Muscle Tissue

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Muscle Tissue
Geoffrey T. Meyer
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Muscle - Prefixes

• Myo (Greek) muscle
• eg. Myology the study of muscle
• Myositis inflammation of muscle
• Sarco (Greek) flesh
• eg. Sarcoplasm the cytoplasm of muscle
• Sarcomere basic contractile unit of muscle

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Contractile mechanisms

• This is fundamental to many cell types -not just
  muscle
• eg. Macrophages

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Contractile mechanisms

• Macrophages phagocytes which move freely to
  engulf (phagocytose) cell debris
  micro-organisms

Macro big Phage swallow Cyte cell
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Muscle

• Packaging of contractile proteins is related to
  the functions required
• Thus there are different such arrangements
• These are classified into different types of
• MUSCLE

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Specialised contractile proteins

• Muscle is a concentration of such proteins
• Myosin
• Actin
• Troponin
• Tropomysin
• many structural
• proteins

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Packaging of muscle proteins

• Depends on the force required
• eg. Slow steady contraction of tubes in the body
  - to maintain tonus or steady contractions
• Use individual cells with orientated packages of
  contractile proteins

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Slow contracting packages of muscle proteins

• Common in tubes of the body
• Arteries veins
• Intestine
• Lungs
• Urinary system
• Reproductive tubes

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Slow contracting packages of muscle proteins

• PROPERTIES
• Cells contract slowly
• Often rhythmically eg. peristalsis in gut tube
• Have tonic and slowly changing tensions
• Under nervous control of the
• Autonomic Nervous System (involuntary)
• Called then INVOLUNTARY muscle

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Slow contracting packages of muscle proteins

• Contractile proteins arranged in a dispersed
  pattern - not in regular parallel arrays as in
  muscle which moves the skeleton
• ie. Skeletal muscle is striped in appearance
• INVOLUNTARY muscle is not striped
• is thus then called
• Smooth muscle

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Skeletal muscle

• Muscles which move the skeleton need
• 1. Much more power
• 2. Tougher connective tissue support
• 3. Much faster contraction

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Skeletal muscle anatomical forms
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Skeletal muscle Connective tissue
Tougher connective tissue support - fascial
layers tendons
Epimysium

• --

Perimysium
Endomysium
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Skeletal muscle Connective tissue

• Aponeurosis
• A fibrous or
• Membranous
• sheet-like tendon
• Fascia
• Fibrous sheet
• binding skin to
• underlying muscles
• or supporting/
• separating muscles
• Tendon

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Skeletal muscle - contraction
Much faster contraction, highly ordered
contractile filaments and a very rapid nerve
supply

• Cross
• striations

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Skeletal muscle

• Design characteristics
• Large cells syncytium of fused myoblasts to
  form long multinuclear muscle fibres
• Highly organised contractile protein myofilaments

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Why multi-nucleation? From a physical
perspective? Contractile force can be efficiently
generated by the shortening of a long tube From
a regulatory view? It takes fewer neurons to
synchronise contraction of a few large cells
versus many individual smaller cells But there
are problems with having such a large cell When
cells become very large, signals from the cell
membrane would not be able to efficiently reach a
single nucleus. Also a single nucleus cannot
efficiently regulate a very large cell So large
cells become multinucleated with each nucleus
controlling a given volume of cytoplasm DNA
unit.
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Skeletal muscle

• Design characteristics
• Large cells syncytium of fused myoblasts to
  form long multinuclear muscle fibres
• Highly organised contractile protein myofilaments

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Skeletal muscle cell fibre

• Packaging
• Myofilaments
• (contractile
• proteins)
• into
• small bundles
• myofibrils

Myofibrils
Myofilaments
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Sarcomere

• i

Z
Z
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Sliding myofilaments
Much faster contraction

• 00

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Skeletal muscle - LS

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Skeletal muscle - tubules

• Transport problem because of huge cells
• 1. To transport wave of depolarisation into
  contractile filaments
• T Tubes, which are extensions of the sarcolemma
• 2. Internal tubules to hold calcium -
• Sarcoplasmic reticulum

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Skeletal muscle tubulesComplex system of tubes
within fibres (cells) for internal transport

• Transport
• Problem
• 1. External
• 2. Internal

T tubes External
Sarcotubules Internal
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Skeletal muscle - TS

• Large fibres
• peripheral
• nuclei

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Skeletal muscle large cells

• Comparison of Smooth Skeletal muscle

5 µm
Central nuclei
Peripheral nuclei
50 µm
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Skeletal muscle Nerve supply

• 2. Much faster contraction very rapid nerve
  supply
• a. Rapid knowledge of muscle position state of
  contraction or stretch
• Muscle spindles are stretch receptors

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Skeletal muscle Nerve supply
Muscle Spindle Stretch Receptor

• .

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Skeletal muscle Nerve supply

• Muscle
• Spindle

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Skeletal muscle Capillaries
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Skeletal muscle Blood supply

• Large muscle fibres metabolically active
  need a large amount of blood oxygen
• But some muscles can work without oxygen for
  short times

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Skeletal muscle Blood supply

• These are
• Fast twitch muscles as in sprinters
• Most muscles use oxygen can work for a long
  time with an adequate blood supply
• These are Slow Twitch muscles

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Skeletal muscle - Types
Fibre Types Fast-slow

• .

Red fibres slow fibres White fibres fast
fibres
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