muscular system ch....

Muscular System

Ch. 24

Dr. Thorson

Lesson Objectives

Upon completion of this lesson, students should be able to:

1.Define and spell the terms to learn for this chapter.

2.Explain the functions of muscle.

3.Identify and discuss types of muscle tissue.

4.Discuss the energy requirements for muscles.

Lesson Objectives

Upon completion of this lesson, students should be able to:

5.Explain the structure of skeletal muscles.

6.List and discuss the three types of skeletal muscle movements.

7.Identify the major skeletal muscle groups of the body.

Muscle Characteristics

• Muscles make up about 42 percent of a person’s total body weight.

• Each muscle is made of specialized cells called muscle fibers.

• Muscle fibers held together by connective tissue.

• Connective tissue held together by fibrous sheath called fascia.


• Each fiber within a muscle has its own nervous system connection with a stored supply of energy in the form of glycogen.

• Muscle must be supplied with proper nutrition and oxygen to perform properly.


• Muscular system permeated by vessels from circulatory and lymphatic systems.

Functions of Muscle

• Movement

• Attributed to muscle contraction

• Contractibility main function of muscular system

• Muscles, attached to bones, internal organs, and blood vessels are responsible for all types of bodily movement

FIGURE 24-1A Selected skeletal muscles (anterior view)

FIGURE 24-1B Selected skeletal muscles and the Achilles tendon (posterior view)

Functions of Muscle

• Stability

• Tonicity

• Body’s ability to maintain posture through a continual partial contraction of skeletal muscles

• Muscular system works in conjunction with skeletal system to provide stability

Functions of Muscle

• Circulation and Respiration

• Heart composed of cardiac muscle tissue

• Involuntary movement and contraction of heart muscle responsible for circulating blood throughout body, providing essential nutrients and oxygen

Functions of Muscle

• Circulation and Respiration

• Respiration controlled by muscle movements

• Diaphragm major muscle responsible for breathing

Functions of Muscle

• Heat Production

• Muscles produce heat through chemical changes involved in muscular contraction

• Helps body maintain a normal temperature

Functions of Muscle

• Heat Production

• Digestion and Elimination

• Involuntary action of smooth muscles of digestive tract transport food through stomach and intestines

• Muscles help in eliminating fecal matter from body

Types of Muscle Tissue

• Muscles composed of:

• 75 percent water

• 20 percent protein

• 5 percent carbohydrates, lipids, inorganic salts, nonprotein nitrogenous compounds


• Three types of muscle tissue

• Skeletal

• Smooth

• Cardiac

FIGURE 24-2 Types of muscle tissue.

Critical Thinking Question

1.What categorizes a muscle tissue as voluntary or involuntary?


• Smooth Muscle

• Involuntary muscle

• Composed of elongated, spindle-shaped cells

• Also called visceral muscles because they are found in body’s organs (viscera)


• Smooth Muscle

• Contain no striations and nucleus centrally located

• It is not voluntarily controlled


• Skeletal Muscle

• Voluntary or striated muscle

• Can perform skeletal movement because it is attached to the bones of the body

• Responsible for voluntary movements

• Made up of cylindrical fibers

• Nucleus toward edge of each striated (striped in appearance) cell


• Cardiac Muscle

• Found in the heart

• Cells have single central nucleus

• Roughly quadrangular in shape

• Cells both striated and involuntary


• Cardiac Muscle

• Supplied with nerve fibers that carry messages to and from central nervous system

• Each involuntary contraction and relaxation of cardiac muscle results in a heartbeat

Energy Production for Muscle

• Adenosine Triphosphate (ATP)

• Type of chemical energy needed for sustained or repeated muscular contractions

• Produced by either aerobic (with oxygen) or anaerobic (without oxygen) means



• Aerobic production of ATP

• With oxygen, body uses carbohydrates, fats, proteins to produce energy

• Provides more energy that is available to use and is required for endurance



• Anaerobic production of ATP

• Body uses stored glucose (glycogen) to make ATP without oxygen

• Glycogen breaks down into ATP and lactic acid simultaneously

• Useful for small bursts of energy rather than endurance



• Creatine phosphate production of ATP

• Another method of acquiring muscular energy (ATP)

