exam 1 musculoskeletal physiology Flashcards
skeletal muscle
striated, tubular and multinucleate
voluntary
attached to skeleton
smooth muscle
non striated, spindle shaped, uninucleate
involuntary
covers walls of internal organs
cardiac muscle
striated, branched and uninucleated
involuntary
covers heart wall
isotonic
load is constant, muscle shortens
isometric
load is increasing, muscle doesn’t shorten
muscle fiber characteristics
very long and multinucleate, surrounded by sarcolemma
fascicle is made of what
made of muscle fibers
muscle is made of
fascicles
myofibrils are made of what and what do they do
thin and thin filaments, surrounded by sarcoplasmic reticulum
these make up the muscle fibers
thick filament
myosin
thin filament
actin
types of troponin
T, I, C
T troponin
tropomyosin
I troponin
inhibits actin binding
C troponin
binds calcium
dystrophin function
holds sarcomeres together
sarcolemma surrounds what?
muscle fibers
what initiates contraction?
high intracellular calcium
what causes relaxation?
low intracellular calcium
where does contractile intracellular calcium come from?
sarcoplasmic reticulum
what protein sequesters calcium into the SR?
SERCA
what regulates calcium release from the SR?
RyR (ryanadine receptor)
what does calsequestrin do?
binds calcium in the SR
what is a dihydropuridine receptor?
it is a voltage gated calcium receptor on T tubules that activates RyR receptors
ATP binds myosin to cause what?
released state
ATP hydrolysis causes
myosin head to move to a cocked position
calcium presence during the cocked state causes what?
binding of myosin to actin
Pi is released and causes what?
strong cross bridge state and power stroke
what happens after the power stroke?
ADP is released, and actin and myosin are bound until ATP binds
what happens when calcium binds troponin C?
tropomyosin (troponin T) moves to reveal the myosin binding site on actin
what causes tetanus?
large intracellular store of Ca++ due to repeated stimulation
slow twitch muscle characteristics
red, do oxidative metabolism with high mitochondria and low glycogen
Fast twitch type IIa muscle fiber characteristics
red, do oxidative metabolism with very high mitochondria and have abundant glycogen
Fast twitch type IIx/b muscle fiber characteristics
fatiguable, white, glycolytic metabolism, fewer mitochondria and high glycogen
what is frequency summation?
increased force within a single fiber by summing multiple twitches
what is a motor unit
motor neuron and the muscle fibers that it innervates
innervation ratio
myofibrils: neuron
fast twitch: 1 neuron innervates many fibers
slow twitch: 1 neuron innervates less fibers
what is CICR
calcium induced calcium release, utilized by cardiac muscles because DHP is not linked to RyR
cardiac action potentials driven by
Ca++ or Na+
relative speed of each muscle
skeletal > smooth > cardiac
what does the IP3 receptor do
mediated calcium release from the endoplasmic reticulum
what does calcium calmodulin do?
activates MLCK to phosphorylate MLC, causes cross bridge cycling in cardiac and smooth muscle
neuron AP causes release of
acetylcholine
Ach receptor in muscle
nicotinic
muscle APs cause depolarization of?
sarcolemma and T tubules, opens voltage gated Na+ channels
what causes muscle contraction
increase in calcium
what initiates fusion of the vesicle with the membrane?
calcium
myasthenia gravis, cause and presentation
destruction of nicotinic receptors: droopy eyes, generalizes muscle weakness
Lambert eaton cause and presentation
destruction of voltage gated calcium channels on the presynaptic side, gets better throughout the day
