Essentials of Human Anatomy

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Essentials of Human Anatomy Physiology
Elaine N. Marieb
Chapter 6The Muscular System
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The Muscular System

• Muscles are responsible for all types of body
  movement they contract or shorten and are the
  machines of the body
• Three basic muscle types are found in the body
• Skeletal muscle
• Cardiac muscle
• Smooth muscle

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Characteristics of Muscles

• Skeletal smooth muscle cells are elongated
  (muscle cell muscle fiber)
• Contraction of muscles is due to the movement of
  microfilaments
• All muscles share some terminology
• Prefix myo refers to muscle
• Prefix mys refers to muscle
• Prefix sarco refers to flesh

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Skeletal Muscle Characteristics

• Most are attached by tendons to bones
• Cells are multinucleated
• Striated have visible banding
• Voluntary subject to conscious control
• Cells are surrounded and bundled by connective
  tissue great force, but tires easily

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Skeletal Muscle
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Connective Tissue Wrappings ofSkeletal Muscle

• Endomysium around a single muscle fiber
• Perimysium around a fascicle (bundle) of fibers

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Connective Tissue Wrappings ofSkeletal Muscle

• Epimysium covers the entire skeletal muscle
• Fascia on the outside of the epimysium

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Skeletal Muscle Attachments

• Epimysium blends into a connective tissue
  attachment
• Tendon cord-like structure
• Aponeuroses sheet-like structure
• Sites of muscle attachment
• Bones
• Cartilages
• Connective tissue coverings

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Smooth Muscle Characteristics

• No striations
• Spindle-shaped cells
• Single nucleus
• Involuntary no conscious control
• Found mainly in the walls of hollow organs
• Slow, sustained contractions (tireless)

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Smooth Muscle
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Cardiac Muscle Characteristics

• Has striations
• Usually has a single nucleus
• Joined to another muscle cell at an intercalated
  disc
• Involuntary
• Found only in the heart
• Steady pace!

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Cardiac Muscle
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Muscle Functions

• Produce movement
• Maintain posture
• Stabilize joints
• Generate heat

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Microscopic Anatomy of Skeletal Muscle

• Cells are multinucleate
• Nuclei are just beneath the specialized plasma
  membrane called ? Sarcolemma

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Microscopic Anatomy of Skeletal Muscle

• Myofibril
• Bundles of myofilaments
• Myofibrils are aligned to give distinct bands
  (striations)
• I band light band
• A band dark band

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Microscopic Anatomy of Skeletal Muscle

• Sarcomere
• Contractile unit of a muscle fiber

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Microscopic Anatomy of Skeletal Muscle

• Organization of the sarcomere
• Thick filaments Myosin filaments
• Composed of the protein myosin
• Contain ATPase enzymes
• Extend the entire length of the dark A band

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Microscopic Anatomy of Skeletal Muscle

• Myosin filaments
• Myosin heads
• Create cross bridges

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Microscopic Anatomy of Skeletal Muscle

• Organization of the sarcomere
• Thin filaments Actin filaments
• Composed of the protein actin
• Anchored to the Z disc

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Microscopic Anatomy of SkeletalMuscle

• Sarcoplasmic reticulum
• Specialized smooth endoplasmic reticulum
• Stores and releases calcium on demand when the
  muscle fiber is stimulated to contract

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Skeletal Muscle Activity

• Stimulation Contraction of Single Skeletal
  Muscle Cells
• Irritability ability to receive and respond to
  a stimulus
• Contractility ability to shorten when an
  adequate stimulus is received

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Nerve Stimulus to Muscles

• Skeletal muscles must be stimulated by a nerve to
  contract (motor neruron)
• Motor unit
• One neuron
• Muscle cells stimulated by that neuron

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Nerve Stimulus to Muscles

• Neuromuscular junctions association site of
  nerve and muscle

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Nerve Stimulus to Muscles

• Synaptic cleft gap between nerve and muscle
• Nerve and muscle do not make contact
• Area between nerve and muscle is filled with
  interstitial fluid

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Transmission of Nerve Impulse to Muscle

• Neurotransmitter chemical released by nerve
  upon arrival of nerve impulse
• The neurotransmitter for skeletal muscle is
  acetylcholine
• Neurotransmitter attaches to receptors on the
  sarcolemma
• Sarcolemma becomes permeable to sodium (Na)

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Transmission of Nerve Impulse to Muscle

• Sodium rushing into the cell generates an action
  potential
• Once started, muscle contraction cannot be stopped

