Chapter 19 | The Cardiovascular System: The Heart
Which primitive area of the heart will give rise to the right ventricle? a. bulbus cordis b. primitive ventricle c. sinus venosus d. truncus arteriosus
A. Bulbus cordis
What happens to preload when there is venous constriction in the veins? a. It increases. b. It decreases. c. It remains constant. d. There is no way to predict.
A. It increases
The cardiovascular centers are located in which area of the brain? a. medulla oblongata b. pons c. mesencephalon (midbrain) d. cerebrum
A. Medulla oblongata
Which valve separates the left atrium from the left ventricle? a. mitral b. tricuspid c. pulmonary d. aortic
A. Mitral
Which of the following lists the valves in the order through which the blood flows from the vena cava through the heart? a. tricuspid, pulmonary semilunar, bicuspid, aortic semilunar b. mitral, pulmonary semilunar, bicuspid, aortic semilunar c. aortic semilunar, pulmonary semilunar, tricuspid, bicuspid d. bicuspid, aortic semilunar, tricuspid, pulmonary semilunar
A. tricuspid, pulmonary semilunar, bicuspid, aortic semilunar
Describe how the major pumping chambers, the ventricles, form within the developing heart.
After fusion of the two endocardial tubes into the single primitive heart, five regions quickly become visible. From the head, these are the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus. Contractions propel the blood from the sinus venosus to the truncus arteriosus. About day 23, the heart begins to form an S-shaped structure within the pericardium. The bulbus cordis develops into the right ventricle, whereas the primitive ventricle becomes the left ventricle. The interventricular septum separating these begins to form about day 28. The atrioventricular valves form between weeks five to eight. At this point, the heart ventricles resemble the adult structure.
Why is afterload important in cardiac function?
Afterload represents the resistance within the arteries to the flow of blood ejected from the ventricles. If uncompensated, if afterload increases, flow will decrease. In order for the heart to maintain adequate flow to overcome increasing afterload, it must pump more forcefully. This is one of the negative consequences of high blood pressure or hypertension.
The force the heart must overcome to pump blood is known as ________. a. preload b. afterload c. cardiac output d. stroke volume
B. Afterload
Most blood enters the ventricle during ________. a. atrial systole b. atrial diastole c. ventricular systole d. isovolumic contraction
B. Atrial diastole
The ________ layer secretes chemicals that help to regulate ionic environments and strength of contraction and serve as powerful vasoconstrictors. a. pericardial sac b. endocardium c. myocardium d. epicardium
B. Endocranium
In a healthy young adult, what happens to cardiac output when heart rate increases above 160 bpm? a. It increases. b. It decreases. c. It remains constant. d. There is no way to predict.
B. It decreases.
The myocardium would be the thickest in the ________. a. left atrium b. left ventricle c. right atrium d. right ventricle
B. Left Ventricle
Ventricular relaxation immediately follows ________. a. atrial depolarization b. ventricular repolarization c. ventricular depolarization d. atrial repolarization
B. Ventricular repolarization
In which septum is it normal to find openings in the adult? a. interatrial septum b. interventricular septum c. atrioventricular septum d. all of the above
C. Atrioventricular septum
Which of the following is a positive inotrope? a. Na+ b. K+ c. Ca2+ d. both Na+ and K+
C. Ca2+
The first heart sound represents which portion of the cardiac cycle? a. atrial systole b. ventricular systole c. closing of the atrioventricular valves d. closing of the semilunar valves
C. Closing of the atrioventricular valves
Of the three germ layers that give rise to all adult tissues and organs, which gives rise to the heart? a. ectoderm b. endoderm c. mesoderm d. placenta
C. Mesoderm
Which of the following is unique to cardiac muscle cells? a. Only cardiac muscle contains a sarcoplasmic reticulum. b. Only cardiac muscle has gap junctions. c. Only cardiac muscle is capable of autorhythmicity d. Only cardiac muscle has a high concentration of mitochondria.
