Ch. 19 The Heart Flashcards
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.
Explanation: The endocardium is the inner lining of the heart chambers, not a structural component involved in valve function. It does not prevent backflow.
Incorrect Answers:
- A) Chordae tendineae: Anchor the valve leaflets and prevent prolapse during contraction.
- B) Papillary muscles: Contract with the ventricles to tighten the chordae tendineae.
- C) AV valves: Directly prevent backflow from ventricles into atria.
Which valve separates the left atrium from the left ventricle?
A) Mitral.
B) Tricuspid.
C) Pulmonary.
D) Aortic.
A) Mitral.
Explanation: The mitral valve (also called bicuspid valve) separates the left atrium and left ventricle.
Incorrect Answers:
- B) Tricuspid: Between the right atrium and right ventricle.
- C) Pulmonary: Between the right ventricle and pulmonary trunk.
- D) Aortic: Between the left ventricle and aorta.
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.
Explanation: This matches the correct flow:
Right atrium → Tricuspid → Right ventricle → Pulmonary semilunar → Lungs → Left atrium → Bicuspid (Mitral) → Left ventricle → Aortic semilunar → Body
Incorrect Answers:
- B, C, D: Other sequences mix up or repeat valves in the wrong order.
Which chamber initially receives blood from the systemic circuit?
A) Left atrium.
B) Left ventricle.
C) Right atrium.
D) Right ventricle.
C) Right atrium.
Explanation: Deoxygenated blood from the systemic circuit enters the heart via the right atrium through the superior and inferior vena cava.
Incorrect Answers:
- A) Left atrium: Part of the pulmonary return.
- B) Left ventricle: Receives blood from left atrium.
- D) Right ventricle: Pumps blood to lungs, but does not receive systemic blood directly.
The (BLANK) 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) Endocardium.
Explanation: The endocardium (inner lining of the heart chambers and valves) secretes regulatory factors, such as endothelin-1, which is a powerful vasoconstrictor.
The myocardium would be the thickest in the (BLANK).
A) Left atrium.
B) Left ventricle.
C) Right atrium.
D) Right ventricle.
B) Left ventricle.
Explanation: The left ventricle pumps blood to the entire body and requires more force, hence it has the thickest myocardium.
Incorrect Answers:
- A) Left atrium: Thin wall.
- C) Right atrium: Thin wall.
- D) Right ventricle: Pumps only to the lungs—less pressure.
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.
Explanation: The atrioventricular septum contains the atrioventricular (AV) openings, which are normal and necessary in the adult heart. These openings are occupied by the tricuspid (right side) and bicuspid/mitral (left side) valves, allowing blood flow from the atria to the ventricles.
Incorrect Answers:
- A) Interatrial septum: Should be closed in adults; a patent foramen ovale is abnormal.
- B) Interventricular septum: Should not have an opening.
- D) All of the above: Incorrect because only the AV septum has normal openings.
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 autorhythmicity.
Explanation: Cardiac muscle can spontaneously depolarize due to pacemaker cells (SA node), a property called autorhythmicity.
Incorrect Answers:
- A) Skeletal muscle also has a sarcoplasmic reticulum.
- B) Smooth muscle also uses gap junctions.
- D) Skeletal muscle, especially red fibers, also has many mitochondria.
The influx of which ion accounts for the plateau phase?
A) Sodium.
B) Potassium.
C) Chloride.
D) Calcium.
D) Calcium.
Explanation: The plateau phase in cardiac contractile cells is sustained by calcium ion influx, balancing potassium efflux.
Incorrect Answers:
- A) Sodium: Responsible for depolarization, not plateau.
- B) Potassium: Involved in repolarization.
- C) Chloride: Not a major player in the action potential plateau.
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.
Correct Answer: D) None of the above: Atrial repolarization is masked by ventricular depolarization.
Explanation: Atrial repolarization does occur but is not visible on the ECG because it is obscured by the much larger electrical signal of the QRS complex.
Incorrect Answers:
- A) P Wave: Atrial depolarization, not repolarization.
- B) QRS Complex: Ventricular depolarization.
- C) T Wave: Ventricular repolarization.
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.
Explanation: Purkinje fibers have the slowest intrinsic firing rate (~20–40 bpm), acting as a last-resort pacemaker if higher centers fail.
Incorrect Answers:
- A) AV Node: Fires at 40–60 bpm.
- B) AV Bundle: Conducts impulses, not a primary pacemaker.
- C) Bundle Branches: Also conduct impulses, not pacemakers.
The cardiac cycle consists of a distinct relaxation and contraction phase. Which term is typically used to refer to ventricular contraction while no blood is being ejected?
A) Systole.
B) Diastole.
C) Quiescent.
D) Isovolumic Contraction.
D) Isovolumic Contraction.
Explanation: Isovolumic contraction is the brief phase during ventricular systole where ventricular pressure rises but no blood is ejected because all valves are closed.
Incorrect Answers:
- A) Systole: General term for contraction—not specific.
- B) Diastole: Relaxation phase.
- C) Quiescent: Refers to rest between cycles.
Most blood enters the ventricle during (BLANK).
A) Atrial Systole.
B) Atrial Diastole.
C) Ventricular Systole.
D) Isovolumic Contraction.
B) Atrial Diastole.
Explanation: Most ventricular filling is passive, occurring during atrial diastole when AV valves are open and blood flows from atria to ventricles.