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The Sliding Filament Theory of Muscle Contraction

• Activation by nerve causes myosin heads
  (crossbridges) to attach to binding sites on the
  thin filament
• Myosin heads then bind to the next site of the
  thin filament

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The Sliding Filament Theory of Muscle Contraction

• This continued action causes a sliding of the
  myosin along the actin
• The result is that the muscle is shortened
  (contracted)

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The Sliding Filament Theory
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Contraction of a Skeletal Muscle

• Muscle fiber contraction is all or none
• Within a skeletal muscle, not all fibers may be
  stimulated during the same interval
• Different combinations of muscle fiber
  contractions may give differing responses
• Graded responses different degrees of skeletal
  muscle shortening, rapid stimulus constant
  contraction or tetanus

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Muscle Response to Strong Stimuli

• Muscle force depends upon the number of fibers
  stimulated
• More fibers contracting results in greater muscle
  tension
• Muscles can continue to contract unless they run
  out of energy

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Energy for Muscle Contraction

• Initially, muscles used stored ATP for energy
• Bonds of ATP are broken to release energy
• Only 4-6 seconds worth of ATP is stored by
  muscles
• After this initial time, other pathways must be
  utilized to produce ATP

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Energy for Muscle Contraction

• Direct phosphorylation
• Muscle cells contain creatine phosphate (CP)
• CP is a high-energy molecule
• After ATP is depleted, ADP is left
• CP transfers energy to ADP, to regenerate ATP
• CP supplies are exhausted in about 20 seconds

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Energy for Muscle Contraction

• Anaerobic glycolysis
• Reaction that breaks down glucose without oxygen
• Glucose is broken down to pyruvic acid to produce
  some ATP
• Pyruvic acid is converted to lactic acid

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Energy for Muscle Contraction

• Anaerobic glycolysis (continued)
• This reaction is not as efficient, but is fast
• Huge amounts of glucose are needed
• Lactic acid produces muscle fatigue

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Energy for Muscle Contraction

• Aerobic Respiration
• Series of metabolic pathways that occur in the
  mitochondria
• Glucose is broken down to carbon dioxide and
  water, releasing energy
• This is a slower reaction that requires
  continuous oxygen

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Muscle Fatigue and Oxygen Debt

• When a muscle is fatigued, it is unable to
  contract
• The common reason for muscle fatigue is oxygen
  debt
• Oxygen must be repaid to tissue to remove
  oxygen debt
• Oxygen is required to get rid of accumulated
  lactic acid
• Increasing acidity (from lactic acid) and lack of
  ATP causes the muscle to contract less

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Types of Muscle Contractions

• Isotonic contractions
• Myofilaments are able to slide past each other
  during contractions
• The muscle shortens
• Isometric contractions
• Tension in the muscles increases
• The muscle is unable to shorten

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Muscle Tone

• Some fibers are contracted even in a relaxed
  muscle
• Different fibers contract at different times to
  provide muscle tone
• The process of stimulating various fibers is
  under involuntary control

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Effects of Exercise on Muscles

• Results of increased muscle use
• Increase in muscle size
• Increase in muscle strength
• Increase in muscle efficiency
• Muscle becomes more fatigue resistant

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Muscle Movements, Types, and NamesTextbook page
192 ?
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Five Golden Rules of Skeletal Muscle Activity

1. With a few exceptions, all muscles cross at least
   one joint
2. Typically, the bulk of the muscle lies proximal
   to the joint crossed
3. All muscles have at least 2 attachments ? origin
   insertion
4. Muscles can only pull they never push
5. During contraction, the muscle insertion moves
   toward the origin

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Muscles and Body Movements

• Movement is attained due to a muscle moving an
  attached bone

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Muscles and Body Movements

• Muscles are attached to bone, or to other
  connective tissue structures, at no less than two
  points
• Origin attachment to the stationary bone
• Insertion attachment to the movable bone

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Types of Body Movements

• Flexion- Decreases the angle of the joint and
  brings 2 bones closer together (Bending the knee
  or elbow)
• Extension Opposite of flexion- increases the
  angle between 2 bones (Straightening the knee or
  elbow)
• Hyperextension- Extension gt180 degrees (Tipping
  your head back so your chin points toward the
  ceiling)

