SMT 2 again Flashcards
what happen when the calcium binds to troponin C in the muscle fiber cytosol?
the troponin complex undergoes a conformational change and Troponin T “pulls” tropomyosin and Troponin I off the myosin-binding site of G-actin subunits
what are the steps of cross-bridge cycle
- ATP hydrolysis
- cross-bridge formation
- power stroke
- detachment of myosin from actin
prior to myosin being able to bind to actin, it must be ?
“energized”
what happens when myosin is bound to ATP
it lowers it’s affinity for actin and there is no cross-bridge formation
what hydrolyses ATP -> ADP + Pi in the myosin head?
intrinsic ATPase activity
hydrolysis causes what change in the mysoin head?
causes the myosin head to pivot, moving down the actin filament so that it lines up with a new actin monomer
calcium binding to troponin, has uncovered what?
the mysoin-binding site on actin
the energized myosin head attached to the mysoin-binding site on actin and what is released?
Pi
when the myosin head is attached to the myosin-binding site, this creates what?
a myosin-actin cross bridge
the cross bridge generates force as what?
as myosin neck rotates toward center or sarcomere
what is getting closer together, shortening the sarcomere and generating force?
Z lines
what dissociates from myosin and the actin-myosin complex is left in a rigid, “attached” state?
ADP
what binds to myosin and myosin detaches from actin
ATP
what is isometric contractions?
muscle contracts against force transducer without decreasing muscle length
when does isometric contractions occur?
occurs when the load is greater than the force of muscle contraction
what is isotonic contractions?
muscle shortens against a fixed load
when does isotonic contractions occur?
occurs when the force fo the muscle contraction is greater than the load and the tension on the muscle remains constant
what binds to free calcium within the SR
calsequestrin and calreticulin
there are 2 main types of muscle fiber types which are?
type 1 (slow fibers)
type II (fast fibers)
which fiber type is generally smaller and innervated by smaller nerve fibers?
type 1 or slow fibers
which fiber type is larger in size and innervated by large nerve fibers
type 2 or fast fibers
what are the two subtypes of type II fast fibers
Type IIA - fast oxidative glycolytic fibers
type IIB - fast glycolytic fibers
which type of muscle fiber has more capillaries to supply higher amounts of oxygen
type I/ slow fibers
which type of muscle fiber has lots of SR for rapid Ca2+ release
type II/ fast fibers
which type of muscle fiber has lots of myoglobin, giving a reddish appearance
type I/slow fibers
which type of muscle fiber has lots of mitochondria to support high levels of oxidative metabolism
type I/slow fibers
proportions of type I and II fibers seems to be partially determined by ?
genetic inheritance
there are 3 different metabolic systems responsible for recycling AMP and ADP back into ATP to provide a continuous supply of ATP in muscle fibers. what are the 3 metabolic systems?
- phosphagen system
- glycogen lactic acid system
- aerobic system
T or F: phosphorylated creatine molecule has a low energy phosphate bond
false, phosphorylated creatine molecule has a high energy phosphate bond
T or F: high energy phosphate bond of phosphocreatine has more energy than the bond of ATP
true
Both phosphocreatine and ATP together constitute the ?
phosphagen system
the phosphagen system provide how long of maximal power?
8-10 seconds of maximal power
what is the initial stage of the glycogen-lactic acid system
glycolysis
in the case of insufficient oxygen, pyruvate will be converted into what?
lactate
what happens after the pyruvate converting into lactate
it diffuses out of the muscle cells into the interstitial fluid and blood
glycogen lactic acid system can sustain maximal muscle contraction for ?
1.3-1.6 minutes
what is the name of the process of glucose -> pyruvate -> lactate -> glucose
cori cycle
what is the overall net loss or gain of ATP in the Cori cycle?
overall loss of 4 ATP
What is the purpose of the cori cycle?
providing muscle fibers with 2 ATP, replenishing NAD+ for glycolysis, prevents build-up of lactic acid in skeletal muscle
in presence of oxygen, what happens to pyruvate?
pyruvate is broken down into carbon dioxide, water, and energy via citric acid cycle and ETC
as long as nutrients in the body last, the aerobic system can be used for ?
unlimited duration
muscle strength is determined mainly by what?
its overall size
what is muscle power?
the measure of the amount of work that the muscle can perform in a given period of time
the endurance of muscle depends on
the amount of glycogen that has been stored in the muscle prior to the period of exercise and depends on the type and size of muscle fibre
what is muscle atrophy
muscle no longer receives contractile signals required to maintain normal muscle size
what is muscle hypertrophy
results from an increase in the number of actin and myosin filaments in each muscle fiber = enlarges individual muscle fibers
what is hyperplasia
formation of new muscle fibers
what is muscle lengthening
occurs when muscles are stretched to a greater than normal length which causes new sarcomeres to be added at the ends of the muscle fibers where they attach to the tendons
