Physiology 2130 Lecture Notes - Lecture 8: Heart Valve, Aortic Valve, Pulmonary Valve
5 Aug 2016
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It transports and distributes hormones and other substances within the body. Myocardial cells: is the basic cell type within the heart, 2 principal types, contractile cells: similar to skeletal muscle cells, nodal/conducting cells: similar to nerve cells. Intercalated discs: contain tight junctions that bind cells together, gap junctions allow ion movement and ion currents between myocardial cells; enables the heart to conduct action potentials from cell-cell without nerves. Bundle of his to purkinje fibers to ventricular muscles. Myocardial cells (ions: sodium (na+), potassium (k+) and calcium (ca++)* are responsible for action potential generation in the heart. K+ tries to leave the inside of sa nodal cell, making inside more negative (hyperpolarization); this is undesired. K+ permeability of sa nodal cell decreases over time (less k+ leaking out over time) Na+ and k+ pumps are always pumping k+ into the cell. Special voltage-gated ca++ channels open, allowing ca++ to flow in and produce depolarization phase of the sa node action potential.
