Chapter 6, cont' Muscular system

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Chapter 6, cont. Muscular system

• What are the three types of muscle tissue?
• What are the functions of the muscular system?
• How are skeletal muscles and muscle fibers
  structured?
• How do skeletal muscles contract?
• How do skeletal muscle cells acquire ATP for
  contraction?
• What are some common muscular disorders?

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Review 3 types of muscle tissue
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What are the functions of skeletal muscles?
12.1 Overview of the muscular system

• Support
• Movement
• Homeostasis
• Protection internal organs and stabilize joints

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How are skeletal muscles arranged?
12.1 Overview of the muscular system

• Attachments
• Tendon
• Origin
• Insertion
• Action
• Antagonistic
• Synergistic

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An example of muscle arrangement
12.1 Overview of the muscular system
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Examples of how skeletal muscles are named
12.1 Overview of the muscular system

• Size gluteus maximus, vastus lateralis
• Shape deltoid, trapezius
• Location frontalis, tibialis anterior
• Direction of muscle fiber the rectus abdominus
  (rectus means straight)
• Attachment brachioradialis
• Number of attachments biceps brachii
• Action extensor digitorum

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Muscle fibers/cells
12.2 Skeletal muscle fiber contraction

• Terminology for cell structure
• sarcolemma
• sarcoplasm
• sarcoplasmic reticulum
• Terminology for structure within a whole muscle
• Fascicles
• Myofibrils
• Myofilaments
• Sarcomeres

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Visualizing muscle structure
12.2 Skeletal muscle fiber contraction
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The sarcomere
12.2 Skeletal muscle fiber contraction

• Made of protein myofilaments
• Thick myosin
• Thin actin, troponin, tropomyosin
• These filaments slide over one another during
  muscle contraction

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The beginning of muscle contraction The sliding
filament model
12.2 Skeletal muscle fiber contraction

• What type of neuron carries information toward
  the muscle?
• What is released from the pre-synaptic cell?
• 3. What does it bind to? (This binding will
  cause calcium to be released from the SR.)

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The beginning of muscle contraction
12.2 Skeletal muscle fiber contraction
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Muscle contraction continued
12.2 Skeletal muscle fiber contraction

• Released calcium combines with troponin
• Myosin binding sites exposed
• Cross-bridges form
• ATP binds and power stroke occurs

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Visualizing the role of calcium and myosin in
muscle contraction
12.2 Skeletal muscle fiber contraction
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What role does ATP play in muscle contraction and
rigor mortis?
12.2 Skeletal muscle fiber contraction

• ATP is needed to attach and detach the myosin
  heads from actin
• After death muscle cells continue to produce ATP
  through fermentation and muscle cells can
  continue to contract
• When ATP runs out some myosin heads are still
  attached and cannot unattach rigor mortis
• Body temperature and rigor mortis helps to
  estimate the time of death

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Where are the fuel sources for muscle contraction?
12.3 Whole muscle contraction

• In the blood
• Glucose
• Fatty acids
• Stored in the muscle
• Glycogen
• Fat

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What are the sources of ATP for muscle
contraction?
12.3 Whole muscle contraction

• Limited amounts of ATP are stored in muscle
  fibers
• Creatine phosphate pathway (CP) fastest way to
  acquire ATP but only sustains a cell for seconds
  builds up when a muscle is resting
• Fermentation fast-acting but results in lactate
  build up
• Cellular respiration (aerobic) not an immediate
  source of ATP but the best long term source

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Muscle fibers come in two forms
12.3 Whole muscle contraction

• Fast-twitch fibers
• rely on CP and fermentation (anaerobic)
• Designed for strength
• Light in color
• Few mitochondria
• Fewer blood vessels

• Slow-twitch fibers
• Rely on aerobic respiration
• Designed for endurance
• Dark in color
• Many mitochondria
• Many blood vessels

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Types of muscle fibers
12.3 Whole muscle contraction
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Muscular diseases
12.4 Muscle disorders

• Fibromyalgia chronic achy muscles that is not
  well understood
• Muscular dystrophy group of genetic disorders
  in which muscles progressively degenerate and
  weaken
• Myasthenia gravis autoimmune disorder that
  attacks ACh receptor and weakens muscles of the
  face, neck and extremities

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Amyotrophic lateral sclerosis (ALS)

• commonly known as Lou Gehrigs disease
• motor neurons degenerate and die leading to loss
  of voluntary muscle movement