This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart, Circulation, and Blood, Subject name: Physiology
During Valsalva Maneuver, the heart rate varies as: 
Select and explain. 
A. Tachycardia f/b bradycardia, B. Bradycardia f/b tachycardia, C. Tachycardia during and after Valsalva, D. Bradycardia during and after Valsalva
A: Tachycardia f/b bradycardia
Answer: A: Tachycardia f/b bradycardia 
Explanation: Ans. A. Tachycardia f/b bradycardiaa. BP rises at the beginning of straining as the intrathoracic pressure rises. It falls soon thereafter as the high I/T pressure compresses veins, decrease the venous return and CO.b. This decrease in BP and Pulse pressure inhibit baroreceptors, leading to tachycardia and increased peripheral resistance. When the glottis is opened and I/T pressure return to normal, cardiac output is restored but the peripheral vessels are constricted. Hence BP rises above normal. This stimulates baroreceptors causing bradycardia and drop in pressure. Phase12a2b34Intrathoracic pressureIncreasedIncreasedIncreasedNormalNormalMean arterial BPIncreasedDecreasedIncrease*Decrease*IncreasedHeart rateDecreasedIncreasedDecrease*Increase*DecreasedSympathetic activityDecreasedDecreasedIncreasedIncreasedIncreasedPS (vagal) activityIncreasedIncreasedDecreasedDecreasedIncreased