Atrial systole begins
immediately before the P wave
During the P wave.
during the Q wave
during the S-T segment
immediately after the T wave
The Correct Answer is B
A. immediately before the P wave: The period before the P wave represents the end of the previous cardiac cycle or the quiescent period of diastole. During this time, the atria are filling but have not yet received the signal to contract. Electrical activity must be recorded before any mechanical action can take place.
B. During the P wave: The P wave on an electrocardiogram represents atrial depolarization, which is the electrical signal for the atria to contract. Atrial systole, the mechanical contraction, begins shortly after the start of this wave as the electrical signal spreads through the myocardium. This coordination ensures blood is pumped into the ventricles.
C. during the Q wave: The Q wave is the initial downward deflection of the QRS complex, signaling the start of ventricular depolarization. By this stage, atrial systole is concluding and the atrioventricular valves are beginning to close. The focus of the cardiac cycle has shifted from the atria to the ventricles.
D. during the S-T segment: This segment represents the plateau phase of ventricular action potentials, during which the ventricles are actively contracting. Atrial tissue is undergoing repolarization and is in a state of diastole during this period. The atria are filling with blood while the ventricles are in systole.
E. immediately after the T wave: The T wave represents ventricular repolarization, and the period immediately following it is part of early diastole for the entire heart. During this phase, both the atria and ventricles are relaxed and filling passively. There is no systolic activity occurring in any chamber at this time.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. C6H12O6 + 6 H2O -> 6 CO2 + 6 O2: This equation incorrectly lists water as a reactant instead of oxygen. Aerobic catabolism requires molecular oxygen as the terminal electron acceptor in the electron transport chain. Metabolism of glucose without oxygen input prevents oxidative phosphorylation.
B. C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O: Hexose oxidation involves the complete breakdown of glucose in the presence of oxygen. This metabolic pathway yields carbon dioxide and water as primary byproducts while capturing chemical energy. It accurately reflects the stoichiometric balance of aerobic cellular respiration.
C. C6H12O6 + 6 CO2 -> 6 O2 + 6 H2O: Carbon dioxide functions as a metabolic waste product rather than a reactant in human cellular respiration. Glucose does not react with carbon dioxide to produce oxygen during heterotrophic metabolism. This chemical arrangement reverses the standard physiological gas exchange.
D. CO2 + 6 H2O -> C6H12O6 + 6 O2: This formula represents the endergonic process of photosynthesis occurring in photoautotrophic organisms. It describes the fixation of inorganic carbon into organic compounds using light energy. Eukaryotic animal cells lack the chloroplasts necessary to drive this specific anabolic reaction.
E. 6 O2 + 6 H2O -> C6H12O6 + 6 CO2: The combination of oxygen and water does not spontaneously synthesize glucose molecules in biological systems. This equation fails to account for the carbon source required for carbohydrate formation. It violates the fundamental thermodynamic principles governing respiratory substrate breakdown and energy release.
Correct Answer is E
Explanation
A. No: Red blood cells with no surface antigens are characteristic of blood type O. Because blood type AB is defined by the codominant expression of specific glycoproteins, the absence of antigens would contradict this blood group's classification. Type O individuals lack both A and B antigens on their erythrocyte membranes.
B. anti-A and anti-B: These are antibodies found in the plasma, not antigens on the red blood cell surface. Type AB individuals lack these antibodies in their plasma to prevent autodestruction of their own cells. Anti-A and anti-B antibodies are typical of type O plasma.
C. anti-A: This antibody is found in the plasma of individuals with type B blood. It is not an antigen found on the surface of AB red blood cells. Type AB blood contains the A antigen itself, so the presence of an anti-A antibody would lead to lethal agglutination.
D. anti-B: This antibody is present in the plasma of type A individuals and targets foreign B antigens. A person with type AB blood cannot possess anti-B antibodies because their cells express the B antigen. The presence of this antibody would cause a life-threatening immune reaction against their own erythrocytes.
E. A and B: Type AB blood is characterized by the presence of both A and B antigens on the surface of the red blood cells. Because both antigens are present, these individuals do not produce anti-A or anti-B antibodies in their plasma. This antigen profile makes them universal recipients of red blood cells.
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