Muscles and Muscle Tissue

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Muscles and Muscle Tissue
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Muscular Tissue

1. Characteristics
2. Excitability tissue is able to respond to a
   stimulus
3. Extensibility tissue is able to be stretched
4. Elasticity tissue is able to return to normal
   after stretching.
5. Contractibility tissue is able to shorten and
   thicken

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• Functions
• Motion- both reflex and voluntary
• Maintenance of posture and organ volume
• Thermogenesis- heat production
• Joint Stability- allows for motion and
  maintenance of posture.

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Muscle Fiber Types

• 3 Types of Muscle-
• 1. Smooth
• 2. Cardiac
• 3. Skeletal/Striated

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Skeletal Muscle

• Fascia sheets or broad bands of fibrous
  connective tissue located beneath skin or around
  muscle or body organs.
• Categories of Fascia
• Superficial Fascia-
• Structure contains adipose, blood vessels,
  nerves
• Functions stores fat, provides insulation,
  protects from injury

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• Categories of Fascia (cont)
• Deep Fascia no fat
• Surrounds muscle groups and divides muscle groups
  (allows individual and independent movement)
• Arrangement
• Endomysium fascia which surrounds each muscle
  fiber
• Perimysium fascia which surrounds a bundle of
  muscle fibers (fascicle)
• Epimysium connective tissue which wraps the
  entire muscle

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Muscle Attachments

• Direct (Fleshy) attachments- perimysium is fused
  to peristeum of bone, or perichndriu of
  cartilage.
• Indirect attachment- the muscle fascia extends
  beyond the muscle and attaches as a rope-like
  tendon or aponeurosis.
• - Muscles are anchored to one another

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Arrangement of Fascicles

• Parallel- run with the longitudinal axis of the
  muscle
• Strap like- belly is uniform
• Fusiform- belly is enlarged

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Arrangement of Fascicles

• Pennate-
• arranged obliquely to the bone
• A. Unipennate- one side
• B. Bipennate- both sides
• Convergent
• broad at origin, narrows to a single tendon.
• Circular- (sphincter)
• control diameter of an opening
• eye squinting, lip puckering

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Muscle Cell Structure

• 1. Sarcolema- plasma membrane surface
• Sarcoplasm cytoplasm and glycogen
• 20 or more nuclei
• Proteins myoglobin- binds oxygen (red protein)
• Usual organelles (mitochondria)
• Sarcoplasmic Reticulum run parallel with
  myofibrils, densly packed

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• Myofibrils protiens
• A. Myosin thick filaments
• 2 globular heads
• B. Actin thin filaments
• Active sights where globular heads of myosin
  attach
• C. Tropomyosin rod shaped spirals around
  actin, stiffens
• D. Troponin 3 polypeptides
• T-Tubules- extensions of sarcolema that extend up
  into the sarcoplasm.
• Conducts nerve impulses deep into muscle cells
• Transports and regulates glucose, oxygen, calcium

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Arrangement of Myofibrils

• Sarcomere functional unit of muscle

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Sliding Filament Theory

• 1. Nerve impulse stimulates muscles. T-tubules
  release Calcium ion. Contraction is triggered.
• Cross-bridge attachment-
• globular heads of myosin attach to active sites
  on actin.
• Power stroke- as myosin binds and pivots
• high energy to low energy
• actin slides over to the center of the sarcomere
• Cross bridge detachment requires ATP
• Cocking of Myosin Heads (rearmed)
• Rigomortis peaks at 12 hours

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• http//highered.mcgraw-hill.com/sites/0072437316/s
  tudent_view0/chapter42/animations.html

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All or None Phenomenon

• When stimulated a muscle fiber contracts to its
  fullest capacity

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Neuromuscular Junction

• Area where axonal end of a neruon fomrs a
  synaptic cleft with a muscle fiber.
• Acetylcholine- neurotransmitter diffueses across
  the synaptic cleft and binds to receptors on the
  sarcolema, then destroyed by cholinesterase.
• 1 impusle causes 1 contraction

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• Muscle Tone-
• Partial contraction of a muscle fiber due to use
• Awake- highest
• Asleep- lower
• unconscious- absent
• Twitch single muscle contraction
• (1/10 of a contraction)
• Tetanus- prolonged muscle contraction required to
  do work.
• Myogram- record of a muscle contraction

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Muscle contraction

• Isotonic contraction muscle shortens, movement
  occurs.
• Isometric contraction muscle tenses but does
  not shorten

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Muscle fiber types

• Type I (red, slow twitch) postural muscles long
  distance
• Large amounts of myoglobin
• Many mitochondria
• Many blood capillaries
• Very good at generating ATP
• Split ATP slowly very resistant to fatigue

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• Type II A- intermediate, fast twitch fast
  oxidative
• - very large amounts of myoglobin
• - many mitochondria
• - very large supply of blood capillaries
• - split ATP very rapidly
• - very quick contraction velocity
• - less resistant to fatigue
• (sprinters, arms)

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• Type II B- white
• fast twitch, fast glycolytic
• - low myoglobin content
• - few mitochondria
• - few capillaries
• - large amounts of glycogen
• - geared for anaerobic respiration
• - split ATP rapidly
• - very little resistance to fatigue

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• Oxygen Debt
• the additional oxygen needed after exercise to
  return to homeostasis
• hyperventilation to get rid of oxygen debt