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Functions and Types of Muscles o Smooth Muscle
• Located in the walls of hollow organs and blood vessels
• Involuntary contraction
• Moves materials through organs and regulates blood flow
• Cylindrical cells with pointed ends
• Each cell is uninucleate

Functions and Types of Muscles o Cardiac Muscle
• Forms the heart wall
• Fibers are uninucleated, striated, tubular, and branched
• Fibers interlock at intercalated disks, which permit contractions to spread quickly throughout the heart
• Contraction does not require outside nervous stimulation
• Nerves do affect heart rate and strength of contraction

Functions and Types of Muscles o Skeletal Muscle
• Fibers are tubular, multinucleated, and striated
• Make up muscles attached to the skeleton
• Contraction is voluntary

Functions and Types of Muscles o Connective Tissue Coverings of Skeletal
Muscle
• Endomysium
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Thin layer of areolar connective tissue
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Surrounds each skeletal muscle fiber
• Perimysium – surrounds bundles of muscle fibers (fascicles)
• Epimysium
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Layer that surrounds the entire muscle
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Becomes part of the fascia (separates muscles from each other)
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Collagen fibers extend from epimysium to form tendons that attach muscles to bone

Functions and Types of Muscles o Functions of Skeletal Muscles
• Support the body
• Make bones and other body parts move
• Help maintain a constant body temperature
• Assists movement in cardiovascular and lymphatic vessels
• Help protect bones and internal organs, and stabilize joints

7.2 Microscopic Anatomy o Muscle fiber components
• Sarcolemma – plasma membrane
• Sarcoplasm – cytoplasm
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Contains glycogen that provides energy for muscle contraction
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Contains myoglobin which binds oxygen until needed
• Sarcoplasmic reticulum – endoplasmic reticulum
• T (transverse) tubules
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Formed by the sarcolemma penetrating into the cell
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Come into contact with expanded portions of the sarcoplasmic reticulum

Microscopic Anatomy o Myofibrils and Sarcomeres
(draw and label)
• Myofibrils run the length of the muscle fiber
• Composed of numerous sarcomeres
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Extends between two vertical Z lines
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Contains two types of protein myofilaments
 Thick filaments – made up of myosin
 Thin filaments – made up of actin, tropomyosin, and troponin
I band contains only thin filaments
A band in the center of the sarcomere contains thick and thin filaments
H zone in the center of the A band has only myosin filaments

7.2 Microscopic Anatomy o Myofilaments
• Thick filaments
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Composed of several hundred of molecules of myosin
Myosin molecules end in a cross-bridge
• Thin filaments
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Two strands of actin
Double strands of tropomyosin coil of each actin strand
Troponin occurs at intervals on the tropomyosin strand

Microscopic Anatomy
• Sliding filaments
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Occurs when sarcomeres shorten (during muscle contraction)
Actin filaments slide past the myosin filaments
Thick and thin filaments remain the same length

Contraction of Skeletal Muscle o Neuromuscular junction
• Axon terminals

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Come into close proximity to the sarcolemma
Have vesicles that contain acetylcholine
(Ach)
• Synaptic cleft – a small gap that separates the axon from the sarcolemma

Fig 7.4

Contraction of Skeletal Muscle o Steps involved in skeletal muscle contraction
• Nerve signal arrives at the axon terminal
• The synaptic vesicles release Ach
• Ach binds to receptors on the sarcolemma
• The sarcolemma generates a signal that travels down the T tubules to the SR
• The SR releases calcium
• Calcium from the SR causes the filaments to slide past one another

Contraction of Skeletal Muscle o The Role of Actin and Myosin
• Myosin binding sites on actin molecules

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Covered by tropomyosin when muscle is relaxed
Released calcium combines with troponin and myosin binding sites are exposed
• Cross-bridges of myosin have two binding sites
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One site binds to ATP
Second binding site binds to actin

Contraction of Skeletal Muscle o Energy for Muscle Contraction
• ATP present before strenuous exercise only lasts a few seconds
• Muscles acquire new ATP in three ways
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Creatine phosphate breakdown
Cellular respiration
Fermentation

Contraction of Skeletal Muscle
• Creatine Phosphate Breakdown
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Does not require oxygen
(anaerobic)
Regenerates ATP by transferring its phosphate to ADP
Fastest way to make ATP available to muscles
ATP produced only lasts about 8 seconds

TA 7.1

• Cellular Respiration
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Usually provides most of a muscle’s
ATP
Uses glucose from stored glycogen and fatty acids from stored fats
Required oxygen
Myoglobin can make oxygen available to muscle mitochondria
Carbon dioxide and water are end products
Heat is a by-product

Contraction of Skeletal Muscle
• Fermentation

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Anaerobic process
Produces ATP for short bursts of exercise
Glucose is broken down to lactate
(lactic acid)

Contraction of Skeletal Muscle o Oxygen Debt
• Occurs when muscles use fermentation to supply ATP
• Requires replenishing creatine phosphate supplies and disposing of lactic acid

Contraction of Smooth Muscle o Smooth muscle fibers contain thick and thin filaments
• Filaments are not arranged into myofibrils that create striations
• Thin filaments are anchored to the sarcolemma or dense bodies o When contracted, the elongated cells become shorter and wider o Contraction occurs very slowly o Contractions can last for long periods of time without fatigue

7.3 Muscle Responses in the
Laboratory o All-or-none law – a muscle fiber contracts completely or not at all o A whole muscle shows degrees of contraction
• Muscle twitch – a single contraction that lasts only a fraction of a second
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Latent period
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Contraction period
Relaxation period
• Summation – increased muscle contraction
• Tetanic contraction – maximal sustained contraction

