Multiple ChoiceWhich feature of cardiac tissue allows for the rapid spread of action potentials through the heart?607views8rank
Multiple ChoiceThe intrinsic conduction system ensures a coordinated and efficient heartbeat. If the sinoatrial (SA) node malfunctions, which part of the heart’s conduction system is most likely to take over as the pacemaker?387views9rank
Multiple ChoiceWhich answer choice below correctly matches the cardiac conduction structure to where it’s found in the heart?420views11rank
Multiple ChoiceThe AV node has fewer gap junctions than the SA node, leading to slower conduction. How does this slower conduction help the heart function?344views12rank
Multiple ChoiceWhat is the primary function of the pacemaker cells in the SA node in the heart?427views6rank
Multiple ChoiceWhich structure or structures are most directly responsible for allowing contraction of the ventricles to begin at the apex of the heart rather than in the septum closer to the AV node?340views7rank
Multiple ChoiceWhich center in the medulla oblongata controls the sympathetic neurons that stimulate the heart?305views2rank
Multiple ChoiceWhich statement best describes a difference between how the sympathetic and parasympathetic nervous system affects the heart?309views11rank
Multiple ChoiceWhich of the following is a difference between cardiac muscle and skeletal muscle?4307views1rank
Multiple ChoiceThe contractile cardiac muscle fibers of the myocardium behave as a single, coordinated unit called a __________.1350views1rank
Multiple ChoiceWhich of the following factors gives the myocardium its high resistance to fatigue?1178views
Textbook QuestionThe autonomic division of the nervous system directs (a) voluntary motor activity, (b) conscious control of skeletal muscles, (c) unconscious control of skeletal muscles, (d) processes that maintain homeostasis, (e) sensory input from the skin.247views
Textbook QuestionWhich four ganglia serve as origins for postganglionic fibers involved in control of visceral structures in the head?205views
Textbook QuestionDescribe the pericardium and distinguish between the fibrous and the serous pericardia relative to histological structure and location.354views
Textbook QuestionHow do pacemaker cardiac muscle cells differ from contractile cardiac muscle cells? What is autorhythmicity?193views
Multiple ChoiceChoose the correct sequence of electrical current flow through the heart wall.1507views1rank
Multiple ChoiceThe __________ nerve carries parasympathetic fibers to the sinoatrial (SA) node.816views
Textbook Questiona. Name the elements of the intrinsic conduction system of the heart in order, beginning with the pacemaker. b. What is the important function of this conduction system?293views
Textbook QuestionThe activity of the heart depends on intrinsic properties of cardiac muscle and on neural factors. Thus, a. vagus nerve stimulation of the heart reduces heart rate, b. sympathetic nerve stimulation of the heart decreases time available for ventricular filling, c. sympathetic stimulation of the heart increases its force of contraction, d. all of the above.278views
Textbook QuestionThe cells of the conducting system differ from the contractile cells of the heart in that (a) conducting cells are larger and contain more myofibrils, (b) contractile cells exhibit pacemaker potentials, (c) contractile cells do not normally exhibit autorhythmicity, (d) both a and b are correct.200views
Textbook QuestionThe autonomic centers for cardiac function are located in (a) the myocardial tissue of the heart, (b) the cardiac centers of the medulla oblongata, (c) the cerebral cortex, (d) all of these structures.199views
Textbook QuestionTrace the normal pathway of an electrical impulse through the conducting system of the heart.186views
Textbook QuestionWhat effect does sympathetic stimulation have on the heart? What effect does parasympathetic stimulation have on the heart?179views
Textbook QuestionWhat role do the chordae tendineae and papillary muscles play in the normal function of the AV valves?178views
Textbook QuestionIf the papillary muscles fail to contract, (a) the ventricles will not pump blood, (b) the atria will not pump blood, (c) the semilunar valves will not open, (d) the AV valves will not close properly, (e) none of these happen.208views
Textbook QuestionThe refractory period of cardiac muscle is much longer than that of skeletal muscle. Why is this a desirable functional property?293views
Textbook QuestionAfter Randy was diagnosed with stomach cancer, nearly all of his stomach had to be removed. Postoperative treatment included regular injections of vitamin B12. Why was this vitamin prescribed, and why were injections specified?140views
Textbook QuestionHow does the heart's ability to contract differ from that of other muscles of the body?213views
Textbook QuestionIdentify the structures in the following diagram of a sectional view of the heart. a. ___ b. ___ c. ___ d. ___ e. ___ f. ___ g. ___ h. ___ i. ___ j. ___ k. ___ l. ___ m. ___153views
Textbook QuestionThe serous membrane covering the outer surface of the heart is the (a) parietal layer of the serous pericardium, (b) endocardium, (c) myocardium, (d) visceral layer of the serous pericardium.183views1rank
Textbook QuestionThe simple squamous epithelium covering the heart valves is the (a) epicardium, (b) endocardium, (c) myocardium, (d) endothelium.151views
Textbook QuestionCardiac muscle cells are joined by structures called:a. T-tubules.b. tight junctions.c. sarcoplasmic reticulum.d. intercalated discs.130views
Textbook QuestionThe portion of the intrinsic conduction system located in the superior interventricular septum is the a. AV node, b. SA node, c. AV bundle, d. subendocardial conducting network.302views
Textbook QuestionMultiple Choice More than one choice may apply. Using the figure, identify the most external part of the pericardium. a. b. c. d. e.133views
Textbook QuestionDraw a diagram of the heart showing the three layers composing its wall and its four chambers. Label each. Show where the AV and semilunar valves are, and name them. Show and label all blood vessels entering and leaving the heart chambers.232views
Textbook QuestionMark the following statements as true or false. If a statement is false, correct it to make a true statement.e. The heart plays a role in the regulation of blood pressure and secretes the hormone atrial natriuretic peptide.138views
Textbook QuestionThe ______is the primary pacemaker of the heart.a. atrioventricular nodeb. sinoatrial nodec. Purkinje fiber systemd. atrioventricular bundle152views
Textbook QuestionThe AV node delay:a. allows the atria and ventricles to depolarize and contract as a unit.b. allows the two ventricles to depolarize and contract separately.c. allows the atria and ventricles to depolarize and contract separately.d. speeds up the impulse transmission from the atria to the ventricles.134views
Textbook QuestionA newer drug, Ivabradine, lowers the heart rate by blocking the nonselective HCN cation channels. Why would this action decrease the heart rate? Would this drug have an effect on pacemaker cells, contractile cells, or both? Explain.144views
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