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 A

Explanation

A. Thyroid: The thyroid gland produces thyroxine (T4) and triiodothyronine (T3), which are essential hormones that regulate metabolism, growth, and development. An elevated T4 level typically indicates hyperthyroidism or other thyroid disorders, making it necessary to assess the function and health of the thyroid gland.

B. Parathyroid: The parathyroid glands regulate calcium levels in the blood through the secretion of parathyroid hormone (PTH). They do not produce T4 or directly influence thyroid hormone levels, so assessing the parathyroid glands would not be relevant in the context of elevated T4.

C. Adrenal: The adrenal glands produce hormones such as cortisol, aldosterone, and adrenaline. While adrenal function can impact overall hormonal balance in the body, they are not directly involved in the production of thyroxine (T4), making them unrelated to the assessment for elevated T4 levels.

D. Parotid: The parotid glands are major salivary glands that secrete saliva. They do not play a role in thyroid hormone production or regulation, so assessing the parotid glands would not be appropriate when investigating elevated T4 levels.

A. Clumped B. Unilateral C. Soft and nontender D. Firm, tender, but freely movable

Correct Answer is D

Explanation

A. Clumped: Clumped lymph nodes are more commonly seen in chronic infections such as tuberculosis or metastatic malignancies, where lymph nodes may fuse together due to prolonged immune stimulation or infiltration by cancerous cells. In acute infections, lymph nodes tend to be more discrete rather than clumped.

B. Unilateral: Lymphadenopathy in acute infections can be either unilateral or bilateral, depending on the site and extent of the infection. While localized bacterial infections may cause unilateral lymph node enlargement, systemic infections such as viral illnesses frequently lead to bilateral lymphadenopathy.

C. Soft and nontender: Normal lymph nodes are small, soft, and nonpalpable or slightly palpable without tenderness. In an acute infection, inflammatory processes lead to lymph node enlargement, making them firm and tender rather than soft and nontender. Soft, painless lymph nodes are more often associated with normal findings or slow-growing malignancies such as lymphomas.

D. Firm, tender, but freely movable: In acute infections, lymph nodes become enlarged, firm, and tender due to inflammatory immune responses against invading pathogens. Despite their enlargement, they remain freely movable because the surrounding tissue is not invaded or fibrotic, unlike in malignancies where nodes may be fixed due to tumor infiltration or fibrosis. The tenderness results from stretching of the lymph node capsule due to rapid immune cell proliferation and increased fluid accumulation.

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

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