Excitation-Contraction Coupling Flashcards
Amyotrophic lateral sclerosis
motor neuron death in the spinal cord; reduced excitation
weakness, spasticity, muscle atrophy
injury
axonal damage; reduced excitation
variable: paralysis, weakness, often some recovery
Demyelination Guillan-Barre
nerve disease; autoimmune response against myelin; reduced excitation
ascending paralysis, weakness
Myasthenia-Gravis
neuromuscular junction disease; autoimmune response against Acetylcholine receptor; reduced excitation
muscle weakness, sometimes paralysis
Muscular Dystrophy
muscle disease; reduced attachment of muscle to ensheathing membrane; reduced contraction
muscle weakness and atrophy
Malignant Hyperthermia
sarcomere disesae; mutation in Ryr1 causing excessive calcium release in muscle. triggered by inhaled anesthetics; reduced contraction
blood CO2 buildup, hyperthermia, circulatory collapse
calsequestrin
binds to calcium in the SR
triad junction
sarcoplasmic reticulum cisterna, transverse tubule, sarcoplasmic reticulum cisterna
ryanodine
plant alkaloid that binds to and opens SR calcium release channels (ryanodine receptors) at nanamolar concentration. Higher concentrations (micromolar) closes ryanodine receptors.
calcium induced calcium release (CICR)
small amount of calcium released into the cytoplasm by ryanodine receptors (at the tried) triggers adjacent ryanodine receptors (away from triad) to open and release calcium which in turn triggers the opening of additional ryanodine receptors
Sarcoplasmic reticulum calcium ATPase (SERCA)
uses energy of ATP hydrolysis to pump calcium back into the SR where it can be bound by calcium binding proteins Calreticulin and Calsequestrin
Sodium Calcium eXchanger (NCX)
NCX lets 3 sodium ions into cell to remove 1 calcium ion from the cell
summation
increase in muscle tension from successive action potentials
tetanus
maintained contraction in response to repetitive stimulation
fused vs unfused tetanus
fused tenatus is tetanus without oscillations
twitch
single action potential
strength of contraction of skeletal muscle determined by
frequency of stimulation (rate coding) and recruitment of additional motor units
treppe
steady increase in tension in successive twitches. different than summation. results in an increase in calcium concentration
motor unit
somatic motor neuron and all the muscle fibers (myofibers) it innervates
size principle
how motor units are recruited. smaller motor units are recruit first before large motor units.
force generated when skeletal muscle is stimulated is related to
size of the motor units stimulated, number of motor units activated, frequency of stimulation of the muscle fibers
muscle pain (burn)
is produced by lactic build up that accumulates in the muscle fiber
delayed onset muscle soreness (DOMS)
occurs in the days following intense muscle use, not correlated with lactic acid levels
muscle fatigue
decline in muscle tension as a result of previous contractile activity. decreased shortening velocity and slower rate of relaxation
high frequency fatigue
accompanies high intensity short duration exercise; failure in the conduction of action potential in the T tubule
low frequency fatigue
seen with low intensity, long duration exercise; due to buildup of lactic acid and phosphates