• Done without the use of oxygen

• Limited to skeletal muscles and is used for small bursts of energy

Oxygen Debt and Muscle Fatigue

• Occurs when skeletal muscles are used vigorously for more than 1 or 2 minutes

• When oxygen is lacking, body is unable to produce energy through aerobic means

• Anaerobic method of creating energy is activated


• Body can only use anaerobic energy for about 60 seconds before severe fatigue sets in, making it very difficult to recover

• To recover from oxygen debt, body must increase respiration to bring more oxygen into the bloodstream to reach the muscles


• Muscle fatigue develops as result of accumulation of lactic acid produced along with ATP during anaerobic metabolism

• Accumulation of lactic acid decreases muscle’s ability to contract


• Muscle cramps may occur

• May occur if blood supply to muscle is stopped or interrupted or if a motor neuron loses its ability to release acetylcholine

Structure of Skeletal Muscles

• More than 600 different skeletal muscles responsible for movement of body

• Contractility

• Extensibility

• Elasticity

FIGURE 24-3 A skeletal muscle consists of a group of fibers held together by connective tissue. It is enclosed in a fibrous sheath (fascia).

Skeletal Muscle Structures

• Fascia

• Covers entire skeletal muscle

• Separates muscles from one another

• Epimysium

• Thin fascia covering on muscle

• Separates skeletal muscles from one another


• Perimysium

• Comprised of connective tissue

• Divides muscle into sections called fascicles


• Endomysium

• Comprised of connective tissue

• Surrounds individual muscle cell

• Tendon

• Thick structure of fibrous connective tissue

• Connect skeletal muscle to bones


• Aponeurosis

• Thin, sheet-like tendon

• Connects muscle to muscle

Attachments to Skeletal Muscles

• Origin

• Muscle’s attachment point to a bone that is primarily fixed or still

• Insertion

• Attachment point of the other end of that muscle to a bone that moves


• Prime Mover or Agonist

• Muscle that is the primary actor in a given movement; produces the movement in muscle contraction

• Antagonist

• Muscle that counteracts, or opposes, the action of another muscle


• Synergist

• Muscle that acts with another muscle, most often a prime mover, to produce movement

Major Skeletal Muscles

• Muscles of the head

• Muscles of the arm, wrist, hand, fingers

• Respiratory muscles

• Abdominal muscles

• Muscles of the pectoral girdle

• Muscles of the leg, ankle, and foot


• Muscles of the Head

• Sternocleidomastoid

• Pulls head from side to side and to the chest

• Splenius capitis

• Rotates head and allows it to bend to the side

• Frontalis

• Raises the eyebrows



• Orbicularis oris

• Allows the lips to pucker

• Orbicularis oculi

• Allows the eyes to close

• Zygomaticus

• Pulls up corners of the mouth

• Platysma

• Pulls down corners of the mouth



• Masseter and temporalis

• Close the jaw

FIGURE 24-4 Muscles of the head, neck, and face.


• Muscles of the Arm, Wrist, Hand, Fingers

• Pectoralis major

• Pulls arm across the chest, also rotates/adducts

• Lattissimus dorsi

• Extension, adduction, and inward rotation of the arm



• Deltoid

• Abduction/extension of the arm at the shoulder

• Serratus anterior

• Pulls scapula forward



• Subscapularis

• Rotates arm medially

• Infraspinatus

• Rotates arm laterally

FIGURE 24-5 Muscles of the posterior torso that are responsible for arm movements.



• Biceps brachii

• Flexes arm at elbow and rotates hand laterally

• Brachialis

• Flexes arm at elbow

• Brachioradialis

• Flexes forearm at elbow



• Triceps brachii

• Extends arm at elbow

• Supinator

• Rotates forearm laterally

• Pronator teres

• Rotates forearm medially

FIGURE 24-6 Muscles of the arm and hand



• Flexor carpi radialis and flexor carpi ulnaris

• Flex/abduct wrist

• Palmaris longus

• Flexes wrist

• Flexor digitorum profundus

• Flexes distal joints of fingers, not thumbs



• Extensor carpi radialis longus and brevis

• Extends wrists, abducts hands

• Extensor carpi ulnaris

• Extends wrists

• Extensor digitorum

• Extends fingers, not thumbs


• Respiratory Muscles

• Diaphragm

• Separates thoracic cavity from abdominal cavity

• Its contraction causes the process of inspiration

• External and internal intercostals

• Contraction expands and lowers ribs during breathing


• Abdominal Muscles

• External and internal obliques

• Compress the abdominal wall

• Transversus abdminis

• Also compresses abdominal wall

• Rectus abdominis

• Flexes vertebral column

• Compresses abdominal wall

FIGURE 24-7 Abdominal muscles.


