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Chapter 11-12: Muscular System
Types and Functions of Muscles
• Skeletal muscle
• Smooth muscle
• Cardiac muscle
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.2
© 2012 Pearson Education, Inc.
Characteristics of Muscles
•Skeletal and smooth muscle cells are elongated (muscle cell = muscle fiber)
•Contraction and shortening of muscles is due to the movement of microfilaments
•All muscles share some terminology
•Prefixes myo and mys refer to “muscle”
•Prefix sarco refers to “flesh”
Whole Muscle Structure
• Fascia– Epimysium– Perimysium– Endomysium
• Fascicles (bundles)• Tendon
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.4
Muscle Fiber: Cell
• Group of myofibrils– Series of sarcomeres– Sarcomere is inside a
myofibril
• Sarcoplasmic reticulum– Covering of each
sarcomere
• T-tubule system– Transmit electrical signal
5
Sarcomeres: Inside the Myofibril
• From Z line to Z line• Thin filaments
– Protein called Actin – Troponin-tropomyosin
• Binding part of Actin
• Thick filaments– Protein called 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
10
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• Animation
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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. Then Muscle relaxes
13
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
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.14
Motor Unit and Recruitment
• Motor unit: The nerve and innervated muscle fibers
• Recruitment: The more motor units activated, the greater the force of contraction.
15
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
16
Neuromuscular Junction (NMJ)
• Space between motor neuron and muscle
• Site of ACh action and activation of muscle membrane– Ach= Acetylcholine
• Neurotransmitter
17
Electrical Events• 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:
– Autoimmune disease: atrophy and weakness
• Curare– Alkaline substance that can
paralyze (poison darts)
• Neurotoxins– Clostridium tetani (tetanus)– Clostridium botulinum
(botulism and Botox)
Muscles Part II
• 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.
20
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
21
Sources of Energy (ATP)
• Aerobic metabolism: need oxygen– Breakdown of fat, and sugars into energy
• Anaerobic metabolism: no oxygen present– Causes lactic acid to build up (soreness)– D.O.M.S.: Delayed onset muscle
• Metabolism of creatine phosphate– Quick boost of ATP
22
Muscle Terms• Origin: Nonmoving part
• Insertion: Movable part
• Prime mover– “Chief” muscle, most
responsible for movement
• Synergist– Helps prime mover
• Antagonist– Opposes prime move– Returns to “normal” position
Muscle Overuse and Underuse
• Hypertrophy: Growth in response to overuse• Atrophy: Wasting
– Disuse atrophy: cast for broken bone– Denervation atrophy: damage to nervous
system– Senile atrophy: wearing down of muscle
(age related)
• Contracture: Abnormal fibrous formation in muscle that “freezes” in flexed position
24
How Skeletal Muscles Are Named• Size: vastus(huge); maximus(large); longus(long);
minimus(small); brevis(short) – Ex.:Gluteus maximus
• Shape: deltoid(triangular); latissimus(wide); trapezius (trapezoid); rhomboideus (rhomboid); teres(round)– Ex. Trapezius, Latissimus dorsi
25
• Direction of fibers: Fibers are lined up; rectus(straight); oblique(diagonal); transverse(across); circularis(circular)– Ex. Rectus abdominis
• Location: reflect location on body; pectoralis (chest); gluteus (buttock); brachii (arm); supra(above); infra(below); Sub(underneath); lateralis(lateral)– Ex.: Pectoralis major, biceps brachii
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• Number of origins: where it’s anchored; Biceps(2), Triceps(3); Quadriceps(4)
• Origin and insertion: Both sites of attachment; Sterno-cleido-mastoid (sternum-clavicle-mastoid)
• Muscle action: type of action; aways from midline(abductor), toward midline(Adductor); levator(elevates); masseter(chews)
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Muscles from Head to Toe
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Facial Muscles• Frontalis: raises eyebrows and wrinkles
forehead
• Orbicularis oculi: closes eye, winking, blinking
• Levator palpebrae superioris: lifts eyelid
• Orbicularis oris: closes mouth, forms words
• Buccinator: flattens cheek, positions food
• Zygomaticus: smiling muscles
• Platysma: open your mouth wide, pout
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Facial Muscles: Chewing
• Masseter: chewing muscles
• Temporalis: temple
• Sternoclediomastoid: flexion and rotation of the head and rotation of the head.
• Trapezius: helps with the extension and hyperextension of the head at the neck
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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
– Transversus abdominis– Internal oblique– Rectus abdominis– External oblique
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Muscles of the Shoulder and Arm
• Trapezius• Serratus anterior• Pectoralis major• Latissimus dorsi• Deltoid
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Muscles of the Forearm
• Biceps brachii• Triceps brachii• Brachialis• Brachioradialis• Supinators and
pronators
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.34
Muscles of the Thigh• Extend thigh, climb stairs, and sitting:
– Gluteus maximus, medius, and minimus
• Iliopsoas: Flexes thigh, opposes gluteual group
• Adductor group: inner thigh, horseback riders muscle
• Quadriceps femoris: Extend Leg(kicking), anterior
• Sartorius: crosses over leg, allows you to sit in crossed leg position
• Hamstrings: posterior side of leg, flex leg opposes quadriceps
35
Muscles: Leg and Foot, Posterior View
• Gastrocnemius: calf• Soleus: calf• Tibialis posterior:
flexes foot, shin splits• Calcaneal or Achilles
tendon: where muscles connect to work foot
36
Muscles with Colorful Names
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.37
Carpal Tunnel Syndrome
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
reserved.38