Copyright © 2010 Pearson Education, Inc. The Muscular System

Copyright © 2010 Pearson Education, Inc. Muscle Fatigue Lab Where was the primary source of energy coming from in order to complete the exercises? What caused the “burning sensation”?

Copyright © 2010 Pearson Education, Inc. Video Questions – Copy Down 1.As it relates to the swimmer, where does most of his energy come from? 2.Carbohydrates are converted to ________. 3.Describe what “hitting the wall” is and why it happens? 4.How does the body get a new fuel source? 5.How does training affect the swimmer’s heart rate? Why is this beneficial?

Copyright © 2010 Pearson Education, Inc. Muscular System State the 3 main types of muscles. Specify the functions of skeletal muscle tissue. Describe the organization of muscle at the tissue level.

Copyright © 2010 Pearson Education, Inc. Introduction 3 types of muscle tissue: –Skeletal –Cardiac –Smooth

Copyright © 2010 Pearson Education, Inc. 7-1: Skeletal Functions 1. Produce movement of skeleton 2. Maintain posture & body position 3. Support soft tissues 4. Guard entrances & exits 5. Regulate body temp

Copyright © 2010 Pearson Education, Inc. 7-2: Skeletal Muscles A.Muscle cells are called fibers B. Blood Vessels C. Nerves D. 3 Layers of Connective Tissue 1.Epimysium: outermost layer, separates muscle from surrounding tissues 2.Perimysium Surrounds muscle fiber bundles (fascicles) Contains blood vessels & nerves 3.Endomysium Surrounds individual muscle fibers Contains stem cells for repair

Copyright © 2010 Pearson Education, Inc. –Collagen from 3 CT layers form: tendons –attach muscle to bone aponeurosis (sheets) –connect muscles

Copyright © 2010 Pearson Education, Inc. Let’s Recap 1.What are the 3 layers of CT in a muscle? List them from superficial to deep. 2.What is the difference between a tendon and an aponeurosis? 3.What is one skeletal function other than movement and support?

Copyright © 2010 Pearson Education, Inc. 7-3: Skeletal Muscle Fibers Sarcolemma (PM) Sarcoplasm (cytoplasm) Transverse tubules - transmit nerve impulses thru entire fiber Sarcoplasmic reticulum - surrounds each myofibril, Stores Ca 2+

Copyright © 2010 Pearson Education, Inc. 7-3: Skeletal Muscle Fibers Myofibrils are bundles of protein filaments called myofilaments: –2 types: 1. Thin filaments made of actin 2. Thick filaments made of myosin

Copyright © 2010 Pearson Education, Inc. 7-3: Skeletal Muscle Fibers Sarcomeres - smallest functional unit –Z lines: boundaries of sarcomere –I Band: ActinA Band: Myosin –Zone of overlap: where thick and thin filaments overlap –H Band: area around the M line has thick filaments but no thin filaments Striations – alternating thick & think filaments

Copyright © 2010 Pearson Education, Inc. Striations

Copyright © 2010 Pearson Education, Inc. 7-3: Skeletal Muscle Fibers Thin filaments –Tropomyosin: covers active sites of actin prevents actin–myosin interaction –Troponin: holds tropomyosin in position Thick filaments – head attaches to active site of actin during contraction, forming a cross-bridge

Copyright © 2010 Pearson Education, Inc. 7-3: Skeletal Muscle Fibers Sliding filament theory 1.SR releases Ca 2+ 2.Ca 2+ binds to troponin  causes shape Δ 3.tropomyosin swings away  exposes active site 4.myosin & actin form cross-bridge  contraction

Copyright © 2010 Pearson Education, Inc. Sarcomere Shortening Figure 7-3

Copyright © 2010 Pearson Education, Inc. Sarcomere Shortening Figure 7-3

Copyright © 2010 Pearson Education, Inc. 7-4: Neuromuscular Junctions (NMJ) NMJ – link btwn motor neuron & muscle fiber (Fig 7-4) 1.Action potential (electrical signal) arrives 2.Neurotransmitter acetylcholine (Ach) is released into synaptic cleft 3.Ach binds to muscle cell at motor end plate  influx of Na + 4.Action potential travels across sarcolemma & down T tubules

Copyright © 2010 Pearson Education, Inc. Structure and Function of the Neuromuscular Junction Figure 7-4 b

Copyright © 2010 Pearson Education, Inc. 7-5: Tension The all-or-none principle: a muscle fiber is either contracted or relaxed But muscle Tension varies –frequency of stimulation ([Ca 2+ ] in sarcoplasm) –fiber’s resting length (length of zones of overlap)

