Which of the following waves represents the ventricular depolarization on ECG?
QRS wave
P wave
T wave
U wave
The Correct Answer is A
a. QRS wave: The ECG (electrocardiogram) measures the electrical activity of the heart. The QRS complex represents ventricular depolarization, the spread of electrical excitation through the ventricles causing them to contract.
b. P wave: The P wave represents atrial depolarization, the electrical impulse moving through the atria.
c. T wave: The T wave represents ventricular repolarization, the ventricles relaxing after contraction.
d. U wave: The U wave is a small wave of uncertain origin, not related to ventricular depolarization.
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Related Questions
Correct Answer is D
Explanation
a. Blood clot formation: This is one of the later stages of hemostasis, involving the formation of a fibrin clot to seal the wound.
b. Platelet aggregation: This occurs after the initial vasoconstriction and is part of the platelet plug formation phase.
c. Activation of prothrombin: This occurs in the coagulation phase where prothrombin is converted to thrombin, leading to the formation of a fibrin clot.
d. Constriction of smooth muscle in blood vessels: This is the first response, known as vascular spasm or vasoconstriction, which reduces blood flow to the area and minimizes blood loss.
Correct Answer is B
Explanation
a. Presence of calcium: Calcium does not directly stimulate the production of Vitamin D in the skin.
b. Exposure to ultraviolet light: UVB rays from sunlight stimulate the skin to produce Vitamin D3 (cholecalciferol).
c. Exposure to cold temperature: Cold temperature does not affect Vitamin D production.
d. Presence of parathyroid hormone: Parathyroid hormone helps regulate calcium levels and can stimulate the conversion of Vitamin D to its active form in the kidneys, but it does not stimulate its production in the skin.
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