Muscle tissue i Flashcards
When is skeletal muscle somewhat involuntary?
breathing (diaphragm) and posture
functions of muscle tissue
body movement
stabilizing position
moving stuff in body (blood/ intestine stuff)
generate heat (shivering)
cell to cell connections in each muscle type
skeletal = none
cardiac = intercalated discs = gap junc. and desmosomes
smooth muscle = sometimes gap junc.
skeletal muscle function
support/protection = abdominal wall / pelvic floor
movement
nutrients = AA for liver to make glucose
posture
heat = 85%
fascia
dense sheet/ broad band of irregular ct that surrounds muscles
epimysium
outermost layer surrounding multiple fasicle bundles
perimysium
separates 10-100 muscle fibers into fascicle bundles
endomysium
separates muscle fibers from each other
NOT plasma membrane
tendon
cord attaching muscle to bone (dense CT)
Aponcurosis
broad, flattened tendon
filament to muscle
filament myofibril muscle fiber fascicle bundle muscle
skeletal muscle attachment to bone
Direct: epimysium fuses to periosteum of bone
Indirect: CT wrappings extend beyond muscle tissue as tendon
Series Elastic Component : CT wrappings have elastic properties
- when muscle contracts, SEC streches b4 bone movement
skeletal muscle nerve supply
somatic motor neurons
-motor unit = axon of somatic motor neuron and the muscle fibers it enervates –> all contract at once
How do muscles grow? what hormones are involved?
- # of fibers stay the same
- hypertrophy = enlargement of existing muscle fibers
- Testosterone and HGH stimulate hypertrophy
- satellite cells retain capacity to regenerate damaged muscle fibers
sarcolemma
plasma membrane of muscle cells
Transverse tubules
deep invagination in sarcolemma
-ap tracels thru them
Sarcoplasm
cytoplasm of muscle fiber
- contains glycogen for ATP synthesis
- contains myoglobin which binds O2
- Myoglobin releases O2 when needed to make ATP
SR
membranous sacs encircling each myofibril
- stores calcium
- release of calcium triggers muscle contraction
myofibrils
thread-like structures with contractile funciton
filament-componenets of myofibrils
- function in contractile process
- thick and thin
- 2 thin for every thick
sarcomeres
- compartments of arranged filaments
- basic functional unit of a myofibril
Z disc
- separates 1 sarcomere from another
- anchors actin filaments
A band
dark middle part of sarcomere
-area of thick filaments whether or not they overlap
I band
lighter –> only thin filaments
-Z disc passes thru middle of I band
H zone
Center of each A band with only thick filaments
M line
supporting proteins that hold the thick filaments together in the H zone
3 types of proteins that make up myofibrils
contractile, regulatory, and structural
Contractile proteins
- Myosin = thick filaments that function as motor proteins to achive motion
- converts ATP to energy of motion
- projections of each molecule protrude outward (myosin head) - Actin = thin filaments providing site for myosin head attachment
- tropomyosin and troponin are part of thin filament
- tropomyosin covers myosin binding sites
- Ca binds to troponin, moving tropomyosin off the site
Regulatory Proteins
Tropomyosin = strand blocking binding site
Troponin = Globular with 3 subunits
- Troponin T = binds to tropomyosin
- Troponin I = binds to actin
- Troponin C = binds to calcium
Structural proteins
- Actinin = cross links thin filaments at z line
- Connectin (titin) = big elastic proteins from z disc to m line
- stabilizes thick filaments and provides elasticity to muscles - Nebulin = big protein along thin filaments at z disc
- stabilizes thin filaments - Dystrophia = links thin filaments to sarcolemma
- get fucked up in muscular dystrophy
