Physiology of Muscle Flashcards
Z line to Z line indicates…
sarcomere, functional unit of skeletal muscle
T tubules invaginate the sarcolemma and are adjacent to…
sarcoplasmic reticulum, providing Ca storage
thick vs thin filaments
thick- myosin, tail of heavy chains and multiple heads with heavy and light chains
thin- actin/troponin/tropomyosin complex, binding sites on actin blocked by tropomyosin and troponin (sensitive to Ca)
motor end plate def
post synaptic region of skeletal muscle cell at NMJ
motor unit
all muscle fibers innervated by one somatic motor neuron
type of receptor at motor end plate
nicotinic Ach receptor, increases permeability to Na and K to propograte action potential
describe end plate potential
Na influx exceeds K efflux, creates depolarizing graded potential
threshold reached every time in human skeletal muscle, voltage gated Na channels open
describe skeletal muscle process in response to action potential in sarcolemma/T tubules
L type Ca channels in T tubules (DHP) open, cause Ca to be released from SR via ryanodine receptors (these receptors are coupled mechanically)
Ca diffuses out of SR, causes cross bridging of filaments
a single action potential is enough to bind all ____ for cross bridgning in skeletal muscle
troponin sites
allows for actin binding
ATP is needed for which part of cross bridging
detachment of the myosin head from actin
H Zone
myosin alone
A band
zone of overlap of thick and thin filaments w/i a sarcomere
I band
only thin actin filaments, centered around Z disc
which bands shorten during contraction
HIZ bands
how is Ca removed from cytosol
mostly from SERCA, reuptake into SR
describe tetanus mechanism
response to repeated stimulation- intracellular Ca never returns to low levels causing continued cross bridging
sustained contraction is called tetanus as opposed to single twitch followed by relaxation
Type 1 skeletal muscle has lots of ___
mitochondria, relies on oxidative phosphorylation (low on glycogen)
myoglobin- more of a red color
fn of type 1 skeletal muscle
slow twitch- oxidative phosphorylation is a slow process
good for sustained contraction, fatigue resistant
1 SLOW red ox
contrast type 2B skeletal muscle to type 1
fewer mitochondria, less myoglobin (appear white)
relies more on glycolysis for energy
fast twitch and fatigues quickly, sprinting and extra ocular muscles
describe type 2a skeletal mucles
features of both red and white
fast twitch but has high myoglobin content, relies on oxidative metab
but has lots of glycogen so fatigue resistant
action potentials in skeletal muscle don’t summate, but _____ can
contractions can summate to cause tetany if Ca levels remain elevated
