Muscle Structures and Organization
Which connective tissue later surrounds individual muscle fibers
What is the Endomysium
Which ion directly triggers the exposure of myosin-binding sites on actin
What is Calcium
approximately how long can stored ATP sustain maximum muscle actively before regeneration is needed
4-6 seconds
define muscle atrophy and explain one primary cause
which neurotransmitter is released at the neuromuscular junction to initiate contraction
acetylcholine (ACh)
The repeating contractile units in myofibrils are called what
What is the sarcomere
What is the role of acetylcholine at the neuromuscular junction
What is binding to receptors on the motor end plate, opening ion channels for depolarizing the sarcomere
which high-energy molecule donates a phosphate to ADP during short bursts of activity
Creatine phosphate, via creatine kinase
What physiological difference between hypotonia and hypertonia
What is decreased tone/flaccidity versus increased tone/flaccidity (respectively)
Describe how the motor unit concept ensures graded control of muscle contraction
What is Motor units allowing graded strength by recruiting varying numbers of fibers
What is the functional difference between a fascicle and a myofibril
What is a bundle of muscle fibers versus an organelle within one fiber that contains contractile proteins (respectively)
During which phase of a muscle twitch is calcium actively pumped back into the sarcoplasmic reticulum
What is relaxation phase
What are the three main pathwyas used by muscles to regenerate ATP
Whatare creatine kinase, anaerobic glycolysis, and aerobic respiraion
Explain the process of muscle hypertrophy on a cellular level
What is enlarging existing fibers via increased myofibrils, mitochondria, and glyocgen stores
What is the physiological importance of the refractory period in muscle fibers
What is reventing overlapping ocntrctions, ensuring proper relaxation, and force coordination
Explain why skeletal muscle fibers are multinucleated
What is formed from myoblast fusion and support high protein synthesis demand
Compare isotonic and isometric contractions in terms of muscle length and tension
What is muscle changing length/ tension constant, tension increases/ length constant (respectively)
Why does lactic acid build up during anaerobic respiration, and what is its physiological consequence
What is the lack of oxygen, preventing pyruvate oxidation, lactic acid lowers pH- causing fatigue
How can denervation (loss of nerve supply) lead to permanent muscle changes
What is irreversible atrophy and fibrosis from lack of nerve stimulation and trophic signals stopping
How do action potentials differ in nerve versus muscle cells
What is neurons producing rapid, brief spikes, while muscle fibers generate longer depolarizations tied with contractions
How do T-tubules contribute to muscle contraction efficiency
What is T-tubules transmitting action potentials deep into the fiber, ensuring simultaneous contraction throughout
Explain the sliding filament theory using both actin and myosin behavior
(Describe how the myosin head attached to actin, pulls filaments towards the M-line, detach, and "reset" using ATP)
Describe how endurance training alters muscle metabolism and mitochondrial denisty
What is increasing mitochondral count and oxidative enzymes, improving ATP yield and resistence to fatigue
why does paralysis lead to muscle generation even if blood flow remains intact
What is the lack of nerve input, which maintains contractile protein turnover necesary to prevent protein degradation and denervation atrophy
Explain how diseases affecting acetylcholine receptors impair muscle contraction
What are autoantibodies blocking ACh receptors, preventing depolarization and leading to muscle weakness