Muscular

• Muscular System


  Allows manipulation of the environment, locomotion, and facial expression. Maintains posture, and produces heat.
• Contractility


  ability of muscle to shorten forcefully or contract
• Excitability


  capacity of muscle to respond to a stimulus
• Extensibility


  means that a muscle can be stretched beyond its normal resting length and still be able to contract
• Elasticity


  ability of muscle to recoil its original resting length after it has been stretched
• Skeletal Muscle


  also called as striated muscle

  
  

  with its associated connective tissue, both constitutes approximately 40% of the body weight
• Epimysium


  a sheath of fibrous elastic tissue surrounding a muscle.

  
• Muscle Fasicles


  each muscle is subdivided into numerous visible bundles called ____________
• Perimysium


  loose connective tissue that separate muscle fascicles from each other

  
• Endomysium


  loose connective tissue that surrounds individual muscle fibers

  
• Sarcolemma


  cell membrane of a muscle fiber
• Transverse Tubules


  occur at regular intervals along the muscle fiber and extend into the center of the muscle fiber
• Terminal Cisternae


  enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubules
• Triad


  T Tubules connect the sarcolemma to the terminal cisternae to form a _______

  
• Sarcoplasm


  cytoplasm of a muscle fiber
• Myofibrils


  bundles of protein filaments within the sarcoplasm
• Actin and Myosin


  two types of myofibrils
• Sarcomere


  basic structural and functional unit of the skeletal muscle

  
• Z disks


  structures that separate one sarcomere to the next

  
• I bands


  light staining bands in the sarcomere; contains only actin filaments

  
• A Band


  dark staining bands in the sarcomere; where myosin and actin myofilaments overlap

  
• H zone


  lighter region in midsection of dark A band where filaments do not overlap and only contains myosin filaments

  
• M line


  middle of sarcomere; it consists of fine protein filaments that anchor the myosin filaments in place

  
• Actin Myofilament


  made up of three components: actin, troponin and tropomyosin
• Troponin


  molecules that have binding sites for Ca2+ and is attached at specific intervals along the actin myofilaments
• Tropomyosin


  molecules that block the myosin myofilament binding sites on the actin myofilaments
• Myosin Myofilament


  thick myofilaments which resemble bundles of golf clubs
• Myosin Heads


  Bind to specific sites on actin molecules to form cross bridges
• Resting Membrane Potential


  electrical charge difference across the cell membrane of an unstimulated cell
• Negatively; Positively


  In resting cells, the inside of the cell membrane is ___________ charged, and the outside of the cell membrane is ___________ charged
• Depolarization


  The process during the action potential when sodium (Na+) is rushing into the cell causing the interior to become more positive.
• Threshold


  the level of stimulation required to trigger a neural impulse
• Action Potential


  the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell.
• Repolarization


  Return of the cell to resting state, caused by reentry of potassium (K+) into the cell while sodium (Na+) exits the cell.
• Motor Neurons


  specialized nerve cells that stimulates muscles to contract
• Neuromuscular Junction


  the junction between a nerve fiber and the muscle it supplies
• Synapse


  general term that refers to the cell-to-cell junction between a nerve cell and either another nerve cell or an effector cell
• Motor Unit


  A single motor neuron and all the skeletal muscle fibers it innervates constitutes the ___________
• Presynaptic terminal


  axon terminal with synaptic vesicles

  
• Synaptic cleft


  space between the presynaptic terminal and the muscle fiber membrane