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Types of Body Movements

• Rotation- Movement of a bone around its
  longitudinal axis Common with ball and socket
  joints ? describes the movement with the atlas
  around the dens of the axis (Shaking your head
  no)
• Abduction Moving a limb away from the midline
  of the body Fanning movement of fingers, toes
• Adduction Movement of a limb towards the body
  midline Opposite of abduction
• Circumduction Combination of flexion,
  extension, abduction and adduction. Proximal end
  of limb is stationary, distal end moves in a
  circle ? Limb as a whole outlines a cone
• See textbook page 195

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Left Abduction moving the leg away from the
midline
Right Circumduction cone-shaped movement,
proximal end doesnt move, while distal end moves
in a circle.
Above Adduction- moving toward the midline
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Special Movements

• Dorsiflexion ? Lifting the foot so that its
  superior surface approaches the shin
• Plantar flexion ? Pointing the toes
• Inversion ? To invert the foot- turn the sole
  medially
• Eversion ? To evert the foot- turn the sole
  laterally

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Special Movements

• Supination- Forearm rotates laterally so that the
  palm faces anteriorly, and the radius and ulna
  are parallel (Carry soup --gt soup-inating)
• Pronation- Forearm rotates medially so the palm
  faces posteriorly (Face down)
• Opposition- Action by which you move your thumb
  to touch the tips of the other fingers on the
  same hand
• (See textbook page 195)

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Interactions of Skeletal Muscles

• Prime mover muscle with the major
  responsibility for a certain movement
• Antagonist muscle that opposes or reverses a
  prime mover
• When the prime mover is active its antagonist is
  stretched and relaxed
• Synergist muscle that aids a prime mover in a
  movement and helps prevent rotation

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Naming Skeletal Muscles

• Direction of Muscle Fiber Rectus femoris
• Relative Size- Gluteus maximus
• Location Temporalis frontalis muscles
  Sterno- on the sternum
• Number of Origins Biceps, triceps, quadriceps
• Shape Deltoid (Triangular)
• Action Flexor extensor adductor

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Gross Anatomy of Skeletal Muscles
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Head and Neck Muscles
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Trunk Muscles
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Deep Trunk and Arm Muscles
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Muscles of the Pelvis, Hip, and Thigh
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Muscles of the Lower Leg
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Superficial Muscles Anterior
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Superficial Muscles Posterior
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Intramuscular Injections(vs. subcutaneous)

• Muscle Injection Site LandmarkLandmarks
• Deltoid Acromion of Scapula Acromion of
  Scapula
• Vastus Lateralis ½ way betweenGreater
  Trochanter of Femur and Patellahalfway of
  between greater trochanter femur and
  patella
• Gluteus Medius lIIiac Crest

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Muscle Strain Website

• What is a Muscle Strain?
• A muscle strain is damage caused by
  over-stretching of muscle tissue. The muscle
  tissue becomes overloaded and reaches a breaking
  point where a tear or partial tear occurs.
• GRADE 1 STRAIN There is damage to individual
  muscle fibers (less than 5 of fibers). This is a
  mild strain which requires 2 to 3 weeks rest.
• GRADE 2 STRAIN There is more extensive damage,
  with more muscle fibers involved, but the muscle
  is not completely ruptured. The rest period
  required is usually between 3 and 6 weeks.
• GRADE 3 STRAIN This is a complete rupture of a
  muscle. In a sports person this will usually
  require surgery to repair the muscle. The
  rehabilitation time is around 3 months.

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Common Injuries

• Hamstring pull/strain
• tears of tendinous origins website
• cause rigorous running/quick stop-start

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Groin Pull

• Strain of distal
• abductors of iliac crest
• website

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• Shin Splints
• -pain in the Distal, medial 2/3 of shin
• -Tendonitis of periosteum
• -running on hard surfaces/
• improper running shoes
• website

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Patello-Femoral Syndrome

• Knee patello-femoral syndrome a.k.a. runners
  knee-lateral tracking of patella-result from
  over-running website

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Plantar Faciitis - chronic irritation at origin
of Calcaneus- -painful-heel syndrome website
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Treatments

• RICE
• Rest/Ice/Compression/Elevation
• Anti-inflammatoryibuprofen (NSAIDS)
• -non-steroidal anti-inflammatory drugs
• Steroidal drugscortisone/hydrocortisone

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Disorders relating to the Muscular System

• Muscular Dystrophy inherited, muscle enlarge
  due to increased fat and connective tissue, but
  fibers degenerate and atrophy
• Duchenne MD lacking a protein to maintain the
  sarcolemma
• Myasthemia Gravis progressive weakness due to a
  shortage of acetylcholine receptors

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Types of Ordinary Body Movements website

• Abduction/Adduction (see slides)
• Circumduction (see slides)