Muscular system

1. Muscular system

2. Over 600 muscles in the human body • Muscles possess certain characteristics • Excitability • Contractibility • Extensibility • Elasticity General Overview

3. Skeletal (Striated) – attached to bones for movement • Can be controlled voluntarily (on purpose) Smooth (Visceral) – mostly on the walls of internal organs (except heart) • Involuntary Cardiac – muscles of the heart • Involuntary 3 types of muscles

5. Skeletal Muscle Smooth Muscle Cardiac Muscle

6. Muscles are made up of fibers (except cardiac) Skeletal muscle fibers look like they have stripes (striated) Cardiac muscles are only found in the heart & contract by their own “pacemaker” Muscle basics

7. Voluntary movement (you can control the movement) Also known as “voluntary muscles” or “striated muscles” Located in appendicular & axial skeletons Skeletal Muscles

8. 4 important functions • Attach to bones to provide voluntary movement • Produce heat & energy for the body • Help maintain posture by holding the body erect • Protect internal organs Skeletal Muscles cont.

16. Endomysium – fibrous, connective tissue that covers muscle fibers (sheath) Perimysium – coarse fibrous membrane that covers several sheathed muscle fibers (fascicle) Epimysium – covers the entire muscle Anatomy of a Skeletal muscle

18. Acetylcholine is released by the nerve to stimulate the skeletal muscle Acetylcholine attaches to the sarcolemma. The sarcolemma becomes more permeable to Na Na rushes into the muscle & K diffuses out The more Na in the cell, the “upset” generates an electrical current called action potential Travels the entire muscle for contraction Nerve Stimulus & Action Potential

19. Broken down by acetylcholinesterase (AchE) into acetic acid & choline Enzyme present on the sarcolemma therefore, ACh can only produce 1 contraction Acetylcholine

20. The nervous system stimulates the muscle Myosin heads attach to binding sites on the thin filaments & slides The cross bridges attach & pull the thin filament toward the middle of the sarcomere causing the muscle cells to shorten (contraction) Myosin’s attachment to actin requires Ca+ Sliding Filament Theory

21. ATP is hydrolyzed to release energy • Muscles only store about 4 – 6 seconds worth of ATP • How is ATP regenerated? • CP (creatine phosphate) is found only in muscle cells • CP & ADP (Adenosine Diphosphate) make ATP within fractions of a second • Muscles store 5 x more CP than ATP (20 sec worth) Energy for Contractions

22. During light to moderate exercise or activity, 95% ATP comes from aerobic respiration Occurs in the mitochondria Glucose is broken down into CO2 & H2O Energy that is released during the breaking down of glucose is captured by ATP (36 ATP/1 glucose) Aerobic Respiration

23. Glycolysis – glucose is broken down to pyruvic acid & small amts of ATP are captured 2 ATP/1 glucose) Pyruvic acid would enter the aerobic pathway in aerobic activity. In anaerobic, the aerobic pathway can not keep up. The pyruvic acid in glycolysis is converted into lactic acid. Anaerobic glycolysis produces only 5% ATP that results from aerobic respiration Anaerobic Glycolysis & Lactic Acid

24. Anaerobic is 2 ½ faster than aerobic & can produce enough ATP for 30 -60 seconds of activity Lactic acid build up results in muscle fatigue & soreness Cont

25. Defined as when a muscle is unable to contract even though it is still being stimulated The muscle will weaken & then not respond to neural stimulation Oxygen debt – result from prolonged muscle activity Muscle Fatigue

26. Isotonic contractions – the muscle fibers slide easily to contract & relax Isometric contractions – the filaments do not successfully slide to contract, they are stalled or “spinning their wheels” Types of contractions

27. Muscular Dystrophy • Inherited disease • Chronic, progressive muscle atrophy (deteriorate) • Duchenne Muscular Dystrophy – genetic defect • Onset 2 – 5 years old • Life expectancy – late teens – early 20’s due to weakening of heart muscles & diaphragm Muscular Diseases

28. Myasthenia Gravis • Autoimmune disease - Chronic • Nerve impulses do not transmit to the muscles properly • Progresses to muscle weakness & paralysis • Death will occur if it affects the respiratory muscles • No treatment/no cure Diseases Continued

29. Muscle Spasms (cramps) – sudden, painful, involuntary muscle contractions • Overexertion • Low electrolytes • Poor circulation Treatment – stretching usually resolves spasm Muscle Injuries

30. Strain – injuries to muscles & tendons • Tendons are stronger than muscle. Therefore, injury is more common in muscle • Overstretching or tearing of muscles • Also know as muscle pull/tear • Results from overexertion • Most common in neck, back, quads, calf • Symptoms • Pain, soreness Muscle Injuries

31. Sprain – injuries to ligaments • Injury to the join that overstretches the ligaments • Joint is stretched beyond the range of motion • Once ligament are injured, susceptible to injure again • Symptoms • Some pain or discomfort

32. Pain Swelling Discoloration Mobility Circulation Sensation/Tingling Cause of injury Assessment

33. Rest – avoid movement or activities that cause pain Immobilization – lessens pain, prevent further damage Compression – decreases swelling Elevation – slows the flow of blood & reduces swelling Treatment

34. COLD until about 48 hours after injury • Prevents swelling • Decreases blood flow • Reduces muscle spasms • Dulls nerve endings to pain • HEAT – speeds up chemical reaction for healing • Heat too early will increase swelling Heat or Cold?