Skeletal Muscle and Nerve Tissue Flashcards
Makes up muscle cells
myofibrils; chains of sarcomeres (contractile unit) linked together form one fiber; surrounded by endomysium
Makes up a fascicle
groups of myofibers (muscle cells) surrounded by perimysium
Makes up a muscle
groups of fascicles surrounded by epimysium
Makes up myosin (thick filaments)
2 heavy chains with globular heads (have actin binding site with ATPase domains) and 2 light chains
What holds myosin in place
Titin proteins connected to the Z disc
Makes up sarcomere
actin and myosin
Makes up actin
F-actin monomers; form double stranded chains
Nebulin
determines the length of the actin filament
Role of tropomyosin in actin
wrap around the actin strands
Role of troponin in actin
sits on top of the tropomyosin and covers the myosin binding sites
M-line
attachment site for myosin
Z-disc/line
separates sarcomeres and is the attachment site for actin and titin
H-band
space on each side of M line with no actin present
A-band
distance from end of myosin head to opposite myosin head (overlap in middle)
I-band
space on either side of Z disc without myosin
How does muscle contraction occur
Ca2+ is released from the SR which binds troponin causing a conformational change; the actin binding sites are then accessible to the myosin heads
Sarcolemma
Membrane around each muscle cell
Transverse (T) tubules
penetrates muscle class to deliver electrical impulses from Sarcolemma into the cell
Sarcoplasm
cytoplasm of muscle cell
Sarcoplasmic reticulum
tubular system acting as smooth ER; terminal cistern are flattened SR space on each side of T tubule
Triad
T tubule and the 2 terminal cisternae attached
End feet
connect T tubule with the SR for Ca release
Neuromuscular spindle apparatus role
Reflexive response to prevent overstretching of a muscle
Extrafusal muscle fibers
contract the muscle
Intrafusal muscle ribers
sense length and rate of change of the muscle
1a sensory nerve fibers
A-fferent (sensory) innervation of the intrafusal fibers
gamma-motor nerve fibers
E-fferent innervation of intrafusal fibers
Schwann Cells
surround axon creating myelin sheath in PNS; wraps around one part of the axon
Oligodendrocyte
Surrounds axon creating myelin sheath in CNS; wraps around MANY axons
