Muscular System

1. Muscular System 2012-2013

2. Vocab development • Calat- something inserted • Erg- work • Fasc- bundle • -gram- something written • Hyper- over, more • inter;- between • Iso-equal • Laten- hidden • Myo- muscle • Reticul- a net • Sarco- flesh • Syn- together • Tetan- stiff • -tonic- stretched • -troph- well fed • Voluntar- of one’s free will

3. Introduction • Muscles are organs made of cells that use chemical energy stored in nutrients to exert a force on the structures they are attached to. • Muscle actions provide: • Muscle tone • Propel body fluids and food • Generate the heartbeat • Distribute heat

4. Introduction • 3 types of muscle • Skeletal • Smooth • Cardiac

5. Structure of Skeletal Muscle • Composed mostly of skeletal muscle tissue, nervous tissue, blood, and other connective tissues • Layers of connective tissue enclose and separate all parts of a skeletal muscle allowing the parts to move somewhat independently.

6. Skeletal Muscle: Connective Tissue Coverings • Fascia • Separates a muscle from its adjacent muscles; covers the whole muscle • Tendon • Connect a muscle to a bone • Aponeuroses • connects muscle to bone and other muscles

7. Skeletal Muscle: Connective Tissue Coverings • Epimysium • Closely surrounds a skeletal muscle • Perimysium • Extends inward from epimysium & separates the muscle tissue into small sections called fascicles • Endomysium • Each muscle fiber within a fascicle is covered by this

8. Skeletal Muscle Fibers • Each muscle fiber forms from many undifferentiated cells that fuse together • Each muscle fiber is multinucleate • Shaped like a long, thin cylinder with rounded ends • Sarcolemma- just beneath the muscle cell membrane • Sarcoplasm- cytoplasm of the fiber

9. Skeletal Muscle Fibers • Myofibrils • Bundles of threadlike structures found within muscle fibers • Fundamental in the muscle contraction mechanism • Consist of 2 types of proteins • Myosin- thick filaments • Actin- thin filaments • Alternating of the myosin & actin causes the striations found in skeletal muscle • Sarcomeres- repeating patterns of striations along each muscle fiber

10. Skeletal Muscle Fibers

11. Skeletal Muscle Fibers

12. Skeletal Muscle Fibers • Sarcoplasmic reticulum • Within the sarcoplasm of a muscle fiber • Network of channels that surrounds each myofibril

13. Skeletal Muscle Contraction • Complex interaction of cellular and chemical pieces • The result is movement within the myofibrils where the filaments of actin and myosin slide past each other causing the sarcomere to shorten

14. Skeletal Muscle Contraction • Energy Sources • ATP • Muscle fiber only has enough ATP to contract briefly so it must be able to regenerate ATP • Creatine Phosphate • Initial source of energy to regenerate ATP • Much more abundant in muscle fibers than ATP, but it cannot supply energy directly to the cell • Cellular Respiration

15. Skeletal Muscle Contraction • 10 steps to muscle contraction 1. An action potential is conducted down a motor neuron axon 2. The motor neuron terminal releases the neurotransmitter acetylcholine (ACh) 3. ACh binds to ACh receptors on the muscle fiber 4. The sarcolemma is stimulated, an action potential is generated, and the impulse is conducted over the surface of the muscle fiber and deep into the fiber through the transverse tubules.

16. Skeletal Muscle Contraction 5. The impulse reaches the sarcoplasmic reticulum, and calcium channels open. 6. Calcium ions diffuse from the sarcoplasmic reticulum into the sarcoplasm and bind to tropin molecules. 7. Tropomyosin molecules move and expose specific sites on actin. 8. Actin and myosin link, forming cross-bridges. 9. Thin (actin) filaments are pulled toward the center of the sarcomere by myosin cross-bridges increasing the overlap of the thin and thick filaments. 10. The muscle fiber contracts.

