Smooth muscle Contraction - Current University of Rio

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Smooth muscle Contraction
• Spindle Shaped
• Central nuclei
• Lack Striations, transverse tubules, and lack well
developed sacroplasmic reticulum
• Actin and myosin thin and randomly distributed
• Multi-unit-Separate units
» Muscle of iris and blood vessels
• Visceral-Sheets of spindle cells
» Respond as a single unit
» Rhythmicity- spontaneous
» peristalsis
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Internal organs• outer longitudinal
• Inner circular
Contraction
Impulses travel across the membraneCalcium diffuses into the cell from the extracellular fluid.
Calcium binds to a protein calmodulin-activating
contraction.
Nt- Ach and Norepi, stimulates/ inhibits contractions
altering degrees of contraction.
Smooth- slow and longer contraction
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Terms
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Origin
Insertion
Prime mover-Agonist
Assist a prime mover-Synergists
Antagonist- movement in the opposite
direction or resist a prime mover,
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Skeletal Muscle Actions
• origin – immovable end
• insertion – movable end
• prime mover (agonist) –
primarily responsible for
movement
• synergists – assist prime mover
• antagonist – resist prime
mover’s action and cause
movement in the opposite
direction
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Muscular Tissue
Three Types of Muscle Tissues
Skeletal Muscle
Cardiac Muscle
• usually attached
to bones
• under conscious
control
Smooth Muscle
• striated
• walls of most viscera,
blood vessels, skin
• not under conscious
control
• not striated
• wall of heart
• not under
conscious control
• striated
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Smooth Muscle Fibers
Compared to skeletal muscle fibers
• shorter
• single nucleus
• elongated with tapering ends
• myofilaments randomly organized
• no striations
• lack transverse tubules
• sarcoplasmic reticula not well developed
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Cardiac Muscle
• only in the heart
• muscle fibers joined together by intercalated discs
• fibers branch
• network of fibers contracts as a unit
• self-exciting and rhythmic
• longer refractory period than skeletal muscle
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Muscles of Facial Expression-CNVII
• Orbicularis oculiblinking/closes eyelids
• Orbicularis oris-closes
lips/protrudes lips-kissing
• Buccinator-compresses
cheeks as in blowing air
• Zygomaticus-raises corner of
mouth/smiling
• Platysma-pouting/draws
mouth downward & elevates
skin
• Frontalis-elevates eyebrows
& creases skin
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Muscles of Mastication-CNV3
• Masseter-elevates mandible
• Temporalis-elevates
mandible
• Pterygoid
– Medial-elevates and moves it
from side to side
– Lateral-depresses and
protracts
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Muscles of Head and Vertebra
• Paired muscles- flex, extend, and rotate
the head and hold the torso erect.
• Sternocleidomastoid-flex and rotates
• Extend and rotate
– Splenius capitis
– Semispinalis capitis
– Erector spinae
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Muscle of the Pectoral Girdle
• Trapezius- raises scapula and shoulders,
elevates clavicle, extends neck and head
• Serratus Anterior -pulls scapula forward and
downward, used when pushing something.
– Damage to the long thoracic nerve-results in winged
scapula
• Rhomboids-retracts, elevates, and rotates
• Levator Scapula-elevates scapula
• Pectoralis minor- pulls scapula in forward and
downward, raise ribs in forceful inhalation
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Muscles That Move the Arm
• Flexors
– Coracobrachialis
– Pectoralis major- also adducts arm
• Extensors
– Teres Major
– Latissimus dorsi- also adducts arm (swimmer muscle)
• Abductors
– Deltoid – most prominent muscle of the shoulder-axillary nerve-fracture
to the neck of humerus-unable to abduct the arm
– Supraspinatus
• Rotators cuff muscles
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Subscapularis
Infraspinatus
Teres minor
Supraspinatus
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• Movement of Forearm
Biceps brachii-flexes and laterally
rotates elbow
Brachialis- strongest flexor of
elbow
Brachioradialis-aids in flexing
Triceps- opposes-extends elbow
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Muscle of the Abdominal area
• Compress the abdominal cavity and increases
pressure, used during forceful exhalation or
defecation
• Rectus abdominis-six pack
• External oblique-fibers runs downward to pelvic
girdle
• Internal oblique-fibers run upward to lower ribs
• Transversus abnominis- deepest layer-runs
horizontally across
• Linea alba- connective tissue band that runs
from xiphoid to symphysis pubis
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Transversus abdnominis
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Muscles of the Thigh
• Anterior group- primary flexors of thigh
– Psoas
– iliacus
• Posterior group- extends the thigh
– Gluteus muscles- maximus-the largest muscle in
the body
– Tensor fasciae latae-extends from ilium to the
iliotibial tract- abducts, rotates, and flexes
• Adductors
– Pectineus-flexes
– Adductor brevis, longus, magnus-flex and rotate
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– Gracilis- straplike band from the pubic bone to tibia
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Pectineus
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Gluteus Muscle
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Quadriceps Femoris group
Extensor
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Extends leg at knee
Rectus femoris
Vastus lateralis
Vastus medialis
Vastus intermedius
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Flexors of knee
Hamstring Muscles
• Biceps femoris
• Semimembranosus
• Semitendinosus
• Sartorius-strap like
that passes obliquely
across the front of
thigh- abducts and
rotates laterally
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• Semimembranosus
• Semitendinosus
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