study q's Smooth Muscle Flashcards
compare smooth muscle cells v skeletal muscle fibers-
cell size, nuclei, caveolae, cytoskeleton
SM- bundles of individual elongated cells with one nucleus. contain caveolae (small cell indentations similar to T tubules acting to increase surface area for Ca into cell). contain dense bodies, equivalent to Z lines but not striated (unaligned), which anchor actin and intermediate fibers to sarcolemma.
describe extracellular matrix-basement membrane complex and their function in adhering smooth muscle tissue
cells connected by dense bodies and reticular CT
dense bodies: anchor myofilaments together and to cell membrane. dense bodies opposite each other in adjacent cells fuse together.
retituclar CT permeates smooth muscle. collagen and elastic ibvers of the CT and endomysium bind to dense bodies for structural integrity.
how do smooth muscle sarcomeres differ from skeletal muscles? how does contraction impact tissues/cells?
smooth muscle cells do not have sarcomeres, they are not striated, they are aligned more like a globular net than a line. actin and myosin overlap and pull on dense bodies, which are pulled inward and the cell membrane balloon out between them
describe how Ca stimulates muscle contraction and how it differs from skeletal muscle. what is the role of phosphate on the myosin light chain and its role in the latch phenomenon
Ca binds with calmodulin (rather than troponin) to activate mysolin light chain kinase (MLCK).
MLCK phosphorylates myosin light chain which allows for the cross bridge cycling.
latch mechanism permits continuous contraction with minimal ATP expenditure
what are the two sources of Ca+ for contraction and how does it differ from skeletal muscle
- smooth muscle- contraction depends on amount of Ca+ available in cell. relies on both SR release of Ca+ and entry of extracellular Ca+
- skeletal muscle- relies solely on Ca+ release from the SR activated by an AP.