17. Skeletal Muscle Relaxation • 1. Acetylcholinesterase decomposes acetylcholine, and the muscle fiber membrane is no longer stimulated. • 2. Calcium ions are actively transported into the sarcoplasmic reticulum. • 3. ATP breaks linkages between actin and myosin filaments without breakdown of ATP itself • 4. Breakdown of ATP “cocks” the myosin heads. • 5. Troponin and tropomyosin molecules inhibit the interaction between myosin and actin filaments. • 6. Muscle fiber remains relaxed until it is stimulated again.

18. Muscle Fatigue • Caused by • Decreased blood flow • Ion imbalances due to repeated stimulation • Psychological loss of desire to continue • Lactic acid accumulation • Oxygen debt • Lactic acid accumulation • Accumulates in the muscles when ATP production goes from aerobic to anaerobic

19. Muscular Responses • Threshold Stimulus • A muscle fiber remains unresponsive until a certain strength of stimulation is reached, once this is reached an action potential is generated and the process of muscle contraction begins

20. Muscular Responses • Recording a Muscle Contraction

21. Muscular Responses • Summation

22. Muscular Responses • Types of Contractions • Isotonic Contractions (equal force –change in length)—allow you to move things • Concentric-muscle contracts with greater force than resistance and shortens • Eccentric- muscle contracts with less force than resistance and lengthens • Isometric Contractions – (equal length- change in force) – allow you to sit and hold your posture

23. Muscular Responses • Fast & Slow Twitch Muscle Fibers • 3 types • Slow twitch fibers (red fibers) • Produce ATP from oxygen making them more resistant to fatigue • These fibers can contract for long periods of time without fatigue • Fast twitch fibers (white fibers) • Produce ATP primarily through glycolysis • Can contract rapidly but also fatigue rapidly as lactic acid accumulates in them • Intermediate Fibers (white fibers) • Can contract rapidly and also have a larger respiratory capacity so they don’t fatigue like fast-twitch fibers

24. Smooth Muscles • Smooth muscles lack striations • Cells have only one nucleus • 2 major types of smooth muscles • Multiunit • Visceral

25. Smooth Muscles • Multiunit Smooth Muscle • Muscle fibers function as separate units • Found in the irises of the eyes & walls of large blood vessels • Contract after stimulation by neurons or certain hormones

26. Smooth Muscles • Visceral Smooth Muscle • Fibers respond as a single unit • Found in the walls of hollow organs (intestines, stomach, bladder, uterus) • Two features- conduction of impulses and rythmicity produce peristalsis • Peristalsis- wavelike motion of contraction • Peristalsis is what help your body move food from organ in the digestive system to the next • Vascular smooth muscle • Found in the walls of small blood vessels where it helps control blood pressure and blood flow

27. Cardiac Muscle • Found only in the heart • Composed of striated cells joined end to end • Opposite ends of cardiac cells are connected by intercalated discs • Help join cells, transmit the force of contraction, & diffuse ions from cell to cell

28. Skeletal Muscle Actions • Skeletal action depends on • Type of joint it is associated with • The way the muscle is attached on either side of the joint

29. Skeletal Muscle Actions • Body Movement • When a body part moves bones and muscles interact as a lever • 3 types of levers • 1st class- resistance-fulcrum, force (seesaw; when the arm straightens at the elbow) • 2nd class- fulcrum- resistance- force (wheelbarrow; when you chew something up) • 3rd class- resistance-force-fulcrum (tweezers- when the arm bends at the elbow)

30. Skeletal Muscle Actions • Origin and Insertion • Origin- less moveable end of the muscle • Insertion- more moveable end of the muscle • When a muscle contracts • Insertion is pulled toward its origin • Head of the muscle is the part closest to its origin

31. Skeletal Muscle Action

32. Skeletal Muscle Actions • Interaction of Skeletal Muscles • Agonist- muscle that causes an action • Synergists- muscles that work together • Prime mover- muscle that does most of the work during an action • Antagonists- muscle that opposes action

33. Major Skeletal Muscles • Muscles of Facial Expression • Innervated by the facial nerve (CN VII) • Lack of symmetry in facial expression may indicate nerve damage

