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Muscular System Function Locomotion Posture Protection Heat production.

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Presentation on theme: "Muscular System Function Locomotion Posture Protection Heat production."— 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




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

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