Skeletal Muscle Action

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Skeletal Muscle Action
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Origin and insertion

• The immovable fixed end of a muscle connects to a
  bone at the origin.
• The movable end of a muscle connects at the
  insertion.
• With contraction, insertion pulls toward the
  origin
• Can have more than one of each.

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Use and Disuse of Skeletal Muscles

• Muscles increase with use hypertrophy
• Muscles decrease with disuse atrophy (cast)

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Fast Twitch vs. Slow Twitch Muscle Fibers

• Aerobic exercise uses slow twitch fibers
• Ex. Swimming long distance, cross country skiing-
  raises amount of ATP and blood flow to muscles.
• Red fibers

5
Fast twitch vs. Slow twitch muscle fibers

• Anaerobic exercise uses fast twitch fibers.
• Ex. Weightlifting, and sprinting - diameter of
  muscle increases by producing more actin and
  myosin fibers.
• White fibers

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Muscle Action of Head

• Facial expression - sadness, surprise, fear,
  disgust.
• Zygomaticus - mouth
• Frontalis - eyebrow
• Occipitalus - eyebrow

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Muscle Action of Head

• Mastication - chewing
• Masseter
• Temporalis

Closes jaw
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Muscle Action of Head

• Movement of Head
• Sternocleidomastoid - prayer position

9
Muscle Action of the Pectoral Girdle (chest and
shoulders)

• Associated with muscles that move arm
• Move scapula up, down, forward, and backward
• Trapezius
• Serratus anterior
• Pectoralis minor

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Muscle action of the pectoral girdle (chest and
shoulders)

• Associated with muscles that move arm
• Move scapula up, down, forward, and backward
• Trapezius
• Serratus anterior
• Pectoralis minor

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Muscles that Move the Arm

• Flexion - bending a joint to decrease the angle
  between bones.
• Extension - movement increasing angles between
  parts in a joint
• Abduction - movement of a body part away from the
  midline.
• Rotation - movement turning a body part along its
  longitudinal axis.

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Muscles that move arm

• Upper arm
• Pectoralis major - flexor
• Latissimus dorsi - extensor
• Deltoid - abductor
• Teres minor - rotator

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Muscles that move arm
flexor
extensor
abductor
rotator
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Lower Arm

• Biceps brachii - flexion
• Brachialis - flexion
• Brachioradialis - flexion
• Triceps brachii - extension

flexion
flexion
flexion
extension
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Muscle Action in Abdominal Wall (Six Pack)

• Connect the rib cage to the pelvic girdle
• External oblique
• Internal oblique
• Rectus abdominus
• Hernia
• A hole in the abdominal muscles.
• Intestines protrude outward to form a lump.
• Repaired by surgery

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Muscle Action in Thigh

• Divided into anterior/posterior sections
• Anterior sections create flexion
• Posterior sections create extension, abduction,
  and rotation.
• Gluteus maximus
• Gluteus medius
• Tensor Fasciae Latae
• Adductors of the thigh

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Muscle Action in Thigh Cont

• Adduction - movement of a body part toward the
  midline.
• Adductor longus
• Gracilus

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Muscles that Move the Leg (Lower Leg)

• Divided into two groups
• Hamstring group are the flexors
• Biceps femoris
• Semitendenosus
• Semimembranosus
• Satorius longest muscle in the body

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Muscles that Move the Leg (Lower Leg)

• Divided into two groups
• Quadriceps Group
• Rectus femoris - middle of the thigh
• Vastus lateralis - outside of thigh
• Vastus medialis - midline of thigh

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Longest Muscle in the Human Body

• Sartorius