Overview of Muscle Tissues and Contraction Mechanisms

1. Chapter 6 The Muscular System

2. I.Overview of Muscle Tissues • Differ in cell structure,location, and how they are stimulated to contract • Smooth and skeletal muscle cells are elongated and called ________________________ • Contraction-shortening-depends on 2 types of myofilaments • Terms myo-,sarco- and mys- refers to muscle-example-muscular cytoplasm is called ___________________. Muscle fibers sarcoplasm

3. skeletal muscle • attach to skeleton and form smoother contours of body • huge,cigar shaped and ______________________ • largest of muscle fibers-as much as 30 cm in length • __________________________with obvious stripes • ___________________since only muscle subject to conscious control Voluntary muscle multinucleate striated

4. However,subject to involuntary reflexes • Tire easily and requires rest • Fairly fragile • Bound by ___________________________which provides strength and support Connective tissue

5. Each muscle fiber contained in a declicate connective tissue sheath called ___________________________ • _________________________-connective tissue wrapping a bundle of fibers called a _________________ perimysium endomysium fascicle

6. ___________________________= many fascicle bound together w/ this tough coat • Epimysia blend into the strong_,cordlike_________ or aponeurose(sheetlike) that connect muscle to bones,cartilages or connective tissue • Other functions of tendons-besides movement-are durability and conservation of space epimysium tendons

8. Smooth Muscle • No striations and is involuntary • Mainly in walls of hallow visceral organs such as ____________________________________________________________________________________ • Propel substances on a definite tract or pathway • Spindle shaped and uninucleate Stomach,bladder,and respiratory passages

9. Scant endomysium • Most often in 2 layers-one running circularily and one running longitudinally-alternately contract or relaxing changing size and shape of organ

11. Cardiac Muscle • Only in heart • Forms most of heart walls • ________________________but involuntary • Cushioned in bundles w/ small amount of endomysium striated

12. When heart contracts,internal chambers get smaller,forcing blood into arteries leaving heart • Branching cells joined by junctions-___________________________________These traits and spiral arrangement of bundles allow heart activity to be closely coordinated,giving steady contraction rate • ______________________can shift heart into “high gear” Nervous system Intercalated discs

13. ****** We focus mostly on skeletal muscle here!

16. Muscle Functions • _______________________as a result of muscle contraction;quick response to environment • Maintaining _____________-maintain erect posture despite gravity • Stabilizing ________________-esp. w/ poorly fitting articulating surfaces as in shoulder • _________________________________-by –product of muscle activity;ATP used for contractions and ~40% released as heat to mostly maintain normal body temp for at least 40% of body mass movement posture joints Generating heat

17. II. Microscopic Anatomy of Skeletal Muscle • ________________________ = plasma membrane of muscle cells • Nuclei pushed aside by ________________-long ribbonlike organelles;have alternating light (I) and dark (D) bands along myofibrils-give striped appearance • I band has midline interruption - darker__________________ sarcolemma Z disc myofibrils

18. A band has lighter central area called _____________-Its M line contains tiny protein rods that hold thick filaments together • Myofibril actually chains of contractile units-_____________________-line up end –to- endalong myofibril length • 2 type of protein myofilaments-larger are ___________________ made of bundled myosin • –extend length of A band sarcomeres H zone Thick flaments

19. Also contain ATP enzymes to generate ATP for energy- • Ends studded w/ small projections-____________________________ • Thin filaments composed of ______________-called actin filaments-anchored to z disc-do not extend into end of relaxed sarcomere,so central region-_________________is sometimes called bare zone Contractile protein H zone cross bridges

20. Sarcoplasmic Reticulum • In a contraction,bare zone does not appear because actin and myosin completely overlapped • ______________________________(SR)-specialized smooth ER-tubules and sacs surround every myofibril-picture a crocheted sleeve-Role is to__________________________________________________________________________ Store calcium and release to stimulated muscle fiber on demand…contraction occurs

