Mascular

• What are the primary functions of muscles?

  Movement, posture, body heat, protection, stabilization, and respiration
• What is myology?

  • The scientific study of muscles
  • "Myo" means muscle
  • "Logy" means study of
  • Muscles develop from the mesoderm of the human embryo
• What are the three types of muscle tissue?

  1. Skeletal muscle
  2. Smooth muscle
  3. Cardiac muscle
• What is the primary characteristic of skeletal muscle?

  Skeletal muscle moves most of the bones of the skeleton and is voluntary
• What is the structure of skeletal muscle cells?

  Multi-nucleated cylindrical cells with striations
• Where is smooth muscle located?

  In the walls of hollow internal structures
• What is the shape of smooth muscle cells?

  Spindle-shaped
• What distinguishes cardiac muscle from other muscle types?

  Cardiac muscle is located in the walls of the heart and has branching cells connected by intercalated discs
• What are the properties of muscular tissue?

  1. Electrical excitability
  2. Contractility
  3. Extensibility
  4. Elasticity
• What is fascia in relation to muscle tissue?

  Fascia is a layer of connective tissue outside of the whole muscle that provides protection and support
• What is the epimysium?

  The epimysium encircles the entire muscle
• What does the perimysium surround?

  The perimysium surrounds 10-100 muscle fibers called fascicles
• What is the endomysium?

  The endomysium surrounds each muscle fiber
• What are the components of a muscle fiber?

  1. Sarcolemma - cell membrane
  2. Sarcoplasm - cytoplasm
  3. Sarcoplasmic reticulum - stores calcium
  4. Transverse (t-tubes) - extensions of sarcolemma
  5. Myofibrils - cylinders of contractile proteins
• What is a sarcomere?

  A sarcomere is the contractile unit of a skeletal muscle
• What are the regions of a sarcomere?

  1. A Band - region with thick filament
  2. I Band - region with thin filament
  3. Z Line - border between sarcomeres
  4. H Zone - space with only thick filament
  5. M Line - holds thick filament together
• What is myosin?

  Myosin is the thick filament protein
• What is actin?

  Actin is the thin filament protein
• What role does tropomyosin play in muscle contraction?

  Tropomyosin blocks actin from binding with myosin
• What is the function of troponin?

  Troponin holds tropomyosin strands together
• What is the neuromuscular junction?

  The neuromuscular junction is the point of contact between a skeletal muscle and a neuron that controls it
• What neurotransmitter excites the muscle?

  Acetylcholine
• What is the sliding filament model of muscle contraction?

  • Skeletal muscle contracts due to thin filaments sliding past thick filaments
  • Acetylcholine binds to receptors in the motor-end plate
  • Sodium ions (Na+) enter the muscle
• What are the steps of skeletal muscle contraction?

  1. Depolarization spreads along the sarcolemma
  2. Calcium ions (Ca$^{2+}$) are released from the sarcoplasmic reticulum
  3. Calcium binds to troponin, removing tropomyosin
  4. Myosin-binding sites in the actin filament are exposed
• What are the steps of relaxation in skeletal muscle tissue?

  1. Signaling from motor neurons ends or energy is depleted
  2. Calcium ions are pumped back to the sarcoplasmic reticulum
  3. Tropomyosin binds to troponin, blocking myosin-binding sites
• How do smooth and cardiac muscle contractions differ from skeletal muscle contractions?

  • Cardiac and skeletal muscles have similar contraction processes
  • Intercalated discs in cardiac muscle allow faster communication
  • Smooth muscle contracts in a corkscrew motion
• What are the two types of smooth muscle?

  1. Single-unit smooth muscle - multiple cells contract as a unit
  2. Multi-unit smooth muscle - cells contract individually
• What is muscle tension?

  Muscle tension is the force generated by the contraction of muscle
• What are the types of muscle contractions?

  1. Isometric contraction - muscle contracts but does not move a load
  2. Isotonic contraction - muscle contracts and moves a load

  • Concentric contraction - muscle shortens to move load
  • Eccentric contraction - muscle lengthens to move load
• What is a myogram?

  • A myogram displays the amount of tension produced by a twitch over time
  • Phases include:

  1. Latent phase - propagation of action potential
  2. Contraction phase - cross-bridges formed
  3. Relaxation phase - calcium ions pumped back
• What is a twitch in muscle physiology?

  A twitch is a singular contraction of a muscle cell
• What is summation in muscle contraction?

  Summation is a series of action potentials that sustain muscle contraction
• What is tetanus in muscle physiology?

  Tetanus is maximal contraction due to action potentials occurring
• What are the components of the muscular system?

  • Multiple sites of attachment
  • Tendons connect muscles to bones
  • Insertion - moveable end of the muscle
  • Origin - attached to a fixed bone
  • Agonist - prime mover
  • Antagonist - produces opposite movement
  • Synergist - assists prime mover
  • Fixator - stabilizes insertion point
• What are the patterns of fascicle organization?

  1. Parallel - arranged in the same direction
  2. Fusiform - large belly in the middle
  3. Circular - fibers wrap in a circle
  4. Convergent - fibers unite on a narrow insertion point
  5. Pennate - fascicles blend into tendon

  • Unipennate - one side of tendon
  • Bipennate - both sides of tendon
  • Multipennate - branches resembling feathers
• What are some muscle shapes?

  • Rhomboid - rhombus
  • Deltoid - upside-down triangle
  • Trapezius - trapezoid
  • Serratus - saw-toothed
  • Orbicularis - circular
  • Pectinate - comb-like
  • Piriformis - pear-shaped
  • Platys - flat
  • Quadratus - square
  • Gracilis - slender
• What are the actions associated with muscles?

  • Flexor - decreases joint angle
  • Extensor - increases joint angle
  • Abductor - moves bone away from midline
  • Adductor - moves bone closer to midline
  • Tensor - makes body part rigid
  • Levator - elevates body part
  • Depressor - lowers body parts
  • Supinator - turns palm anteriorly
  • Pronator - turns palm posteriorly
  • Sphincter - decreases size of an opening
• What are the classifications of muscle size?

  • Maximus - largest
  • Medius - medium size
  • Minimus - smallest
  • Brevis - short
  • Longus - long
  • Magnus/Vastus - large/huge
  • Major - larger of two
  • Minor - smaller of two
  • Latissimus - widest
  • Longissimus - longest
• What are the classifications based on the number of origins?

  • Uni- 1
  • Bi/Di- 2
  • Tri- 3
  • Quad- 4
  • Multi- many
• What are the classifications based on fiber orientation?

  • Rectus - parallel to midline
  • Transverse - perpendicular to midline
  • Oblique - diagonal to midline