chapter 009

The Human Body in Health and Illness, 4th edition

Barbara Herlihy

Chapter 9: Muscular System

Lesson 9-1 Objectives• Identify three types of muscle tissue.• Describe the sliding filament mechanism of

muscle contraction.• Describe the motor unit and recruitment.• Explain the role of calcium and ATP in muscle

contraction.• Describe the events at the neuromuscular

junction.• Trace events from nerve stimulation to muscle

contraction.

Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights

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Types and Functions of Muscles

• Skeletal muscle

• Smooth muscle

• Cardiac muscle


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Whole Muscle Structure

• Fascia– Epimysium– Perimysium– Endomysium

• Fascicles (bundles)• Tendon


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Muscle Fiber: Cell

• Group of myofibrils– Series of sarcomeres

• Sarcoplasmic reticulum

• Sarcolemma• T-tubule system


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Sarcomeres: Inside the Myofibril

• From Z line to Z line• Thin filaments– Actin – Troponin-tropomyosin

• Thick filaments– Myosin


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Two Aspects of Muscle Contraction

Electrical • Involves motor

neuron and NMJ• Results in calcium

release from SR• Happens first

Contractile • Involves actin and

myosin • Sliding filaments• Happens second


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Contractile Function: Sliding Filament Mechanism

• Myosin heads make contact with actin. • Myosin heads rotate.• Actin is pulled to the center of the sarcomere.• Sarcomere shortensmuscle contraction


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Contracting Muscles Need Calcium

• Calcium is stored away from thin and thick filaments in the sarcoplasmic reticulum (SR).

• When stimulated, the SR releases calcium.• Calcium allows actin, myosin, and ATP to

interact, causing muscle contraction.• Why does muscle relax? Calcium returns to

the SR.


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Whole Muscle Contraction

• A single muscle fiber has an “all or nothing” response, but a whole muscle can vary its force of contraction.

• Two characteristics of a whole muscle allow this– Motor unit– Recruitment


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Motor Unit and Recruitment

• Motor unit: The nerve and innervated muscle fibers

• Recruitment: The more motor units activated, the greater the force of contraction.


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Two Aspects of Muscle Contraction

Electrical • Involves motor

neuron and NMJ• Results in calcium

release from SR• Happens first

Contractile • Involves actin and

myosin • Sliding filaments• Happens second


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Neuromuscular Junction (NMJ)

• Space between motor neuron and muscle

• Site of ACh action and activation of muscle membrane


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Electrical Events


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• Electrical signal travels to axon terminal, releasing ACh.

• ACh diffuses across NMJ and activates muscle receptors.

• Activated receptors send electrical signal along muscle membranes and T tubules.

• Electrical signal stimulates the SR to release calcium, initiating the sliding filament.

• Electrical signal travels to axon terminal, releasing ACh.

• ACh diffuses across NMJ and activates muscle receptors.

• Activated receptors send electrical signal along muscle membranes and T tubules.

• Electrical signal stimulates the SR to release calcium, initiating the sliding filament.

Impairment at the NMJ

• Myasthenia gravis• Curare• Neurotoxins– Clostridium tetani

(tetanus)– Clostridium

botulinum (botulism and Botox)


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Lesson 9-2 Objectives

• Define twitch and tetanus.• Identify the sources of energy for muscle

contraction.• State the basis for naming muscles.• List the actions of the major muscles.


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Responses of a Whole Muscle

• Twitch: Single muscle response in which muscle contracts and then fully relaxes

• Tetanus: Sustained muscle contraction caused by repeated stimulation

• Tonus: Normal, continuous state of partial muscle contraction


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Sources of Energy (ATP)

• Aerobic metabolism• Anaerobic metabolism• Metabolism of creatine phosphate


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Muscle Terms

• Origin• Insertion• Prime mover• Synergist• Antagonist


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Muscle Overuse and Underuse

• Hypertrophy: Growth in response to overuse• Atrophy: Wasting – Disuse atrophy– Denervation atrophy– Senile atrophy

• Contracture: Abnormal fibrous formation in muscle that “freezes” in flexed position


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How Skeletal Muscles Are Named

• Size: Gluteus maximus• Shape: Trapezius• Direction of fibers: Rectus abdominis• Location: Pectoralis• Number of origins: Biceps• Origin and insertion: Sternocleidomastoid• Muscle action: Adductors


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Muscles from Head to Toe


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Facial Muscles• Frontalis• Orbicularis oculi• Levator palpebrae

superioris• Orbicularis oris• Buccinator• Zygomaticus• Platysma


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Facial Muscles: Chewing

• Masseter• Temporalis


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Muscles of the Neck

• Sternocleidomastoid• Scalene muscles (three)• Trapezius


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Muscles of the Trunk: Breathing

• Intercostal muscles– Internal– External

• Diaphragm


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More Muscles of the Trunk• Abdominal wall– Internal oblique– External oblique– Transversus abdominis– Rectus abdominis

• Vertebral column– Erector spinae– Sternocleidomastoid– Trapezius– Abdominal muscles– Iliopsoas


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Muscles of the Shoulder and Arm

• Trapezius• Serratus anterior• Pectoralis major• Latissimus dorsi• Deltoid• Teres major• Rotator cuff muscles


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Muscles of the Forearm

• Biceps brachii• Triceps brachii• Brachialis• Brachioradialis• Supinators and

pronators


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Muscles of the Wrist and Hand

• Flexor carpi group • Extensor carpi group• Flexor digitorum• Extensor digitorum


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Carpal Tunnel Syndrome


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Muscles of the Thigh

• Gluteus maximus, medius, and minimus• Iliopsoas• Tensor fasciae latae• Adductor group• Pectineus • Quadriceps femoris• Sartorius• Hamstrings


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Muscles: Leg/Foot, Anterior View

• Quadriceps femoris– Rectus femoris– Vastus lateralis– Vastus medialis– Vastus intermedius

• Sartorius• Tibialis anterior• Peroneus longus


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Muscles: Leg and Foot, Posterior View

• Hamstrings– Biceps femoris– Semitendinosus– Semimembranosus

• Gastrocnemius• Soleus• Tibialis posterior• Calcaneal or Achilles

tendonCopyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights

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Muscles with Colorful Names


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chapter 009

Health & Medicine