Muscle Flashcards
What are the features of cardiac muscle?
smaller (than skeletal) interconnected cells arranged in series, less organized that skeletal muscle but still in sarcomeres
What are the identifying features of skeletal muscle?
bundles of long multinucleated cells that span the length of the muscles and are surrounded by connective tissue that provide muscles with structural and metabolic support; arranged in parallel array in direction that muscle contracts
What are the features of smooth muscle?
spindle shaped cells that lack striation arranged in series and orthogonally so that muscles can contract in many different directions
What is the function of smooth muscle?
Found around most organs and bv in the body; provide tone but also allow organs to change morphology; controls the diameter of blood vessels and bronchioles
What types of myosin are found in the different muscle cells?
- Skeletal (slow -type 1, and fast - type 2)
- Cardiac (slow and fast)
- Smooth (only slow, because goes through an enzymatic process for contraction to occur, slower but maintains force for longer)
How are the contractile units of skeletal muscle cells organized?
myofibrils are bundles of myosin and actin arranged into sacromeres in a skeletal muscle cell (nucleus pushed off to the side to make room for myofibrils and many mitochondria)
Actin are attached at Z discs by + ends and then attached to myosin at the middle; Z discs, I band (just actin), A band (actin and myosin, whole length actin), H band (just myosin)
How are smooth muscle actin and myosin organized?
joined to diff parts of cell membrane by proteins and then at the center by dense bodies (collection of protein) so that can contract in many different directions
What is the function of the ECM in relation to the contraction of skeletal muscle ?
provides stability and protection for the cell membrane as cell contracts and allows force to be passed along to the fibers of the ECM so can pass contractility to whole muscle
How are sacromeres joined to the ECM in skeletal muscle?
dystrophin (protein) attaches to Z disc and then binds to dystroglycan which is attached to the cell membrane
What disease is caused by mutations in dystrophin?
muscular dystrophy, cell membrane lacks protection of ECM and so is susceptible to damage during contraction
How are skeletal and cardiac muscles stimulated?
action potential spreads to NMJ and stimulates Ca channels to let Ca into the cell, Ca stimulates vessels to fuse with membrane and release neurotransmitter Ach into synaptic clef ; Ach stimulates nicotinic receptors on plasma membrane in target cell; Na into cell; action potential spreads down T tubules, triggers DHP receptor to induce a mechanical change in ryanodine receptor in SR that releases Ca from SR; calcium binds to troponin that moves tropomyosin out of the way, partially activates it so myosin can bind, when myosin binds moves the trypomyosin even further and myosin actin binding complete and crossbridge cycle can start ; acetylcholinesterase breaks down ach in junction to cause relaxation, ca back into SR and out of cell
How is signal transmitted in cardiac cells?
via gap junctions
How is contraction triggered in smooth muscles?
calcium into the cell binds with calmodulin (CAM) and then triggers myosin light chain kinase that phosphorylates light chains in myosin heads and lets myosin bind to actin and trigger a cross bridge cycle
What is the difference between multiunit and unitary smooth muscle?
multi-unit is where each cell has a different neuron stimulating it
Unitary -> one neuron to one cell and then AP is passed by gap junctions
