anaphy 7

• Contractility


  the ability of muscle to shorten forcefully, or contract
• Excitability


  the capacity of muscle to respond to a stimulus
• Extensibility


  the ability to be stretched beyond its normal resting length and still be able to contract
• Elasticity


  the ability of the muscle to recoil to its original resting length after it has been stretched
• epimysium


  Each skeletal muscle is surrounded by a connective tissue sheath called the
• fascicles


  A skeletal muscle is subdivided into groups of muscle cells, termed
• perimysium


  Each fascicle is surrounded by a connective tissue covering, termed the
• endomysium


  Each skeletal muscle cell (fiber) is surrounded by a connective tissue covering, termed the
• transverse tubules, or


  T tubules.Thesarcolemma(cell membrane) has many tubelike inward folds, called
• sarcoplasmic reticulum


  The T tubules are associated with enlarged portions of the smooth endoplasmic reticulum called the
• terminal cisternae


  The enlarged portions are called
• muscle triad


  Two terminal cisternae and their associated T tubule form a
• sarcoplasm


  •The cytoplasm of a muscle fiber is called the__________, which contains many bundles of protein filaments.
• myofibrils


  Bundles of protein filaments are called
• sarcomeres


  Actin and myosin are arranged into repeating units called
• actin


  (thin filaments) andmyosin(thick filaments).•Myofibrils consist of two types ofmyofilaments
• Z disks


  are network of protein fibers that serve as an anchor for actin myofilaments and separate one sarcomere from the next
• sarcomere


  is the basic structural and functional unit of skeletal muscle.

  join end to end to create myofibrils.
• Light bands/


  I bandsconsist only of actin

  They extend from the Z disc, toward the center of the sarcomere, to the ends of the myosin myofilaments.
• A bands


  Dark staining bands.They extend the length of the myosin myofilaments.
• actin, troponin, and tropomyosin.

  •Actin myofilaments are made up of three components:
• motor neuron


  is a nerve cell that stimulates muscle cells.
• neuromuscular junction


  is a synapse where a neuron connects with a muscle fiber.
• synapse


  refers to the cell-to-cell junction between a nerve cell and either another nerve cell or an effector cell, such as in a muscle or a gland.
• motor unit


  is a group of muscle fibers that a single motor neuron stimulates.
• presynaptic terminal


  is the end of a neuron cell axon fiber.
• synaptic cleft


  is the space between the presynaptic terminal and postsynaptic membrane.
• postsynaptic membrane


  is the muscle fiber membrane (sarcolemma).
• synaptic vesicle


  is a vesicle in the presynaptic terminal that stores and releases neurotransmitter chemicals.
• Acetylcholine


  is the neurotransmitter that stimulates skeletal muscles
• Neurotransmitters


  are chemicals that stimulate or inhibit postsynaptic cells.
• Sliding Filament Model


  •When a muscle contracts, the actin and myosin myofilaments in the sarcomere slide past one another and shorten the sarcomere.
• Leak channels


  allow the slow leak of ions down their concentration gradient.
• Gated channels


  may open or close in response to various types of stimuli.
• resting membrane potential


  .•The electrical charge difference across the cell membrane of an unstimulated cell is called the
• Action potentials


  are due to the membrane having gated channels
• action potential


  reverses the resting membrane potential so that the inside of the cell becomes positive and the outside negative.
• depolarization


  This increase in positive charge inside the cell membrane is called
• threshold


  •If the depolarization changes the membrane potential to a value called__________, an action potential is triggered.
• repolarization


  Opening of gated K+ channels starts__________of the cell membrane.