1. The Muscular System

2. Did you know that ? -more than 50% of body weight is muscle ! -And muscle is made up of proteins and water

3. Info About Muscles Only body tissue able to contract create movement by flexing and extending joints Body energy converters (many muscle cells contain many mitochondria)

4. There are four characteristics associated with muscle tissue:  Excitability  Contractility  Extensibility  Elasticity - Tissue can receive & respond to stimulation - Tissue can shorten & thicken - Tissue can lengthen - After contracting or lengthening, tissue always wants to return to its resting state

5. The characteristics of muscle tissue enable it to perform some important functions, including:  Movement – both voluntary & involuntary  Maintaining posture  Supporting soft tissues within body cavities  Guarding entrances & exits of the body  Maintaining body temperature

6. The Muscular System Muscles are responsible for all movement of the body There are three basic types of muscle –Skeletal –Cardiac –Smooth

7. 3 Types of Muscles

8. Three types of muscle SkeletalCardiacSmooth

9. Classification of Muscle Skeletal- found in limbs Cardiac- found in heart Smooth- Found in viscera Striated, multi- nucleated Striated, 1 nucleus Not striated, 1 nucleus voluntaryinvoluntary

10. Skeletal Muscle Most are attached by tendons to bones Cells have more than one nucleus (multinucleated) Striated- have stripes, banding Voluntary- subject to conscious control Tendons are mostly made of collagen fibers Found in the limbs Produce movement, maintain posture, generate heat, stabilize joints

12. Cardiac Muscle Striations Branching cells Involuntary Found only in the heart Usually has a single nucleus, but can have more than one

13. Cardiac muscle tissue Makes up myocardium of heart Microscopically appears striated Cells connect to each other at intercalated discs

14. Cardiac muscle Main muscle of heart Pumping mass of heart Critical in humans Heart muscle cells behave as one unit Heart always contracts to it’s full extent

15. Structure of cardiac muscle Cardiac muscle cells (fibres) are short, branched and interconnected Cells are striated & usually have 1 nucleus Adjacent cardiac cells are joined via electrical synapses (gap junctions) These gap junctions appear as dark lines and are called intercalated discs

16. Cardiac muscle - Summary Found in the heart Involuntary rhythmic contraction Branched, striated fibre with single nucleus and intercalated discs

17. Smooth Muscle No striations Spindle shaped Single nucleus Involuntary- no conscious control Found mainly in the walls of organs and blood vessels Tissue is extremely extensible, while still retaining ability to contract

19. Smooth muscle Lines walls of viscera Found in longitudinal or circular arrangement Alternate contraction of circular & longitudinal muscle in the intestine leads to peristalsis

20. Structure of smooth muscle Spindle shaped uni-nucleated cells Striations not observed Actin and myosin filaments are present( protein fibers)

21. Smooth muscle - Summary Found in walls of hollow internal organs Involuntary movement of internal organs Elongated, spindle shaped fiber with single nucleus

22. Characteristics of Muscle Skeletal and smooth muscle are elongated Muscle cell = muscle fiber Contraction of a muscle is due to movement of microfilaments (protein fibers) All muscles share some terminology –Prefixes myo and mys refer to muscle –Prefix sarco refers to flesh

23. Anatomy of skeletal muscles Skeletal muscle fiber (cell) Muscle Fascicle Surrounded by perimysium Surrounded by endomysium endomysium perimysium Skeletal muscle Surrounded by epimysium epimysium tendon

24. Microanatomy of a Muscle Fiber (cell)

25. Microanatomy of a Muscle Fiber (Cell) sarcolemma transverse (T) tubules sarcoplasmic reticulum terminal cisternae myofibril thin myofilament thick myofilament triad mitochondria nuclei myoglobin

26. Muscle fiber myofibril Thin filamentsThick filaments Thin myofilament Myosin molecule of thick myofilament sarcomere Z-line

27. Thin Myofilament (myosin binding site) Z-line (Z-disc)

28. Thick myofilament ( has ATP & actin binding site) M-line  Play IP sliding filament theory p.5-14 for overview of thin & thick filaments

