Consider the following statements about the heart: 1. The SA node is the natural pacemaker. 2. The AV node delays the impulse before it passes to ventricles. 3. The Purkinje fibers conduct impulses through the ventricular walls. Which of the above is/are correct? MCQ with Answer and Explanation
Consider the following statements about the heart:
1. The SA node is the natural pacemaker.
2. The AV node delays the impulse before it passes to ventricles.
3. The Purkinje fibers conduct impulses through the ventricular walls.
Which of the above is/are correct?
A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2, and 3
Answer: Option D
Solution (By JKSSB Mock Tests)
All three are correct: SA node initiates impulse, AV node delays it to allow atrial emptying, Purkinje fibers spread impulse through ventricles.
Explanation:
Mature human RBCs have a lifespan of approximately 120 days, after which they are phagocytosed by macrophages in the spleen, liver, and bone marrow.
Consider the following statements about the nitrogen cycle:
1. Nitrogen fixation converts N₂ to ammonia.
2. Nitrification converts ammonia to nitrates.
3. Denitrification returns nitrogen to the atmosphere.
Which of the above is/are correct?
Explanation:
All three processes are part of the nitrogen cycle: fixation (N₂ → NH₃), nitrification (NH₃ → NO₂⁻ → NO₃⁻), and denitrification (NO₃⁻ → N₂).
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