Copyright © 2005, Elsevier, Inc. All rights reserved. Slide 0 0 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Chapter 7 The Muscular System Presented by Dawn Duran, PT, MHS, CSCS Adjunct Faculty, Kaplan University

1 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Introduction Muscular tissue enables the body and its parts to move  Movement is caused by ability of muscle cells, called fibers, to shorten or contract  Muscle cells shorten by converting chemical energy obtained from food into mechanical energy, which causes movement  Three types of muscle tissue exist in the body

2 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Question What are the three types of muscle tissue?

3 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Tissue Skeletal muscle (aka striated or voluntary) Cardiac muscle (involuntary) Smooth muscle (involuntary; aka non- striated or visceral)

4 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Tissue Skeletal muscle—also called striated or voluntary muscle  Represents 40% to 50% of body weight  Microscope reveals crosswise stripes or striations

5 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Functions of Skeletal Muscle  Produce movement  Contractions can be voluntarily controlled  Help to maintain posture  Help to generate heat required for maintaining a core body temperature

6 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Tissue  Cardiac muscle—composes the bulk of the heart  Cardiac muscle cells branch frequently  Characterized by unique dark bands called intercalated disks where the plasma membranes of adjacent cardiac fibers contact each other  Interconnected nature of cardiac muscle cells allows heart to contract efficiently as a unit

7 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Tissue  Nonstriated muscle or involuntary muscle—also called smooth or visceral muscle  Lacks cross stripes or striation when seen under a microscope; appears smooth  Found in walls of hollow visceral structures, such as digestive tract, blood vessels, and ureters  Contractions not under voluntary control; movement caused by contractions is involuntary

8 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Structure of Skeletal Muscle Skeletal muscle is an organ composed mainly of skeletal muscle fibers and connective tissue. Most muscles extend from one bone across a joint to another bone.

9 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Structure of Skeletal Muscle Parts of a skeletal muscle:  The origin of a muscle is its’ point of attachment to the bone that remains relatively fixed when movement at the joint occurs  The insertion of a muscle is its’ point of attachment to the bone that moves when a muscle contracts  The muscle body is the main part of the muscle and is also called the muscle belly.  A tendon attaches each muscle to a bone

10 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Functions of Skeletal Muscle Movement  Muscles produce movement  As muscle contracts, it pulls the insertion bone closer to the origin bone  Movement occurs at the joint between the origin and the insertion

11 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Attachments of a Skeletal Muscle Structure of Skeletal Muscle

12 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Structure of Skeletal Muscle Muscles attach to the bone by tendons—strong cords of fibrous connective tissue that do not easily detach from bone. Some tendons are enclosed in synovial-lined tubes and lubricated by synovial fluid which facilitates movement Bursae are small synovial-lined sacs containing a small amount of synovial fluid. They lie between a tendon and a bone. They make it easier for a tendon to slide over a bone.

13 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Microscopic structure  Muscle tissue consists of specialized contractile cells called fibers  Another name for a muscle cell is a muscle fiber  Each fiber contains two kinds of very fine, threadlike structures which are also proteins:  Thick myofilaments (myosin)  Thin myofilaments (actin) Structure of Skeletal Muscle

14 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.  Sarcomere is the basic functional or contractile unit of the muscle  Separated from each other by dark bands called Z lines  The accepted explanation for how skeletal muscle contracts is known as the “sliding filament model”  Thick and thin myofilaments slide past each other as a muscle contracts Structure of Skeletal Muscle

15 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Structure of a Sarcomere

16 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Question What are the functions of skeletal muscle ?

17 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Functions of Skeletal Muscle 1.Movement 2.Posture, or muscle tone 3.Heat production

18 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Functions of Skeletal Muscle Movement  Groups of muscles usually contract to produce a single movement  Prime mover/agonist—contraction is mainly responsible for producing a specific movement  Synergist—contractions help the prime mover produce a movement  Antagonist—actions oppose the action of a prime mover in a movement

19 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Movement

20 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Functions of Skeletal Muscle Posture  Tonic contraction: A continuous low strength muscle contraction that enables us to maintain body posture  Only a few of a muscle’s fibers shorten at one time  Tonic contractions produce no movement  Tonic contractions maintain muscle tone and muscle tone maintains posture

21 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Poor Posture Poor posture causes fatigue and may lead to deformity

22 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Functions of Skeletal Muscle Heat production  Survival depends on the ability to maintain constant body temperature  Fever: An elevated body temperature; often a sign of illness  Hypothermia: A reduced body temperature  Contraction of muscle fibers produces most of the heat required to maintain normal body temperature

