This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
Regulation of coronary circulation is 
Select and explain. 
A. Autonomic, B. Antoregulatory, C. Chemical, D. All of them
D: All of them
Answer: D: All of them 
Explanation: Coronary circulation is regulated by chemical factors, physical factors, hormonal factors, neural factors, and autoregulation. Products of metabolism like CO2, H+, K+, lactic acid, adenosine, bradykinin, prostaglandin, adenine nucleotide etc produces vasodilation. Physical factors are BP, Peripheral resistance, Hea rate and phases of the cardiac cycle. Thyroxine, catecholamines, Ach increases coronary blood flow whereas angiotensin decreases.Neural regulation by sympathetic and parasympathetic supply.Autoregulation refers to the ability of an organ to maintain a relatively constant blood flow over a wide range of aerial blood pressure. Ref: Textbook of medical physiology by N Geetha, 2nd edition, page no. 200,201