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