Skeletal Muscle Tissue Flashcards
What are the myofiber types in skeletal muscle?
Type IA- slow red: high mitochondria, intense staining for oxidative enzymes, rich in NADH transferase, myoglobin and ATPase, oxidative phosphorylation used most.
Type II A- intermediate: resistance to fatigue, contracts faster than type I, uses both aerobic and anaerobic respiration. Intermediate staining for oxidative enzymes.
Type IIB- fast white: fatigues quickly, low staining for oxidative enzymes, anaerobic respiration, contracts more rapidly.
Compare skeletal muscle to cardiac and smooth muscle.
Skeletal Cardiac Smooth
N- Multi Mono Mono
P- Periphery Central Central
S- Yes Yes No
I- Motor neuron Gap junctions ANS/Gaps
What are the three types of tissue and what are the 3 types of muscle tissue?
Muscle, epithelial, connective, and nervous.
The three types of muscle are:
Cardiac
Skeletal
Smooth
What is the hierarchy of skeletal muscle?
Epimysium-covers the muscle made up of fascicles
Perimysium- made up of fibroblasts and type I collagen, covers the fascicles or myofibers.
Endomysium- consists of a basal lamina and reticular fibers and covers the myofibril.
What are the H,I,A, M, bands and Z lines?
H bands- myosin filaments, shorten during contraction.
I bands- actin filaments p, shorten during contraction.
A band - consists of only myosin, doesn’t move
M line- middle of myosin tails
Z line- end of sarcomere where actin attaches
What is the purpose of creating phosphate?
Replenishes ATP levels during muscle contraction as a back up energy source.
What is the structure of myosin?
It’s a dimeric protein with 2 heads at one end with binding sites for actin, ATP, and light chains.
What is the structure of actin?
Polymer of G-actin
2 polymers wound in an alpha helix.
What are actin associated molecules?
Troponin and tropomyosin
What are the three types of troponin?
I-inhibits binding between actin and myosin
C- binds calcium ions
T- binds to tropomyosin
What is A beta crystallin
A beta crystallin-heat shock protein that protects desmin from mechanical stress
What is dystrophin?
Links alpha actinin/desmin complex to cytoplasmic side of the sarcolemma.
Reinforces sarcolemma during muscle contraction.
What is dystroglycan complex?
Links dystrophin (intracellular) to laminin-2 (extracellular)
What is alpha actinin?
Attaches actin to Z line
What is Titin?
Extends from Z line to middle of H band and connects thick filaments to Z line.
Gives myosin elasticity-centers them
What are Desmin intermediate filaments?
Surrounds the z line and Links myofibrils laterally to the sarcolemma.
What is plectin?
Binds desmin filaments
What is nebulin?
Regulates actin’s length.
What is dystrophin?
Gives stability during muscle contraction.
What is muscular dystrophy?
Degeneration of skeletal muscle due to lack of dystrophin- Duchenne’s
Or abnormal dystrophin- Becker’s
What are satellite cells?
Stem cells that repair and maintain skeletal muscle that already exists, doesn’t make new muscle.
What is a neuromuscular spindle? And what are its parts?
Sensory portion of the muscle.
Extrafusal-skeletal muscle fibers
Intrafusal- sensory region in the nuclear bag.
What type of neurons innervate the neuromuscular spindle?
Alpha- innervates extrafusal
Gamma- innervates intrafusal fibers
Primary and secondary afferent- send signals back to the nervous system.
