<prompt> In contrast to epinephrine, norepinephrine does the following:Increase cardiac output, BradycardiaIncrease cardiac output, tachycardiaDecrease cardiac output, bradycardiaDecrease cardiac output, tachycardia  <response>: Ans. a Increase cardiac output, BradycardiaRef .KDT h ed. 122 Epinephrine adrenaline and Norepinephrine NA are endogenous catecholamine. These are the hormones responsible for actions like bradycardia and tachycardia by acting on their specific receptors. Systolic blood pressure SBP is determined by cardiac output b1 action,. b1 receptors are present on heart which upon stimulation causes tachycardia. Diastolic BP DBP depends on the state of blood vessels. b2 receptors are present on blood vessels which upon stimulation causes vasodilation - DBP Alpha receptors are present on vessel wall, which upon stimulation constricts vessel wall and increase total peripheral resistance - DBP Increased DBP stimulates baroreceptor mediated release of ACh reflex action that decreases heart rate via activation of M2 receptors. Reduction in DBP increases central sympathetic outflow and thereby increases heart rate. NOTE: NA normally decreases heart rate but if given after a dose of atropine, increase in heart rate will be seen reflex action is abolished because of blockage of M2 receptor. Adrenaline acts on al, a2, b1, b2 receptors whereas Noradrenaline acts on al, a2, b1. Which means. Activation of adrenaline causes tachycardia b1 action and NO effect on DBP because action of al and b2 are crossed by each other. Activation of NA causes tachycardia and DBP. SBP b1DBP b2 and alHEART RATEDirectIndirectNet EffectAdrenaline epinephrine--Noradrenaline NE 