Ans. is 'b' i.e., T1- T5 * Parasympathetic supply to heart - Vagus.* ympathetic supply to heart - T1- T5Innervation of Heart* Innervations of heart are :-A) Sympathetic innervation of heart:# All parts of the heart (SA node, atria, AV node and ventricles) recieve sympathetic innervations.# The sympathetic innervation on right side is distributed primarily to the SA node, while on the left side is distributed primarily to the AV node.# Sympathetic fibers are mostly distributed to the epicarium.# Sympathetic discharge has following effects :i) Positive ionotropic (Increase in force of contraction).ii) Positive chromotropic (Increased heart rate).iii) Positive dromotropic (Increased conduction).iv) Positive bathmotropic (increased automaticity).v) Decreased refractory period of all types of cardiac cells. -# The main neurotransmitter is nor-adrenaline.B) Parasympathetic innervation of heart:# Parasympathetic fibers to the heart reach through the vagus nerve.# The right vagus is distributed mainly to SA node while the left vagus mainly innervates the AV node. Vagal fibers are mostly endocardial in distribution.# Vagal stimulation has following effects :i) Negative chronotropic (decreased heart rate).ii) Negative dromotropic (decreased conduction).iii) Increased refractory period of all types of cardiac cells.# But vagal stimulation does not have a negative inotropic effect because vagal (parasympathetic) fibers do not innervate the myocardial cells of the ventricles in sufficient numbers; there is slight decrease in force contraction of atria only.# Major neurotransmitter is acetylcholine.