Unit 3 slide 1 Muscular System ____ Human skeletal muscles

Unit 3 slide 2 Muscular System Helps maintain homeostasis by … –_______ –__________ –Communication –Control of body openings and passages –_____ production

Unit 3 slide 3 Muscle Tissues 3 types of muscle tissue –Skeletal muscle –_______ muscle –_____ muscle Trivia: about ____% of body mass is skeletal muscle in someone of “normal” height and weight

Unit 3 slide 4 Muscles A particular muscle, e.g., the biceps brachii, is an organ composed of skeletal muscle tissue, connective tissue, etc. “Muscular system” really refers to the ________ muscles

Unit 3 slide 5 Skeletal Muscle Connective tissues –____mysium, around individual muscle cells (muscle cells = muscle fibers) –____mysium, around fascicles –____mysium, around entire muscle, blends into CT sheets called fascia

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Unit 3 slide 7 Skeletal Muscle Attachment to bone –________ attachment – epimysium blends into periosteum –__________ attachment – tendon composed of dense regular CT –Aponeurosis – broad, flat tendon connecting muscle to muscle

Unit 3 slide 8 Origin & Insertion ______ – the muscle attachment at the relatively stationary end ________ – the muscle attachment at the more mobile end Example, triceps brachii –O: scapula, proximal humerus –I: olecranon

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Unit 3 slide 10 Skeletal Muscle Histology “_____” = flesh, so many terms in this unit have “sarco” in their name Sarcoplasm = cytoplasm _________ reticulum = modified endoplasmic reticulum ________ = contractile unit

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Unit 3 slide 12 Sarcomere Functional unit of skeletal muscle Thick filaments –______ Thin filaments –_____ –Troponin –__________ Transverse tubules (T tubules)

Unit 3 slide 13 Thick and Thin Filaments Thick: –Myosin sort of looks like a golf ____ Thin: –“_____” of g-actin form a twisted pair of strands –Troponin and tropomyosin attached

Unit 3 slide 14 Sarcomere A band I band H band Z disc Sarcomere = Z disc to Z disc Myofibril = many sarcomeres, end to end

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Unit 3 slide 16 Contraction Occurs when myosin head groups pull on actin filaments Binding site blocked by _______ –Ca +2 ions bind to troponin, troponin changes shape and pulls tropomyosin out of the way –Now myosin can get at the actin

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Unit 3 slide 18 Excitation-Contraction Action potential hits T tubules and dives down into sarcoplasm 1. Voltage-gated Ca +2 channels open in terminal cisternae of SR, Ca +2 flows out of the SR and into the sarcoplasm 2. Ca +2 binds to troponin Troponin pulls tropomyosin away from myosin binding sites on actin filaments

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Unit 3 slide 20 Excitation-Contraction Myosin-ATP complex hydrolyses ATP to ADP and P i (activation) 3. Myosin-ADP-P i complex binds to actin 4. ADP and P i float away (power stroke) 5. Myosin releases actin when new ATP binds to head group

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Unit 3 slide 22 Excitation-Contraction Motor neuron stops releasing ACh Acetylcholinesterase (AChE) clears ACh from synaptic cleft Ca +2 pumped back into SR Tropomyosin moves back to block the binding sites on the actin filaments

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Unit 3 slide 24 Muscle Metabolism Immediate energy sources –Use the O 2 that’s already there in the muscle –Use myokinase and creatine kinase to make ATP Short-term energy sources –Emergency use only! –Anaerobic glycolysis (glycogen, lactic acid) Long-term energy sources –Back to aerobic cellular respiration as the blood flow to the muscle increases –A marathon runner tries to go from immediate energy to long-term energy without short-term

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Unit 3 slide 27 Slow- & Fast-Twitch ____-twitch fibers (oxidative) –Endurance fibers, dark meat –Lots of myoglobin, mitochondria, capillaries ______-twitch fibers (glycolytic) –Run-away-from-the-tiger fibers, white meat –Low myoglobin and mitochondria, not so many capillaries, plenty of glycogen

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Skeletal Muscle Shapes 1

Skeletal Muscle Shapes 2 ________ muscles –thick in middle and tapered at ends –biceps brachii m. _________ muscles have parallel fascicles –rectus abdominis m. ___________muscle –broad at origin and tapering to a narrower insertion Pennate muscles –fascicles insert obliquely on a tendon –unipennate, bipennate or multipennate –palmar interosseus, rectus femoris and deltoid ________ muscles –ring around body opening –orbicularis oculi

Unit 3 slide 31 Cardiac Muscle Striated like skeletal muscle Shorter cells, often branched Only one nucleus per cell ____________ discs between cells

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Unit 3 slide 33 Smooth Muscle One nucleus per cell No visible _________ Contracts in response to changes in the local environment –chemical stimuli (hormones, low O 2, low pH, etc.) –stretch (bladder,stomach) Or in response to ____________ nerve fibers

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Unit 3 slide 35 Smooth Muscle Still myosin pulling on actin, but not arranged in ______________ Actin anchors to plasma membrane, twisted Nerf football effect Calmodulin: Ca +2 binding protein, sort of equivalent to troponin in skeletal muscle

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