When a person stands suddenly from lying down posture, there is: (A) Increased tone of capacitance vessels., (B) Increase efferent discharge from IX cranial nerve, (C) Decreased heart rate, (D) All of the above
Answer is A. (A) Increased tone of capacitance vessels. > It occurs due to noradrenergic impulses causing venoconstriction via their action on a1 and a2 - adrenergic receptors on systo veins.