Multiple choice Adrenaline directly affects the islet of langerhans sinoatrial node oxyntic cells of stomach dorsal root ganglia of spinal cord Reveal answer Fill a bubble to check yourself B Correct answer Explanation Adrenaline (epinephrine) directly stimulates the sinoatrial (SA) node, increasing heart rate and cardiac output. It binds to beta-1 adrenergic receptors on SA node cells, enhancing the rate of depolarization and firing frequency.