1. Teresa Thomas, RN, BSN, MBA The Muscular System Seminar 6

2. Types of Muscle Tissue  Remember these from Chapter 3? ◘ Skeletal Striated Voluntary ◘ Smooth Striated Involuntary ◘ Cardiac Nonstriated Involuntary

3. Muscle Tissue  Types of muscle tissue ◘Skeletal muscle  Striated or voluntary muscle  Represents 40% to 50% of body weight  Attached to bones  Microscope reveals crosswise stripes or striations  Contractions can be voluntarily controlled

4. Muscle Tissue  Types (cont’d) ◘Cardiac muscle—composes bulk of heart  Cardiac muscle cells branch frequently  Characterized by unique dark bands called intercalated disks  Interconnected nature of cardiac muscle cells allows heart to contract efficiently as a unit

5. Muscle Tissue  Types (cont’d) ◘Smooth (Visceral)  Nonstriated muscle or involuntary ‒ Lacks cross stripes or striation when seen under a microscope; appears smooth ‒ Found in walls of hollow visceral structures, such as digestive tract, blood vessels, and ureters ‒ Contractions not under voluntary control; movement caused by contractions is involuntary  Function—all muscle cells specialize in contraction (shortening)

6. Structure of Skeletal Muscle  Parts of a skeletal muscle: ◘Origin—attachment to the bone that remains relatively fixed when movement at the joint occurs ◘Insertion—point of attachment to the bone that moves when a muscle contracts ◘Body—main part of the muscle

7. Structure of Skeletal Muscle (cont’d)  Muscles attach to the bone by tendons—strong cords of fibrous connective tissue ◘Some tendons are enclosed in synovial-lined tubes and lubricated by synovial fluid  Bursae—small synovial-lined sacs containing a small amount of synovial fluid

8. Attachments of a Skeletal Muscle Structure of Skeletal Muscle (cont’d)

9.  Microscopic structure ◘Muscle tissue consists of specialized contractile cells called fibers ◘Each fiber contains two kinds of very fine, threadlike structures:  Thick myofilaments  Thin myofilaments Structure of Skeletal Muscle (cont’d)

10.  Sarcomere: basic functional (contractile) unit ◘ Separated from each other by dark bands called Z lines ◘ Sliding filament model explains mechanism of contraction  Thick and thin myofilaments slide past each other as a muscle contracts Structure of Skeletal Muscle (cont’d)

11. Structure of a Sarcomere

12. Functions of Skeletal Muscle  Three primary functions ◘Posture (or muscle tone) ◘ Heat production ◘ Movement ◘ Now let’s talk about each…

13. Functions of Skeletal Muscle (cont’d.)  Posture ◘Tonic contraction: specialized muscle contraction that enables us to maintain body position  Only a few of a muscle’s fibers shorten at one time  Tonic contractions produce no movement ◘Tonic contractions maintain muscle tone called posture

14. Posture

15. Functions of Skeletal Muscle (cont’d.)  Heat production ◘Survival depends on the ability to maintain constant body temperature  Fever: An elevated body temperature; often a sign of illness  Hypothermia: A reduced body temperature ◘Contraction of muscle fibers produces most of the heat required to maintain normal body temperature

16. Functions of Skeletal Muscle  Movement ◘Muscles produce movement ◘As muscle contracts, it pulls the insertion bone closer to the origin bone ◘Movement occurs at the joint between the origin and the insertion

17. MOVEMENTS – Muscle Contractions  Hand positions that result from rotation of the forearm ◘ Supination  results in a hand position with the palm turned to the anterior position ◘ Pronation occurs when the palm faces posteriorly  Foot Movements ◘ Dorsiflexion results in elevation of the dorsum or top of the foot ◘ Plantar flexion the bottom of the foot is directed downward ◘ Inversion inversion moves ankle to side so that sole faces inward toward midline ◘ Eversion eversion turns ankle so that the sole faces out to the side

18. Examples of Body Movements Types of Movements Produced by Skeletal Muscle Contractions (cont’d.) Types of Movements Produced by Skeletal Muscle Contractions (cont’d.)

19. Types of Movements Produced by Skeletal Muscle Contractions Types of Movements Produced by Skeletal Muscle Contractions Flexion: Decreases the angle between two bones at their joint Extension: Increases the angle between two bones at their joint Abduction: Movement of a part away from the midline of the body Adduction: Movement of a part toward the midline of the body Rotation: Movement around a longitudinal axis

20. Movement….

21. Types of Movements Produced by Skeletal Muscle Contractions (cont’d.)

22. Muscles Involved…. Slide 21

23. Movement…..

24. Muscles Involved…..

25. Slide 24

26. Functions of Skeletal Muscle (cont’d.)  Movement (cont’d) ◘Groups of muscles usually contract to produce a single movement  Prime mover—contraction is mainly responsible for producing a movement  Synergist—contractions help the prime mover produce a movement  Antagonist—actions oppose the action of a prime mover in a movement

27. Effects of Exercise on Skeletal Muscles  Regular, properly practiced exercise improves muscle tone and posture  Results in more efficient heart and lung functioning  Reduces fatigue  Helps muscle tissue develop  Helps maintain a healthy weight What is Hypertrophy? What is Atrophy?