Copyright © 2010 Pearson Education, Inc. Effects of Repeated Stimulations Complete Tetanus (tetany) –maximum tension produced when rate of stimulation eliminates relaxation phase Figure 7-7

Copyright © 2010 Pearson Education, Inc. 7-5: Tension Motor unit – all the muscle fibers controlled by a single motor neuron –Tension varies based on the # of motor units activated –smaller motor unit  more precise control Recruitment – activation of more and more motor units in a muscle  smooth ↑ in tension

Copyright © 2010 Pearson Education, Inc. Motor Units Figure 7-8

Copyright © 2010 Pearson Education, Inc. 7-5: Tension Muscle tone – tension at rest  stabilizes bones & joints Isotonic contraction: muscle Δ’s length Isometric “ ”: muscle develops tension but does NOT Δ length

Copyright © 2010 Pearson Education, Inc. 7-6: ATP (cellular E) Glucose is stored in muscles as glycogen Creatine phosphate (CP) –stores excess ATP in resting muscle –can provide E for ~15 sec.

Copyright © 2010 Pearson Education, Inc. 7-6: ATP A. Aerobic metabolism in mitochondria resting fibers use ATP to form glycogen & CP Contracting fibers use glycogen 1 st, then fat for ATP production provides 95% of ATP in resting cell yields ~34 ATP B. Glycolysis (anaerobic) - breakdown of glucose in sarcoplasm primary E source for peak activity results in lactic acid formation if no O 2 is present yields 2 ATP

Copyright © 2010 Pearson Education, Inc. 7-6: ATP Muscle fatigue results from exhaustion of E reserves OR lactic acid accumulation Recovery period Liver converts lactic acid to pyruvic acid & releases glucose into blood to recharge muscle glycogen reserves –Oxygen debt: additional O 2 is needed

Copyright © 2010 Pearson Education, Inc. 7-7: Fiber Type & Conditioning Hypertrophy: muscle growth –↑’s # of myofibrils, mitochondria & glycogen reserves & muscle fiber diameter Atrophy: fibers become small & weak due to lack of stimulation –↓’s muscle size & tone

Copyright © 2010 Pearson Education, Inc. 7-7: Fiber Type & Conditioning Anaerobic activities: use fast fibers –improved by frequent, brief, intense workouts Aerobic activities (endurance): –supported by mitochondria –improved by cardiovascular training

Copyright © 2010 Pearson Education, Inc. 7-7: Fiber Type & Conditioning Fast fibers –strong, quick contractions –large diameter, few mitochondria –fatigue quickly –large glycogen reserves Slow fibers –slow to contract –small diameter, more mitochondria –high O 2 supply –contain myoglobin (red pigment that stores O 2 )

Copyright © 2010 Pearson Education, Inc. 7-8: Cardiac & Smooth Muscle Cardiac Muscle Cells –1 nucleus –striated, involuntary –branched –connected by intercalated discs contain gap junctions  allow ion movement btwn cells  pass action potentials from cell to cell

Copyright © 2010 Pearson Education, Inc. 7-8: Cardiac & Smooth Muscle –Automaticity: contraction w/o neural stimulation controlled by pacemaker cells –Longer contraction time –No tetanus (sustained contractions)…why is this important? –Ca 2+ come from SR and ECF –Aerobic metabolism only

Copyright © 2010 Pearson Education, Inc. 7-8: Cardiac & Smooth Muscle Smooth Muscle Cells –1 nucleus –nonstriated, involuntary –spindle-shaped –found in walls of blood vessels & organs regulate movement of materials form sphincters (rings)

Copyright © 2010 Pearson Education, Inc. 7-8: Cardiac & Smooth Muscle –Ca 2+ mostly from ECF –contract over greater range of lengths  enable large Δ’s in volume –many cells not innervated (involuntary) contract automatically (by pacesetter cells) or in response to surrounding conditions

Copyright © 2010 Pearson Education, Inc. 7-12: Effects of Aging Skeletal muscle fibers become: – smaller in diameter fewer myofibrils, myoglobin, glycogen, ATP, CP –less elastic (increasing amounts of fibrous tissue (fibrosis)  restricts movement & circulation) Decreased tolerance for exercise –Slower delivery of blood to muscles during exercise, faster fatigue –Impaired ability to eliminate heat  overheating Decreased ability to recover from injury Rate of decline in muscle performance is = in all people