Muscle Anatomy and Contraction Muscle Music

Muscle Terms---Anatomy Fascia = fibrous connective tissue that separates individual skeletal muscle, connects to tendon then to periosteum of the bone. Aponeuroses broad fibrous sheets that attach to bone or to coverings of other muscles.  Sarcoplasm  cytoplasm of a muscle cell Sarcolemma cell membrane of a muscle Sarcomere 1 muscle unit of actin and myosin I bands  light bands (actin) attached to Z lines A bands dark bands (myosin) thin filaments slide towards the thick

I. Nerve Stimulus and Action Potential A. One motor neuron can stimulate 1 or 1000’s of muscle fibers 1. One neuron + muscle cell = motor unit 2. Neuromuscular junction = where nerve and muscle almost meet Draw a Neuromuscular Junction Fig. 8.5 pg. 180

B. The start of a nerve impulse… Axon terminals of nerve release a “neurotransmitter” called… Acetylcholine (ACH) which… 1. Makes muscle temporarily permeable to Na+, creates an electrical current called an action potential which is unstoppable, runs the entire length of the muscle 2. Then it returns to a resting stage (K+ out of cells)

II. The “Sliding Filament” theory A. Myosin heads attach and detach to actin repeatedly; each time “pulling” on actin… muscle shortens/contracts 1. Myosin heads “cock” forward and some are always in touch with actin … no backsliding 2. Requires Ca+2, it moves proteins so binding sites are free B. While action potential is occurring, the ACH is being broken down… prevents contraction in absence of impulse Sliding Filament Theory

III. Types of Contractions Part 2 Sliding Filament Theory A. Graded response = “all or none” law to muscle cell not whole muscle; full contraction never partial 1. Twitches (sometimes brief and jerky)= nerve impulses are rapid, contractions are summed up which creates a smooth sustained contraction 2. Strongest contraction = all cells stimulated to fullest potential

B. Isotonic vs. Isometric 1. Isotonic = “same tone/tension” ex. Smiling, bending knee 2. Isometric = “same measurement”, myosin heads are “spinning their wheels” Ex. Lifting 400lbs. Or pushing a car 3. Muscle tone = continuous partial contraction (even when relaxed) 4. Opposite of muscle tone = Flaccid or flabby, muscles atrophy when not used

IV. Muscle Fatigue and O2 debt AKA: Anaerobic Respiration * Can’t contract even if stimulated. Person can’t consume enough oxygen quick enough; lactic acid builds up, ATP runs low, rarely occurs to us. Afterwards, breathe deeply until enough O2 is absorbed to remove lactic acid.