1. Chapter 7 Chapter 7 The Muscular System

2. Function of Muscles  Produce movement  Maintain posture  Stabilize joints  Generate heat  Guards openings

3. Fun Facts about Muscles There are 656 muscles in the human body. It takes 17 muscles to smile and 43 to frown. The tongue is the strongest muscle in the body. The gluteus maximus (the buttocks) is the largest muscle in the body. The sartorius muscle is the longest muscle in the body.

4. The Muscular System Three types of muscle tissue :  Skeletal 1)Attach to the bony skeleton 2)Have longest fibers, fibers are striated (striped) 3)Controlled voluntarily  Smooth 1)Linings of organs and cavities 2)Fibers are non-striated 3)Controlled involuntarily, function constantly  Cardiac 1)Found only in the heart 2)Fibers are striated 3)Controlled involuntarily

5. Smooth Muscle Characteristics  Has no striations  Single nucleus  Found mainly in the walls of hollow organs

6. Smooth Muscle

7. Cardiac Muscle Characteristics  Has striations  Usually has a single nucleus  Joined to another muscle cell at an intercalated disc  Found only in the heart

8. Cardiac Muscle

9. Functional Characteristics of Muscles  Four properties of muscle: 1)Excitability: ability to receive and respond to a stimulus 2)Contractility: ability to shorten with force when stimulated 3)Extensibility: ability to be stretched or extended 4)Elasticity: ability of a muscle fiber to return to its original or resting length

10. Skeletal Muscle Organization Muscle fascicle (bundle) Muscle fiber (cell) Myofibril Sarcomere (Contractile unit of muscle fiber) Thick and thin filaments Skeletal Muscle

11. Anatomy of a Skeletal Muscle Consists of many bundles, called fascicles, of fibers covered by connective tissue Each muscle contains at least one artery and one or two veins … why? Most attach to bones by tendons (connective tissue extensions) 1) insertion: bone that moves during contraction 2) origin: bone that stays still during contraction Some muscles attach directly to bone by their connective tissue coverings

12. Connective Tissue Wrappings of Skeletal Muscle  Epimysium – covers skeletal muscle  Perimysium – covers fascicle (bundle) of fibers  Endomysium – around single muscle fiber

13. Microscopic Anatomy of a Skeletal Muscle Muscle fiber: muscle cell with many nuclei Sarcolemma: plasma membrane of a muscle cell Sarcoplasm: cytoplasm of muscle cell, contains large amounts of glycogen and oxygen-binding protein Each muscle fiber contains large numbers of myofibrils in the sarcoplasm, with mitochondria packed around them Myofibrils: contractile portion of the muscle cell, made up of units called sarcomeres Sarcomeres contain two types of filaments: 1)thick: contain the protein myosin 2)thin: contain the protein actin

14. Microscopic Anatomy of the Muscle

15.  At rest, there is a bare zone that lacks actin filaments (no filament overlap) Muscle Contraction: Sliding Filament Theory  To start contraction, calcium unlocks active sites on actin  Myosin heads bind to actin active sites – connections are called cross-bridges  Myosin pulls the actin microfilaments toward the bare zone - muscle shortens  Myosin detaches, then reattaches to another active site, shortening the muscle further

16. Muscle Contraction: Sliding Filament Theory

19. Sliding Filament Animation Sliding Filament Animation

20. Muscle Contraction: Rigor Mortis After death, there is an influx of calcium Calcium causes myosin to bind with actin (forming cross bridges) Breathing stops, no energy is available to detach cross bridges, so they stay attached Muscles stiffen after 3 to 4 hours, peaks at 12 hours, and decreases between 48 and 60 hours

21. Nerve Stimulus for Muscle Contraction  Skeletal muscles must be stimulated by a motor neuron (nerve) to contract  Motor neuron plus the fibers it supplies is called the “motor unit”

22.  Neuromuscular junctions (NMJ) – site where nerve and muscle meet Nerve Stimulus for Muscle Contraction  Nerve and muscle do not make direct contact  Synaptic cleft – gap between nerve and muscle fiber, filled with fluid  Each muscle fiber has only one neuromuscular junction

23. Nerve Stimulus for Muscle Contraction: Neuromuscular Junction

24. Nerve Stimulus for Muscle Contraction  Upon arrival of nerve impulse, a chemical called a neurotransmitter is released by nerve  The neurotransmitter for skeletal muscle is acetylcholine  Neurotransmitter attaches to receptors on the sarcolemma of the muscle fiber  Brain or spinal cord sends a nerve impulse down the motor neuron in response to a stimulus

25. Nerve Stimulus for Muscle Contraction  Sarcolemma becomes permeable to sodium ions (Na + )  Sodium rushes into the cell and generates an action potential - an explosion of electrical activity  This electrical stimulus starts the muscle contraction  Once the contraction starts, it cannot be stopped - ALL OR NOTHING PRINCIPLE Neuromuscular Junction Animation

26. Contraction of a Skeletal Muscle  Within a skeletal muscle, not all fibers may be stimulated at the same time  Different combinations of muscle fiber contractions may give differing responses  Graded responses – different degrees of skeletal muscle contraction Example: finger muscles help you pick up a penny or a textbook

