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🔬 Biology  ·  Body Fluids and Circulation  ·  NEET

Deoxygenated blood returning from the body first enters the ___ of the heart:

Answer: right atrium.

  • A right atrium
  • B left atrium
  • C right ventricle
  • D left ventricle

Correct answer: A. right atrium

Explanation: The vena cava empties deoxygenated blood into the right atrium.

ECG: The Three Key WavesP wave(atrial depol.)QRS complex(ventricular depol.)T wave(ventricular repol.)QRS is the tallest spike - ventricles have far more muscle mass than the atria

A single ECG cycle: the P wave marks atrial depolarisation (contraction signal), the large QRS complex marks ventricular depolarisation, and the T wave marks ventricular repolarisation (recovery) before the next cycle begins.

Concept context

Blood, lymph, the heart, the cardiac cycle, blood pressure, and ECG. High NEET weightage.

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