29. Sarcomere Z line A band H zone I band Zone of overlap M line Zone of overlap Thin myofilaments Thick myofilaments

30. Sliding Filament Theory Myosin heads attach to actin molecules (at binding (active) site) Myosin “pulls” on actin, causing thin myofilaments to slide across thick myofilaments, towards the center of the sarcomere Sarcomere shortens, I bands get smaller, H zone gets smaller, & zone of overlap increases

31. As sarcomeres shorten, myofibril shortens. As myofibrils shorten, so does muscle fiber Once a muscle fiber begins to contract, it will contract maximally This is known as the “all or none” principle

32. Physiology of skeletal muscle contraction Skeletal muscles require stimulation from the nervous system in order to contract Motor neurons are the cells that cause muscle fibers to contract cell body dendrites axon Synaptic terminals (synaptic end bulbs) telodendria axon hillock motor neuron End bulbs contain vesicles filled with Acetylcholine (Ach)

33. telodendria Synaptic terminal (end bulb) Neuromuscular junction Synaptic vessicles containing ACh Motor end plate of sarcolemma Synaptic cleft Neuromuscular junction

34. Overview of Events at the neuromuscular junction 10 STEPS 1.An action potential (AP), an electrical impulse, travels down the axon of the motor neuron to the end bulbs (synaptic terminals) 2. The AP causes the synaptic vesicles to fuse with the end bulb membrane, resulting in the release of Acetylcholine (ACh) into the synaptic cleft

35. 3. ACh diffuses across the synaptic cleft & binds to ACh receptors on the motor end plate 4. The binding of ACh to its receptors causes a new AP to be generated along the muscle cell membrane 5. Immediately after it binds to its receptors, Ach will be broken down by Acetylcholinesterase (AChE) – an enzyme present in the synaptic cleft

36. Figure 7-4(b-c) 2 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Synaptic cleft Arrival of an action potential at the synaptic terminal Sarcolemma of motor end plate Arriving action potential Vesicles ACh AChE molecules ACh receptor site Action potential Synaptic terminal Axon Sarcolemma Muscle fiber 6. An action potential (AP), an electrical impulse, travels down the axon of the motor neuron to the end bulbs (synaptic terminals)

37. Figure 7-4(b-c) 3 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Synaptic cleft Vesicles in the synaptic terminal fuse with the neuronal membrane and dump their contents into the synaptic cleft. Release of acetylcholine Arrival of an action potential at the synaptic terminal Sarcolemma of motor end plate Arriving action potential Vesicles ACh AChE molecules ACh receptor site Action potential Synaptic terminal Axon Sarcolemma Muscle fiber 7. The AP causes the synaptic vesicles to fuse with the end bulb membrane, resulting in the release of Acetylcholine (ACh) into the synaptic cleft

38. Figure 7-4(b-c) 4 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Synaptic cleft Vesicles in the synaptic terminal fuse with the neuronal membrane and dump their contents into the synaptic cleft. The binding of ACh to the receptors increases the membrane permeability to sodium ions. Sodium ions then rush into the cell. ACh binding at the motor and plate Release of acetylcholine Arrival of an action potential at the synaptic terminal Sarcolemma of motor end plate Arriving action potential Vesicles ACh AChE molecules ACh receptor site Action potential Synaptic terminal Axon Sarcolemma Muscle fiber Na + 8. ACh diffuses across the synaptic cleft & binds to ACh receptors on the motor end plate

39. 9. The binding of ACh to its receptors causes a new AP to be generated along the muscle cell membrane 10. Immediately after it binds to its receptors, ACh will be broken down by Acetylcholinesterase (AChE) – an enzyme present in the synaptic cleft

40. Table 7-1 Physiology of Skeletal Muscle Contraction Once an action potential (AP) is generated at the motor end plate it will spread like an electrical current along the sarcolemma of the muscle fiber The AP will also spread into the T-tubules, exciting the terminal cisternae of the sarcoplasmic reticula This will cause Calcium (Ca +2 ) gates in the SR to open, allowing Ca +2 to diffuse into the sarcoplasm Calcium will bind to troponin (on the thin myofilament), causing it to change its shape. This then pulls tropomyosin away from the active sites (myosin binding sites) of actin molecules. The exposure of the active sites allow myosin to bind to actin, and cause the sliding of the filaments

41. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7-5 3 of 7 Resting sarcomere Myosin head Active-site exposure Troponin Actin Tropomyosin ADP P + P + P + Active site Sarcoplasm Ca 2+ ADP P + Calcium (Ca +2 ) gates in the SR open, allowing Ca +2 to diffuse into the sarcoplasm Calcium will bind to troponin (on the thin myofilament), causing it to change its shape. This then pulls tropomyosin away from the active sites of actin molecules. Physiology of skeletal muscle contraction – events at the myofilaments

42. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7-5 4 of 7 Resting sarcomere Myosin head Active-site exposure Cross-bridge formation Troponin Actin Tropomyosin ADP P + P + P + Active site Sarcoplasm Ca 2+ ADP P + + P Ca 2+ ADP + P Ca 2+ Myosin heads are “energized” by the presence of ADP + PO 4 3- at the ATP binding site (energy is released as phosphate bond of ATP breaks) Once the active sites are exposed, the energized myosin heads hook into actin molecules forming cross-bridges Physiology of skeletal muscle contraction – events at the myofilaments

43. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7-5 5 of 7 Resting sarcomere Myosin head Active-site exposure Cross-bridge formation Pivoting of myosin head Troponin Actin Tropomyosin ADP P + P + P + Active site Sarcoplasm Ca 2+ ADP P + + P Ca 2+ ADP + P Ca 2+ ADP + P Ca 2+ ADP + P Using the stored energy, the attached myosin heads pivot toward the center of the sarcomere The ADP & phosphate group are released from the myosin head Physiology of skeletal muscle contraction – events at the myofilaments

44. Resting sarcomere Myosin head Active-site exposure Cross bridge detachment Cross-bridge formation Pivoting of myosin head Troponin Actin Tropomyosin ADP P + P + P + Active site Sarcoplasm Ca 2+ ADP P + + P Ca 2+ ADP + P Ca 2+ ADP + P Ca 2+ ADP + P Ca 2+ ATP Ca 2+ A new molecule of ATP binds to the myosin head, causing the cross bridge to detach from the actin strand The myosin head will get re-energized as the ATP  ADP+P As long as the active sites are still exposed, the myosin head can bind again to the next active site Physiology of skeletal muscle contraction – events at the myofilaments

45. Resting sarcomere Myosin head Myosin reactivation Active-site exposure Cross bridge detachment Cross-bridge formation Pivoting of myosin head Troponin Actin Tropomyosin ADP P + P + P + Active site Sarcoplasm Ca 2+ ADP P + + P Ca 2+ ADP + P Ca 2+ ADP + P Ca 2+ ADP + P Ca 2+ ATP Ca 2+ ADP P + + P http://www.youtube.com/watch?v=CepeYFvqmk4http://www.youtube.com/watch?v=CepeYFvqmk4 - animation http://www.youtube.com/watch?v=kvMFdNw35L0http://www.youtube.com/watch?v=kvMFdNw35L0 – animation with Taylor Swift song Physiology of skeletal muscle contraction – events at the myofilaments

46. Physiology of Skeletal Muscle Contraction If there are no longer APs generated on the motor neuron, no more ACh will be released AChE will remove ACh from the motor end plate, and AP transmission on the muscle fiber will end Ca +2 gates in the SR will close & Ca +2 will be actively transported back into the SR With Ca +2 removed from the sarcoplasm (& from troponin), tropomyosin will re-cover the active sites of actin No more cross-bridge interactions can form Thin myofilaments slide back to their resting state Table 7-1

47. These physiological processes describe what happen at the cellular level – how skeletal muscle fibers contract But what about at the organ level? How do skeletal muscles (like your biceps brachii) contract to create useful movement?

