body muscels system 1

1. body muscels system 1 دکترامیر هوشنگ واحدی متخصص طب فیزیکی و توانبخشی قسمت 2

3. Muscle Tissue Properties • Skeletal muscle tissue has 4 properties related to its ability to produce force & movement about joints • Irritability • Contractility • Extensibility • Elasticity

4. Muscle Tissue Properties • Irritability - property of muscle being sensitive or responsive to chemical, electrical, or mechanical stimuli • Contractility - ability of muscle to contract & develop tension or internal force against resistance when stimulated

5. Muscle Tissue Properties • Extensibility - ability of muscle to be stretched back to its original length following contraction • Elasticity - ability of muscle to return to its original length following stretching

6. Muscle Terminology • Intrinsic - pertaining usually to muscles within or belonging solely to body part upon which they act • Ex. small intrinsic muscles found entirely within the hand

7. Muscle Terminology • Extrinsic - pertaining usually to muscles that arise or originate outside of (proximal to) body part upon which they act • Ex. forearm muscles that attach proximally on distal humerus and insert on fingers

8. Muscle Terminology • Action - specific movement of joint resulting from a concentric contraction of a muscle which crosses joint • Ex. biceps brachii has the action of flexion at elbow • Actions are usually caused by a group of muscles working together

9. Muscle Terminology • Innervation - segment of nervous system defined as being responsible for providing a stimulus to muscle fibers within a specific muscle or portion of a muscle • A muscle may be innervated by more than one nerve & a particular nerve may innervate more than one muscle or portion of a muscle

10. Muscle Terminology • Amplitude - range of muscle fiber length between maximal & minimal lengthening • Gaster (belly or body) • central, fleshy portion of the muscle that generally increases in diameter as the muscle contracts • the contractile portion of muscle

11. Muscle Terminology • Origin - proximal attachment, generally considered the least movable part or the part that attaches closest to the midline or center of the body • Insertion - distal attachment, generally considered the most movable part or the part that attaches farthest from the midline or center of the body

12. Muscle Terminology • When a particular muscle contracts • it tends to pull both ends toward the gaster • if neither of the bones to which a muscle is attached are stabilized then both bones move toward each other upon contraction • more commonly one bone is more stabilized by a variety of factors and the less stabilized bone usually moves toward the more stabilized bone upon contraction

13. Isometric Isotonic Concentric Eccentric Types of muscle contraction Muscle Contraction (under tension)

14. Types of muscle contraction • Isotonic contractions involve muscle developing tension to either cause or control joint movement • dynamic contractions • the varying degrees of tension in muscles are causing joint angles to change • Isotonic contractions are either concentric or eccentric on basis of whether shortening or lengthening occurs

15. Types of muscle contraction • Movement may occur at any given joint without any muscle contraction whatsoever • referred to as passive • solely due to external forces such as those applied by another person, object, or resistance or the force of gravity in the presence of muscle relaxation

16. Types of muscle contraction • Concentric contractions involve muscle developing tension as it shortens • Eccentric contractions involve the muscle lengthening under tension • Contraction is contradictory regarding eccentric muscle activity, since the muscle is really lengthening while maintaining considerable tension • Eccentric muscle action is perhaps more correct

17. Types of muscle contraction • Concentric contraction • muscle develops tension as it shortens • occurs when muscle develops enough force to overcome applied resistance • causes movement against gravity or resistance • described as being a positive contraction

18. Types of muscle contraction • Concentric contraction • force developed by the muscle is greater than that of the resistance • results in joint angle changing in the direction of the applied muscle force • causes body part to move against gravity or external forces

19. Types of muscle contraction • Eccentric contraction (muscle action) • controls movement with gravity or resistance • described as a negative contraction • force developed by the muscle is less than that of the resistance • results in the joint angle changing in the direction of the resistance or external force • causes body part to move with gravity or external forces (resistance)

20. Types of muscle contraction • Eccentric contraction (muscle action) • muscle lengthens under tension • occurs when muscle gradually lessens in tension to control the descent of resistance • weight or resistance overcomes muscle contraction but not to the point that muscle cannot control descending movement

21. Types of muscle contraction • Isokinetics - a type of dynamic exercise using concentric and/or eccentric muscle contractions • the speed (or velocity) of movement is constant • muscular contraction (ideally maximum contraction) occurs throughout movement • not another type of contraction, as some have described • Ex. Biodex, Cybex, Lido

22. Muscle fibers • a long cylindrical cell with hundreds of nuclei 10-100 mm in diameter 1-30 cm in length • contractile component: myofabril • non-contractile component: endomyosium types • slow twitch fiber (type I) red in color because of abundant blood supply slower to the peak when contracted fatigue resistant • fast twitch fiber (type IIA) pale in color because of less blood supply rapidly to the peak when contracted easy fatigue • intermediate fiber (type IIB)

