Cardiac Physiology: 1.Regulating Blood pressure: With the nervous system: -Sensory neurons a several places in the body detect blood pressure(baroceptors) and send impulses to brain stem (medulla oblongata) -Atrial pressures vary during cardiac cycle and thus atrial pressuresshown are averages. -When too high, the autonomic nervous system releases neurotransmitters that causes the smooth muscle around blood vessels to relax (vasodilation), elevating blood pressure. With the endocrine/ excretory system: -Hormones produced by the heart and other organs cause kidneys to remove more water from the blood when blood pressure is too high, reducing blood volume and lowering blood pressure. 2.Cardiac Muscle Structure: -intercalated disks are anchoring structures containing gap junctions. Help to make the heart contract at the same time from the action potentials. -Cardiac muscle cells are faintly striated, branching, mononucleated cells, which connected by means of intercalated disks to form a functional network.