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Chapter 9 The Muscular System
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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
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The Types of Muscle
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The Types of Muscle (cont’d.)
Skeletal: voluntary, striated, multinucleated Smooth: involuntary, nonstriated and uninucleated Cardiac: involuntary, striated and uninucleated
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The Anatomy of Skeletal or Striated Muscle
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The Anatomy of Skeletal or Striated Muscle (cont’d.)
Skeletal muscle cell surrounded by sarcolemma Fasciculi: bundles of fascicles Fascicles: individual bundles of muscle fibers
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The Anatomy of Skeletal or Striated Muscle (cont’d.)
Perimysium: surrounds each fascicle Epimysium: covers the perimysium Fascia: covers the epimysium Myosin: A bands Actin: I bands Z lines H zone
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The Anatomy of Skeletal or Striated Muscle (cont’d.)
Sarcomere: between two adjacent Z lines Actual contraction process occurs here Sarcotubular system T system and sarcoplasmic reticulum
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The Physiology of Muscle Contraction
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Introduction Motor unit: all muscle cells innervated by one motor neuron Muscle cell properties Excitability Conductivity Contractility Elasticity
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Neuroelectrical 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
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Neuroelectrical Factors (cont’d.)
Action potential Calcium released Troponin and tropomyosin action inhibited Activated myosin links to actin filaments
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Chemical Interactions
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
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Energy Sources ATP: energy source for muscle contraction
ATP production Glycolysis Krebs citric acid cycle Electron transport Alternate sources: fatty acids and phosphocreatine
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The Muscle Twitch
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The Muscle Twitch (cont’d.)
Stimulus > latent period > contraction > relaxation Contraction strength depends on Strength, speed and duration of stimulus Weight of load Temperature All-or-none law
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Muscle Tone
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Muscle Tone (cont’d.) State of partial contraction throughout whole muscle Maintains pressure on abdominal contents Helps maintain blood pressure Aids digestion Types Isotonic, isometric
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The Anatomy of Smooth Muscle
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The Anatomy of Smooth Muscle (cont’d.)
Found in hollow structures Involuntary, uninucleated, nonstriated Arrangement (two layers) Longitudinal (outer) Circular (inner)
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The Anatomy of Cardiac Muscle
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The Anatomy of Cardiac Muscle (cont’d.)
Autonomic nervous system control Involuntary, uninucleated, striated Intercalated disks: coordinate contraction Cardiac muscles: contract, relax and contract 75 times/minute
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The Naming and Actions of Skeletal Muscles
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The Naming and Actions of Skeletal Muscles (cont’d.)
Shape Origin and insertion Location Direction of fibers
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The Naming and Actions of Skeletal Muscles (cont’d.)
Origin: more fixed attachment of muscle Insertion: movable attachment of muscle Tendons: attach muscle to bone Aponeurosis: wide flat tendon
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The Naming and Actions of Skeletal Muscles (cont’d.)
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
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The Naming and Actions of Skeletal Muscles (cont’d.)
Dorsiflexors: raise the foot Plantar flexors: lower the foot Supinators: turn palm upward Pronators: turn palm downward
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The Naming and Actions of Skeletal Muscles (cont’d.)
Levators: raise a part of the body Depressors: lower a part of the body Prime movers or agonists: bring about an action Antagonists: oppose agonists Synergists: assist prime movers
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The Function and Location of Selected Skeletal Muscles
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Superficial Muscles Superficial muscles of the body, anterior view
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Superficial Muscles (cont’d.)
Superficial muscles of the body, posterior view
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Muscles of Facial Expression
Occipitalis Frontalis Zygomaticus Levator labii superioris Orbicularis oris and buccinator
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Muscles of Facial Expression (cont’d.)
Muscles of the head and neck, anterior view
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Muscles of Facial Expression (cont’d.)
Muscles of the head and neck, lateral view
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Muscles of Mastication
Masseter Temporalis Pterygoid
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Muscles of the Eye Superior rectus Inferior rectus Medial rectus
Lateral rectus Superior and inferior oblique
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Muscles Moving the Head
Sternocleidomastoid Contraction of both causes flexion of neck Contraction of one causes rotation to left or right
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Muscles Moving the Shoulder Girdle
Levator scapulae Rhomboids Pectoralis minor Trapezius Serratus anterior
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Muscles Moving the Humerus
Pectoralis major Latissimus dorsi Teres minor Deltoid Supraspinatus Infraspinatus
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Muscles Moving the Elbow
Brachialis Biceps brachii Brachioradialis Triceps brachii Anconeus
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Muscles Moving the Wrist
Flexor carpi Extensor carpi
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Muscles Moving the Hand
Supinator Pronator teres Pronator quadratus
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Muscles Moving the Thumb
Flexor pollicis Extensor pollicis Adductor pollicis Abductor pollicis Opponens pollicis
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Muscles Moving the Fingers
Flexor digitorum Extensor digitorum Interossei
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Muscles of the Abdominal Wall
External oblique Internal oblique Transversus abdominis Rectus abdominis
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Muscles of the Abdominal Wall (cont’d.)
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Muscles of Respiration or Breathing
Diaphragm Main muscle External and internal intercostals Expand the ribs
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Muscles Moving the Femur
Psoas Iliacus Gluteus maximus Gluteus medius Gluteus minimus Tensor fascia lata
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Muscles Moving the Knee Joint
Biceps femoris Semitendinosus Semimembranosus Popliteus Gracilis Sartorius Quadriceps femoris
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Muscles Moving the Foot
Gastrocnemius Tibialis posterior Soleus Peroneus longus Plantaris Tibialis anterior Peroneus tertius
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Muscles Moving the Toes
Flexor hallucis Extensor hallucis Flexor digitorum Extensor digitorum Abductor hallucis Abductor digiti minimi
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Animation – Accessory Muscle Use
The following animation illustrates how the accessory muscles assist with the breathing process [Insert accessorymuscle.swf]
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Summary Described the gross and microscopic anatomy of skeletal muscle
Contrasted skeletal, smooth and cardiac muscle anatomy Described muscle contraction and the role of neuroelectrical and chemical factors and energy sources Named major muscles of the body
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