21. III. Skeletal Muscle Activity • A)Stimulation and Contraction of Single Muscle Cells • Functional properties include 1)___________________(irritability/responsiveness)-abilty to receive and respond to stimulus • 2) _______________________-ability to forcibly shorten when stimulated • 3) _________________________-ability of muscle cells to stretch • 4)__________________________-ability to recoil and resume resting length contractility Excitability elasticity extensibility

22. Nerve stimulus and Action Potential: • Must receive nerve stimulus • May be a few or 100’s of muscles cells stimulated by a nerve cell______________________ • _____________________= 1 neuron and all skeletal muscles stimulated • __________-long extension of nerve cell-branches into axon terminals when it reaches muscle,each forming a junction w/sarcolemma=_________________junctions Motor unit neuron Neuromuscular junction Nerve fiber or axon

23. Nerve and muscle are close but do not totally meet-forming ____________________(has interstitial fluid) • When nerve impulse reaches terminals-___________________________is released-Ach-________________________in the case of skeletal muscles neurotransmitter Synaptic cleft acetylcholine

24. Ach attaches to receptors(membrane proteins)part of sarcolemma.With enough Ach ,sarcolemma is more permeable to Na+ that diffuse out of cell….more Na enters than K+ leaves----creates a current called ___________________________-now unstoppable-result in muscle contraction • Ach is broken down into ____________________________by enzymes acetylcholinesterase-AChE-during action potential,so one impulse makes one contraction action potential Acetic acid and choline

25. Returns to resting state by… • diffusion of ___________out of cell • operations of ________________pumping NA+ and K+ ions back to original position Sodium potassium pump K+

26. Mechanism of Muscle Contraction • _________________________TheoryWhen muscle fibers are activated by nervous system,myosin heads attach to binding sites on thin filaments and sliding begins.Each cross bridge attach and detach several times during a contraction-pulling filaments towards center of sacromere and cell shortens • The movement of myosin cross bridges is somewhat like that of a centipede • The attachment of myosin cross bridges to actin requires Ca2+ ions,which come from inside the cell where action potentials stimulate sarcoplasmic retuiculum to release Ca2+ into cytoplasm.This triggers the binding of myosin to actin causing filaments sliding • When action potential ends,Ca2+ ions are reabsorbed into SR storage areas and muscle cell relaxes Sliding filament theory

27. Contraction of skeletal muscles as a whole • Whole muscle responds to “all or none principle ”,but whole muscle reacts in _____________________ • Can be changed by ________________________of muscle stimulation and by changing # muscle fibers stimulated • ____________________________=brief jerky contractions • Normally,nerve impulses are delivered at a very fast rate w/o much relaxation Changing frequency Graded responses Muscle twitches

28. Smooth,rapid sustained contractions called _____________or complete,tetanus • Until complete tetanus is reached,the muscle is said to be ______________________________tetanus • Muscle contractions can be slight or vigorous depending on work to be done and thus innervation • Energy for muscle contractions-needs to make ATP Unfused or incomplete fused

29. Energy for muscle contractions-needs to make ATP: • Direct phosphorylation of ADP by creatine phosphate(CP)-found in ______________but not other cell types.As ATP is used,reactions between CP and ADP generates more ATP.(CP supply quickly exhausted • ________________-for light to moderate exercise,95% ATP comes from aerobic-cellular respiration-from mitochondrion….the collection of chemical pathways are also called ______________________.Glucose broken down to CO2 and H2O 36 ATP/1 g glucose-fairly slow and requires continuous O2. Muscle fibers Aerobic respiration Oxidative phosphorylation

30. ____________________________- occurs to provide pyruvic acid for cell respiration---occurring in cytosol.After this ,w/o O2,fermentation via production of _______________________occurs-5% of ATP from each glucose-promotes muscle fatigue and soreness Lactic acid fermentation or anaerobic glycolysis glycolysis

