The Muscular System

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

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

5. Info About Muscles • Only body tissue able to contract • create movement by flexingand extendingjoints • Body energyconverters (many muscle cells contain many mitochondria)

6. 3 Types of Muscles

7. Skeletal Cardiac Smooth Three types of muscle

8. Classification of Muscle

9. 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

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

11. 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. Structure of skeletal muscle • Each cell (fibre) is long and cylindrical • Typically 50-60mm in diameter, and up to 10cm long • The contractile elements ofskeletal muscle cells aremyofibrils

13. Skeletal muscle structure • Endomysium- sheath of connective tissue covering each individual fiber • Perimysium- course fibrous membrane wrapping several fibers • Fascicle-bundle of fibers wrapped by perimysium • Epimysium- tough connective tissue wrapping entire muscle

14. Attaching to bone Tendon- strong cordlike collagenic fibers (strong and durable) Aponeurosis- sheet-like attachment of muscle to bone.

15. Smooth Muscle • No striations • Spindle shaped • Single nucleus • Involuntary- no conscious control • Found mainly in the walls of hollow organs

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

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

18. 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

19. 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

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

21. Muscle Contractions • Muscle fibers are made of tiny cylindrical structures called myofibrilsmade of protein filaments • Myofibrils- 2 parts • Thick filaments- protein called myosin • Thin filaments- protein called actin Sarcomere- unit of alternating think and thin filaments, separated from one another by dense matter called z lines

22. Muscle Contractions Continued During a muscle contraction thin filaments slide past thick filaments shortening the sarcomere. Actin- 2 important proteins Tropomyosin Troponin When a muscle is about to contract Ca is released and binds to troponin which moves the tropomyosin away from myosin binding sites

23. Muscle Contractions Cont. • Myosin heads split ATP becoming energized and in position • Once the binding sites are accessible myosin heads can bind to the actin forming crossbridges. • Myosin heads rotate and pulling the actin filament along with it (power stroke) • Contractions continue while ATP and Ca are available • When more ATP binds to the myosin head it releases from the actin filament

25. Powering the Process • Muscles use energy in the form of ATP! ATP resets the myosin head and releases the actin filament. To make ATP, the muscle does the following: • Breaks down creatine phosphate, converting ADP into ATP • Carries out anaerobic respiration, breaks glucose down into lactic acid and ATP is formed • Carries out aerobic respiration, by which glucose, fats and amino acids are broken down in the presence of oxygen to produce ATP

26. 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

27. 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)

28. 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

29. Insertion Origin Muscle Attachments

30. Types of Musculo-Skeletal Movement Flexion

31. Extension

32. Hyperextension

33. Abduction, Adduction & Circumduction

34. Rotation

35. 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

36. The Skeletal MusclesThere 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.

37. Sternocleidomastoideus Flexes and Rotates Head

38. Masseter Elevate Mandible

39. Temporalis Elevate & Retract Mandible

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

41. Latissimus Dorsi Extend, Adduct & Rotate Arm Medially

42. Deltoid Abduct, Flex & Extend Arm

43. Pectoralis Major Flexes, adducts & rotates arm medially

44. Biceps Brachii Flexes Elbow Joint

45. Triceps Brachii Extend Elbow Joint

46. Rectus Abdominus Flexes Abdomen

47. External Oblique Compress Abdomen

48. External Intercostals Elevate ribs

49. Internal Intercostals Depress ribs

50. Diaphragm Inspiration