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Chapter 7

The Muscular SystemThe Muscular System

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Types of MuscleTypes of Muscle

Smooth Cardiac Skeletal

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Smooth Muscle Makes up walls of hollow body organs, respiratory passageways Involuntary movement Cell structure

Tapered ends Single, central nucleus No visible bands (striations)

Stimulated by nerve impulses, hormones, stretching

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Cardiac Muscle Makes up wall of heart Involuntary movement Cell structure

Branching interconnections Single, central nucleus Striated Membranes are intercalated disks

Stimulated by electrical impulses, nervous stimuli, hormones

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Skeletal Muscle

Attached to bones, muscles, or skin Voluntary movement Cell structure

Long and cylindrical Multiple nuclei per cell Heavily striated

Stimulated by nervous system

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Checkpoint 7-1: What are the three types of muscle?

Smooth

Cardiac

skeletal

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The Muscular SystemThe Muscular System

Skeletal muscle has three primary functions Skeletal movement Posture maintenance Heat generation

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Checkpoint 7-2: What are the three main functions of skeletal muscle? Skeletal movement Posture maintenance Heat generation

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Structure of a Muscle Connective tissue layers

Endomysium Around individual fibers

Perimysium Around fascicles (bundles of muscle fibers)

Epimysium Over entire muscle Part of deep fascia

Tendon Attaches muscle to bone

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Structure of a skeletal muscle.

ZOOMING  IN• What is the innermost layer of connective tissue in a muscle?

What layer of connctive tissue surrounds a fascicle of muscle fibers?

The perimysium

The endomysium

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Muscle Cells in Action

Motor unit is a single neuron and all the muscle fibers it stimulates

Neuromuscular junction (NMJ) Neurotransmitter Synaptic cleft Receptors Motor end plate

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Nervous stimulation of skeletal muscle.

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Neuromuscular junction (NMJ).

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Checkpoint 7-3: Muscles are activated by the nervous system. What is the name of the special synapse where a nerve cell makes contact with a muscle cell? The neuromuscular junction

Checkpoint 7-4: What neurotransmitter is involved in the stimulation of skeletal muscle cells? Acetylcholine

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Properties of Muscle Tissue

Excitability Action potential

Contractility Actin Myosin Sarcomere ATP

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Electron microscope photograph of skeletal muscle cell (x6500).

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Sliding filament mechanism of skeletal muscle contraction.

ZOOMING  IN• Do the actin or myosin filaments change in length as contraction proceeds?

They do not change in length, they overlap more

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Checkpoint 7-5: What are two properties of muscle cells that are needed for response to a stimulus? Excitability and contractility

Checkpoint 7-6: What are the filaments that interact to produce muscle contraction? Actin and myosin

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The Role of Calcium Stored in endoplasmic reticulum

(ER) Is released when nerve fiber

stimulates muscle cell Attaches to proteins blocking

receptor sites Allows cross-bridges to form

between actin and myosin Returns to endoplasmic reticulum

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Role of calcium in muscle contraction.

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Energy Sources Muscle contraction requires energy (ATP)

Generated by oxidation of glucose or other usable nutrient

Compounds stored in muscle cells for energy production

Myoglobin Stores reserves of oxygen

Glycogen Storage form of glucose

Creatine phosphate Stores energy

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Checkpoint 7-7: What mineral is needed to allow actin and myosin to interact? Calcium

Checkpoint 7-8: Muscle cells obtain energy for contraction from the oxidation of nutrients. What compound is formed in oxidation that supplies the energy for contraction? ATP

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Oxygen Consumption Aerobic metabolism

Requires oxygen Used during normal activities

Anaerobic metabolism Does not require oxygen Used during strenuous activity Less ATP produced Lactic acid accumulates Oxygen debt develops

Recovery oxygen consumption needed

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Checkpoint 7-9: When muscles work without oxygen, a compound is produced that causes muscle fatigue. What is the name of this compound? Lactic acid

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Effects of Exercise Improved balance, joint flexibility Increase in muscle size (hypertrophy) Improvements in muscle tissue Vasodilation Strengthened heart muscle Improved breathing and respiratory

efficiency Weight control Stronger bones

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Types of Muscle Contractions

Partial (muscle tone or tonus) Isotonic

No change in tension Muscle length shortens Movement

Isometric Great increase in tension Muscle length unchanged No movement

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The Mechanics of The Mechanics of Muscle MovementMuscle Movement

Tendons attach muscles to bones Origin—attached to more fixed

part of skeleton Insertion—attached to more

moveable part of skeleton

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Muscle attachments to bones. ZOOMING  IN• Does contraction of the biceps brachii produce flexion or extension at the

elbow?