31. ___________________________occurs if muscle is unable to contract even though it is still innervated…usually caused from ___________________________________________ during prolonged muscle activity….alot dependent on muscle supply….breathing rapidly and deeply will generate more ATP Muscle fatigue O2 deficit

32. Types of Muscle contractions: • ________________________________-myofilaments are successful in sliding movements,muscle shortens and causes movement-eg. Knee bending • _______________________________________-myosin myofilaments are “spinning their wheels”and tensions continually increases -trying to slide but you are attempting to move something immovable Isotonic contractions Isometric contraction

33. ____________________________--state of continuous partial contraction-firm and ready for action • ____________________-if muscle is not innervated and becomes soft and flabby • ___________wasting away of a muscle • Aerobic –or endurance-exercise-results in stronger,more flexible muscles and subjected to less fatigue(jogging,biking)-results partly because of greater blood supply-also enhances metabolism in general-improving digestion,elimination,coordination and cardiovascular system………..but does not increase muscle size much • Resistance –or ______________________exercises increases muscle size-increase individual muscle cell size(make more contractile filaments and increases connective tissue0 flaccid Muscle tone atrophy isometric

34. IV.Muscle Movements,Types and names

35. Types of Body Movement • Every one of our 660+skeletal muscles is attached to bone or other connective tissue at no fewer than 2 points: • ____________attached to immovable or less movable bone • ______________attached to more movable bone • Muscle moves toward origin in contraction origin insertion

36. flexion extension Most common movements : • ___________________movement mainly in sagittal plane that decreases < of joint and brings 2 bones closer together-eg.knee and elbow • ____________________opposite of flexion and increases >-eg straightening knee • ________________________movement of bone around longitudinal axis-eg in ball- and- socket joints • __________________________-moving limb away from midline • ___________________________opposite of abduction-toward bodyline • ___________________________-combination of flexion,extension,abduction,adduction commonly seen in ball-and socket-proximal end of limb is stationary,and its distal end moves in a circle-outlines a cone abduction rotation circumduction adduction

37. Dorsiflexion and plantar flexion B.Special Movements • ____________________________-Up and Down movement of foot at ankle:pulled toward shin is dorsiflexion and pointing towards toe is plantar flexion • _____________________________invert turn sole medially and evert,turn sole laterally • ___________________________________-supination-turn backwards @ radius and ulna-forearm rotates laterally to turn palm anterior laterally-radius and ulna parallel/pronation when forearm rotates medially-palm faces posterior-radius and ulna form X. • ___________________________-opposition from saddle joint in hand-moves ththumb to touch other fingers Inversion and eversion opposition Supination and pronation

38. C. Interactions of Skeletal Muscles in the Body • Muscles can only pull • ____________________________-major muscle responsible for designated movement • _________________________ -oppose or reverse a movement • __________________________-help prime movers by doing same movement or reducing undesirable movement-example:making a fist w/o moving wrist • Fixators-specialized synergists-hold a bone still or stabilize origin of prime mover so all tension used to move insertion bone synergists antagonists Prime mover

39. Size of muscle Naming skeletal muscles # of origins • Direction of muscle fibers-in re to an imaginary line-example-rectus(straight)-rectus femoris-straight muscle of thigh • _____________________________________-maximus,minimus,longus • location of muscle-associated bone used in name often eg-temporalis muscle overlies temporal bone • _____________________________________-eg. Biceps-2 origins • Location of muscle’s origin and insertion-eg.sternocleidomatstoid-origin in sternum and clavicle-inserts in mastoid process of temporal bone • _________________________________-eg.deltoid means triangular • _________________________________-eg-flexor Muscle shape Action of muscle

40. convergent circular E. Arrangement of Fascicles • ________________-fascicles in concentric circles(spinchters • __________________-meet at a single insertion-triangular or fan shaped • ________________________-parallel to long axis of muscle • __________________________-spindle –shaped muscle w/expanded center(biceps brachii) • _____________________-short fascicles attach obliquely to a central tendon parallel fusiform pennate