Muscular System

1. Muscular System

2. Key Word Parts • My/o-, mys-, and sarco- refer to muscle • Spas- (draw, pull), tens- (stretch), -plegia (paralysis), therap- (treatment), therm- (heat), dynam- (power)

3. Functions • The human body has more than 600 muscles • The functions of the muscular system • Movement • Maintain Posture • Stabilization of joints • Generation of heat • Protection of some internal organs

4. Structures • Muscle Fibers -(mean thread like) are long, slender cells • Fascia - Tough, sheet or band of fibrous connective tissue that covers, supports and separates muscle • Tendons - Narrow, band of non-elastic, dense, fibrous connective tissue that attaches a muscle to a bone • Aponeurosis- broad, flat sheet of fibrous connective tissue that is similar to a tendon; however an aponeurosis attaches a muscle to bone OR to other tissues

5. Types of Muscles • Cardiac • Visceral/Smooth • Skeletal

6. Cardiac • Form walls of heart • Contract to circulate blood • Striated (banded) • Involuntary • Efferent nerves control rate of contraction • Afferent nerves concerned with sensations • Contract at steady rate except for brief bursts of rapid rate, automaticity

7. Visceral/smooth • Found in the internal organs of the body • Walls of hollow, visceral organs • No striations = smooth • Involuntary • Efferent (motor) neurons less important • Afferent nerves concerned with sensations of pain, spasm, and stretch • Steady constant contractions, automaticity

8. Skeletal • Attaches to and covers bony skeleton • Longest fibers of all muscle cells • Striated • Voluntary (central and peripheral nervous system control) • Efferent nerve fibers from brain and spinal cord send impulses for contraction • Afferent nerve fibers from muscle send message to CNS to inform brain of the degree of contraction

9. Properties • Excitability: ability to receive & respond to stimulus • Contractility: ability to shorten forcibly • Extensibility: ability to be stretched • Elasticity: ability to resume resting length (of muscle fiber) after being stretched • Automaticity: ability of muscle to contract without a nerve supply

10. Contractility • When muscle fibers are stimulated by nerves they contract (become short and thick) which causes movement • Contraction depends on myofilaments: actin and myosin

11. Muscle Contraction • Isotonic contraction is muscle shortening that produces movement • Muscle tone or tonus is a state of partial contraction that maintains a person’s posture • Isometric contraction does not cause muscle shortening or movement • A twitch is a quick, jerky contraction of a whole muscle from one stimulus

12. Muscle Contraction (continued) • Tetanic contraction is more sustained than a twitch and is caused by many stimuli in rapid succession • Fibrillation is uncoordinated contraction of muscle fibers • Convulsions are contractions of groups of muscles in an abnormal manner • Spasmsare involuntary, sudden, and prolonged contractions

13. All or None Response • Once the muscle fiber has been stimulated to contract, the muscle fiber will contract to its fullest extent • Each muscle is served by at least one motor nerve, which contains hundreds of neuromuscular junctions with each single muscle fiber • Motor neuron and all the muscle fibers that it supplies is called a motor unit • When a motor neuron fires, all the muscle fibers that it innervates respond by contracting • Average 150 muscle fibers per motor unit • Average 4 to several hundred muscle fibers per motor unit for fine motor control i.e. controlling fingers and eye movements

14. Loss of muscle tone When muscles are not used for a long period of time: atrophy, waste away (degeneration and loss of mass) Complete immobilization - strength decreases 5% per day; paralysis = atrophy to ¼ initial size; eventually muscle tissue replaced by fibrous connective tissue Lack of use can result in contracture • Severe tightening of a flexor muscle • Results in bending of a joint

15. Muscle fatigue • Muscle unable to contract • Tension drops to zero • Inability to generate enough ATP to power the contractile process • Relative deficit of ATP NOT total absence • Excessive accumulation of lactic acid and ionic imbalances

16. Other Conditions • Spasm: sudden involuntary contraction of muscle • Clonic: alternating spasm with relaxation • Tonic: sustained • Tetanus: smooth sustained contraction • Tetany: result of low calcium; increases excitability of neurons; loss of sensation, muscles twitching, convulsions; untreated - spasms of larynx, respiratory paralysis, death

17. Interactions of Skeletal Muscles • Prime Mover/Agonist • Provides major force for producing a specific movement • Initiates movement • Example: biceps brachii - elbow flexion • Antagonist • Oppose or reverse a particular movement • Example: triceps brachii - elbow extension • Synergist • Aid agonists by promotion of same movement or by reducing undesirable/unnecessary movements • Example: muscles which help make fist without bending wrist • Fixator • Synergists which immobilize a bone or a muscle origin • Example: muscles to stabilize scapula

18. Actions or Movements of Skeletal Muscles • Goniometry: measurement of joint movement • Adduction: moving a body part toward the midline • Abduction: moving a body part away from the midline • Flexion: decreasing the angle at a joint • Extension: increasing the angle at a joint • Hyperextension: increases the angle beyond the anatomical position • Circumduction: the distal end of an extremity inscribes a circle while the shaft inscribes a cone

19. Actions or Movements of Skeletal Muscles • Rotation: revolving a part about the longitudinal axis • Internal: move toward the midline or medially • External: move away from the midline or laterally • Supination: turn the palm upward; “what’s up?” • Pronation: turn the palm downward • Inversion: turn the plantar surface away from the midline • Plantar flexion (extension): move the sole of the foot downward as in standing on the toes • Dorsiflexion: move the sole of the foot upward • Range of Motion – change in joint position produced by the muscles

20. Figure 14-5 Basic Types of Muscle Movement

21. Muscle Nomenclature • Locationi.e. vastus lateral and vastus medialis; external and internal oblique, pectoralis • Origin and insertion i.e. brachioradialis, occipitofrontal • Function/Actioni.e. ulnar flexor (flexes wrist), extensor capri muscles (extension motions of the wrists)

22. Muscle Nomenclature • Number of heads/divisions forming them i.e. biceps, triceps • Sizei.e. gluteus maximus • Shapei.e.deltoid • Fiber direction i.e. rectus abdominus (straight muscle of abdomen), orbicularis oris (circular around mouth)

23. Adjectives to describe muscles • bi-, tri-, quadri- : 2, 3, 4 • Externus: exterior • Gracilis: slender • Latissimus: wide • Longissimus: long • Longus: long • Medius: intermediate

24. Adjectives to describe muscles • Orbicularis: around • Quadratus: square • Rectus: straight • Rhomboideus: diamond shaped • Scalenes: irregular triangle • Teres: round • Transverse: crosswise • Vastus: great

25. Medical Specialties • Orthopedic Surgeon • Rheumatologist • Neurologist • Sports Medicine • Physical Therapist

26. Assessment Techniques • Reflex tests • Joint motion • Blood tests • Electromyography tests • Muscle biopsy

27. Treatment Procedures of the Muscular System • Medications – • Anti-inflammatory • antispasmodics (anticholinergics) • Muscle relaxants • Physical Therapy • ROM • ADLs

28. Treatment Procedures of the Muscular System • Fascia (sheet or band of connective fibrous connective tissue that covers, supports, and seperates muscles) • Fasciotomy • Facioplasty • Muscles • Myectomy • Mypoplasty • Myorrhaphy

29. Treatment Procedures of the Muscular System • Tendon • Carpal tunnel release • Tenectomy • Tenodesis • Tenolysis • Tenonectomy • Tenotomy • Tenoplasty • Tenorrhaphy

30. Proud of your Muscles?