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The Muscular System

The Muscular System. Functions of Muscle Tissue. Movement Facilitation Thermogenesis Postural Support Regulation of Organ Volume Pumps Blood (HEART). Characteristics of Muscle Tissue. Contractility ability to become short and thick while producing movement.

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The Muscular System

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  1. The Muscular System

  2. Functions of Muscle Tissue • Movement Facilitation • Thermogenesis • Postural Support • Regulation of Organ Volume • Pumps Blood (HEART)

  3. Characteristics of Muscle Tissue • Contractility • ability to become short and thick while producing movement

  4. Characteristics of Muscle Tissue • Extensibility • The ability of muscle tissue to be elongated or stretched • Smooth muscle

  5. Characteristics of Muscle Tissue • Elasticity • ability to return to its normal resting length • Skeletal: from being shorter • Smooth: from being extended

  6. Characteristics of Muscle Tissue • Excitability (irritability) • ability to receive and respond to a stimulus

  7. Cardiac Muscle • Forms heart wall (myocardium) • Striated • Involuntary • Fibers quadrangular & branching • Centrally located nucleus • Sarcolemmas connected by intercalated discs • Gap junctions

  8. Smooth (Visceral) Muscle • Walls of hollow internal surfaces such as: • Blood vessels/stomach • Urinary bladder/intestines • Non striated • Involuntary • Can be stretched to great lengths • Allows for tremendous size variability

  9. Skeletal Muscle • Attached to bones • Striated • Voluntary • Multinucleated

  10. Characteristics of Skeletal Muscle • Muscle origin: where muscle begins--tendon attaches to immovable bone (proximal) • Muscle insertion: where muscle ends--tendon attaches to moveable bone (distal) • Belly (gastr): fleshy portion of muscle between tendons

  11. SKELETAL MUSCLE ORGANIZATION • Muscle fibers: elongated muscle cells • Endomysium: membrane around muscle fibers • Perimysium: membrane around fascicles • Epimysium: membrane around entire muscle (fascia)

  12. Key terms • Sarcolemma = muscle cell membrane • Sarcoplasm = muscle cell cytoplasm

  13. Key terms • Myofilaments --contain contractile elements of muscle fiber • Sarcomere: one section of contractile filaments

  14. Actin • Thin Myofilaments • Receptor site for Ca+ • Anchored to the Z line • 2 regulatory proteins • Tropomyosin- follows contour of filament • Troponin = protein on tropomyosin

  15. Myosin • Thick myofilaments • Globular head • AKA cross bridges • Overlap free ends of actin myofilaments • Shaped like a golf club

  16. Sliding Filament Theory of Muscular Contraction • Due to an action potential, the actin and myosin myofilaments slide past one another, shortening the sarcomere • No change in length of myofilaments • H Zone narrows or disappears • I Band narrows or may disappear • A Band remains the same length

  17. SLIDING FILAMENT THEORY OF MUSCLE CONTRACTION • SEE HANDOUT

  18. Muscle--Nerve Interaction • Motor Neuron = nerve cell that excites muscle fiber • Axon – long, threadlike structure that transmits the impulse away from the cell body. • Motor Unit = motor neuron & all the muscle fibers it can effect

  19. Neuromuscular Junction • Neuromuscular Junction = place between nerve & muscle fiber • Motor End Plate - location on muscle fiber next to the nerve

  20. Muscle Nerve Interaction • Synaptic End Bulb - distal end of axon terminal • Synaptic Vesicles - membrane enclosed sacs within the synaptic end bulbs that store neurotransmitters

  21. Acetylcholine • Acetylcholine (Ach) = neurotransmitter released to begin muscle contraction (action potential) • Acetylcholine Receptors—on motor end plate-makes membrane more permeable to Na+

  22. Muscle Contraction Events(refer to handout)

  23. Muscle Response to Nervous Stimuli • All or None Principle • Once a threshold stimulus is applied to a motor unit the muscle fibers innervated by that motor unit will contract to their fullest potential • Threshold Stimulus - the weakest stimulus from a neuron that will initiate a muscular contraction

  24. Roles of Skeletal MusclesAgonist--Antagonist • Agonist (Prime Mover) • Main muscle • Antagonist • opposite movement

  25. Roles of Skeletal MusclesSynergist • Synergist—assistsagonist • provides additional force

  26. Roles of Skeletal MusclesFixator • Fixator (Stabilizer) • stabilizes a body segment • prime mover can act more effectively

  27. Deltoid Location: “caps” the shoulder Action: shoulder abduction Biceps brachii Location: front of upper arm Action: elbow flexion Selected Superficial Skeletal Muscles (Anterior View) Pectoralis major Location: front of chest Action: shoulder adduction

  28. More Anterior Muscles Sternocleidomastoid Location: front of neck Action: turn head to opposite side Diaphragm Location: beneath the ribs Action: breathing Quadriceps rectus femoris vastus medialis vastus lateralis vastus intermedius Location: front of thigh Action: hip flexion; knee extension

  29. Anterior Skeletal Muscles

  30. Trapezius Location: top of shoulder/neck Action: neck extension; elevation Triceps brachii Location: posterior upper arm Action: elbow extension Selected Superficial Skeletal Muscles (Posterior View) • Gastrocnemius • Location: calf • Action: plantarflexion

  31. More Posterior Muscles • Hamstring Group • semimembranosus • biceps femoris • semitendinosus • Location: posterior thigh • Action: Hip extension; knee flexion • Gluteus maximus • Location: buttocks • Action: Hip extension • Latissimus dorsi • Location: mid back • Action: shoulder extension

  32. Posterior Skeletal Muscles

  33. Intramuscular Injections • Injections that penetrate the skin and subcutaneous tissue • Used for prompt absorption • Used when large doses are necessary • Preferred sites: • Gluteus medius muscle • Vastus lateralis muscle • Deltoid muscle

  34. Muscle Diseases and Disorders

  35. Fibromyalgia • Painful disorder of muscles, tendons, and surrounding soft tissue • Muscles feel like they have been pulled or overworked. • Sometimes muscles twitch & other times they burn. • Most patients say that they ache all over.

  36. FIBROMYALGIA PAIN POINTS

  37. Muscular Dystrophies • Muscle destroying diseases • Degeneration of individual muscle fibers • Progressive atrophy of skeletal muscles • Due to a genetic defect

  38. Muscular Dystrophy in lower limbs

  39. Shinsplints • Pain in the anterior lower leg • Tendonitis of tibialis posterior muscle • Inflammation of periosteum • Stress fracture of the tibia • Exaggerated enlargement of muscles within the epimysium • Pulling away of the periosteum from the underlying bone • Treatment: • RICE • Strengthen tibialis anterior muscle

  40. Shinsplints

  41. Abnormal Contractions • Unintended muscular contraction not stimulated by normal mechanisms • May be caused by dehydration, electrolyte imbalances or neurological disorders & abnormalities • Examples--tic, twitch, spasm, Charlie horse

  42. Myasthenia Gravis (MG) • A weakness of skeletal muscle • An auto-immune disorder • Caused by antibodies that block the Ach receptors at the motor end plate

  43. Myasthenis gravis eye droop

  44. The End

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