23 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Fatigue

24 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Fatigue Reduced strength of muscle contraction results from repeated stimulation of fibers without sufficient rest Repeated muscular contraction depletes cellular ATP store and outstrips the ability of the blood supply to replenish oxygen and nutrients

25 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Fatigue Contraction in the absence of adequate oxygen produces lactic acid, which contributes to muscle soreness Oxygen debt: The continued metabolic effort required to burn excess lactic acid that may accumulate during prolonged periods of exercise Labored breathing is required to help the body pay the oxygen debt. This is an example of homeostasis at work. During labored breathing, the body is attempting to return the cells’ energy and oxygen reserves to pre-exercise levels

26 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Motor Unit Stimulation of a muscle by a nerve impulse is required to produce movement  Motor neuron: Specialized nerve that transmits an impulse to a muscle, causing contraction.  A nerve fiber that innervates or stimulates muscle fibers is called a motor neuraon.  Neuromuscular junction: Specialized point of contact between a nerve ending and the muscle fiber it innervates  Neurotransmitters are released here  Motor unit is a single motor neuron and the muscle fibers it innervates.

27 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Stimulus A muscle will contract only if an applied stimulus reaches a certain level of intensity  Threshold stimulus: Minimal level of stimulation required to cause a muscle fiber to contract Once stimulated by a threshold stimulus, a muscle fiber will contract completely, a response called all or none

28 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Stimulus Different fibers in a muscle are controlled by different motor units with different threshold-stimulus levels  Although individual muscle fibers always respond all or none to a threshold stimulus, the muscle as a whole does not  This allows the muscle to give a graded response so that we are easily able to pick up a pencil or a 20 pound weight  It also prevents the muscle as a whole from becoming fatigued too quickly

29 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Types of Skeletal Muscle Contraction 1.Twitch contractions 2.Tetanic contractions 3.Isometric 4.Isotonic Concentric Eccentric

30 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Types of Skeletal Muscle Contraction  Twitch contractions: A quick, jerky response to stimulus  Single contraction of muscle fibers caused by a single threshold stimulus  Also called a fasciculation  Tetanic contractions—sustained, steady muscular contractions  Caused by a series of stimuli bombarding a muscle in rapid succession  Also referred to as tetany, or tetanus

31 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Types of Skeletal Muscle Contraction Isotonic contractions  Contraction of a muscle that produces movement at a joint  The muscle changes length, causing the insertion end of the muscle to move relative to the point of origin  Most types of body movements such as walking and running are the result of isotonic contractions

32 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Types of Skeletal Muscle Contraction Types of Isotonic Contractions: Concentric – muscle shortening occurs Eccentric – muscle lengthening occurs. Also called a “negative” contraction. –We can produce more strength eccentrically than we can concentrically –Eccentric contractions are associated with slowing down moving body parts, or lowering objects from a lifted position achieved via a concentric contraction

33 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Isometric contractions  Muscle contractions that do not produce movement  The muscle as a whole does not shorten  No movement occurs during isometric contractions, but tension within the muscle increases Types of Skeletal Muscle Contraction

34 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Types of Skeletal Muscle Contraction

35 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Effects of Exercise on Skeletal Muscles Regular, properly practiced exercise improves muscle tone and posture Results in more efficient heart and lung functioning with improved circulation Reduces fatigue Helps muscle tissue develop Helps maintain a healthy weight Proper exercise will strengthen muscles, improve breathing and improve the efficiency of the heart.

36 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Effects of Exercise on Skeletal Muscles  Prolonged inactivity causes muscular wasting, or atrophy  A patient that is bedridden due to illness and does not use their muscles for months is likely to experience muscle atrophy  Regular exercise increases muscle size, called hypertrophy

37 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Strength training: Exercise involving contractions of muscles against heavy resistance  Increases the number of myofilaments in each muscle fiber  Total mass of the muscle increases  Does not increase the number of muscle fibers Effects of Exercise on Skeletal Muscles

38 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Endurance training: Exercise that increases a muscle’s ability to sustain moderate exercise over long periods.  Sometimes called aerobic training  Allows more efficient delivery of oxygen and nutrients to a muscle via increased blood flow  Increases the number of blood vessels in a muscle  Does not usually result in muscle hypertrophy Effects of Exercise on Skeletal Muscles

Copyright © 2005, Elsevier, Inc. All rights reserved. Slide Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. An Overview of Movement