Flexion

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Checkpoint 7-10: Muscles are attached to bones by means of tendons: one attached to a less movable part of the skeleton and one attached to a movable part. What are the names of these two attachment points? The less movable part is the origin. The more movable part is the insertion.

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Muscles Work Together

Many muscles function in pairs Prime movers

Produce given movement Synergists

Assist prime movers

Antagonists Oppose a given movement

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Checkpoint 7-11: Muscles work together to produce movement. What is the name of the muscle that produces a movement as compared with the muscle that produces an opposite movement? The prime mover produces a

movement and the antagonist produces the opposite movement

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Levers and Body Levers and Body MechanicsMechanics Musculoskeletal system as a lever

system Lever—bone Fulcrum—joint Force—applied by muscle

Three classes of levers First class Second class Third class—most body movements

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Levers

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Checkpoint 7-12: Muscles and bones work together as lever systems. Of the three classes of levers, which one represents the action of most muscles?

Third class – the fulcrum is behind the point of effort and the weight

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Skeletal Muscle GroupsSkeletal Muscle Groups Characteristics for naming muscles (often

combined) Location

Biceps brachii Size

Gluteus maximus Shape

Trapezoid Direction of fibers

Transversus abdominus Number of heads (attachment points)

Triceps brachii Action

Extensor carpi ulnaris

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Superficial muscles, anterior view

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Superficial muscles, posterior view

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Muscles of the Head

Facial expression (orbicularis) muscles Orbicularis oculi Orbicularis oris Levator palpebrae superioris Buccinator

Mastication (chewing) muscles Temporalis Masseter Tongue

Intrinsic Extrinsic

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Muscles of the headZOOMING  IN• Which of themuscles in this illustration isnamed for a bone it is near?

Frontalis, nasalis, mentalis and temporalis

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Muscles of the Neck

Are ribbonlike Extend up, down, or obliquely Extend in several layers in a

complex manner Main one is sternocleidomastoid

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Muscles of the Upper Extremities

Position the shoulder Move the arm Move the forearm and hand

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Muscles That Move the Shoulder and Arm Trapezius Latissimus dorsi Pectoralis major Serratus anterior Deltoid Rotator cuff

Supraspinatus Infraspinatus Teres minor Subscapularis

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Muscles That Move the Forearm and Hand

Biceps brachii Brachioradialis Triceps brachii Flexor carpi Extensor carpi Flexor digitorum Extensor digitorum

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Muscles that move the forearm and hand

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Muscles of the Trunk

Breathing muscles Abdominal muscles Pelvic floor muscles Deep back muscles

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Muscles of Respiration

Diaphragm Intercostal muscles

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Muscles of respiration

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Checkpoint 8-13: What muscle is most important in breathing?

The diaphragm

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Muscles of the Abdomen and Pelvis

External oblique Internal oblique Transversus abdominis Rectus abdominis Levator ani

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Muscles of the abdominal wall

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Muscles of the female perineum (pelvic floor)

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Checkpoint 7-14: What structural feature gives strength to the muscles of the abdominal wall?

The fibers of the muscles of the abdominal wall run in different directions.

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Deep Muscles of the Back

Erector spinae Deeper muscles in the lumbar area

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Muscles of the Lower Extremities

Among the longest and strongest in the body

Specialized for locomotion and balance

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Muscles That Move the Thigh and Leg

Gluteus maximus Gluteus medius

Site of injection of many medications Iliopsoas Adductors Sartorius Hamstrings

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Muscles of the thigh

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Muscles That Move the Foot

Gastrocnemius Achilles tendon Soleus Tibialis anterior Peroneus longus Flexor and extensor muscles

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Muscles that move the foot

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Effects of Aging on Effects of Aging on MusclesMuscles

Beginning at about age 40 Gradual loss of muscle cells Loss of power Tendency to flex hips and knees Decrease in height