A&P Mylab and Mastering Ch. 17
What vessel(s) deliver oxygenated blood to the left atrium?
Pulmonary Veins
Name the needle like ridges of muscle lining the ventricles.
Trabeculae carneae are the small elevated ridges of muscle arranged in a web type fashion found in both the right and left ventricles.
The P wave on an electrocardiogram (ECG) represents the depolarization of cells in the:
atria
The right side of the heart receives:
deoxygenated blood from the systemic circuit.
Which heart chamber receives blood from the pulmonary veins?
left atrium
During what phase does blood flow from the ventricles into the pulmonary trunk and aorta?
ventricular ejection phase
What vessel delivers oxygenated blood to systemic capillaries for gas exchange?
Aorta
Bundle Branches
Convey(s) the impulse down the interventricular septum
AV nodes
Delay(s) occurs here while atria contract
Internodal Pathways
Link(s) between the SA node and AV node
What surface groove separates the right and left ventricles?
interventricular sulcus
The visceral pericardium is also known as the _
the epicardium, also is considered the most superficial layer of the heart wall.
According to the Frank-Starling law, a bigger preload will result in __________.
A bigger preload means increased stretch of the ventricular muscle cells and therefore, a stronger contraction.
How would a decrease in blood volume affect both stroke volume and cardiac output?
a decreased blood volume would decrease the end diastolic volume, thus lowering the stroke volume. Although this would initially lead to a decrease in the cardiac output, heart rate would increase because of increased activity of the sympathetic nervous system in an effort to maintain cardiac output.
How would an increase in the sympathetic nervous system increase stroke volume?
an increase in sympathetic nervous system activity would increase contractility (by increasing available calcium), thus increasing stroke volume. Contractility causes an increase in stroke volume by decreasing end systolic volume; it does not change end diastolic volume.
By what mechanism would an increase in venous return increase stroke volume?
an increase in venous return increases the end diastolic volume. The fibers are stretched more, resulting in an increase in the force of contraction (preload, or the Frank-Starling Mechanism).
Which of the following would increase cardiac output to the greatest extent?
increased heart rate and increased stroke volume
The apex of the heart is situated toward the:
left hip
Venous Return
the volume of blood per minute flowing into one atrium
The chambers that have just emptied when the second heart sound is heard are the __________.
ventricles; The second heart sound is caused by the closing of the semilunar valves, which happens shortly after ventricular systole is over.
What does the QRS complex represent in the ECG wave tracing?
ventricular depolarization
Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.
ventricular diastole
Blood from the systemic circuit returns to the heart via the _
The two veins that drain the majority of the systemic circuit are the superior and inferior venae cavae.
The main negative chronotropic effect on the heart is exerted by
The vagus nerve's effect on the SA node slows down heart rate.
Bicuspid (Mitral) Valve
The valve found between the left atrium and left ventricle.
Autorhythmicity is the responsibility of:
cardiac pacemaker cells.
The cusps of the atrioventricular valves attach to the papillary muscles via the __________.
chordae tendineae
Hemorrhage would lead to a __________ preload and therefore __________ cardiac output.
decreased; decreased ;Blood loss will diminish the venous return and therefore decrease the preload. A decreased preload would cause a decrease in the stroke volume and therefore a decrease in the CO.
What does the ECG wave tracing represent?
electrical activity in the hear
steps of a cardiac contractile cell action potential
The rapid depolarization phase occurs in response to action potentials of pacemaker cells. Voltage gated sodium channels open and the influx of sodium ions depolarizes the membrane to around +20 mV. During the initial repolarization phase, the membrane potential becomes slightly more negative as some potassium channels open and some potassium ions leave the cell. The depolarization is sustained at around 0 mV during the plateau phase. Potassium ions continue to leave the cell as calcium channels open and calcium ions enter the cell. Finally, sodium and calcium channels close during the repolarization phase as potassium ions continue to leave the cell. This causes the membrane potential to return to its resting state of -85 mV.
Which chamber of the heart exits into the pulmonary trunk?
The right ventricle pumps deoxygenated blood through the pulmonary semilunar valve into the pulmonary trunk to be distributed to the lungs.
What largely determines preload?
end-diastolic volume (EDV)
Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane?
gap junctions
What causes the aortic semilunar valve to close?
greater pressure in the aorta than in the left ventricle
The heart is located _________.
in the mediastinum
What characteristic differentiates cardiac muscle cells from skeletal muscle cells?
intercalated discs
Unlike skeletal muscle action potentials, cardiac muscle action potentials __________.
involve calcium voltage-gated channels
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.
Parietal pericardium
is the outer layer of the serous pericardium. It is fused to the inner surface of the fibrous pericardium.
Put the phases of the cardiac cycle in the correct order, starting after ventricular filling.
isovolumetric contraction, ventricular ejection, isovolumetric relaxation
Ventricular systole begins during the __________ phase of the cardiac cycle.
isovolumetric contraction; During the isovolumetric contraction phase, ventricular systole and atrial diastole begin and the AV valves close.
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
Afterload is described as:
the force the ventricles must overcome to eject blood into their respective arteries.
Heart Rate
the number of heart beats per minute
Which chamber pumps oxygenated blood out the aorta to the systemic circuit?