28. Effects of Exercise on Skeletal Muscles (cont’d.)  Effects of exercise on skeletal muscles ◘Prolonged inactivity causes disuse, or atrophy ◘Regular exercise increases muscle size, called hypertrophy

29.  Strength training: Exercise involving contractions of muscles against heavy resistance ◘Increases number of myofilaments in each muscle fiber ◘Total mass of the muscle increases ◘Does not increase the number of muscle fibers Effects of Exercise on Skeletal Muscles (cont’d.)

30.  Endurance training: Exercise that increases a muscle’s ability to sustain moderate exercise over long periods ◘Sometimes called aerobic training ◘Allows more efficient delivery of oxygen and nutrients to a muscle via increased blood flow ◘Increases the number of blood vessels in a muscle ◘Does not usually result in muscle hypertrophy Effects of Exercise on Skeletal Muscles (cont’d.)

31. Muscle Fatigue  Reduced strength of muscle contraction  Caused by repeated muscle stimulation ◘Repeated muscular contraction depletes cellular ATP store and outstrips the ability of the blood supply to replenish oxygen and nutrients  Contraction in the absence of adequate oxygen produces lactic acid, which contributes to muscle soreness  Oxygen debt: The continued metabolic effort required to burn excess lactic acid that may accumulate during prolonged periods of exercise

32. Types of Skeletal Muscle Contraction  Twitch and tetanic contractions ◘Twitch contractions: A quick, jerky response to stimulus  Single contraction of muscle fibers caused by a single threshold stimulus ◘Tetanic contractions—sustained, steady muscular contractions  Caused by a series of stimuli bombarding a muscle in rapid succession

33. Types of Skeletal Muscle Contraction (cont’d.)  Isotonic contractions ◘Contraction of a muscle that produces movement at a joint ◘The muscle changes length, causing the insertion end of the muscle to move relative to the point of origin ◘Most types of body movements such as walking and running are isotonic contractions

34.  Isometric contractions ◘Muscle contractions that do not produce movement  The muscle as a whole does not shorten ◘No movement occurs during isometric contractions, but tension within the muscle increases Types of Skeletal Muscle Contraction (cont’d.)

36. Motor Unit  Stimulation of a muscle by a nerve impulse is required to produce movement ◘Motor neuron: Specialized nerve that transmits an impulse to a muscle, causing contraction ◘Neuromuscular junction: Specialized point of contact between a nerve ending and the muscle fiber it innervates ◘Motor unit: The combination of a motor neuron with the muscle cell(s) it innervates

37. Muscle disorders  Take a look at these on your own… ◘ Strain—injury from overexertion or trauma ◘ Cramps are painful muscle spasms (involuntary twitches) ◘ Infections ◘ Muscular dystrophy ◘ Myasthenia gravis

38. Let’s Review! Chapter 7

39. Review Question Which is a function of muscle tissue? A. Support B. Heat Production C. Movement D. All of the above

40. Review Question Which of these is not one of the three types of muscle tissue? A. Skeletal B. Smooth C. Cardiac D. Connective

41. Review Question Which of these is usually under conscious control? A. Cardiac muscle B. Smooth muscle C. Skeletal muscle Slide 40

42. Review Question Calcium triggers the contraction of a muscle fiber. Where in the muscle fiber is this calcium stored? A. Nucleus B. Calcium vesicles C. Endoplasmic reticulum D. Golgi apparatus E. Mitochondria

43. Review Question A person picks up a pencil, thus flexing the elbow. Contraction of the biceps brachii muscle during flexion is mainly A. Isometric B. Isotonic Slide 42

44. Review Question Contraction of the masseter muscle causes what action? A. Flexion of the head and neck B. Mouth closes C. Mouth opens D. Eye opens E. Eye closes Slide 43

45. Review Question Plantar flexion A. Bends the elbow B. Causes you to stand on your toes C. Causes you to stand on your heels D. Bends the wrist E. Moves the leg out to the side of the body Slide 44

46. KNOW ALL OF THESE!!

47. Know the Body Movements  Rotation  Adduction and abduction  Pronation and supination  Dorsiflexion and plantarflexion

48. Skeletal Muscle Groups  Give examples of each: ◘ Muscle of head and neck ◘ Muscles that move the upper extremities ◘ Muscles of the trunk ◘ Muscles that move the lower extremities

49. Time for Q and A! Final Project  Don’t forget you should be working on your final project… It is due at the end of Week 9 (no later than 11;59 p.m. on Tuesday).  Plan ahead and be sure that your PowerPoint meets the APA requirements, content is thorough and proper grammar, spelling and sentence structure rules are followed on the slides as well as the speaker notes!  Citations are to be used within the speaker notes and slides.  Reference slide is required as well. Questions ?