Muscle Responses in the Laboratory o Fatigue
• Muscle relaxes even though stimulation continues
• Reasons for fatigue
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ATP is depleted
Accumulation of lactic acid in the sarcoplasm inhibits muscle function
ACh may become depleted

Muscle Responses in the Body o Motor unit
• A nerve fiber together with all of the muscle fibers it innervates
• Obeys the all-or-none law o Recruitment
• As the intensity of nervous stimulation increases, more motor units are activated
• Results in stronger muscle contractions o Tone
• Some muscle fibers are always contracting
• Important in maintaining posture

Muscle Responses in the Body o Athletics and muscle contraction
• Size of muscles
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Atrophy – a decrease in muscle size
Hypertrophy – an increase in muscle size

• Slow-twitch fibers (Type I fibers)
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Tend to be aerobic
Have more endurance
Have many mitochondria
Dark in color because they contain myoglobin
Highly resistant to fatigue

Muscle Responses In the Body
• Fast-twitch fibers (Type II fibers)
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Tend to be anaerobic
Designed for strength
Light in color
Have fewer mitochondria, little or no myoglobin, and fewer blood vessels than slow-twitch fibers
Vulnerable to accumulation of lactic acid and can fatigue easily

7.4 Skeletal Muscles of the Body o Basic Principles
• Origin – attachment of a muscle to the immovable bone
• Insertion – attachment of a muscle to the bone that moves
• Prime mover – muscle that does most of the work in a movement
• Synergist – muscles that assist the prime mover
• Antagonists – muscles that work opposite one another to bring about movement in opposite directions

7.4 Skeletal Muscles of the Body o Naming Muscles
(details follow, so do not copy)
• Size
• Shape
• Direction of fibers
• Location
• Attachment
• Number of attachments
• Action

• Size, examples: maximus (biggest), minimus (smallest), vastus (huge), longus (long), brevis (short)
• Shape, examples: deltoid
(triangular), trapezius (trapezoidal), latissimus (wide), teres (round)
• Direction of fibers, examples: rectus
(straight), transverse (across), oblique (diagonal)

• Location frontalis (over frontal bone), pectoralis (chest), gluteus (buttock), brachii (arm), sub (beneath), external includes directional terms such as anterior, posterior, lateral, medial, proximal, distal, superficial, deep

• Attachment, examples: sternocleidomastoid (attached to sternum, clavicle, and mastoid process), brachioradialis (attached to the brachium, arm, and the radius)

• Number of attachments, examples: biceps brachii (bi=2 attachments or origins), quadriceps femoris
(quadric=4 origins, also note femoris as a location)
• Action, examples: extensor digitorum
(extends fingers or digits), adductor magnus (large muscle that adducts the thigh), flexor (to flex), masseter
(to chew), levator (to lift)

Skeletal Muscles of the Body o Muscles of the Head
• Muscles of Facial
Expression
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Frontalis
Orbicularis oculi
Orbicularis oris
Buccinator
Zygomaticus
• Muscles of Mastication
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Masseter muscles
Temporalis muscles
Fig 7.13

Skeletal Muscles of the Body o Muscles of the Neck
• Swallowing
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Tongue and buccinators
Suprahyoid and infrahyoid muscles
Palatini muscles
Pharyngeal constrictor muscles
• Muscles that move the head
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Sternocleidomastoid
Trapezius muscles

Contraction of Skeletal Muscle

Skeletal Muscles of the Body o Muscles of the Trunk
• Muscles of the thoracic wall
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External intercostal muscles
Diaphragm
Internal intercostal muscles
• Muscles of the abdominal wall
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External and internal obliques
Transversus abdominis
Rectus abdominis

Skeletal Muscles of the Body o Muscles of the Shoulder
• Muscles that move the scapula
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Trapezius
Serratus anterior
• Muscles that move the arm
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Deltoid
Pectoralis major
Latissimus dorsi
Rotator cuff muscles
 Supraspinatus
 Infraspinatus
 Teres minor
 Subscapularis

Fig 7.15

Skeletal Muscles of the Body o Muscles of the Arm
• Biceps brachii
• Brachialis
• Triceps brachii o Muscles of the Forearm
• Flexor carpi and extensor carpi
• Flexor digitorum and extensor digitorum

Skeletal Muscles of the Body o Muscles of the Hip and Lower Limb
• Muscles that move the thigh
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Iliopsoas
Gluteus maximus
Gluteus medius
Adductor group muscles
 Pectineus
 Adductor longus
 Adductor magnus
 Gracilis

Skeletal Muscles of the Body
• Muscles that move the leg

Quadriceps femoris group
 Rectus femoris
 Vastus lateralis
 Vastus medialis
 Vastus intermedius
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Sartorius
Hamstring group
 Biceps femoris
 Semimembranosus
 Semitendinosus

Skeletal Muscles of the Body
• Muscles that move the ankle and foot
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Gastrocnemius
Tibialis anterior
Fibularis longus
Fibularis brevis
Flexor and extensor digitorum longus

7.5 Effects of Aging o Muscle mass and strength tend to decrease o Endurance decreases o Exercise at any age can stimulate muscle buildup

7.6 Homeostasis o Cardiac muscle contraction forces blood into the arteries and arterioles o Smooth muscle in arteries and arterioles help maintain blood pressure o Smooth muscle contraction moves food along the digestive tract and assists in the voiding of urine

o Skeletal muscles protect internal organs and stabilizes joints o Skeletal muscles are active during breathing o Heat produced by skeletal muscle contraction helps maintain normal body temperature o Skeletal muscle contraction allows us to relocate our bodies