Left Ventricle
Calculate the cardiac output if heart rate (HR) is 90 beats per minute, stroke volume (SV) is 110 ml/beat, end diastolic volume (EDV) is 140 ml, and end systolic volume (ESV) is 30 ml.
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.
Which part of the intrinsic conduction system delays the impulse briefly before it moves on to the ventricles?
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
Which of the following happens immediately after the P wave?
After the atrial depolarization (P wave), the atria contract, allowing them to empty and causing the ventricles to reach their EDV.
The maximum amount of blood in the ventricles at the end of the ventricular filling phase is called __________.
At the end of atrial systole, each ventricle contains about 120 milliliters of blood, a volume known as the end-diastolic volume (EDV) because it is the ventricular volume at the end of ventricular diastole.
The anatomy of the intrinsic conduction system causes contraction of the ventricles to begin at the apex and move superiorly. Why is this important?
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.
What fibrous structure functions to anchor the atrioventricular valves in a closed position?
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.
Purkinje Fibers
Convey(s) the impulse throughout the ventricular walls
The AV valves close when __________.
During the isovolumetric contraction phase, the pressure in the ventricles rises rapidly as the ventricles begin to contract. This high pressure closes the AV valves.
AV bundles
Electrical link(s) between atria and ventricles
The first branch off the arch of the aorta is the brachiocephalic artery in both the sheep and the human.
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.
Digoxin is a positive inotropic agent derived from the foxglove family of plants. Which of the following is an effect of digoxin?
Increased contractility and SV would lead to a decrease in the ESV.
An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________.
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.
Blood returning from the lungs enters the
Left Atrium
Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat?
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.
The pulmonary circuit involves blood flow from the heart to and from the:
Lungs
Which of the following is correct about the filling of the ventricles?
Most blood flows passively into the ventricles through open AV valves.
Flow of Oxygenated Blood
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.
Contraction of the atria results from which wave of depolarization on the ECG tracing?
P wave
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 ;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 the pressure in the ventricles.
Blood that leaves the right ventricle enters the __________.
Pulmonary Trunk via pulmonary semilunar valves
Which of the following vessels carries oxygenated blood?
Pulmonary Vein
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.
Pectinate Muscles
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.
Calculate the stroke volume (SV) of a patient whose EDV is 140 milliliters and whose ESV is 60 milliliters.
SV = EDV - ESV; 80 milliliters
SA Node
Sets the pace for the entire heart
The vessels that deliver oxygen to the tissues of the body are part of the _
Systemic Circuit
Blood on the right never mixes with blood on the left, once the heart is fully developed.
TRUE; 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.
What heart chamber pushes blood through the aortic semilunar valve?
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.
The aortic valve opens at _____.
The aortic valve opens when the pressure in the ventricle rises above aortic pressure.
Apex
The apex of the heart is the inferior tip of the heart and points toward the left side.
Tricuspid Valve
The atrioventricular valve located on the right side of the heart. It separates the right atrium from the right ventricle.
Identify the ear like flaps that are attached to the top chambers of the heart.
The auricles are flap like extensions of the atria that are observed on the external surface of the heart.
How will the cardiac output change if you double the heart rate but reduce the stroke volume by one-half?
The cardiac output will remain the same, because CO = HR × SV = 2HR × SV/2.
What is the function of the coronary circulation?
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.
Innermost lining of the heart
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.
The cardiac chamber with the thickest wall is the __
The left ventricle has the thickest wall because it has to generate the most pressure.
Most Muscular Chamber
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.
What is the ligamentum arteriosum?
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 heart is actually (one, two, or three) pumps?
Two; the right side of the heart pumps to/from the lungs (pulmonary circuit) and the left side of the heart pumps to/from the rest of the body (the systemic circuit).
Both the left and right atria receive blood from:
Veins
Which hormone decreases cardiac output by decreasing blood volume and preload?
atrial natriuretic peptide
The heart is situated in the middle of the thoracic cavity in a region known as the:
mediastinum
Repolarization of an autorhythmic cell is due to the opening of which 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.
The aortic valve closes when __________.
pressure in the left ventricle falls below aortic pressure
What valve prevents the backflow of blood from the right ventricle into the right atrium?
right atrioventricular valve (tricuspid valve)
Which chamber receives blood from the superior and inferior vena cavae?
right atrium
Which heart chamber pumps unoxygenated blood out the pulmonary trunk?
right ventricle
What normally serves as the pacemaker of the entire heart?
sinoatrial (SA) node
What two values are needed in order to calculate cardiac output (CO) for a ventricle?
stroke volume (SV) and heart rate (HR)
Which part of the conduction system initiates the depolarizing impulse, which spreads throughout the heart?
the SA Node spontaneously depolarizes, causing the wave of depolarization that spreads through the rest of the conduction system and heart.
Pulmonary valve
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.
End-Systolic Volume (ESV)
the volume of blood in one ventricle after contraction
End-diastolic Volume (EDV)
the volume of blood in one ventricle before contraction
Stroke Volume (SV)
the volume of blood per heart beat pumped out by one ventricle
Cardiac Output (CO)
the volume of blood per minute pumped out by one ventricle
Right coronary artery
travels inferiorly and laterally along the right atrioventricular sulcus, where it gives off several branches that supply the right atrium and ventricle.
When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane?
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).
