Overview of Muscle Tissue & How it Contracts

1. Overview of Muscle Tissue & How it Contracts Anatomy & Physiology

2. Muscle Tissue: Comparisons • Skeletal • attached to bones or skin • cells singular, very long, cylindrical, multinucleated • voluntary • striated • contractions slow to fast

3. Skeletal Muscle Fibers

4. Muscle Tissue:Comparisons • Cardiac: • walls of the heart • branching chains of cells connected by intercalated discs, • uninucleated & striated • involuntary: pacemaker & nervous system control • slow contraction, rhythmic

5. Cardiac Muscle

6. Muscle Tissue: Comparisons • Smooth: • walls of hollow viscera (except heart) • cells singular, fusiform • uninucleated, no striations • involuntary, controlled by nervous system, hormones, some chemicals, & stretch • contractions slow

7. Smooth Muscle Fibers

8. Muscle Fibers • all skeletal muscle cells referred to as fibers • all 3 muscle tissue type contract because of same 2 microfilaments: actin & myosin • all have subunits with prefixes: myo- or sarco-

9. Connective Tissue Wrappings of Skeletal Muscle

10. Smooth Muscle Layers in GI Tract: Circular Inner/ Longitudinal Outer

11. Muscle Functions • Movement • Posture /Balance • Stabilizing Joints • Generating Heat

12. Skeletal Muscle Microanatomy • Sarcolemma: plasma membrane • Sarcoplasma: cytoplasm • Myofilaments: actin or myosin • Myosin: 1 of 2 principle contractile proteins • Actin: 2nd principle contractile protein • Sarcoplasmic Reticulum: SER • T-Tubules: ordered invaginations of sacroplasmic reticulum into sarcoplasma

14. Skeletal Muscle Properties • Irritability • ability to receive & respond to stimuli • Contractility • ability to forcibly shorten when adequate stimulus received

15. Nerve Stimulus • 1 motor neuron (nerve cell that innervates a muscle fiber) may stimulate a few fibers or hundreds of them • motor unit: 1 motor neuron & all the muscle fibers it stimulates

16. Nerve Stimulus • axon: extension from cell body that carries the nerve impulse (action potential) to wherever neuron needs to send it • axon terminal: end of axon

17. Neuromuscular Junction • junction between axon terminals surface of muscle fiber • Synapse: (synaptic cleft) gap filled with interstitial fluid

18. NMJ • neurotransmitter : chemical (messenger molecule) released from axon terminal • synaptic vesicles: vesicles that store neurotransmitter molecules in axon bulb until action potential hits which causes vesicle  exocytose • acetylcholine: neurotransmitter in all motor neurons • motor end plate: portion of sarcolemma that has receptor proteins for acetylcholine

20. Neuromuscular Junction

21. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__function_of_the_neuromuscular_junction__quiz_3_.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__function_of_the_neuromuscular_junction__quiz_3_.html • http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP2804 • http://faculty.massasoit.mass.edu/whanna/201/201_content/topicdir/muscle/muscle_media/muscle_VD/page142/page142.html

22. Mechanisms of Muscle Contraction

23. Sliding Filaments Animation • http://www.sci.sdsu.edu/movies/actin_myosin_gif.html • http://www.3dotstudio.com/zz.html • http://www.blackwellpublishing.com/matthews/myosin.html

25. Muscle Movements • Origin: muscle attachment to the immovable or less movable bone • Insertion: muscle attachment to the movable bone

26. Flexion • generally in sagittal plane • decreases the angle of the joint & brings 2 bones closer together • Hinge Joints • Ball-and-Socket Joints

27. Extension • movement that increases the distance between 2 bones or parts of the body • If > 180◦ it is hyperextension

28. Rotation • movement of a bone around its longitudinal axis • Ball-and-Socket Joints • Atlas/Dens (shaking head “no”)

29. Abduction • moving a limb away fro the midline, or median plane • includes fanning fingers or toes

30. Adduction • movement of a limb toward midline

31. Circumduction • proximal end stationary • distal end moves in a circle • limb as a whole outlines a cone

32. Dorsiflexion • lifting foot so the dorsum of the foot (top of foot) approaches the shin • corresponds to extension of the hand

33. Plantar Flexion • depressing the foot ( pointing the toes) • corresponds to flexion of the hand

34. Inversion of the Foot • turn sole medially

35. Eversion of the Foot • turn sole laterally

36. Supination • “turning backward” • forearm rotates laterally so palm faces anteriorly • radius &ulna are parallel

37. Pronation • “turning forward” • forearm rotates medially so palm faces posteriorly • radius crosses ulna

38. Opposition • thumb touches tips of other fingers on same hand