23. Skeletal muscle architecture parallel fiber arrangement： parallel to the longitudinal axis of the muscle • longitudinal：sartorius • quadrate or quadralateral： rhomboid • triangular or fan-shaped：pectoralis major • fusiform or spindle-shaped： biceps brachii pennate fiber arrangement： at an angle to the longitudinal axis of the muscle • unipenniform：extnesordigitorumlongous • bipenniform： flexor hallucislongus • multipenniform： middle fibers of the deltoid Note：Lieber RL(1992) divided skeletal muscle architecture into 3 general types • longitudinal architecture： biceps brachii • unipennate architecture：vastuslateralis • multipennate architecture：  gluteus medius

24. Angle of Pennation Angle of Pennation – the angle of orientation between the muscle fibers and tendon With an increase in the angle of pennation, less force from each individual fiber is transmitted along the long axis of the muscle’s tendon Despite a less efficient transfer of force per muscle fiber, a greater degree of pennation allows for more muscle fibers to attach to the tendon as compared to a fusiform muscle A multipennate muscle structure (gastrocnemius) has an even greater force generation potential due to more fibers fitting into a given length of muscle, attaching on its’ central tendon

25. effect of the angle of pennation • the greater the angle of pennation, the smaller the amount of effective force transmitted to the tendon • the angle of the pennation increases as tension progressively increases in the muscle fibers • The pennate arrangement will allow the packing of more fibers given the same space.

26. Types based on changes in length • concentric contraction (shortening contraction) · • isometric contraction (static contraction) isos = equal；metron = measure definition： muscle contraction with muscle length kept no change The joint angle remains the same when an isometric strength is developed. There is no motion existed during isometric contraction • eccentric contraction (lengthening contraction) definition： muscle contraction with the length of the entire muscle lengthened In daily activities, if the gravity is the only external force acting on the body, the antagonist muscle contracts eccentrically during gravity-assisted motions

27. Types of muscle contraction, based on development of tension isotonic iso = equal； tonus = tension Muscle physiologists defined a kind of muscle contraction that develops constant tension throughout the whole muscle excursion as isotonic contraction; however, it is seldom seen in the living body Clinicians use isotonic contraction commonly and refer to a muscle contraction that causes a joint to move through some range of motion. Even though the resistance remains the same, the tension generated by the muscle is not equal tension because 1.    the moment arm to the joint axis is changing throughout the motion 2.    the resistance with respect to the gravity is changing throughout the motion isometric equal muscle length and same joint angle zero motion speed with varying resistance isokinetic iso = equal；kinetos = move definition： one kind of muscle contraction that occurs when the rate of movement is constant not occur in the living body without using special machine (isokinetic dynamometer) first introduced by Hislop and Perrine in 1967 equal motion speed with accommodating resistance

28. · comparison of different types of muscle contraction

30. mechanical model of muscle fiber • contractile component：actin and myosin crossbridges structures • parallel elastic component： muscle connective tissue e.g. epimyosium, perimyosium, or endomyosium • series elastic component： connective tissues within the tendon

31. tension generated by active contraction resting length of a sacromere： the length that allows the greatest number of cross-bridge attachments and the greatest potential active force active length-tension curve： an inverted U-shape with its peak at the resting length tension generated by passive stretch developed when series and parallel elastic components are stretched passive length-tension curve： the tissue is slack before stretched and then the tension builds as an exponential function total length tension curve of muscle at shortened lengths： active contraction dominates force generation just beyond its resting length： passive tension begins to contribute and active tension is compromised at more elongated lengths： passive tension accounts for most of the total force

32. Passive Length-Tension Passive Length Tension Curve • Connective tissues (CT) located within the muscle (epi, peri & endomysium) have some elastic properties and therefore can generate resistive force when elongated or stretched • Passive Tension – The resistive force (stiffness) generated within a muscle’s CT and its tendon in response to an applied stretch to the muscle • Passive tension of a muscle stabilizes skeletal structures against gravity and responds to loads imposed upon the body • Stretched muscle tissue exhibits both elastic (allows a stretched muscle to return to its original length) and viscoelastic (increasing resistance to elongation as rate of stretch increases) properties. Stress-Strain Curve

33. Active Length-Tension • Myofibrils – contractile structures within the individual muscle fiber; hundreds to thousands of myofibrils are housed within each fiber • Myofibrils contain the contractile components (myofilaments) of the muscle fiber Actin & Myosin • The active force or “tension” generated within a myofibril is directly dependent on the number of simultaneous cross-bridges formed • The ideal resting length of a muscle fiber or sarcomere is the length that allows the greatest number of cross-bridge attachments, and therefore, the greatest potential active force • As the sarcomere is lengthened or shortened from its resting length, the number of potential cross-bridge attachments decreases, lessening the active force potential even at full muscle fiber activation Actin Myosin Actin & Myosin cross-bridging

34. Sequential Events of Contraction Myosin head (high-energy configuration) 1 Myosin cross bridge attaches to the actin myofilament Thin filament ADP and Pi (inorganic phosphate) released Thick filament As ATP is split into ADP and Pi, cocking of the myosin head occurs 2 4 Working stroke—the myosin head pivots and bends as it pulls on the actin filament, sliding it toward the M line Myosin head (low-energy configuration) As new ATP attaches to the myosin head, the cross bridge detaches 3