34. Muscles of Facial Expression • Orbicularisoculi • orbicular= circular • Oculi= eye • Origin: orbital rim, frontal & maxillary bones • Insertion: lateral region of eye, some encircle the eye • Action: closing the eyelid • Expression: form’s crows feet

35. Muscles of Facial Expression • Corrugator • Origin: frontal bone • Insertion: eyebrow • Action: draws eyebrow medially & inferiorly • Expression: frowning & suffering

36. Muscles of Facial Expression • Procerus • Origin: fascia covering the lower nasal bone & upper lateral nasal cartilage • Insertion: skin between and above the eyebrows • Action: causes transverse wrinkles over the bridge of the nose • Expression: squinting

37. Muscles of Facial Expression • Nasalis • Circles the opening of the nostrils • Has 2 parts: • Dilator naris • Compressor naris • Action: dilates & compresses nostrils • Wiggles your nostrils

38. Muscles of Facial Expression • Epicranius • Origin: occipital bone • Insertion: skin around the eye & orbicularisoculi • Action: elevates eyebrows, moves scalp forward & backward • Expression: surprise

39. Muscles of Facial Expression • OrbicularisOris • Oribicular= circle • oris = mouth • Origin: encircles mouth • Insertion: angle of mouth • Action: encloses & protrudes up; helps keep food on occlusal surfaces during chewing • Expression: closing or pursing lips

40. Muscles of Facial Expression • QuadratusLabiiSuperioris • 4 muscles of the upper lip • Levatorlabiisuperiorisalaequenasi • Levatorlabiisuperioris • Zygomaticus minor • Zygomaticus major • Allow you to frown and smile

41. Muscles of Facial Expression • QuadratusLabiiSuperioris cont… • Levatorlabiisuperiorisalaequenasi • Origin: maxilla • Insertion: nose • Action: dilates nostrils & raises upper lip

42. Muscles of Facial Expression • QuadratusLabiiSuperioris • Levatorlabiisuperioris • Origin: maxilla • Insertion: upper lip • Action: raises upper lip • Expression: scorn

43. Muscles of Facial Expresssion • QuadratusLabiiSuperioris Cont… • Zygomaticus minor • Origin: zygomatic bone • Insertion: upper lip • Action: raises upper lip • Expression: scorn • Zygomaticus major • Origin: zygomatic bone • Insertion: angle of mouth • Action: elevates the corner of the mouth • Expression: smiling

44. Muscles of Facial Expression • LevatorAnguliOris • Origin: canine fossa (on the maxilla) • Insertion: orbicularisoris • Action: elevates the angle of the mouth • Expression: smiling (laughing)

45. Muscles of Facial Expression • Smiling • Produced by the contraction of 2 facial muscles: • Zygomaticus major • Oribicularisoculi

46. Muscles of Facial Expression • Risorius • Origin: fasica superficial to masseter muscle • Insertion: angle of the mouth • Action: pulls angle of the mouth laterally • Expression: smiling widely; grinning

47. Muscles of Facial Expression • Depressor labiiinferioris • Origin: mandible • Insertion: lower lip • Action: depresses the angle of the mouth • Expression: sadness; grief

48. Muscles of Facial Expression • Depressor AnguliOris • A.K.A triagularis • Origin: mandible • Insertion: angle of the mouth • Action: depresses angle of the mouth • Expression: frowning

49. Muscles of Facial Expression • Mentalis • Origin: mandible near the incisive fossa • Insertion: skin of the chin • Action: pulls skin of chin upward; protrudes lower lip; raise lower lip • Expression: doubt; disdain

50. Muscles of Facial Expression • Buccinator • 2 origins: • Pterygomandibularraphe • Alveolar process of the mandible & maxilla • Insertion: orbicularisoris • Action: draws the corners of the lips laterally, compresses cheek, helps keep food on occlusal surface during chewing • Plays and important role in chewing • Makes up the musculature of the cheek