The Muscular System J Hinson Human Anatomy and

The Muscular System J. Hinson Human Anatomy and Physiology JCHS

I. Introduction The human body has over 400 skeletal muscles, which accounts for ~ 50% of the body weight! Muscles are generally named for their location, size, direction of fibers, or number of attachments. The gluteus maximus is the largest muscle in the body. The strongest muscle in the body is the masseter.

II. Some Key Terms origin: muscle attachment on immovable bone; usually proximal insertion: muscle attachment on movable bone; usually distal prime mover: major contractile muscle producing movement synergist: muscle assisting PM antagonist: muscle stretched when PM contracts

Major Muscle Groups

III. Functions - Characteristics A. Contractility: ability to shorten** B. Excitability: (responsiveness or irritability) ability to receive and respond to stimuli C. Extensibility: ability to be stretched or extended D. Elasticity: ability to recoil after stretch

III. Functions - General A. PROVIDES FOR MOVEMENT via contraction of fibers B. Maintaining posture C. Stabilizing joints D. Generating heat E. Protect internal organs

IV. Types A. Voluntary (skeletal) 1. Attached to bone 2. Controlled by the individual 3. Responsible for body movements http: //www. medical-look. com/systems_images/Muscular_System. jpg

IV. Types A. Voluntary (skeletal) 4. Wrapped in layers of connective tissue called fascia 5. Fascia merges to form a tendon (connects two!) http: //www. ditchfieldpt. com/assets/fascia_1244463_white. jpg http: //www. eorthopod. com/images/Content. Images/foot_achilles/foot_achilles_tendon_anatomy 01 a. jpg

IV. Types B. Smooth (involuntary) 1. Found in walls of digestive and urinary system 2. Found in blood vessels and bronchi http: //webanatomy. net/histology/muscle/smooth_muscle_arrangement. jpg

IV. Types 3) Cardiac (Involuntary) 1. Found only in the heart 2. Can go without blood for only a short time http: //webanatomy. net/ histology/cardiac/cardia c_muscle. jpg http: //eduspace. fr ee. fr/vs_pages/bi onic_heart_fichier s/real_heart. jpg

V. Structures A. Epimysium: “overcoat” of dense irregular connective tissue surrounding entire muscle B. Perimysium: fibrous connective tissue surrounding each fascicle C. Endomysium: reticular connective tissue surrounding each individual muscle fiber

V. Structures D. E. F. G. H. I. Muscle: organ Fascicle: bundle of muscle cells Muscle fiber: striated cell; covered by sarcolemma (membrane) Myofibril: rod-like contractile unit of muscle fiber Sarcomere: contractile unit of a myofibril Tendon/Aponeurosis: connective tissue wrapping extending from muscle

SLIDING FILAMENT THEORY J. Hinson Human Anatomy and Physiology JCHS

I. The Neuromuscular Junction A. Connection b/w nerve and muscle fiber B. In response to a motor nerve impulse, the end of a motor nerve secretes a neurotransmitter, Acetylcholine (ACh), which stimulates a muscle fiber.

1. http: //academic. wsc. edu/faculty/jatodd 1/351/motor_unit. jpg

http: //camilolab. slu. edu/444/graphics/Leeson 6 -12. jpg

I. The Neuromuscular Junction C. Threshold stimulus – minimal stimulus needed to cause a muscular contraction 1. “all or none” response http: //www. bbraunusa. com/stimuplex/graphics/hi_speed_nerve. jpg

II. Skeletal Muscle Contraction A. Muscle fiber contraction results from actin sliding over myosin. 1. The SARCOMERE is the structural and functional unit of the muscle. http: //www. 3 dotstudio. com/zz. html

http: //www. ucl. ac. uk/~sjjgsca/Muscle. Sarcomere. gif Myosin Actin

http: //www. peprotech. com/uploadedimages/Sarcomere 2. jpg

http: //gilead. org. il/hcm/sarcomere. jpg

II. Skeletal Muscle Contraction Animation: B. Contraction Stimulus http: //highered. mcg raw 1. Acetylcholine stimulates. hill. com/sites/00724 95855/student_view 0/chapter 10/animati 2. Nerve impulse travels over the mm. on__action_potentia ls_and_muscle_cont fiber surface and via transverse raction. html tubules into fiber. 2+ 3. Sarcoplasmic reticulum releases Ca. 4. Cross-bridge forms b/w filaments, and actin moves inward causing the muscle to shorten.

http: //www. ivyrose. co. uk/Topics/M uscles/Sliding. Filament_Theory. jpg

II. Skeletal Muscle Contraction B. Contraction Stimulus 2+ 5. Fiber relaxes w/ uptake of Ca. 6. Cholinesterase decomposes ACh. 7. Actin-myosin cross-bridge breaks. 8. Muscle fiber relaxes. Myofilament Contraction: http: //highered. mcgrawhill. com/sites/0072495855/student_view 0/chapter 10/animation__myofila ment_contraction. html Sarcomere Contraction Animation: http: //highered. mcgrawhill. com/sites/0072495855/student_view 0/chapter 10/a nimation__sarcomere_contraction. html

http: //www. octc. kctcs. edu/GCaplan/anat/Notes/API%20 Notes%20 J%20%20 Muscle%20 Contraction. htm

II. Skeletal Muscle Contraction C. ATP supplies the energy for mm. fiber contraction, and creatine phosphate stores energy that can be used to synthesize ATP. ** Contraction will sustain as long as enough ATP and Ca 2+ is available!

II. Skeletal Muscle Contraction D. Other responses 1. Twitch: short, single contraction 2. Sustained contraction: rapid succession of twitches (fluid movement). 3. Tetany: forceful, sustained contraction 4. Muscle tone: minimal sustained contraction (Posture!) 5. Myogram: recording of muscle contraction

http: //media. wiley. com/Lux/05/21805. nfg 002. jpg

III. Muscular Response to Exercise A. Myoglobin: mm. cell protein that stores Oxygen B. Oxygen supply is sufficient at rest or during moderate exercise to support aerobic respiration. 1. Energy released is lost as heat.

III. Muscular Response to Exercise C. During vigorous exercise, an O 2 deficiency may develop, and lactic acid may be produced, thus DOMS (delayed onset muscle soreness). 1. Lactic acid accumulation responsible for fatigue. D. Oxygen Debt – O 2 needed to convert LA to glucose and restore ATP and CP

http: //img. sparknotes. com/figures/1/18 b 9012870 c 85 fba 3 a 8046 a 767 b 52 ddf/anaerobic. gif