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 6

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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 shortens  muscle contraction Animation 11

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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 26

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) 27

Muscles from Head to Toe 28

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 29

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 30

Muscles of the Trunk: Breathing Intercostal muscles – Internal – External Diaphragm 31

More Muscles of the Trunk Abdominal wall – Transversus abdominis – Internal oblique – Rectus abdominis – External oblique 32

Muscles of the Shoulder and Arm Trapezius Serratus anterior Pectoralis major Latissimus dorsi Deltoid 33

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