27. Muscle Tone  Slightly contracted state while muscle is at rest  Keeps muscles ready to respond to stimulation  Helps maintain posture  Stabilizes your joints  Atrophy – decrease in muscle tone; fibers become small and weak without stimulation

28. a.Twitch – single, jerky contraction from a single stimulus  Not a normal contraction b.Tetanus – smooth, sustained contraction from multiple stimuli building upon each other  Cannot go on indefinitely or results in fatigue c.Treppe effect – increasingly forceful contractions due to increased efficiency of muscle, even with same stimulus  As muscle warms up, more calcium is available, and enzymes are more effective Muscle Responses to Stimuli

29. Types of Muscle Contractions 1) Isotonic contractions  Tension remains constant  The muscle changes length so movement can occur a.Concentric – muscle shortens as it contracts b.Eccentric – muscle lengthens as it contracts 2) Isometric contractions  Tension in the muscles increases  The muscle does not change length so positions can be held **Most body movements are a combination of both types.**

30. Force of Muscle Contraction Depends on four things: 1)# of muscle fibers contracting – greater the number of motor units contracting, the greater the force 2)Size of the muscle – bigger the muscle, the greater the force 3)Elastic elements (tendons, tissue coverings) – greater the tension on the elastic elements, the greater the force 4)Degree of muscle stretch – slight stretch increases the force of contraction

31.  ATP is the only energy source used for muscle contraction  Only 4-6 seconds worth of ATP is stored by muscles  After this initial time, other pathways must be utilized to produce ATP a.Anaerobic glycolysis/lactic acid fermentation b.Aerobic respiration Energy for Muscle Contraction

32.  Anaerobic Glycolysis/Lactic Acid Fermentation (NO OXYGEN AVAILABLE)  Series of chemical reactions that makes ATP from glucose without oxygen  This reaction FAST, but inefficient  Huge amounts of glucose are needed to make ATP  Lactic acid is a waste product of the reactions, causes muscle fatigue and soreness  Provides 90 seconds of energy – weightlifting, sprints

33. Energy for Muscle Contraction  Aerobic Respiration (OXYGEN IS AVAILABLE)  Series of chemical reactions that makes ATP from glucose in the presence of oxygen  This is a slow reaction, but makes huge amounts of ATP  Breaks down glycogen (chains of glucose) stored in muscles and liver  Carbon dioxide and water are waste products of the reactions (breathing out and sweating)  Provides 15-20 minutes of energy – long distance running, endurance exercises

34. Critical Thinking Question: After 20 minutes of exercise, your body has used up all the stored glycogen. What do you use for energy after that? What does this help with?

35. Effects of Exercise on Muscle Results of increased muscle use:  Increase in muscle size (size of fiber, not number of fibers increases)  Increase in muscle strength  Increase in muscle efficiency (more capillaries, more mitochondria)  Muscle becomes more fatigue resistant (more glycogen is stored, more mitochondria)

36. Muscles and Body Movements  Movement is attained due to a muscle moving an attached bone  Insertion – muscle attachment to bone that MOVES during contraction Review:  Origin – muscle attachment on bone that DOES NOT MOVE during contraction

37. Types of Body Movements Review:  Flexion  Extension  Rotation  Abduction  Circumduction

38. Types of Body Movements

39. Producing Body Movements: Skeletal Muscle Interactions 1)Prime Mover or Agonist: muscle(s) that provides the greatest force of a movement 2)Antagonist: muscle(s) that oppose or reverse a particular movement, to regulate or resist the agonist 3)Synergist: muscle that aids the agonist by: a.Promoting the same movement b.Reducing unnecessary movement by stabilizing or fixating a joint and/or bone

40. Naming of Skeletal Muscles 1) Location of the muscle  Example: temporalis (located on the temporal bone) 2) Number of origins  Example: triceps (three origins)

41. Naming of Skeletal Muscles 3) Direction of muscle fibers  Example: rectus abdominis (straight) 4) Relative size of the muscle  Example: gluteus maximus (largest)

42. Naming of Skeletal Muscles 5) Location of the muscles origin and insertion  Example: sternocleidomastoid (originates on the sternum and clavicle, inserts on the mastoid) 6) Shape of the muscle  Example: deltoid (triangular) 7) Action of the muscle  Example: extensor digitorum longus (extends the fingers)

43. Head and Neck Muscles Figure 6.14

44. Superficial Trunk and Arm Muscles

45. Deep Trunk and Arm Muscles

46. Muscles of the Anterior Pelvis, Hip, and Thigh

47. Muscles of the Posterior Pelvis, Hip, and Thigh

48. Superficial Muscles: Anterior

49. Superficial Muscles: Posterior

50. Muscular System Disorders Chronic Fatigue Syndrome Fibromyalgia Duchenne’s Muscular Dystrophy Rotator Cuff Syndrome Anterior Compartment Syndrome Rhabdomyolysis Cardiomyopathy Myasthenia Gravis Rhabdomyosarcoma Inguinal Hernia Polio Carpal Tunnel Syndrome