C. Only cardiac muscle is capable of audtorhythmicity
Which chamber initially receives blood from the systemic circuit? a. left atrium b. left ventricle c. right atrium d. right ventricle
C. Right Atrium
The influx of which ion accounts for the plateau phase? a. sodium b. potassium c. chloride d. calcium
D. Calcium
The two tubes that eventually fuse to form the heart are referred to as the ________. a. primitive heart tubes b. endocardial tubes c. cardiogenic region d. cardiogenic tubes
D. Cardiogenic tubes
Which of the following is not important in preventing backflow of blood? a. chordae tendineae b. papillary muscles c. AV valves d. endocardium
D. Endocardium
The earliest organ to form and begin function within the developing human is the ________. a. brain b. stomach c. lungs d. heart
D. Heart
The cardiac cycle consists of a distinct relaxation and contraction phase. Which term is typically used to refer ventricular contraction while no blood is being ejected? a. systole b. diastole c. quiescent d. isovolumic contraction
D. Isovolumic contraction
Which portion of the ECG corresponds to repolarization of the atria? a. P wave b. QRS complex c. T wave d. none of the above: atrial repolarization is masked by ventricular depolarization
D. None of the above: atrial repolarization is masked by ventricular depolarization
Which component of the heart conduction system would have the slowest rate of firing? a. atrioventricular node b. atrioventricular bundle c. bundle branches d. Purkinje fibers
D. Purkinje fibers
The pulmonary trunk and aorta are derived from which primitive heart structure? a. bulbus cordis b. primitive ventricle c. sinus venosus d. truncus arteriosus
D. Truncus arteriosus
How do gap junctions and intercalated disks aid contraction of the heart?
Gap junctions within the intercalated disks allow impulses to spread from one cardiac muscle cell to another, allowing sodium, potassium, and calcium ions to flow between adjacent cells, propagating the action potential, and ensuring coordinated contractions.
Why does increasing EDV increase contractility?
Increasing EDV increases the sarcomeres' lengths within the cardiac muscle cells, allowing more cross bridge formation between the myosin and actin and providing for a more powerful contraction. This relationship is described in the Frank-Starling mechanism.
How does the delay of the impulse at the atrioventricular node contribute to cardiac function?
It ensures sufficient time for the atrial muscle to contract and pump blood into the ventricles prior to the impulse being conducted into the lower chambers.
Why is the plateau phase so critical to cardiac muscle function?
It prevents additional impulses from spreading through the heart prematurely, thereby allowing the muscle sufficient time to contract and pump blood effectively.
Describe one cardiac cycle, beginning with both atria and ventricles relaxed.
The cardiac cycle comprises a complete relaxation and contraction of both the atria and ventricles, and lasts approximately 0.8 seconds. Beginning with all chambers in diastole, blood flows passively from the veins into the atria and past the atrioventricular valves into the ventricles. The atria begin to contract following depolarization of the atria and pump blood into the ventricles. The ventricles begin to contract, raising pressure within the ventricles. When ventricular pressure rises above the pressure in the two major arteries, blood pushes open the two semilunar valves and moves into the pulmonary trunk and aorta in the ventricular ejection phase. Following ventricular repolarization, the ventricles begin to relax, and pressure within the ventricles drops. When the pressure falls below that of the atria, blood moves from the atria into the ventricles, opening the atrioventricular valves and marking one complete heart cycle.
Why is it so important for the human heart to develop early and begin functioning within the developing embryo?
The human embryo is rapidly growing and has great demands for nutrients and oxygen, while producing waste products including carbon dioxide. All of these materials must be received from or delivered to the mother for processing. Without an efficient early circulatory system, this would be impossible.
Why is the pressure in the pulmonary circulation lower than in the systemic circulation?
The pulmonary circuit consists of blood flowing to and from the lungs, whereas the systemic circuit carries blood to and from the entire body. The systemic circuit is far more extensive, consisting of far more vessels and offers much greater resistance to the flow of blood, so the heart must generate a higher pressure to overcome this resistance. This can be seen in the thickness of the myocardium in the ventricles.
Describe how the valves keep the blood moving in one direction
When the ventricles contract and pressure begins to rise in the ventricles, there is an initial tendency for blood to flow back (regurgitate) to the atria. However, the papillary muscles also contract, placing tension on the chordae tendineae and holding the atrioventricular valves (tricuspid and mitral) in place to prevent the valves from prolapsing and being forced back into the atria. The semilunar valves (pulmonary and aortic) lack chordae tendineae and papillary muscles, but do not face the same pressure gradients as do the atrioventricular valves. As the ventricles relax and pressure drops within the ventricles, there is a tendency for the blood to flow backward. However, the valves, consisting of reinforced endothelium and connective tissue, fill with blood and seal off the opening preventing the return of blood.
Why do the cardiac muscle cells demonstrate audtorhythmicity?
Without a true resting potential, there is a slow influx of sodium ions through slow channels that produces a prepotential that gradually reaches threshold.