40 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Types of Movements Produced by Skeletal Muscle Contractions Types of Movements Produced by Skeletal Muscle Contractions Flexion: Decreases the angle between two bones at their joint: bending Extension: Increases the angle between two bones at their joint: straightening Abduction: Movement of a part away from the midline of the body Adduction: Movement of a part toward the midline of the body Rotation: Movement around a longitudinal axis

41 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Types of Movements Produced by Skeletal Muscle Contractions Types of Movements Produced by Skeletal Muscle Contractions Flexion and Extension of the Elbow

42 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Supination and pronation: Hand positions from rotation of the forearm  Supination: Palm turned to the anterior position  Pronation: Palm faces posteriorly Dorsiflexion and plantar flexion: Foot movements  Dorsiflexion: Elevation of the dorsum or top of the foot (pulling the toes up towards the ceiling)  Plantar flexion: Bottom of the foot is directed downward (pointing the toes) Types of Movements Produced by Skeletal Muscle Contractions Types of Movements Produced by Skeletal Muscle Contractions

43 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Examples of Body Movements Types of Movements Produced by Skeletal Muscle Contractions Types of Movements Produced by Skeletal Muscle Contractions

44 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Skeletal Muscle Groups Give examples of each (reference Table 7- 1 and Figures 7-6 and 7-7):  Muscle of head and neck  The masseter is a muscle of mastication, or chewing. It is considered one of the strongest muscles in the body.  Muscles that move the upper extremities  Muscles of the trunk  Muscles that move the lower extremities

45 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Nomenclature (ie the naming of muscles) Muscles may be named according to…  Function  Direction of Fibers  Points of attachment (sternocleidomastoid)  Size (gluteus maximus)  Shape  Location (brachialis)  Number of origins (triceps brachii, biceps, quadriceps)

46 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. KNOW ALL OF THESE!! You will need to be able to identify all of the superficial anterior and posterior muscles of the body.

47 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscles of the Head and neck Sternocleidomastoid Frontal Orbicularis Oculi Zygomaticus Major Zygomaticus Minor

48 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscles of Facial Expression Orbicularis oris Orbicularis oculi Zygomaticus

49 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscles that move the Upper Extremities Pectoralis Major Latissimus Dorsi Deltoid Biceps Brachii Triceps Brachii

50 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscles the Move the Lower Extremities Gluteus Maximus Hamstrings Quadriceps Femoris group Adductor Longus Tibialis Anterior Gastrocnemius Soleus

51 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscles of the Trunk Transversus Abdominus Rectus Abdominus External Oblique Internal Oblique Erector Spinae Multifidus

52 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Descriptions The frontal muscle attaches to the skull and the skin above the eyebrows. It raises the eyebrows. The orbicularis oculi closes the eye. It has its origin and insertion on the maxilla and frontal bone.

53 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Descriptions Zygomaticus elevates the corners of the mouth. It originates on the “cheek bone” and inserts in the corners of the mouth. The masseter closes the jaw. It originates on the zygomatic arch and inserts on the mandible.

54 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Descriptions Orbicularis Oris is the “kissing” muscle. Trapezius elevates the shoulders and extends the head and neck. It originates on the skull and upper vertebrae and inserts on the scapula.

55 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Descriptions Pectoralis Major helps flex and adduct the upper arm. It originates on the sternum and clavicle. The deltoid abducts the upper arm. It originates on the clavicle and scapula and inserts on the humerus. It is often the site of an intramuscular injection.

56 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Muscle Descriptions Triceps Brachii extends the elbow. Rectus Abdominus flexes the trunk. It originates on the pubic bone and inserts on the lower rib cage. Rectus femorus extends the knee. It originates on the ilium and inserts on the tibia.

57 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Random Fact When the foot ligaments and tendons weaken, an individual may experience fallen arches, or flat feet.

Copyright © 2005, Elsevier, Inc. All rights reserved. Slide Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Let’s Review! Chapter 7

59 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Slide 59 Question Which of these is usually under conscious control? A.Cardiac muscle B.Smooth muscle C.Skeletal muscle

60 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Answer A.Skeletal muscle

61 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Slide 61 Question A person picks up a pencil, thus flexing the elbow. Contraction of the biceps brachii muscle during flexion is mainly A.Isometric B.Isotonic

62 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Answer Isotonic

63 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Slide 63 Question Plantar flexion A.Bends the elbow B.Causes you to stand on your toes C.Causes you to stand on your heels D.Bends the wrist E.Moves the leg out to the side of the body

64 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. Answer Causes you to stand on your toes

65 Copyright (c) 2008, 2005 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. That’s All, Folks! Do you have any questions?