Chapter 7 Muscular System

3 Functions of Muscular System Body heat to maintain body temperature Body movement Body form and shape to maintain posture

Types of Muscles Skeletal muscle Under voluntary (conscious) control Striped or striated Attached to bones Provide limb movement Contract quickly Tire easily Most of focus of this chapter!!

Types of Muscles 2. Smooth muscle Also called visceral muscle Involuntary control Controlled by autonomic nervous system No striations Not attached to bones Act slowly Peristalsis Childbirth

Types of Muscles Cardiac muscle Found only in the heart Involuntary Requires continuous supply of 02

Types of Muscle 4. Sphincter muscle Not considered on of the major muscle types Circular muscles Esophagus Stomach Anus Urethra

Characteristics of Muscles Contractibility Exclusive quality of muscle tissue Reduces distance between parts

Characteristics of Muscles Excitability or irritability Ability to respond to a stimulus and create an impulse

Characteristics of Muscles Extensibility Ability to be stretched

Characteristics of Muscles Elasticity Returns to original length when relaxing

Muscle Attachments and Functions Over 650 muscles in the body Muscles must be attached to bones for leverage Muscles only pull, never push Attached to bone by tendons

Muscle Attachments and Functions Muscles are attached at both ends Attachments may be to bones, cartilage, ligaments, tendons, skin or to each other Origin-least movable Insertion-where movement occurs

Muscle Functions Prime mover-moves in one direction Antagonist-moves in opposite direction Synergists-Help steady or stabilize joint activity

Sources of Energy and Heat ATP (adenosine triphosphate) Need oxygen, glucose, and other material to make By-product is lactic acid When muscle is stimulated releases ATP this gives us heat

Contraction of Skeletal Muscle Skeletal muscles must be stimulated by nerve impulses to contact Excitability or irritability

Muscle Fatigue Caused by accumulation of lactic acid Excess lactic acid causes fatigue and cramps Need to repay oxygen debt

Muscle Tone Muscle tone Proper nutrition and regular exercise Isotonic-contract and shorten Isometric-tense the muscle Atrophy and hypertrophy

Naming of Skeletal Muscles Location Size Direction Number of origins Location of origin and insertion Not all muscles are named by above method

Muscles 656 muscles 327 antagonistic muscles and two unpaired muscles Orbicularis oris Diaphragm

Muscles of the Head and Neck Muscles of Facial Expression 1. Frontalis: raises the eyebrows and wrinkles the forehead Orbicularis oris: used to close the mouth, form words, and pucker the lips 3. Orbicularis oculi: used to wink, blink, squint 4. Buccinator: used to compress the cheek when whistling, sucking, or blowing out air 5. Zygomaticus: used to raise the corner of mout when smiling

Muscles of the head & neck

Muscles of the head & neck Muscles responsible for chewing movements (mastication) a. Temporalis: closes jaw b. Masseter: closes jaw

Muscles of the head & neck Sternocleidomastoid: flexes and rotates the head Trapezius: extends head, adducts, elevates, and rotates scapula (shrugging the shoulders)

Muscles of the trunk Erector spinae: extends the vertebral column to maintain erect posture 2. Latissimus dorsi: adducts & rotates arm, lowers the shoulder. Important for swimming & rowing motions The widest & strongest muscle in the back

Thoracic wall muscles Involved primarily in the process of breathing. External intercostal muscles: inspiration Internal intercostal muscles: forced expiration

Forms a partition between thorax and abdomen When diaphragm contracts: increases the volume of thoracic cavity and results in inspiration When diaphragm relaxes: decreases volume of thoracic cavity and forces air out during expiration Diaphragm

Abdominal wall muscles 1. External oblique: compresses abdomen 2. Internal oblique: compresses abdomen 3. Transversus abdominis: compresses abdomen Rectus abdominis: flexes vertebral column and compresses abdomen (the 6-pack)

Pelvic floor muscles Pelvic diaphragm: forms the floor of the pelvic cavity Formed by the two levator ani muscles Supports and maintains position of pelvic viscera Urogenital diaphragm: fills the space within the pubic arch Supports pelvic viscera and assists in function of genitalia

Upper extremity muscles Serratus anterior: pulls shoulder downward and forward as in pushing something 2. Pectoralis major: adducts and flexes arm across the chest

Upper extremity muscles 3. Deltoid: abducts the arm to a horizontal position Common site for administering intramuscular (IM) injections 4. Rotator cuff Group of four muscles that attach humerus to scapula Form cap or cuff over humerus Rotates arm

UPPER ARM MUSCLES Triceps brachii: extends the forearm Biceps brachii: flexes and supinates forearm

Muscles of the lower extremity 1. Gluteus maximus Largest gluteal muscle Extends thigh 2. Gluteus medius Common site for intramuscular injections Abducts and rotates thigh 3. Gluteus minimus Smallest and deepest

Muscles that move the leg Quadriceps femoris: extends leg at the knee Vastus lateralis Vastus intermedius Vastus medialis Rectus femoris

Muscles that move the leg Sartorius Longest muscle in the body Flexes thigh and flexes and rotates leg Hamstrings: flexes leg and extends thigh a. Biceps femoris b. Semimembranosus c. Semitendinosus

Muscles that move the ankle and foot 1. Tibialis anterior: dorsiflexes foot 2. Peroneus: plantar flexes and everts foot 3. Gastrocnemius and soleus: plantar flexes foot Have a common tendon: calcaneal tendon (Achilles tendon) Allow you to stand on tiptoe

Skeletal Muscles