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The Muscular System.

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Presentation on theme: "The Muscular System."— Presentation transcript:

1 The Muscular System

2 The Muscular System Muscles are responsible for all types of body movement Three basic muscle types are found in the body Skeletal muscle Cardiac muscle Smooth muscle

3 Characteristics of Muscles
Muscle cells are elongated (muscle cell = muscle fiber) Contraction of muscles is due to the movement of microfilaments All muscles share some terminology Prefix myo refers to muscle Prefix mys refers to muscle Prefix sarco refers to flesh

4 Smooth Muscle Characteristics
Has no striations Spindle-shaped cells Single nucleus Involuntary – no conscious control Found mainly in the walls of hollow organs

5 Cardiac Muscle Characteristics
Has striations Usually has a single nucleus Joined to another muscle cell at an intercalated disc Involuntary Found only in the heart

6 Classification of muscle
Voluntary Involuntary Skeletal Cardiac Smooth Limbs Heart Viscera Striated Non-striated Note: Control, Location and Structure

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

8 Skeletal Muscle 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. There are about 650 muscles in the human body. They enable us to move, maintain posture and generate heat. In this unit will only study a sample of the major muscles.

9 Function of Skeletal Muscles
Produce movement Maintain posture Stabilize joints Generate heat

10 Skeletal Muscle Characteristics
Most are attached by tendons to bones

11 Skeletal Muscle Characteristics
Cells are multinucleate Striated – have visible banding Voluntary – subject to conscious control Cells are surrounded and bundled by connective tissue

12 Connective Tissue Wrappings of Skeletal Muscle
Endomysium – around single muscle fiber Perimysium – around a fascicle (bundle) of fibers

13 Connective Tissue Wrappings of Skeletal Muscle
Epimysium – covers the entire skeletal muscle Fascia – on the outside of the epimysium

14 Skeletal Muscle Attachments
Epimysium blends into a connective tissue attachment Tendon – cord-like structure Aponeuroses – sheet-like structure Sites of muscle attachment Bones Cartilages Connective tissue coverings

15 Microscopic Anatomy of Skeletal Muscle
Cells are multinucleate Nuclei are just beneath the sarcolemma

16 Microscopic Anatomy of Skeletal Muscle
Sarcolemma – specialized plasma membrane Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum

17 Microscopic Anatomy of Skeletal Muscle
Myofibril Bundles of myofilaments Myofibrils are aligned to give distinct bands I band = light band A band = dark band

18 Microscopic Anatomy of Skeletal Muscle
Sarcomere Contractile unit of a muscle fiber

19 Microscopic Anatomy of Skeletal Muscle
Organization of the sarcomere Thick filaments = myosin filaments Composed of the protein myosin Has ATPase enzymes

20 Microscopic Anatomy of Skeletal Muscle
Organization of the sarcomere Thin filaments = actin filaments Composed of the protein actin

21 Microscopic Anatomy of Skeletal Muscle
Myosin filaments have heads (extensions, or cross bridges) Myosin and actin overlap somewhat

22 Microscopic Anatomy of Skeletal Muscle
At rest, there is a bare zone that lacks actin filaments Sarcoplasmic reticulum (SR) – for storage of calcium

23 To Summarize . . . Skeletal muscle tissue is made of cells called muscle fibers. Muscle fibers contain small cylinders called myofibrils. Myofibrils are made of sarcomeres linked end-to-end.

24 Muscle Contraction

25 Properties of Skeletal Muscle Activity
Irritability – ability to receive and respond to a stimulus Contractility – ability to shorten when an adequate stimulus is received

26 Nerve Stimulus to Muscles
Skeletal muscles must be stimulated by a nerve to contract Motor unit One neuron Muscle cells stimulated by that neuron

27 Nerve Stimulus to Muscles
Neuromuscular junctions – association site of nerve and muscle

28 Nerve Stimulus to Muscles
Synaptic cleft – gap between nerve and muscle Nerve and muscle do not make contact Area between nerve and muscle is filled with interstitial fluid

29 Transmission of Nerve Impulse to Muscle
Neurotransmitter – chemical released by nerve upon arrival of nerve impulse The neurotransmitter for skeletal muscle is acetylcholine Neurotransmitter attaches to receptors on the sarcolemma Sarcolemma becomes permeable to sodium (Na+)

30 Transmission of Nerve Impulse to Muscle
Sodium rushing into the cell generates an action potential Once started, muscle contraction cannot be stopped

31 The Steps in Muscle Contraction
When a muscle is relaxed, myosin and actin filaments are not attached.

32 The Steps in Muscle Contraction
Myosin attaches to a binding site on an actin filament. Calcium is required to make a binding site available for myosin.

