Lecture 4 Flashcards
what does force production depend on
formation of cross bridges between actin and myosin
what does magnitude and force depend on
number of cross bridges and thus on number of actin and myosin molecules
what does atrophy of muscle fiber diameter result in
reduced force
what does hypertrophy of muscle fiber diameter result in
increased force producing potential
why does force produced by different muscle fibers vary with fiber type
fiber diameter and cross sectional area varies with type rather than due to differences in the contractile proteins or cross bridge formation process
what does the speed of force production depend on
the rate at which a fiber can form, break, and reform a cross bridge
why does ATP affect the speed of force production
because ATP is needed to break the actin/myosin cross bridge so rate of ATP hydrolysis at myosin head matters
how does ATP affect fast twitch muscle fibers
the myosin heads of fast twitch fibers contain myosin ATPase isoforms that catalyze ATP hydrolysis faster
what would a graph of twitch force production of fast twitch muscle fibers look like compared to slow twitch
the line would be steeper
what do MU velocity of force production depend on
differences in fiber type
what are differences in the magnitude of force produced due to in motor units
size of fibers and the number of fibers in the motor unit
what determines force potential in motor units
total cross sectional area
what are energy sources for muscle fibers
creatine phosphate, glycolysis, and oxidative metabolism
how do you determine if a fiber relies on glycolysis or oxidative metabolism
it depends on the concentration and activity of metabolic enzymes, availability of blood flow, and diameter of a fiber
what does FG stand for
glycolytic and fatiguable
