CHAPTER 6 – THE MUSCULAR SYSTEM

MUSCLE VOCABULARYBi = 2; Tri = 3; Quad = 4; Ceps =

Heads Biceps = 2 Heads Triceps = 3 Heads Quadriceps = 4 Heads

Brachium = Arm Example: Brachialis

Communis = Common Example: Extensor Digitalis

Communis

MUSCLE VOCABULARY, CONT’D

Deltoid = Triangle Example: Deltoideus

Digastric = Two Bellies Extrensic = From the Outside Fascia = Band or Girdle

Example: Superficial Fascia; Deep Fascia

Femoris = Thigh or Femur Example: Biceps Femoris

MUSCLE VOCABULARY, CONT’D

Glossus = Tongue Gluteus = Pertaining to the Buttocks

Example: Gluteus Maximus, Gluteus Medias, Gluteus Minimus

Dorsi = On or of the Back Example: Latissimus Dorsi

Intrinsic = Within or Inside Gracilis = Slender Infra = Below or Inferior

MUSCLE VOCABULARY, CONT’D

Latissimus = WidestExample: Latissimus Dorsi

Longissimus = Longest Masseter = Chewer Maximus = Largest Minimus = Smallest Myology = Study of Muscles Oblique = Slanted Orbicularis = An Orb or Circle

MUSCLE VOCABULARY, CONT’D

Pectoralis = Breasts and Chest Quadratus = Four Sides or Square

Example: Quadrilaterals Rectus = Straight Semi = Prefix denoting Half

Example: Semipermeable Membrane

Supra = Above or upon Example: Supraspinatus

I. OVERVIEW OF MUSCLE TISSUES

~ Muscles make up approximately 40% of Body Mass~

A.Characteristics of MusclesSkeletal and smooth muscle cells are elongated (muscle cell = muscle fiber)

Contraction of muscles is due to the movement of microfilaments (myofibril)

All muscles share some terminologyPrefixes myo and mys refer to “muscle”

Prefix sarco refers to “flesh”

Muscle Types (Know anatomy of skeletal muscle #1 – diagram and terms)

I. OVERVIEW OF MUSCLE TISSUES…CONT’D

TendonBelly

Epimysium

PerimysiumEndomysium

Fiber (Cell)

Bundle

Sarcolemma – Cell MembraneSarcoplasm – Cell Cytoplasm

I. OVERVIEW OF MUSCLE TISSUES…CONT’D

B.Muscle Functions1. Produces movement2. Maintains posture3. Stabilizes joints4. Generates heat

II. PROVIDING ENERGY FOR MUSCLE

CONTRACTIONS ~ ATP – Source of energy for contractions~A.Muscle Fatigue – unable to

contract while being stimulated. Due to:Oxygen Debt

Depends on blood supplyLactic Acid builds up (sore & tired muscles)

Oxygen debt payback rapid, deep breathing

Low supply of ATP

B.Types of ContractionsIsotonic – muscle shortens & movement occursex: bending knee, rotating arm, smiling

Isometric – tension increases; muscle does not shortenex: pushing against a wall

II. PROVIDING ENERGY FOR MUSCLE CONTRACTIONS, CONT’D

C.Muscle ToneSustained partial contractionDue to nerve supplyKeeps muscle healthy & ready to react

Paralysis – no stimulation; muscle becomes flaccid & atrophy

II. PROVIDING ENERGY FOR MUSCLE CONTRACTIONS, CONT’D

D. Effects of Exercise on Muscle“Use it or Lose it”Aerobic (endurance) Exercise

Does little to increase massStronger, Flexible, Less fatigueBenefits: skeletal muscle, metabolism, digestion (elimination), neuromuscular coordination, skeleton, blood vessels, lungs

Ex: jogging, biking, aerobics

II. PROVIDING ENERGY FOR MUSCLE CONTRACTIONS, CONT’D

D. Effects of Exercise on Muscle, Cont’d…

Resistance exercise – isometricMuscles contract with force

Enlarges muscle cellsEx: Weightlifting

II. PROVIDING ENERGY FOR MUSCLE CONTRACTIONS, CONT’D

1.All muscles cross at least one joint.2.Typically, the bulk of the muscle lies

proximal to the joint crossed.3.All muscles have at least two

attachments: the origin and th insertion.

4.Muscles can only pull; they never push.

5.During contraction, the muscle insertion moves toward the origin.

THE 5 GOLDEN RULES OF SKELETAL MUSCLE ACTIVITY: (TABLE 6.2)

III. MUSCLE MOVEMENTS, TYPES & NAMES

A. Types of Body MovementsOrigin: attached to the immovable or less movable bone

Insertion: attached to movable bone

III. MUSCLE MOVEMENTS, TYPES & NAMES, CONT’D

Flexion – Decreases the angle of the joint

Extension – increases the angle

Abduction – moving away from midline

Adduction – moving toward midline

III. MUSCLE MOVEMENTS, TYPES & NAMES, CONT’D

Rotation – movement around longitudinal axis

Circumduction – circular motion

Depression – movement downward

Pronation – face down

III. MUSCLE MOVEMENTS, TYPES & NAMES, CONT’D

Supination – face upDepression – movement

downwardElevation – movement

upwardRetraction – movement

posteriorly

III. MUSCLE MOVEMENTS, TYPES & NAMES, CONT’D

Inversion – sole faces medially

Eversion – sole faces laterally

Dorsiflection – heel down, sole up; “flex”

Plantar Flexion – toe down, heel up; “point”

III. MUSCLE MOVEMENTS, TYPES & NAMES, CONT’D

B. Types of MusclesPrime Mover: muscle with major responsibility for a particular motion

Antagonists: muscle that acts in opposition to prime moverEx: Elbow flexion

Biceps – Prime MoverTriceps - Antagonist

III. MUSCLE MOVEMENTS, TYPES & NAMES, CONT’DB. TYPES OF MUSCLES, CONT’D

Synergist: muscles cooperating with another to produce a movement; stabilize jointsEx: Finger flexors; make fist without bending wrist

Fixators: stabilize the origin of a prime moverEx: Muscles that anchor scapula to thorax

III. MUSCLE MOVEMENTS, TYPES & NAMES, CONT’D

B. Naming Skeletal Muscles1. Direction of muscle fiber2. Relative size of the muscle3. Location of the muscle4. Number of origins5. Location of origin &

insertion6. Shape of Muscle7. Action of the muscle

IV. DEVELOPMENTAL ASPECTS OF THE

MUSCULAR SYSTEMMuscle develops early in embryo –

16th weekCongenital disease – muscular

dystrophyMuscle fibers degenerate and

atrophyEx: Duchenne Muscular

DystrophyMost common and seriousMales 2-6; wheelchair 12;

death – young adult

IV. DEVELOPMENTAL ASPECTS OF THE MUSCULAR SYSTEM

Muscle ControlReflex – at birth (nervous system

must mature)Develops – cephalic to caudal and

proximal to distalSkeletal muscles – rich in blood

supply; resist infectionAging – muscle tissue decreases Decreased body weight Decreased strength