histology 7- muscle Flashcards
3 types of muscle tissue
skeletal
cardiac
smooth
skeletal muscle
- strong, quick discontinuous voluntary contractions
- long striated strings (muscle fibers)
cardiac muscle
- strong, quick continuous involuntary action
- only found in heart
- presence of larger nuclei and intercalated discs distinguish it from skeletal
smooth muscle
- weak, slow involuntary contraction
- non-striated, group of cells
special characteristics of muscle tissue
- excitability/ irritability
- contractility
- extensibility
- elasticity
excitability
can be excited by electrical potentials
contractility
fibers condense unilaterally to move bones without stretching cell
extensibility
fibers can be overextended without stretching/deforming cells
elasticity
fibers are elastic, can stretch and deform
function of muscle tissue
- Production of movement
- Maintaining posture
- Stabilizing joints
- Generate heat (thermogenesis)
list the different types of skeletal muscle
type 1
type 2a
type 2b
type 1 skeletal muscle fibers
Slow, red oxidative fibers
- a.k.a. Slow twitch, fatigue resistant fibers
- Many mitochondria and lots of myoglobin
- Derive energy from aerobic oxidative phosphorylation of fatty acids
- Adapted for slow, continuous contractions over time
type 2a skeletal muscle fibers
Fast, intermediate oxidative-glycolytic fibers
- a.k.a. Fast twitch, fatigue resistant fibers
- Many mitochondria, lots of myoglobin and glycogen (intermediate)
- Derive energy from aerobic oxidative metabolism and anaerobic glycolysis
- Adapted for rapid contractions and short bursts of activity
type 2b skeletal muscle fibers
Fast, white glycolytic fibers
- a.k.a. Fast twitch, fatigable fibers
- Fewer mitochondria and myglobin, but LOTS of glycogen (pale color)
- Derive energy from anaerobic glycolysis
- movement
Describe the organization of muscle tissue from the organ level down to the myofilaments.
Molecules → myofilaments → myofibril → muscle fiber → muscle fascicle → skeletal muscle
Sarcomeres
- Interlocking rods of actin and myosin
- Z line (Z disc) endpoints of sarcomere
- M line: midpoint of sarcomere, myosin
- A band: length of myosin fibers in sarcomere, actin & myosin
- H band: (H zone) length of myosin fibers not surrounded by actin, shortens with contraction, myosin
- I band: length from ends of myosin fibers on adjacent sarcomeres, shortens with contraction, actin & titin
Describe the filament sliding hypothesis and changes in the appearance of the sarcomere during contraction. Filament sliding hypothesis in relaxed, partial contraction, and full contraction
relaxed muscle- sarcomere, I band, H zone all at relaxed length
partial contraction:
- thick (myosin) and thin (actin) filaments slide past one another
- I band and H zone almost nonexistent
- thick fibers meet at M line (here, M line = H zone)
full contraction:
- thick filaments overlap
- adjacent I bands overlap, H zone nonexistent
- shortest length of sarcomere
thick and thin filaments don’t _________, just interlock and slide against each other
change length
excitation-contraction coupling
1) Action potential generated along sarcolemma down t-tubules.
2) Action potential triggers Ca2+ release from terminal cisternae of sarcoplasmic reticulum
3) Ca2+ binds to troponin, cross-bridges form…contraction
Sarcoplasmic reticulum
-endoplasmic reticulum of muscle cells, stores and pumps Ca2+ ions
T-tubules
-invaginations of sarcolemma designed so action potentials can travel into cell
Terminal cisternae
-enlarged areas of SR that surround t-tubules. Stores Ca2+ to release when action potential travels down t-tubule
Triad
-structure (group) formed by T-tubule and 2 sarcoplasmic reticula/terminal cisterna
Describe the process of cross-bridge formation, the power stroke, and cross-bridge detatchment. Describe how this relates to rigor mortis.
1) Head of myosin cross bridge attaches to actin myofilament
2) Working stroke – myosin head pivots and bends to pull actin filament toward M line
- ADP and Pi released
3) New ATP attaches to myosin head, head detaches from actin filament
4) ATP hydrolysis splits ATP on myosin head, cocking of myosin head occurs
- Repeat
