would close the AV valves.

Identify the valve found between the left atrium and left ventricle.

Bicuspid (mitral) valve; The atrioventricular valve on the left is the bicuspid valve. The mitral valve is also called the mitral valve.

Name the inner lining of the heart.

Endocardium; 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.

Oxygenated blood flows through the right side of the heart.

False Correct. 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.

The moderator band is found on both the right and left side of the heart.

False Correct. 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.

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 the pressure in the ventricles. Yes, 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 a blood supply to the heart; Correct. 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.

Identfiy the valve located at the exit of the right ventricle.

Pulmonary semilunar valve Correct. 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; The right ventricle pumps deoxygenated blood through the pulmonary semilunar valve into the pulmonary trunk to be distributed to the lungs.

The capillaries receiving blood flow from the left side of the heart are the

systemic capillaries