Muscle Tissue Flashcards
3 types of muscle
skeletal, cardiac, and smooth
Sarcomere
contractile unit of striated muscle. Expands from one Z disc to the next Z disc
G-actin
globular actin monomer. assembles to form a polymer that kinda looks like a string of beads
Filamentous actin
two polymers twisted together
Thin filaments
made up of actin and troponin
Tnt
attaches to tropomyosin
TnC
binds calcium ions during muscle contraction
TnI
attaches to actin monomer to block actin/myosin interation
Tropomyosin
consists of two polypeptide chains that come together to form an alpha helix.
Myofibril
sacromeres attached to one another to form a large cylindrical series
Vesiculus
msucel fibers come together to form these
A-band
Dark band. contains thick and thin filaments. bisected by H band
I band
contains only thin filaments
bisected by Z disc
H band
contains only thick filaments
Sarcomere accessory proteins
attach, space, and align myofilaments for an even, prcise and orderly arrangment. HOld think and thick filaments in place
Nebulin
nonelastic protein. 2 molecules hold thin filament in place
Titin
elastic protein. HOlds thick filament in place. Acts like an ianchor
Myomesin and c prtein
hold thick filaments in place
Endomysium (reticular fibers)
delicate layer of connective tissue. surrounds each muscle cell/fiber
Perimysium Icollagenous CT)
surround each bunch/bundle of muscle cells
Epimysium (collagenous CT, deep fascia)
surrounds many bundels
Skeletal muscle
voluntary control.
T-tubules
run peripendicular to longitudinal acis of cell. Open into extraceullular space. Lumen is continuous.
Triad - at A-I of sarcomere
two terminal cisternae with a T-tubule. Contain calcium in lumen for muscle contraction
Axon terminal branches
nerve branch has dilated structure closely attached to skeletal muscle cells/fibers
Myoneural junction
point of contact between terminal and cell
Presynaptic terminal
contains synaptic vesciles.
Moto unit
nerve cell and all the muscle fibers it innervates
Myasthenia Gravis
autoimmune disease. Autoantibodies inferfere with muscle contraction. Specifically fucks with actylcholine
Duchenne Muscular Dystrophy
affect striated muscle. Most common and most severe form.
Purkinje Gibers
specialized cardiac muscle fibers. Relay electrical impulses to regular cardiac muscles to cause contractino. Located in endocardium
Smooth muscle
No sacromere. No alternating light and dark bands. Cells packed very tightly, without extracellular space. Has euchromatic nucleus located in wider part of cell
Smooth muscle cells
Has caveolae on interior surface of cell membrane to release Ca++ into cell fo rtraction. Pinocytotic vesciles located all along inner surface of smooth muscle membrane.
Dense bodies
found in smooth muscle cells. Can either be anchored to inner surface of cell membrane or locacted at point of contact of myofilament bundles imbedded within the cytoplasm.
What happens to nucleus when smooth muscle contracts
It curls
How does nerve impulse spread in skeletal muscle
Sweep oer entire sarcolemma, comes to openings of T-tubules along sacrolemma surface. Spread deep into muscle. Changes permeability of sarcoplasmic reticulum
Myofibrils
found in cytoplasm. Made of sarcomeres
How is Ca++ released
by terminal cisternae on myofibril surface
What does Ca++ do
binds to TC subunit, changes confirmation of troponin. TnT bound to tropomyosin pushes tropmyosin filament deeper into groove on actin filament. Myosin biding site of actin monomer on the actin filament is exposed. This whole process requires ATP
What happens during muscle contraction
- Thick filaments pull on thin filaments and slide over them
- Globular heads attach to thin filament actin sites and drag them to midline
- Z-discs get closer to each other and closer to midline
- The length of the thick and thin filaments stay the same.
