Untitled Flashcards Set

Chapter 08: Skeletal Muscle

·       Epimysium: surround entire muscle

·       Perimysium: surrounds bundles of muscle fibers (fascicles)

·       Endomysium: surrounds individual muscle fibers

·       Basement membrane: just below the endomysium

·       Sarcolemma: muscle cell membrane

·       Satellite cells play a key role in muscle growth and repair

o   During muscle growth, satellite cells increase the number of nuclei in mature muscle fibers (reside above the sarcolemma)

·       Myonuclear domain: the volume of cytoplasm surrounding each nucleus (each nucleus can support a limited myonuclear domain)

·       More nuclei allow for greater protein synthesis

o   Important for muscle growth in response to strength training

·       NMJ is the junction between motor neuron and muscle fiber

·       Motor end plate: pocket formed around motor neuron by sarcolemma

·       Neuromuscular cleft: short gap between neuron and muscle fiber

·       Acetylcholine is released form the motor neuron

o   Causes an end-plate potential (EPP): depolarization of the muscle fibe

·       Sliding filament theory – Huxley

·       Sarcomere shortening – what theory is this called?

o   Crossbridge formation = power stroke

·       What are myofilaments?

·       What lines shorten/get closer together? Z lines

·       Excitation contraction coupling: depolarization of motor end plate (excitation) is coupled to muscular contraction

o   Action potential travels down transverse tubules and causes release of Ca++ from the sarcoplasmic reticulum

o   Ca++ binds to troponin and causes tropomyosin to move

§  Exposes myosin binding sites on actin

o   Strong binding site formed between filaments’

o   Contraction occurs (power stroke)

·       Myosin ATPase

·       Muscle biopsy: small piece of muscle removed, may not be representative of entire body

·       Immunohistochemical staining: selective antibody binds to unique myosin isoforms, fiber types differentiated by differences in color

·       Gel electrophoresis: identify myosin isoforms by separating myosin isoforms on gel

·       Number and types of motor units recruited’

o   More muscle units = greater force

o   Fast muscle units = greater force

·       Muscle length

o   “ideal” length for force generation

o   Increased cross-bridge formation

·       Firing rate of motor units: frequency of stimulation

o   Simple twitch, summation, tetanus

·       Contractile history of muscle: rested muscle vs muscle exposed to fatiguing exercise, warmup exercise results in “post activation potentiation”