• Muscles of the Pectoral Girdle

• Trapezius

• Raises arms

• Pulls shoulders downward

• Pectoralis minor

• Pulls scapula downward

• Raises the ribs


• Muscles of the Leg, Ankle, and Foot

• Psoas major

• Flexes thigh

• Iliacus

• Also flexes thigh

• Gluteus maximus

• Extends thigh

• Gluteus medius and minimus

• Abduct thigh and rotate it laterally



• Hamstring group

• Flex leg at knee and extend leg at thigh; muscles include biceps femoris, semitendinosus, semimembranosus



• Quadriceps group

• Extend leg at knee; muscles include vastus lateralis, vastusmedialis, vastus intermedius, rectus femoris

• Sartorius

• Performs multiple functions including flexing knee and thigh, abducting thigh, enabling act of being able to sit cross-legged



• Gastrocnemius

• Flexes foot and aids in pushing body forward

• Tibialis anterior

• Causes dorsiflexion and inversion of the foot



• Peroneus

• Everts foot and helps bring about plantar flexion

• Flexor digitorum longus and extensor digitorum longus

• Flexes and extends toes and assist in other movements of feet

Muscles of the buttocks, leg, and foot

Critical Thinking Question

1.What types of conditions occur in the muscular system?

Common Disorders Associated with the Muscular System

• Atrophy

• Occurs with disuse of muscles over a long period of time

• Lipoatrophy is atrophy of fat tissue, common at injection sites

• Signs and symptoms

• Apparent “wasting away” appearance of a muscle group

• Extreme weakness and fatigue associated with atrophic muscle groups


• Atrophy

• Treatments

• Isometric exercises of immobilized muscle

• Active exercise of uninjured limbs helps prevention


• Fibromyalgia

• Musculoskeletal pain and fatigue disorder

• More common in women than men

• No obvious known cause; evidence of possible genetic predisposition


• Fibromyalgia


• Mild to severe muscle pain and fatigue

• Sleep disorders

• Irritable bowel syndrome

• Depression

• Chronic headaches


• Fibromyalgia

• American College of Rheumatology has identified specific criteria for diagnosis

• Patient must show:

• Pain at 11-18 trigger or tender points to be considered for this diagnosis

• History of widespread pain lasting at least three months


• Fibromyalgia

• No known cure

• Treatment geared toward improving quality of sleep and reducing pain

• Muscle relaxants, pain relievers, anti-inflammatory drugs, antidepressants, anti-anxiety drugs

• Chiropractic, acupuncture, acupressure, relaxation techniques, massage

FIGURE 24-9 The 18 tender points of fibromyalgia.


• Ganglion Cyst

• Benign saclike swelling or cyst that typically develops over a joint or tendon

• More common in women than men

• No known cause


• Ganglion Cyst


• Fluid-filled masses occur on hands, feet, wrists, and ankles and are very painful

• Erratic swelling can occur, developing and disappearing without cause


• Ganglion Cyst

• Anti-inflammatory drugs

• Aspiration of fluid (74% effective rate)

• Surgery if pain or decreased range of motion occurs


• Lyme Disease

• Caused by the Borrelia burgdorferi bacterium

• Carried by ticks and transmitted through bite of an infected tick


• Lyme Disease


• Round “bull’s eye” rash

• Headache

• Fatigue

• Neck stiffness

• Fever


• Lyme Disease

• Prevention

• Wearing long sleeves and pants while in heavily wooded areas

• Proper use of insect repellant

• Prompt removal of any tick that may be lodged in the skin


• Lyme Disease

• Treatment

• Erythromycin

• Penicillins

• Doxycycline


• Muscular Dystrophy (MD)

• Genetic disease

• Progressive weakness and degeneration of the skeletal or voluntary muscles

• Nine major forms

• Signs and symptoms (general)

• Muscle weakness

• Loss of coordination

• Immobility


• Muscular Dystrophy (MD)