35. Total Length Tension • Total Length Tension –the combination of passive and active tension of a muscle • The combination of the two tensions allows for a large range of muscle force over a wide range of muscle length • As the active force (tension) begins to decline with increasing muscle fiber length, the passive tension rises • Passive tension declines as a muscle fibers approaches its resting length; this is accompanied by an optimal cross-bridge arrangement, which increases active force potential within the fiber Total Length Tension Curve

36. Force-Velocity Relationship force decreased as velocity increased during concentric contraction · force increased as velocity decreased during eccentric contraction · force = 0 during isometric contraction

37. Force-Velocity Relationship • During concentric & eccentric activation, the rate of change of a muscle’s length is significantly related to the muscle’s maximal force potential • As the velocity of a contraction increases, the F generating capabilities of the muscle decreases. This is demonstrated by the Force Velocity Curve. Conversely, as the velocity of a contraction slows, F generating capabilities increase • From this F-V curve, it is evident that the greatest force production capability is with slow eccentric activities (i.e. eccentric component of a squat) • Activities requiring high velocity concentric actions produce the lowest force (i.e. throwing a wiffle ball)

38. Muscle activities during motion • focal muscle • agonist or prime mover agon = contest the principal muscle that produces a joint motion or maintains a static posture can be concentric, isometric, or eccentric • antagonist anti = against; agon = contest the muscle that contracts in the opposite direction of the agonist passively elongates or shortens to allow motion acted by agonist • synergist syn = together; ergon = work the muscle that contracts together with the agonist • stabilizer： to stabilize the proximal component of the joint involved • neutralizer： to rule out unwanted motions

40. Actions of multi-joint muscles single-joint muscle： a muscle that cross one joint only, e.g. the brachialis, the short head of the biceps brachii two-joint muscle： a muscle that cross two joints, e.g. the long-head of the biceps brachii, the grastrocnemius, etc. multi-joint muscle： a muscle that cross more than one joint e.g. the long finger flexors, the long finger extensors, etc.

41. active insufficiency unable to reach the contraction force because of the limit of muscle length passive insufficiency unable to reach full range of motion because of the limit of muscle length NOTE： The totally insufficient grip strength produced with the wrist fully flexed is due to the combination of active insufficiency of the long finger flexors and passive insufficiency of the long finger extensors

42. FASCICLE ARRANGEMENT TO MUSCLE STRUCTURE

43. Arrangement of Fascicles • (a): Circular pattern: • Fascicles arranged in concentric rings • Muscles with this arrangement surround external openings, which they close by contracting • General term for these muscles is sphincters (squeezers) • Examples: • Orbicularis muscles surrounding the eyes (Orbicularis oculi) and the mouth (Orbicularis oris)

44. Arrangement of Fascicles • (b): Convergent pattern: • Muscle has a broad origin, and its fascicles converge toward a single tendon of insertion • Such a muscle is triangular or fan shaped like the pectoralis major muscle of the anterior thorax

45. Arrangement of Fascicles • (c)(f): Parallel pattern: • The long axes of the fascicles run parallel to the long axis of the muscle • Such muscles are either: • straplike (c: parallel) • spindle (f: fusiform) • shaped with an expanded belly (midsection) • Examples: • Sartorius of thigh (c) • Biceps brachii muscle of the arm (f)

46. Arrangement of Fascicles • (d)(e)(g): Pennate pattern: • In a pennate (feather) pattern of arrangement the fascicles are short and attach obliquely to a central tendon that runs the length of the muscle • Types: • Unipennate: d • Fascicles insert into only one side of the tendon • Example: extensor digitorum muscle of the leg • Bipennate: g • Fascicles insert into the tendon from opposite sides (muscle grains resemble a feather) • Example: rectus femoris muscle of the thigh • Multipennate: e • Arrangement looks like many feathers situated side by side, with all their quills inserted into one large tendon • Example: deltoid muscle, which forms the roundness of the shoulder

47. Organization of Skeletal Muscle Fibers • 4 patterns of fascicle organization: • parallel • convergent • pennate • circular

48. Contraction – muscle gets shorter but body increases in diameter • Fascicles are parallel to the long axis of the muscle (most muscles) • Firm attachment by a tendon extends from the free tip to a movable bone of the skeleton – flat bands with aponeuroses; spindle shaped with cordline tendons; have a central body, belly or gaster (‘stomach) Fig 9.14

49. Muscle fibers cover a broad area, but all fibers come together at a common attachment site and pull on a tendon, a tendinous sheet, or a raphe (band of collagen fibers) • Fibers on opposite sides of the tendon pull in different directions Fig 9.14

50. Unipennate – all muscle cells are on the same side of the tendon • Pennate muscles have 1 or more tendons that run through the body, fascicles form an oblique angle to the tendon • Have more fibers than a parallel - generates more tension than a parallel muscle of the same size Fig 9.14