Chapter 9. The Muscular System

Transcription

1 Chapter 9 The Muscular System

2 Introduction Skeletal muscles - movement in environment Smooth muscles - intestines, ureters, veins and arteries Cardiac muscle - pumps blood through heart and blood vessels 40% - 50% of body weight 2

3 The Types of Muscle Skeletal - voluntary, striated, multinucleated Smooth - involuntary, nonstriated and uninucleated Cardiac - involuntary, striated and uninucleated 3

4 The Anatomy of Skeletal or Striated Muscle

5 Skeletal/Striated Muscle Skeletal muscle cell surrounded by sarcolemma Fasciculi - bundles of fascicles Fascicles - individual bundles of muscle fibers 5

6 Skeletal/Striated Muscle Perimysium - surrounds each fascicle Epimysium - covers the perimysium Fascia - covers the epimysium 6

7 Physiology of Muscle Contraction

8 Muscle Contraction Motor unit - all muscle cells innervated by one motor neuron Muscle cell properties excitability conductivity contractility elasticity 8

9 Neuroelectric Factors Na + higher concentration outside muscle cell K + higher concentration inside muscle cell Resting potential - charge outside positive and inside negative Electrical potential - rush of Na + inside cell K + moves outside cell attempting to balance 9

10 Muscle Contraction Action potential calcium released troponin and tropomyosin action inhibited activated myosin links to action filaments 10

11 Chemical Factors Myosin heads contain ATP ATP releases energy upon myosin/action link Energy released used to pull action Sodium - potassium pump pumps out sodium Resting potential restored 11

12 Energy Sources ATP - energy source for muscle contraction ATP production glycolysis Krebs citric acid cycle electron transport Alternate sources - fatty acids and phosphocreatine 12

13 The Muscle Twitch Stimulus > latent period > contraction > relaxation Contraction strength depends on strength, speed and duration of stimulus weight of load temperature All-or-none law 13

14 Muscle Tone State of partial contraction throughout whole muscle Maintains pressure on abdominal contents Helps maintain blood pressure Aids digestion Types isotonic, isometric 14

15 The Anatomy of Smooth Muscle Found in hollow structures Involuntary, uninucleated, nonstriated Arrangement (two layers) longitudinal (outer) circular (inner) 15

16 The Anatomy of Cardiac Muscle Autonomic nervous system control Involuntary, uninucleated, striated Intercalated disks - coordinate contraction Cardiac muscles - contract, relax and contract at 75/minute 16

17 The Naming and Actions of Skeletal Muscles Action Shape Origin and insertion Location Direction of fibers 17

18 The Naming and Actions of Skeletal Muscles Origin - more fixed attachment of muscle Insertion - movable attachment of muscle Tendons - attach muscle to bone Aponeurosis - wide flat tendon 18

19 The Naming and Actions of Skeletal Muscles Flexors - bend limb at a joint Extensor - straighten limb at a joint Abductors - move limb away from midline Adductors - bring limb toward midline Rotators - revolve limb around axis 19

20 The Naming and Actions of Skeletal Muscles Dorsiflexors - raise the foot Plantar flexors - lower the foot Supinators - turn palm upward Pronators - turn palm downward 20

21 The Naming and Actions of Skeletal Muscles Levators - raise a part of the body Depressors - lower a part of the body Prime movers - bring about an action Synergists - assist prime movers 21