• Treatment

• No specific treatment for any of the forms

• Physical therapy to prevent contractures

• Orthoses for support

• Corrective orthopedic surgery

• Emery-Dreifuss and myotonic forms may necessitate a pacemaker due to associated cardiac problems


• Myasthenia Gravis (MG)

• Chronic autoimmune neuromuscular disease

• Most common in young adult women and older men

• Affects any voluntary muscle, but more often found in the eye and jaw areas



• Muscle weakness increases during periods of activity, improves after rest

• Weakness may also occur in muscles that control breathing and arm and leg movements



• Treatment

• No cure

• Controllable

• Corticosteroids and anticholinesterase

• Surgery, including removal of thymus gland, may be required


• Rotator Cuff Tears

• Common in shoulder muscles and tendons

• Due to many years of overuse of these muscles and tendons

• Also caused by one single traumatic injury



• Limited ROM and function of shoulder area

• Considerable pain

• Atrophy of shoulder muscle

• Cracking sensation when shoulder moved into certain positions



• Rest

• Narcotic and nonsteroidal anti-inflammatory drugs (NSAIDs)

• Splinting

• Physical therapy

• Range of range-of-motion exercises

• Severe injuries may require steroid injections and possibly surgery

FIGURE 24-10 A rotator cuff tear Images


• Shin Splints

• Caused by overuse or improper conditioning of the leg muscles

• Common in running sports, military training, high impact dancing

• Also found with flat feet or rigid arches

• Increased pain, tenderness, possible swelling along shin area


• Shin Splints

• Rest

• Ice or cold compresses to shin area

• Aspirin and NSAIDs for pain management and to reduce swelling

• Use of proper footwear to prevent future episodes


• Sprain

• Stretching or tearing

• Injury to ligament (connective tissue that connects bones or connects cartilage to joint)

• Strain

• Injury to either a muscle or a tendon


• Sprains

• Occur after ligament has been overstretched or torn, especially in ligaments of major joints (elbows, knees, wrists, ankles, feet)

• Ankle sprains most common injury in United States


• Sprains

• Pain

• Swelling

• Bruising

• Loss of joint mobility and function

• Vary in intensity


• RICE Method

• Rest (if joint is weight bearing, use canes, crutches, or other walking devices)

• Ice (ice pack or cold compress)

• Compression (bandages to encourage proper healing)

• Elevation (above or at same level as heart)


• Sprains

• Range of motion exercises

• Physical therapy

• NSAIDS

• Surgery in rare instances


• Strains

• Twisting or pulling of a muscle

• Chronic: prolonged, repetitive movements

• Acute: improper lifting of a heavy object


• Strains

• High risks found in sports such as:

• Soccer

• Football

• Hockey

• Tennis

• Gymnastics


• Strains


• Pain

• Muscle weakness

• Muscle spasms

• Loss of muscle function

• Inflammation

• Cramping

• Swelling


• Sprains

• Treatment

• Similar to that of a sprain (RICE method)

• Anti-inflammatory medications

• Gentle stretching

• Heat application

• On occasion, brace to limit mobility of injured muscle


• Tendonitis

• Tendon

• Band of connective tissue at each end of muscle that attaches muscle to a bone

• Excessive and repetitive movements causing inflammation and tears of the tendon


• Tendonitis

• Common areas include:

• Elbow and wrist

• Biceps and shoulder

• Hip, leg, knee

• Achilles


• Tendonitis

• Pain and stiffness in affected area

• Burning sensation surrounding joint or inflamed tendon

• Pain can worsen during or right after activity


• Tendonitis

• Proper care can lessen symptoms over three weeks

• Healing does not occur for at least six weeks following initial injury

• Support and protect via braces to affected area

• Physical therapy, including exercises to increase range of motion


• Tetanus

• Often fatal, infectious disease

• Caused by Clostridium tetani bacteria


• Tetanus

• Toxin enters body through puncture, cut or open wound

• Profound painful muscle spasms

• Lockjaw

• Difficulty swallowing due to neck stiffness

• Stiffness of chest, abdominal, back muscles

• Fever


• Tetanus

• Prevention best course of treatment

• All children should be immunized against tetanus by receiving a full series of five diphtheria, pertussis, and tetanus (DPT, or Tdap) vaccinations

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