Anatomy and Physiology

1. Anatomy and Physiology The Muscular System Chapter 9 Community Education Mr. Kestner

3. Introduction • Muscles are throughout body • Skeletal muscles • In eyes to read • Turn pages in book • Smooth muscles • Pushing blood through vessels • Digesting food • Transporting urine • Cardiac muscle • Pumping heart

4. Introduction • Muscles make up about 40% to 50% of body weight • Contraction causes movement • 3 types of muscle • Skeletal • Smooth • Cardiac

5. SkeletalMuscle Cardiac Muscle SmoothMuscle

6. Skeletal Muscle • When viewed under microscope, appears to have alternating dark and light bands • Dark bands (A bands) are made of thick filaments of the protein myosin: thick, therefore appear dark • Light bands (I bands) are made of the thin filaments of the protein actin: thin, therefore appear light • Z line – a dark staining band found in the central region of the I bands • H zone – a darker section in the middle of the A band, where myosin filaments are thickest • Sarcomere – area between two adjacent z lines – actual contraction occurs via chemical reaction

7. Skeletal Muscle

8. Muscle Anatomy • Skeletal Muscle • Muscle cells wrapped together in a fibrous network • Many muscle fibers together make a muscle – akin to strings into a cord, cord into a rope • All of the muscle cells or fibers innervated by one motor neuron – called motor unit • Excited together, contract together (all or none law) • Smooth and Cardiac Muscle • Under control of autonomic nervous system

9. Muscle Anatomy

10. Muscle Cell Properties • Excitability • Fibers excited by stimulus • In body – nerve cell • In lab – electrical charge • Conductivity • Allows response to travel throughout the cell • Contractility • Response to stimulus • Elasticity • Allowing muscle cells to return to original shape

11. Neuroelectric Factors • Greater number of K+ ions inside cell • Greater number of Na+ ions outside cell • Unequal distribution allows inside cell to be negatively charged • Known as resting potential • Neurotransmitters release acetylcholine causing Na+ ions to enter cell • Causes action potential (cell contraction) and K+ to exit cell • Causes Ca++ ions to be released bringing about contraction process of myofilaments (muscle contraction)

12. Neuroelectric Factors

13. Neuroelectric Factors • Sodium-potassium pump restores resting potential • Sodium pumped back outside cell • Potassium pumped back inside cell • Calcium ions reabsorbed • Contraction ceases • Actin filaments released from myosin filaments • Z lines return further apart • During and after contraction • If oxygen is present, more ATP molecules created • If no oxygen present, lactic acid is built up in muscle cells until oxygen becomes available (causes muscle pain)

14. Muscle Tonicity • Muscle tone • A property of muscle in which a steady or constant state of partial contraction is maintained in a muscle • Isotonic contraction • When lifting weight, muscles become shorter and thicker; tension remains the same • Isometric activity • Pushing against wall, muscles remain constant length; tension increases

15. Naming Muscles • According to action • Adductor, flexor, extensor • According to shape • Quadratus, trapezius • According to origin and insertion • Sternocleidomastoid • According to location • Frontalis, tibialis, radialis • According to their number of divisions • Biceps, triceps, quadriceps • According to the direction their fibers run • Transverse, oblique

16. Muscle Terms • Origin • Fixed attachment of a muscle that serves as a basis for the action • Proximal • Insertion • Moveable attachment, where the effects of contraction are seen • Distal • Tendon • Attaches muscle to bone • Aponeurosis • Wide, flat tendon (head, foot)

17. Muscle Layers • Superficial • Closest to skin • Middle • In between two other muscles • Deep • Closest to center of body (toward the bone)

19. Muscle Movements • Adduction – moving a body part toward the midline • Abduction – moving a body part away from the midline • Flexion – decreasing the angle between two bones, or bending a body part • Extension – increasing the angle between two bones, or straightening a body part

20. Abduction Adduction Ad- Versus Ab- Extension Flexion

22. Muscles to Know (203 – 217) • Sternocleidomastoid (SCM) – 208 • Trapezius – 208 • Pectoralis Major (Pecs) – 210 • Deltoid – 210 • Latissimus Dorsi (Lats) – 210 • Triceps Brachii (Triceps) – 210 • Biceps Brachii (Biceps) – 210 • External Oblique (Obliques) – 213 • Rectus Abdominus (6-pack) – 213 • Diaphragm (Breathing Muscle) – 213 • Gluteus Maximus (Glutes) – 214 • Biceps Femoris (Hamstrings - part of) – 214 • Quadriceps Femoris (Quads) – 214 • Gastrocnemius (Calf) – 217

23. Muscular Disorders • Contracture • A condition in which a muscle shortens its length in the resting state • Commonly occur in individuals who are bedridden for long periods of time and muscles are not properly exercised • Can be prevented by keeping the body in proper alignment, shifting positions, and periodically exercising muscles • Treated by slow and painful procedure of relengthening and exercising the muscle

24. Contractures Foot Drop

25. Muscular Disorders • Muscle spasms – or cramps • sudden, painful, involuntary muscle contractions • Usually occur in legs and feet and may result from overexertion, low electrolyte levels, or poor circulation • Gentle pressure and stretching of the muscle are used to relieve the spasm

26. Cramps?

27. Muscular Disorders • Atrophy • Decrease in muscle bulk due to lack of exercise, as when a limb in in a cast for a prolonged period • Stimulation of nerves with a mild electric current can keep muscular tissue viable until full muscular activity can return • In severe cases, muscle fibers are actually lost and replaced with connective tissue

29. Muscular Disorders • Muscular Dystrophy – a group of inherited diseases that lead to chronic, progressive muscle atrophy • Usually appears in early childhood • Occurs most often in males • Most types result in total disability and early death • Although no cure, physical therapy is used to slow progress of disease

30. Muscular Disorders • Myasthenia Gravis – a chronic condition where nerve impulses are not properly transmitted to the muscles • Leads to progressive muscular weakness and paralysis • Usually begins in facial muscles; if it affects respiratory muscles, can be fatal • Caused by abnormal destruction of acetylcholine receptors • No cure, treatment is supportive

32. Muscular Disorders • Amyotrophic Lateral Sclerosis (ALS) • Also known as Lou Gehrig’s disease • Progressive degenerative disease of the motor neurons of the body • Affects people in middle age • Around 10% is genetically inherited (chromosome 21) • begins with muscular weakness & atrophy • 1st involves legs, forearm and hands, then spreads to face and other muscles of body • Within 2-5 years, loss of control and death • No known cure, sometimes known as wasting palsy