<prompt> Which of the following causes increase in conduction velocity of impulse through hea ?Vagal stimulationParasympathetic stimulationSympathetic stimulationAll of the above  <response>: Ans. is c i.e., Sympathetic stimulationEffects of sympathetic stimulation are :i Hea :- positive chronotropic 1 hea rate, ii Positive ionotropic 1 contractility, iii Positive dromotropic 1 conduction velocity, iv Positive bathmotropic increased automaticity, v Decreased refractory period in all cardiac cells.ii Vasoconstriction :- T total peripheral resistance due to aeriolar constriction, venous capacitance due to venoconstrictioniii Increased stroke volume, cardiac output and BP.Effects of parasympathetic stimulation are :?i Negative chronotropic decreased hea rate : - Vagal stimulation cause decrease in slope flattening of prepotential pacemaker potential and therefore the time taken to reach the threshold levelis increased -- Hea rate is decreased.ii Negative dromotropic decreased conduction.iii Increased refractory period of all type of cardiac cells. 