Cardiac and Smooth Muscle

Cardiac Muscle Remember that intercalated disks contain gap junctions. When one cell is stimulated, all cells are stimulated. Cardiac myocytes each have one nucleus - they undergo spontaneous depolarization

EXCITATION-CONTRACTION COUPLING IN A CARDIAC MYOCYTE Excitation/contraction coupling is similar to skeletal muscle --no neurotransmitter required. --Contains T-tubes -- Ca2+ channels linked indirectly.

SMOOTH MUSCLE --No striations, no sarcomeres --contains actin and myosin -- extremely long filaments, which attach to the plasma membrane and to proteins called dense bodies. --lines blood vessels, bronchioles, digestive tract (peristaltic waves), ureters, ductus deferens, uterine tubes

Single-unit & Multi-unit smooth muscle --Neurotransmitter is released along the length of an autonomic neuron from varicosities. --Form synapses en passant (synapses in passing) --Receptor proteins are on the entire surface of smooth muscle cells --A number of smooth muscle cells are stimulated at once.

EXCITATION-CONTRACTION COUPLING: Smooth Muscle Relaxation involves pumping Ca2+ out of cell