33 The Sliding Filament Theory

34 The Steps in Muscle Contraction
The myosin head rotates and causes the actin filament to slide along the myosin filament. The sliding causes the filaments to overlap more, and the sarcomere becomes shorter.

35 The Steps in Muscle Contraction
During contraction, myosin attaches to binding sites on actin, forming cross-bridges. Using ATP, the cross-bridges pull the actin toward the center of the sarcomere.

36 The Steps in Muscle Contraction
After the myosin head has rotated as far as it can, it must let go of the actin fiber. ATP is required for myosin to detach from actin. The myosin head snaps back into its original position, using the energy in the ATP. The ATP becomes ADP and releases a phosphate ion.

37 The Steps in Muscle Contraction
Calcium exposes a new actin binding site and myosin reattaches to actin. Steps 1 through 3 happen again.

38 The Steps in Muscle Contraction
The cross-bridges break, myosin binds to another site, and the cycle begins again until the muscle fiber is contracted. In this way, the myosin heads walk along actin filaments and step at available binding sites. This grabbing and pulling action repeats, the sarcomere shortens, and the Z lines are pulled closer together.

39 To summarize . . . Myosin filaments bind to actin filaments, actin filaments move inward, and sarcomeres shorten to cause muscle contraction.

40 Contraction of a Skeletal Muscle
Muscle fiber contraction is “all or none” Within a skeletal muscle, not all fibers may be stimulated during the same interval Different combinations of muscle fiber contractions may give differing responses Graded responses – different degrees of skeletal muscle shortening

41 Types of Graded Responses
Twitch Single, brief contraction Not a normal muscle function

42 Types of Graded Responses
Tetanus (summing of contractions) One contraction is immediately followed by another The muscle does not completely return to a resting state The effects are added

43 Types of Graded Responses
Unfused (incomplete) tetanus Some relaxation occurs between contractions The results are summed

44 Types of Graded Responses
Fused (complete) tetanus No evidence of relaxation before the following contractions The result is a sustained muscle contraction

45 Muscle Response to Strong Stimuli
Muscle force depends upon the number of fibers stimulated More fibers contracting results in greater muscle tension Muscles can continue to contract unless they run out of energy

46 Energy for Muscle Contraction
Initially, muscles used stored ATP for energy Bonds of ATP are broken to release energy Only 4-6 seconds worth of ATP is stored by muscles After this initial time, other pathways must be utilized to produce ATP

47 Energy for Muscle Contraction
Direct phosphorylation Muscle cells contain creatine phosphate (CP) CP is a high-energy molecule After ATP is depleted, ADP is left CP transfers energy to ADP, to regenerate ATP CP supplies are exhausted in about 20 seconds

48 Energy for Muscle Contraction
Aerobic Respiration Series of metabolic pathways that occur in the mitochondria Glucose is broken down to carbon dioxide and water, releasing energy This is a slower reaction that requires continuous oxygen

49 Energy for Muscle Contraction
Anaerobic glycolysis Reaction that breaks down glucose without oxygen Glucose is broken down to pyruvic acid to produce some ATP Pyruvic acid is converted to lactic acid

50 Energy for Muscle Contraction
Anaerobic glycolysis (continued) This reaction is not as efficient, but is fast Huge amounts of glucose are needed Lactic acid produces muscle fatigue

51 Begin October 18, 2010

52 The Muscular System

53 Five Golden Rules of Gross Muscle Activity
all muscles cross at least one joint bulk of muscles lies proximal to the joint crossed all muscles have at least 2 attachments: origin & insertion muscles only pull/never push during contraction the muscle insertion moves toward the origin

54 Muscles and Body Movements
Movement is attained due to a muscle moving an attached bone

55 Muscles and Body Movements
Muscles are attached to at least two points Origin – attachment to an immoveable bone Insertion – attachment to a movable bone

56 The Muscular System

57 Types of Muscle Contractions
Isotonic contractions Myofilaments are able to slide past each other during contractions The muscle shortens Isometric contractions Tension in the muscles increases The muscle is unable to shorten Myofilaments “skidding their wheels”

