Rise in the carotid sinus pressure leads to

Correct Answer: C

Rationale: The carotid sinus baroreceptors detect increased pressure, triggering a reflex via the vagus nerve (parasympathetic) to slow heart rate (bradycardia) and reduce blood pressure. Hypercapnia (high CO₂) and hyperpnea (increased breathing) are unrelated, and tachycardia would counter the response.

Correct Answer: D

Rationale: Cardiac output (CO, D) is the volume of blood ejected by the heart per minute (CO = HR × SV, ~5 L/min at rest). EDV (A) is pre-contraction volume, SV (B) is per beat, HR (C) is beats per minute, and BP (E) is pressure, not volume.

Correct Answer: B

Rationale: The first heart sound (S₁, ‘lub’) occurs when AV valves (tricuspid, mitral) close at the start of ventricular systole (B). Semilunar valve closure (A) is S₂ (‘dub’), and atrial contraction (C) precedes S₁, not causing it.

Correct Answer: C

Rationale: Fibrillation (C) is rapid, uncoordinated beating (e.g., atrial or ventricular). Heart block (A) is conduction failure, tachycardia (B) is fast but coordinated, and bradycardia (D) is slow.

Correct Answer: B

Rationale: Blood flows from the left ventricle through: artery (aorta), arteriole, capillary, venule, vein (B). A reverses artery-arteriole, C misorders, D starts with veins.