skeletal , smooth and cardiac muscle

• Skeletal muscle


  Produces body movements, stabilizes body positions

  
• Cardiac/Smooth muscle


  Moves substances within the body
• Skeletal muscle


  Generates heat
• Fascia


  • Dense sheet or broad band of irregular connective tissue that surrounds muscles

  
• Epimysium


  • The outermost layer which encircles the whole muscle

  
• Perimysium


  • Separates 10-100 muscle fibers into bundles called fascicles

  
• Endomysium


  • Separates individual muscle fibers from one another

  
• Tendon


  • Cord that attaches a muscle to a bone
• The epimysium, perimysium, and endomysium all are continuous with the connective tissues that form tendons, ligaments and muscle fascia

  
• Sarcolemma


  The plasma membrane of a muscle cell

  
• Myofibrils


  Thread-like structures which have a contractile function, 2um in diameter, extend whole length of fibre
• Filaments (myofilament)


  Function in the contractile process, two types (Thick-myosin and Thin-actin), two thin filaments for every thick filament

  
• Sarcomere


  A band (darker middle part), I band (lighter, contains thin filaments but no thick filaments), H zone (centre of each A band which contains thick but no thin filaments), M line (supporting proteins that hold the thick filaments together at the middle of the H zone), Z discs (separate one sarcomere from the next)
• Thin filaments


  Structural protein actin
• Thick filaments


  Structural protein myosin
• Both thin and thick filaments have other structural and regulatory proteins
• Cardiac muscle


  • Shorter, less circular, single nucleus, branching, intercalated discs, gap junctions, desmosomes, bigger and more numerous mitochondria

  
• Skeletal muscle


  • Longer, more circular, multinucleated, no branching, no intercalated discs, no gap junctions, smaller and less numerous mitochondria

  
• Intercalated discs


  Connect the ends of cardiac muscle fibers to one another, allow action potential conduction from one fiber to the next
• Autorhythmic cells


  Specialized cardiac muscle fibers that are self-excitable, repeatedly generate action potentials that trigger heart contractions, act as pacemaker and form conduction system

  
• Conduction system


  Begins in sinoatrial (SA) node, propagates through atria via gap junctions, reaches atrioventricular (AV) node, enters atrioventricular (AV) bundle, enters right and left bundle branches, extends to Purkinje fibers which conduct action potential to remainder of ventricular myocardium
• Smooth muscle


  Single unit (found in skin and part of the wall of tubular structures, autorhythmic, connected via gap junctions, contract in unison), Multiple unit (found in wall of large arteries, lung, erector pili, iris, ciliary body, individual fibres innervated by own motor neurons, few gap junctions)

  
• Smooth muscle structure


  • Smooth muscle cells are small, spindle-shaped with one central nucleus, lack the coarse connective tissue coverings of skeletal muscle, usually arranged into sheets of opposing fibers forming a longitudinal layer and a circular layer, contraction of the opposing layers leads to rhythmic peristalsis

  
• Smooth muscle


  Lacks neuromuscular junctions, has varicosities instead which release neurotransmitters to a wide synaptic cleft
• Smooth muscle contains both thick and thin filaments, not arranged in orderly sarcomeres, no regular pattern of overlap thus not striated, contain only a small amount of stored Ca2+, no T-tubules but have caveolae as source of extracellular Ca2+, filaments attach to dense bodies and stretch from one dense body to another, during contraction the filaments pull on the dense bodies causing shortening of the muscle fiber