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The Muscular System

Learn about the different types of muscles, their roles in body movements, and how they work together. Discover the naming conventions for skeletal muscles and explore specific muscle groups. Also, understand common muscle disorders such as Duchenne Muscular Dystrophy and Myasthenia Gravis.

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The Muscular System

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  1. The Muscular System Part Two

  2. 1. Body movements are often the result of the activity of two or more muscles acting together or against each other.

  3. 2. Muscles are arranged in such a way that whatever one muscle (or group of muscles) can do, other muscles can reverse.

  4. 3. The prime mover is the muscle that has the major responsibility for causing a particular movement. Muscles that oppose or reverse this movement are called antagonists. When a prime mover is active, its antagonist is stretched and relaxed.

  5. 4. Synergists help prime movers by producing the same movement or reducing undesirable movements. Often, synergists stabilize joints during muscle activity.

  6. 5. Fixators are specialized synergists that hold a bone still or stabilize the origin of a prime mover so that all the tension can be used to move the insertion bone.

  7. Naming Skeletal Muscles • Rectus: straight • Oblique: slanted • Maximus: largest • Longus: long • Biceps: two origins • Triceps: three origins • Quadriceps: four origins

  8. Naming Skeletal Muscles • Deltoid: triangular • Flexor: causes flexion • Extensor: causes extension • Adductor: causes adduction

  9. 7. The two groups of head muscles are facial muscles and chewing muscles.

  10. 8. Facial muscles are unique because they are inserted into soft tissues such as other muscles or skin.

  11. Sternocleidomastoid Muscle Shape: two-head muscle found on each side of the neck Origins: the sternum and the clavicle Insertion: mastoid process of the temporal bone Action: together, they contract to flex the neck (bowing the head)

  12. 3 Types of Muscles That Make Up the Trunk • Those that move the vertebral column • Anterior thorax muscles, which move the ribs, head, and arms • Abdominal wall muscles

  13. Pectoralis Major • Shape: large, fan-shaped muscle covering the upper chest • Origins: shoulder girdle and first 6 ribs • Insertion: proximal end of the humerus • Action: adduction and flexion of the arm

  14. Muscles of the Abdominal Girdle • The muscles of the abdominal girdle are naturally strong because they resemble the structure of plywood. The fibers of each muscle pair run in a different direction, making the girdle exceptionally strong for its thickness

  15. 13. The main function of the rectus abdominus is to flex the vertebral column. Like the rectus abdominus, the external obliques flex the vertebral column, but they also rotate the trunk and bend it laterally.

  16. Muscles of the back

  17. 15. All anterior arm muscles cause elbow flexion.

  18. Anterior Arm Muscles

  19. Muscles of the Buttocks

  20. The Hamstring Group

  21. The Sartorius Muscle Location: most superficial muscle of the thigh, running obliquely across the quadriceps Origin: anterior iliac crest Insertion: medial side of the tibia Action: weak thigh flexor and synergist of crossing the legs

  22. 20. The quadriceps group consists of two groups of muscles, the rectus femoris and three vastus muscles.

  23. Rectus Femoris Location: long fleshy muscle of the upper thigh Origin: pelvis Insertion: tibial tuberosity via the patellar ligament Action: extends the knee and flexes the hip

  24. Vastus Muscle Group Location: long fleshy muscles of the upper thigh Origin: femur Insertion: tibial tuberosity via the patellar ligament Action: extends the knee powerfully

  25. 5 Muscles That Move the Foot

  26. 5 Muscles That Move the Foot

  27. 22. The first movements of the fetus, called the quickening, are often felt by the mother in the sixteenth week of pregnancy.

  28. Duchenne Muscular Dystrophy Symptoms: males between ages 2 and 6 become clumsy and fall frequently Causes: diseased muscle fibers lack a protein that helps maintain sarcolemma Results: most victims use wheelchairs by age 12 and generally die before adulthood

  29. Myasthenia Gravis Symptoms: drooping of upper eyelids, difficulty swallowing and talking, generalized muscle weakness and fatigue Causes: shortage of acetylcholine receptors at the neuromuscular junction Results:muscles become progressively weaker; death results from inability of respiratory muscles to function

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