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

6. 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

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

11. 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?

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

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

15. 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

16. Somatic Muscles
Myotome derivatives primarily
Some from hypomere

17. Key Points
What is a myotome?

19. Somatic Muscles
Orient the body in the environment

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

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

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

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

25. 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

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

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

31. Muscle shapes

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

34. Skeletal Muscle Actions
Supinator/Pronator
Tensor (taut)

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

36. Development & Phylogeny
Position
Embryology
Nerve supply

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

39. AXIAL MUSCLES
Trunk
Tail
Hypobranchial
Tongue
Extrinsic Eye

41. Axial Muscles
Metamerism as in myomeres

43. Axial Muscles
Agnathans
Simple
Segments (myomeres)
Myotome derivatives

44. 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

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

49. 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

51. Axial Muscles - Tetrapods
Epaxial trunk muscles
Dorsal muscles from skull to tail
Dorsalis trunci in amphibians
Longissimus – long dominant spine extensor in amniotes
Iliocostalis – most lateral epaxial spine muscle important in reptiles

54. Epaxial Muscles
See Vertebrate Muscles page

55. Epaxial Muscles in Tetrapods
Trends
Decreased except in neck
Fewer myosepta

56. Axial Muscles - Tetrapods
Hypaxial Muscles
Tend to form sling-like sheets
Lateral muscles support & compress body wall
Obliques
Transversus
Intercostals in amniotes only

58. Hypaxial Muscles - Tetrapods
Rectus abdominis – ventroflexes and compresses abdomen
Diaphragm – unique to mammals for breathing

60. Hypaxial Muscles in tetrapods
See Vertebrate Muscles page

61. Hypobranchial and Tongue Muscles - tetrapods
Function – stabilizes hyoid and larynx
E.g. geniohyoid, sternohyoid, sternothyroid, thyrohyoid

63. Hypobranchial & Tongue muscles in tetrapods
Lingu-; Gloss-
Anchors to hyoid
E.g. lingualis, styloglossus

64. Hypobranchial & Tongue muscles in Tetrapods
See Vertebrate Muscles page

65. Extrinsic Eye muscles in tetrapods
Voluntary
Obliques – rotates eye along its transverse axis
Rectus – up, down, left, right
Retractor in some

67. Extrinsic Eye muscles
See Vertebrate Muscles Page