Which sequence does the electrical stimulus of the cardiac cycle follow?

SA node AV node → bundle branches → purkinje fibers

AV node SA node → purkinje fibers → bundle branches

Bundle branches → AV node → SA node → purkinje fibers

AV node → SA node → bundle branches→ purkinje fibers

Answer and Explanation

The Correct Answer is A

A. SA node → AV node → bundle branches → Purkinje fibers: The sinoatrial (SA) node, located in the right atrium, is the heart's natural pacemaker, initiating electrical impulses. These impulses travel to the atrioventricular (AV) node, where conduction slows to allow ventricular filling. The signal then moves through the bundle of His, dividing into the right and left bundle branches, and finally reaches the Purkinje fibers, which stimulate ventricular contraction. This is the correct sequence.

B. AV node → SA node → Purkinje fibers → bundle branches: The AV node does not initiate the electrical impulse under normal conditions; it receives the impulse from the SA node. The Purkinje fibers are the final part of the conduction pathway, not an intermediate step before the bundle branches.

C. Bundle branches → AV node → SA node → Purkinje fibers: Electrical conduction does not begin at the bundle branches. The SA node initiates the impulse, and the AV node delays transmission before passing the impulse to the ventricles via the bundle branches and Purkinje fibers.

D. AV node → SA node → bundle branches → Purkinje fibers: The SA node, not the AV node, initiates the cardiac cycle. The AV node functions as a relay station that briefly delays the impulse before it proceeds to the bundle branches and Purkinje fibers.

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Free Nursing Study Resources

Correct Answer is D

Explanation

A. Perform a complete cardiac assessment because these signs are probably indicative of early heart failure: While congenital heart disease can present with respiratory distress, the presence of nasal flaring and retractions in an infant with a prolonged upper respiratory infection strongly suggests respiratory distress due to a pulmonary cause, such as bronchiolitis or pneumonia. A cardiac assessment may be necessary, but immediate intervention for respiratory distress is the priority.

B. Have the mother attempt to bottle feed the infant: Infants in respiratory distress often struggle with feeding due to increased work of breathing. Attempting to bottle feed could further compromise oxygenation and increase fatigue, worsening the child's condition.

C. Assure the mother that these signs are normal symptoms of a cold: Nasal flaring and intercostal retractions are signs of increased respiratory effort, indicating significant respiratory distress rather than a mild viral upper respiratory infection. These findings warrant prompt medical evaluation.

D. Recognize that these are serious signs, and contact the physician: Nasal flaring, sternal retractions, and intercostal retractions indicate significant respiratory distress, which can rapidly progress to respiratory failure in infants. Immediate assessment and intervention by a healthcare provider are necessary to ensure appropriate treatment and monitoring.

A. Bronchophony B. Wheezes C. Bronchial sounds D. Whispered pectoriloquy

Correct Answer is B

Explanation

A. Bronchophony: Bronchophony is an increase in clarity of spoken sounds when auscultating the lungs, typically indicating lung consolidation or pathology. It is not an adventitious sound associated with airflow through narrowed bronchioles.

B. Wheezes: Wheezes are high-pitched, musical sounds that occur when air passes through narrowed or obstructed airways, such as in cases of severe asthma. They are often heard during expiration and indicate bronchoconstriction or inflammation in the airways. This is the correct answer for the scenario presented.

C. Bronchial sounds: Bronchial sounds are normal breath sounds typically heard over the trachea and major bronchi. They are characterized by a higher pitch and a hollow quality. They are not classified as adventitious sounds and are not indicative of asthma.

D. Whispered pectoriloquy: Whispered pectoriloquy is a clinical finding where whispered sounds are heard more clearly over areas of lung consolidation. Like bronchophony, it does not represent an adventitious sound caused by airflow through narrowed bronchioles and is more indicative of lung pathology.

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Which sequence does the electrical stimulus of the cardiac cycle follow?

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Naxlex Comprehensive Predictor Exams

Correct Answer is D

Explanation

The nurse is listening to the breath sounds of a patient with severe asthma. Air passing through narrowed bronchioles would produce which of these adventitious sounds?

Correct Answer is B

Explanation

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