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Understanding the Muscular System: Functions, Classifications, and Key Concepts

This comprehensive overview of the muscular system covers its essential functions, including locomotion, posture, protection, and heat production. The classification of muscle types—skeletal, cardiac, and smooth—along with their unique characteristics, is examined. Key points about muscle contraction mechanics, such as the role of myofilaments (actin and myosin), motor neurons, and the functional unit of contraction (sarcomere) are detailed. Additional insights into somatic and axial muscles, muscle actions, and embryological development are also provided for a better understanding of muscle physiology.

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Understanding the Muscular System: Functions, Classifications, and Key Concepts

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Presentation Transcript

  1. Muscular System • Function • Locomotion • Posture • Protection • Heat production

  2. Muscle Classification • Skeletal Muscle • Attached to skeleton • Striated • Muscle fiber = Muscle cell • Multinucleate • Myofibrils are striated cylinders within myofiber

  3. Skeletal Muscle • Myofilaments are proteins within the myofibrils that result in contraction • Actin – thin & has a receptor site for myosin • Myosin – thick & has a receptor site for actin and ATP • Contraction – Myosin heads attach to actin and with ATP perform a Power Stroke

  4. Skeletal Muscle • Sarcomere • The distance from Z line to Z line • The basic unit of contraction • Sarcomere gets smaller as Power Stroke occurs

  5. Key Points • Why is the sarcomere the functional unit of contraction? • Why does the power stroke result in contraction? • What would happen to contraction if you ran out of ATP?

  6. Motor Neurons • Skeletal muscle cannot contract without stimulation from a motor neuron • Motor Unit = The motor neuron plus the myofiber(s) it innervates

  7. Key Points • Why would a spinal cord injury result in paralysis?

  8. Somatic Muscles • All of the body’s skeletal muscles except the branchiomeric muscles • Voluntary • Body wall & Appendage muscles • Trunk and Tail • Hypobranchial • Tongue • Extrinsic Eyeball

  9. Somatic Muscles • Myotome derivatives primarily • Some from hypomere

  10. Key Points • What is a myotome?

  11. Somatic Muscles • Orient the body in the environment

  12. Somatic Muscles • Red Fibers • More blood supply for aerobic metabolism • Myoglobin for oxygen storage • Fatigue resistant • Fish for cruising long distances, tetrapods for posture

  13. Somatic Muscles • White fibers • Less blood supply; geared for anaerobic metabolism • Fatiguable • Fish for spurts of swimming • Tetrapods for sprints

  14. Key Points • Why is the breast meat of the goose dark, but the breast meat of the chicken is white?

  15. Cardiac Muscle • Striated with intercalated disks • Involuntary • Lateral plate mesoderm (hypomere) in origin

  16. Smooth Muscle • Involuntary • Lateral plate mesoderm in origin • Regulates internal environment • Innervated by Autonomic Nervous System • Found in the wall of tubes and hollow organs • Intrinsic Eye muscles • Erectors of feathers and hairs

  17. Key Points • Besides those mentioned, give a specific example of where might you find smooth muscle?

  18. Gross features of skeletal muscle • Origin, insertion • Tendon • Aponeurosis • Fascia

  19. Muscle shapes

  20. Skeletal Muscle Actions • Flex/Extend • Adduct/Abduct • Levator/Depressor • Protract/Retract • Constrictor/Dilator • Rotator

  21. Skeletal Muscle Actions • Supinator/Pronator • Tensor (taut)

  22. Skeletal Muscle Actions • Agonist – primary mover • Antagonist – opposes primary mover • Synergist – helps primary mover

  23. Development & Phylogeny • Position • Embryology • Nerve supply

  24. Development • Dorsal Mesoderm – Epimere – Somite • Myotome • Sclerotome & Dermatome • Lateral plate Mesoderm – Hypomere • Somatic – body wall muscles • Splanchnic – smooth muscle of viscera

  25. AXIAL MUSCLES • Trunk • Tail • Hypobranchial • Tongue • Extrinsic Eye

  26. Axial Muscles • Metamerism as in myomeres

  27. Axial Muscles • Agnathans • Simple • Segments (myomeres) • Myotome derivatives

  28. Axial Muscles – Jawed Fish • Horizontal or Lateral Septum • Epaxial Muscles • From myotomes in embryology • Innervated from dorsal rami of spinal nerves • Extend spine & some lateral bending • Extrinsic eye muscles (innervated by cranial nerves) • Epibranchial muscles

  29. Axial Muscles – Jawed Fish • Hypaxial Muscles • From Myotomes • Innervated by ventral rami of spinal nerves • Ventroflex and lateral bending

  30. Hypaxial Muscles – Jawed fish • Hypobranchial muscles • Located on floor of pharynx, pectoral girdle to jaw • Are hypaxial muscles that migrated forward • Function in respiration & feeding • E.g. Coracomandibularis, Coracohyoid

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