-
what is the neuromuscular junction?
region where a motor neuron communicates with a skeletal musle fiber
-
how does the acetylcholine (ACh) cross to the sarcolemma?
- axon terminal of the neuron vesicles filled with ACh can cross the synaptic cleft to bind to receptors on the sarcolemma
- ACh binds to receptor on the motor end plate.
- Neurons stimulate sarcolemma by generating an action potential
- AChE breaks down ACh thus inactivating the signal
-
what is calsequestrin?
special protein filaments that sequester Ca2+ in bunches inside SR
-
how is calcium stored and released?
- calcium ion pumps in the SR pulls Ca+2 in
- calsequestrin sequester Ca+2 in bunches
- when stimulated, Ca+2 channels open, releasing flood of Ca+2
- Ca+2 channels relcose instantly and Ca+2 is pumped back into SR
-
what happens when sarcomeres contract?
- so does th entire muscle fiber
- as fibers contract, tension is created by tendons pulling on bones
-
how does movement occur?
when tension is greater than the resistance
-
how does variation in tension occur?
- amount of overlap of the myofilaments
- frequency of stimulation
-
what is the maximal strength that a muscle can develop directly related to?
initianl length of its fibers
-
define a muscle twitch
a single stimulus-contraction-relaxation cycle in a muscle fiber or whole muscle
-
what happens in the latent period of muscle twitch?
includes the action potential, release of Ca2+, activitation of troponin/tropomyosin
-
describe the contraction phase
development of tension b.c of the cross-bridge cycle of mysosin and actin
-
what happens in the relaxation period?
tension decreases due to the restorage of Ca2+ and covering of actin active sites
-
wave summation
repeated, frequent stimuli that tirgger a response before full relaxtion has occured
-
incomplete tetanus
near peak tension with little relaxation, while complete tetanus occurs when stimuli are so frequent that relaxtion does not occur
-
treppe?
gradual increase in muscular contraction following rapidly repeated stimulation
-
why is the initial contraction weaker than subsequent?
- increase in ca+2 within sarcoplasm, so more active sites exposed, more cross-bridgin gof actin-myosin
- neural component: more moto units firing
-
what is a motor unit?
a single motor neuron and all the muscle fibers it innervates
-
what are two types of motor unit?
- fine control movement: use motor units with very few fibers per neuron
- gross movements: use motor units have a high fiber-to-neuron ration
-
how are motor units recruited?
activiation of more and more units to produce adequate tension beginning with the small neurons first (smooth gradation of increasing strength)
-
-
what is isotonic muscle contraction?
when the length of the muscle changes, but the tension remains the same until relaxation
-
what is isometric contraction?
when the whole muscle length stays the same, the tension produced does not exceed the load
-
elongation of muscle after contraction passively uses a combination of what?
gravity, elastic forces, oposing muscle movement
-
what happens to glucose and fatty acids as being catabolized
ATP produced to used to power contractions
-
what are the products for lactic acid fermentation?
- pyruvate reduced to lactate and NADH oxidzed to NAD+
- lactate is carrie by the blood to theliver, whiere it is converted to another time
-
energy sources of skeletal muscle during work?
- ATP
- creatine phosphate
- anaerobic
- aerobic glycolysis
|
|