lecture 3, exam 1 study guide Flashcards
what is sarcoplasm?
gives the cell its shape
stores molecules for cellular processes
what is sarcolemma?
membrane that surrounds striated muscle fiber cells
what is a sarcomere?
ultimate force generator
what are actin and myosin?
contractile (active) proteins
what is a myofibril?
responsible for contraction of the whole muscle
what is epimysium?
fibrous elastic tissue surrounding muscle belly
tough collagen fibers resistant to stretch
what is endomysium?
connective tissue surrounding individual muscle cells/fibers
transfers contractile force from actin/myosin to tendon
what is perimysium?
connective tissue surrounding bundle of muscle fibers.
tough and resistant to stretch
what is fusiform?
fibers run parallel
designed for mobility, low force over long range
example: biceps brachii
what is pennate?
fibers approach central tendon obliquely - larger number of fibers per area
larger forces
example: unipennate, bipennate, multipennate (triceps)
what is physiologic cross sectional area?
amount of active proteins available to generate active force
thicker muscle generates more force
what is the cross sectional area like in pennation angle?
perpendicular to fiber direction
pennation angle = 0 –> all force in tendon
series vs parallel
series = all components connected end to end forming a single path
- length increases –> muscle grows in series
parallel = all components connected across each other –> all at the same time
- stronger muscle –> grows in parallel
what is series elastic components (SEC)?
tissues attached end to end with active proteins - tendon, titin
what is parallel elastic components (PEC)?
tissues that lie parallel with active proteins
epi/peri/endomysium
what are noncontractile elements?
- structural proteins
- extracellular connective tissues (epi/peri/endo)
what does stretching a muscle do?
elongates both parallel and series components
generates a stiffness or resistance within the muscle
what 2 properties of muscle are components of plyometric exercise?
elasticity
viscoelasticity
what is happening to the actin and myosin in the eccentric pre stretch phase?
pulling apart
what is happening to the actin and myosin in the concentric phase?
pulling together
what is amortization?
“time to rebound” when you bend down, you stay there –> you lost the elastic recoil
do active proteins shorten?
no - slide back and forth, recruit more
what is the active length-tension curve?
how sarcomeres of different lengths produce different force (A-D)
what is the optimal length and force on the length-tension curve?
B-C (middle of graph)
what are intrafusal muscle fibers?
inside the muscle spindles
contains receptors for sensory and proprioception
sends signals to CNS its being pulled
what are extrafusal muscle fibers?
force generating structures
for contraction
what is rate coding?
rate of sequential activation (action potentials)
smoothly increasing muscle force
what is recruitment of motor units?
activation of specific motor neurons and its fibers
which fibers are recruited first?
small recruited before large –> we tend to use less energy first if possible
are more or less units required for eccentric? concentric?
eccentric = less units required
concentric = more units required for same force
which motor unit type is recruited first? what size is the motor unit?
slow oxidative
- slower contractile characteristics
- little loss of force during sustained activation
small motor unit
which motor type is recruited last? what size is the motor unit?
fast glycolytic/fast fatigable
- large forces required
- i.e. sprinters
large motor unit
what happens in a concentric contraction?
length - shortens
torque - muscle > load
velocity - low load = max velocity
- increase load = max contraction velocity decreases
what happens in an eccentric contraction?
length - lengthens
torque - load > muscle
velocity -
load greater isometric = muscle lengthens slowly
increased load applied = increase contraction velocity
at some point load level is too heavy to be resisted
what happens in a isometric contraction?
length - constant
torque - muscle = load
velocity - no velocity