58 Muscle Tone Some fibers are contracted even in a relaxed muscle
Different fibers contract at different times to provide muscle tone The process of stimulating various fibers is under involuntary control

59 Muscle Tone When muscles are not worked they atrophy (waste away) and become flaccid.

60 Effects of Exercise on Muscle
Aerobics result in stronger muscles due to increase blood supply Muscle fibers increase mitochondria and oxygen storage Muscle becomes more fatigue resistant Heart enlarges to pump more blood to body Does not increase skeletal muscle size

61 Effects of Exercise on Muscle
Results of increased muscle use from resistance training Individual muscle cells make more contractile filaments & connective tissue increases Increase in muscle size Increase in muscle strength

62 Begin October 19, 2010

63 Muscle Fatigue and Oxygen Debt
When a muscle is fatigued, it is unable to contract The common reason for muscle fatigue is oxygen debt Oxygen must be “repaid” to tissue to remove oxygen debt Oxygen is required to get rid of accumulated lactic acid Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less

64 The Muscular System

65 Types of Ordinary Body Movements
Flexion Extension Rotation Abduction Circumduction

66 Flexion & Extension

67 Flexion & Extension

68 Rotation

69 Abduction & Adduction

70 Special Movements Dorsiflexion Plantar flexion Inversion Eversion
Supination Pronation Opposition

71 Dorsiflexion & Plantar Flexion

72 Inversion & Eversion

73 Pronation & Supination

74 Opposition




78 Diseases and Disorders of the Muscular System
Myalgia: Muscle pain due to strain, tearing of muscle fibers. It also is a symptom of an immune response along with a fever. Myositis: Inflammation of muscle tissue due to injury or disease. Charley Horse (fibromyositis): Inflammation of muscle tissue and the tendons associated with that muscle due to injury (tear or severe bruising- contusion) Cramps: Painful, involuntary muscle spasms

79 Cerebral Palsy This disorder is characterized by paralysis and or weakened muscles due to loss of muscle tone. It can be caused due to lack of oxygen to the region of the motor region of the cerebrum of the brain which controls conscious control of muscles. This is often attributed to complication during birth.

80 Poliomyelitis Poliomyelitis: Polio is due to a viral infection which affects the motor neurons that control skeletal muscles. It often leads to paralysis and can result in death by paralysis of the diaphragm. Due to vaccine developed by Jonas Salk, the virus has been virtually eliminated in the US. However, it still poses a threat in developing countries.

81 Muscular Dystrophy Congenital muscle-destroying disease affect specific muscle groups Muscle fibers degenerate & atrophy due to an absence of dystrophin, a protein that helps keep muscle cells intact Duchenne’s M.D Most common & serious— Mostly in males (diagnosed between2-6 yrs) Survival is rare beyond early 30’s X-linked recessive

82 Myasthenia gravis Rare adult disease caused by antibodies to acetylcholine receptors at the neuromuscular junction which prevents the muscle contraction from occurring Drooping upper eyelids, difficulty swallowing & talking, muscle weakness & fatigue Death occurs when respiratory muscles cease to function

83 Aging Connective Tissue increases Amount of Muscle tissue decreases
Muscles become stringier(sinewy) Body weight declines due to loss of muscle mass By age 80, muscle strength usually decrease by 50% without weight training exercises

84 Types of Muscles Prime mover – muscle with the major responsibility for a certain movement Antagonist – muscle that opposes or reverses a prime mover Synergist – muscle that aids a prime mover in a movement and helps prevent rotation Fixator – stabilizes the origin of a prime mover

85 Naming of Skeletal Muscles
Direction of muscle fibers Example: rectus (straight) Relative size of the muscle Example: maximus (largest)

86 Naming of Skeletal Muscles
Location of the muscle Example: many muscles are named for bones (e.g., temporalis) Number of origins Example: triceps (three heads)

87 Naming of Skeletal Muscles
Location of the muscle’s origin and insertion Example: sterno (on the sternum) Shape of the muscle Example: deltoid (triangular) Action of the muscle Example: flexor and extensor (flexes or extends a bone)

88 Head and Neck Muscles

89 Trunk Muscles

90 Deep Trunk and Arm Muscles

91 Muscles of the Pelvis, Hip, and Thigh

92 Muscles of the Lower Leg

93 Superficial Muscles: Anterior

94 Superficial Muscles: Posterior

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