48. Skeletal muscles are made up of thousands of muscle fibers A single motor neuron may directly control a few fibers within a muscle, or hundreds to thousands of muscle fibers All of the muscle fibers controlled by a single motor neuron constitute a motor unit

49.  The size of the motor unit determines how fine the control of movement can be –  small motor units  precise control (e.g. eye muscles  large motor units  gross control (e.g. leg muscles) Play IP Contraction of motor units p. 3-7

50.  Recruitment is the ability to activate more motor units as more force (tension) needs to be generated  There are always some motor units active, even when at rest. This creates a resting tension known as muscle tone, which helps stabilize bones & joints, & prevents atrophy Play IP Contraction of motor units p. 3-7  Hypertrophy – “stressing” a muscle (i.e. exercise) causes more myofilaments/myofibrils to be produced within muscle fibers; allows for more “cross bridges” resulting in more force (strength) as well as larger size

51. Shapes of Muscles Triangular- shoulder, neck Spindle- arms, legs Flat- diaphragm, forehead Circular- mouth, anus

52. Muscle Control Type of muscle Nervous control Type of control Example Skeletal Controlled by CNS Voluntary Lifting a glass Cardiac Regulated by ANS Involuntary Heart beating Smooth Controlled by ANS Involuntary Peristalsis

53. Types of Responses Twitch- –A single brief contraction –Not a normal muscle function Tetanus –One contraction immediately followed by another –Muscle never completely returns to a relaxed state –Effects are compounded

54. Where Does the Energy Come From? Energy is stored in the muscles in the form of ATP ATP comes from the breakdown of glucose during Cellular Respiration This all happens in the Mitochondria of the cell When a muscle is fatigued (tired) it is unable to contract because of lack of Oxygen

55. Exercise and Muscles Isotonic- muscles shorten and movement occurs ( most normal exercise) Isometric- tension in muscles increases, no movement occurs (pushing one hand against the other)

56. How are Muscles Attached to Bone? Origin-attachment to a movable bone Insertion- attachment to an immovable bone Muscles are always attached to at least 2 points Movement is attained due to a muscle moving an attached bone

57. Muscle Attachments Origin Insertion

58. Flexion Types of Musculo-Skeletal Movement

59. Extension

60. Hyperextension

61. Abduction, Adduction & Circumduction

62. Rotation

63. More Types of Movement…… Inversion- turn sole of foot medially Eversion- turn sole of foot laterally Pronation- palm facing down Supination- palm facing up Opposition- thumb touches tips of fingers on the same hand

64. The Skeletal Muscles There are about 650 muscles in the human body. They enable us to move, maintain posture and generate heat. In this section we will only study a sample of the major muscles.

65. Sternocleidomastoideus Flexes and Rotates Head

66. Masseter Elevate Mandible

67. Temporalis Elevate & Retract Mandible

68. Trapezius Extend Head, Adduct, Elevate or Depress Scapula

69. Latissimus Dorsi Extend, Adduct & Rotate Arm Medially

70. Deltoid Abduct, Flex & Extend Arm

71. Pectoralis Major Flexes, adducts & rotates arm medially

72. Biceps Brachii Flexes Elbow Joint

73. Triceps Brachii Extend Elbow Joint

74. Rectus Abdominus Flexes Abdomen

75. External Oblique Compress Abdomen

76. External Intercostals Elevate ribs

77. Internal Intercostals Depress ribs

78. Diaphragm Inspiration

79. Forearm Muscles Flexor carpi—Flexes wrist Extensor carpi—Extends wrist Flexor digitorum—Flexes fingers Extensor digitorum—Extends fingers Pronator—Pronates Supinator—Supinates

80. Gluteus Maximus Extends & Rotates Thigh Laterally

81. Rectus Femoris Flexes Thigh, Extends Lower Leg

82. Gracilis Adducts and Flexes Thigh

83. Sartorius Flexes Thigh, & Rotates Thigh Laterally

84. Biceps Femoris Extends Thigh & Flexes Lower Leg

85. Gastrocnemius Plantar Flexes Foot & Flex Lower Leg

86. Tibialis Anterior Dorsiflexes and Inverts Foot