SKELETAL PART 1 Flashcards
what are the four functions of muscle tissue
produce movement, maintain posture and body position, stabilize joints, generate heat (as they contract)
what are then four characteristics of muscle tissue
excitability, contractility, extensibility, elasticity
does muscle need to be attached to bone to be moved
yes
what are myotendinous junctions
where muscle fibers connect to tendons; prone to damage
where are the primary sources of force transmission
myotendinous junctions
what do myotendinous junctions allow for
allow force generated by muscle fibers to be applied through the tendons to the bones to produce desired movements
describe three main traits of skeletal muscle fibers
multinucleated; technically differentiated; highly plastic
describe the highly plastic part of skeletal muscle
load-driven size alterations; increase activity = hypertrophy; decrease activity = atrophy; activity-determined phenotype (I, IIa,IIx)
describe the length of skeletal muscle fibers
varies considerably in human muscles; length + width affect force production potential
differentiate between short and long muscle fibers
short fibers = more force, long fibers = higher velocities
describe numbers of skeletal muscle fibers
several number fibers in small muscles to a million+ in large muscles; coordination and relaxation of many individual cues that occurs during standing, running, walking etc
whats the sacrolemma
muscle fiber plasma membrane
whats the sacroplasm
muscle fiber cytoplasm (contains proteins, minerals, fats, organelles, glycogen, myoglobin)
what are the modified organelles for contractions
transverse tubules, sarcoplasmic reticulum, myofibrils
what are transverse tubules
inholdings of sarcolemma that protrude inwards + conduct electrical impulses from surface of cell to terminal cisternae
whats the sarcoplasmic reitculum
membranous channel parallel to myofibril and storage site for Ca2+ (basically smooth ER of muscle cells)
describe myofibrils
roughly 80% of cellular volume and contain the contractile elements of muscle cells (myofilaments)
what are striations
occur because of repeating series of dark A bands and light I bands
what are the light I bands
actin
how do the light and dark bands appear
dark because light can’t go through because of the myosin
what are the two types of myofilaments
myosin (thick filaments) + actin (thin filaments)
what are tropomyosin and troponin
regulatory proteins on actin
describe the sacromere
smallest contractile unity; length-tension relationship; distance from one Z-disk to the next
whats G-actin
individual subunits of F-actin; globular actin; actin monomers
whats F-actin
filamentous actin; arranged in double helix; many G-actin come together to form
describe actin
myosin binding site; exposed by removal of tropomyosin; attaches to myosin crossbridge
whats myosin
~300 myosin molecules in one thick filament; important for muscular force and velocity of contraction; different myosin isoforms have diff force/velocity charcterstrics; different muscle types
describe the different types of myosin heavy chains in animals
slow: type I
fast: Type IIA
Type IIX
describe Type I fibers
endure low intensity activity (like sitting in a chair), slow contraction, high myoglobin, colored red
describe Type IIA fibers
high force of contraction; cannot sustain effort for long time; fast contraction; high myoglobin; colored red to pink; fatigue more quickly
describe Type IIX fibers
fast contraction, low myoglobin, colored white, tired out very quickly; strongest, quick/explosive movemenrs
describe fiber recruitment
based on need for force production; recruit type I first and then move to type IIA and type IIX depending on needs
why is Type I red
more capillaries in type I; some in Type IIA which is why its pink and none in Type IIX which is why its white
what happens to muscle fiber content as people get more fit
Type I remains stable, Type IIA increases a ton and type Iix decreases a ton
describe exercise + MHS content with age
as fit people age, their MHC IIA content increases and type Iix disappears
