In contrast to epinephrine, norepinephrine does the following:
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 (b1)DBP (b2 and al)HEART RATEDirectIndirectNet EffectAdrenaline/ epinephrine||-|-|Noradrenaline/ NE||||||||
Increase cardiac output, Bradycardia
Increase cardiac output, tachycardia
Decrease cardiac output, bradycardia
Decrease cardiac output, tachycardia
Adrenergic System