Muscle

Muscle

1. Types of Muscle

   • Skeletal
     • Striated and volentary
     • only muscle that is voluntary
     • tires easily
   • Smooth
     • found in hollow organs
     • no striations.
     • non voluntary slow and sustained contractions
   • Cardiac
     • heart muscles
     • non voluntary

2. Characteristics of Muscle

   • excitability
     • responsiveness
   • contractility
     • shorten forcibly
   • extensiblity
     • extend or stretch
   • elasticity
     • recoil

3. Connective Tissue Sheeths

   • Epimysium
     • surronds the whole muscle
   • perimysium
     • surrounds fascicles
   • endomysium
     • surronds muscle fibers

4. Structure

   • muscle
     • thousands of muscle cells blood vessels
   • fasicle
     • a fascilie is a discrete muscle cells
   • muscle fiber
     • a muscle fiber is elongated multinucleate cell
   • myofibril
     • myofibrils are rodlike contactile elements that occupy most of the muscle cell volume
   • sacromere
     • a sarcomere is the contractile unit, composed of myofilaments made up of contractile protiens
   • myofilament
     • contractile myofilaments are of two types thick and thin
       • thick
         • contain myosin
       • thin
         • contain actin

5. Neuromuscular junction

   • Action potential arrives at the axon terminal
     • Voltage gated Ca+ challes open. Ca+ enters the axon terminal
       • Ca+ entry causes ACH to be released by exocytosis
         • ACH diffuses across the synaptic cleft and binds to ACh receptors on the sarcolemma
           • ACh binding opens chemically gated ion channels that allow passage of Na into and K out of the fiber more Na enter then K exits
             • Ach effects are terminated by its breakdown in the synaptic cleft

6. Excitation contraction coupling

   • the action potential propagates along the sarcolemma and down the T tubules
     • calcium ions are released Ca release cannels open
       • calcium binds to troponin and removes he blocking action of tropomyosin
         • Contraction begins

7. Contractions

   • isometric
     • tension is increased muscle does not shorten
   • wave summation
     • contraction from completely relaxed muscle
   • treppe
   • tetanus
     • sustained but quivering contraction
   • isotonic
     • muscle shortens tension does not change
   • muscle tone
     • the theory that muscles are always slightly contracted

8. Muscle metabolism

   • direct phosphorylation
     • uses CP no oxygen
   • anaerobic pathway
     • uses glucose no oxygen
   • aerobic pathway
     • usues fatty acid uses oxygen