Identify the structure pointed by the line
chordae tendinae
Papillary Muscles
Septal leaflet
Pulmonary vein
The Correct Answer is A
A. Chordae tendinae: The structure pointed to by the line is the chordae tendineae. The chordae tendineae are strong, fibrous collagen cords that connect the atrioventricular valve leaflets (mitral and tricuspid valves) to the papillary muscles within the ventricles. They prevent valve prolapse during ventricular systole. When the ventricles contract, papillary muscles also contract, maintaining tension on the chordae tendineae to keep the valves closed and prevent backflow into the atria.
B. Papillary Muscles: Papillary muscles are cone-shaped projections from the ventricular walls that anchor chordae tendineae. During ventricular contraction, they prevent valve prolapse by maintaining tension on valve leaflets, ensuring unidirectional blood flow
C. Septal leaflet: The septal leaflet is part of the tricuspid valve attached to the interventricular septum. Chordae tendineae connect it to papillary muscles, stabilizing the valve during systole and preventing backflow into the right atrium.
D: Pulmonary vein: Pulmonary veins are vessels transporting oxygenated blood from the lungs to the left atrium. They are not directly connected to chordae tendineae but are adjacent to atrial structures influencing left atrial filling and valve dynamics.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. It directly causes the initial calcium release from the sarcoplasmic reticulum: Calcium release from the sarcoplasmic reticulum is triggered by depolarization of the T-tubules and activation of ryanodine receptors, not directly by ATP. ATP provides energy for the mechanical steps of contraction but does not initiate calcium release.
B. It expands the H band by pushing thick filaments apart: The H band changes length passively as thin filaments slide over thick filaments during contraction. ATP does not mechanically push filaments apart; instead, it energizes myosin heads for cross-bridge cycling.
C. It prevents the troponin-tropomyosin complex from exposing binding sites: The troponin-tropomyosin complex blocks actin binding sites in the absence of calcium. ATP does not regulate this exposure; calcium binding to troponin shifts tropomyosin to allow myosin attachment.
D. It binds to myosin heads, allowing them to detach from actin: ATP binds to the myosin head after the power stroke, causing detachment from actin and breaking the actomyosin cross-bridge. ATP hydrolysis then re-cocks the myosin head, storing energy for the next contraction cycle. This is essential for continuous muscle contraction and relaxation in both skeletal and cardiac muscle.
Correct Answer is C
Explanation
Correct answer: B.
B: Ventricular depolarization is the electrical activation of the ventricles that triggers ventricular contraction. It occurs after the impulse travels from the sinoatrial . On an electrocardiogram (ECG), ventricular depolarization is represented by the QRS complex, labelled as B in the diagram.
D: artrial depolarization - Atrial depolarization initiates atrial contraction, driven by impulses from the SA node. This electrical activity spreads across atrial myocardium, generating the P wave on the ECG and enabling ventricular filling.
E: ventricular repolarization - Ventricular repolarization restores the ventricles to their resting state after contraction. Represented by the T wave, it prepares the heart for the next depolarization, ensuring rhythmic cardiac cycles and effective pumping.
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