This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: NEET 2019, Subject name: Physiology
Bainbridge reflex is due to:- 
Select and explain. 
A. Stretching of atria, B. Baroreceptor reflex, C. Decreased venous return, D. Increased ventricular activity
A: Stretching of atria
Answer: A: Stretching of atria 
Explanation: Bainbridge reflex: Increase in atrial pressure causes increase in hea rate by nervous reflex called Bainbridge reflex 40 - 60 % increase in rate is due to this reflex while 15% increase is by direct effect of increased atrial volume to stretch sinus node. Stretch receptors of atria that elicit Bainbridge reflex transmit their afferent signals through vagus nerve to medulla of brain. These efferent signals are transmitted back through vagal & sympathetic nerves to increase H.R & strength of hea contraction. This reflex helps prevent damming of blood in atria, veins & pulmonary circulation Best known nerve mechanisms for aerial pressure control Reflex is initiated by stretch receptors called baroreceptors /pressoreceptors located at specific points in walls of several large systemic aeries A rise in aerial pressure stretches baroreceptor & causes them to transmit signals into CNS. "feedback" signals are then sent back through autonomic nervous system to circulation to reduce aerial pressure downward towards the normal level