Incorrect Answers:
- A) Atrial Systole: Contributes only 20–30% of filling.
- C) Ventricular Systole: Occurs after ventricles are already full.
- D) Isovolumic Contraction: Happens after filling is complete.
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.
Explanation: The first heart sound (“lub”) is caused by closure of the AV valves as ventricular systole begins.
Incorrect Answers:
- A) Atrial Systole: Happens earlier.
- B) Ventricular Systole: Happens simultaneously but isn’t the sound source.
- D) Semilunar Valve Closure: Produces the second heart sound (“dub”).
Ventricular relaxation immediately follows (BLANK).
A) Atrial Depolarization.
B) Ventricular Repolarization.
C) Ventricular Depolarization.
D) Atrial Repolarization.
B) Ventricular Repolarization.
Explanation: Relaxation of ventricles begins after they repolarize, which is visible on the ECG as the T wave.
Incorrect Answers:
- A) Atrial Depolarization: Leads to atrial contraction, unrelated to ventricular relaxation.
- C) Ventricular Depolarization: Triggers contraction, not relaxation.
- D) Atrial Repolarization: Hidden in QRS complex and unrelated to ventricular relaxation.
The force the heart must overcome to pump blood is known as (BLANK).
A) Preload.
B) Afterload.
C) Cardiac Output.
D) Stroke Volume.
B) Afterload.
Explanation: Afterload is the resistance the ventricles must overcome to eject blood (e.g., arterial pressure).
Incorrect Answers:
- A) Preload: Degree of stretch before contraction.
- C) Cardiac Output: Volume pumped per minute.
- D) Stroke Volume: Volume per beat—not a pressure or resistance measure.
The cardiovascular centers are located in which area of the brain?
A) Medulla Oblongata.
B) Pons.
C) Mesencephalon (Midbrain).
D) Cerebrum.
A) Medulla Oblongata.
Explanation: The medulla oblongata houses the cardioacceleratory and cardioinhibitory centers that regulate heart rate.
Incorrect Answers:
- B) Pons: Involved in respiration.
- C) Mesencephalon: Visual/auditory reflexes.
- D) Cerebrum: Controls voluntary and cognitive functions.
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.
Explanation: Above ~160 bpm, ventricular filling time decreases so much that stroke volume drops—reducing cardiac output.
Incorrect Answers:
- A) It Increases: True only at lower heart rates.
- C) It Remains Constant: Stroke volume prevents constancy.
- D) No Way To Predict: The outcome is predictable physiologically.
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.
Explanation: Venous constriction pushes more blood back to the heart, increasing preload (i.e., end-diastolic volume).
Incorrect Answers:
- B) It Decreases: Opposite effect.
- C) Constant: It increases, not constant.
- D) No Way: This is a well-known physiological outcome.
Which of the following is a positive inotrope?
A) Na⁺
B) K⁺
C) Ca²⁺
D) Both Na⁺ and K⁺
C) Ca²⁺
Explanation: Calcium ions (Ca²⁺) increase the strength of cardiac muscle contraction, making them positive inotropes.
Incorrect Answers:
- A) Na⁺: Affects depolarization, not directly inotropy.
- B) K⁺: High extracellular K⁺ decreases contractility.
- D) Na⁺ and K⁺: Together do not act as positive inotropes.
The earliest organ to form and begin function within the developing human is the (BLANK).
A) Brain.
B) Stomach.
C) Lungs.
D) Heart.
D) Heart.
Explanation: The heart is the first functional organ to develop, starting to beat around day 22 post-fertilization.
Incorrect Answers:
- A) Brain: Develops early, but begins functioning later.
- B) Stomach: Forms later and functions postnatally.
- C) Lungs: Also form and become functional after birth.
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.
Explanation: The heart develops from mesoderm, specifically the cardiogenic region of the mesoderm layer.
Incorrect Answers:
- A) Ectoderm: Forms the nervous system and skin.
- B) Endoderm: Forms internal linings such as the GI tract.
- D) Placenta: Not one of the embryonic germ layers.
The two tubes that eventually fuse to form the heart are referred to as the (BLANK).
A) Primitive Heart Tubes.
B) Endocardial Tubes.
C) Cardiogenic Region.
D) Cardiogenic Tubes.
B) Endocardial Tubes.
Explanation: The endocardial tubes are paired structures that fuse around day 21–22 to form the primitive heart tube.
Incorrect Answers:
- A) Primitive Heart Tubes: Not the standard embryological term.
- C) Cardiogenic Region: Refers to the area in the mesoderm where the heart forms.
- D) Cardiogenic Tubes: Not a recognized term in embryology.
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.
Explanation: The bulbus cordis becomes part of the right ventricle and also contributes to outflow tracts.
Incorrect Answers:
- B) Primitive Ventricle: Forms the left ventricle.
- C) Sinus Venosus: Contributes to the right atrium and SA node.
- D) Truncus Arteriosus: Forms the aorta and pulmonary trunk.
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.
Explanation: The truncus arteriosus splits to form the aorta and pulmonary trunk, establishing the major arterial outflow paths.
Incorrect Answers:
- A) Bulbus Cordis: Contributes to outflow tracts and ventricles but not the vessels.
- B) Primitive Ventricle: Forms the left ventricle.
- C) Sinus Venosus: Develops into parts of the atria, not outflow vessels.
