Which of the following physiological change can occur when there is vagal stimulation of hea?: (A) Increased R-R interval, (B) Increased hea rate, (C) Increased cardiac output, (D) Increased force of contraction
Answer is A. Stimulation of parasympathetic (vagus) fibers causes decrease in the hea rate (increased R-R interval), reduce the force of contraction, and constrict the coronary aeries. Stimulation of sympathetic nerves increases hea rate (decreased RR interval). Ref: Moon D.A., Foreman K.B., Albeine K.H. (2011). Chapter 4. Hea. In D.A. Moon, K.B. Foreman, K.H. Albeine (Eds), The Big Picture: Gross Anatomy.