HistoLab Muscle

• Excitability


  The ability to respond to a stimulus by producing action potentials
• Muscular action potential


  An electric signal produced by the body to respond to a stimuli
• Types of signals

  • Autorhythmic signals
  • Chemical signals
  • Neurotransmitters
• Autorhythmic signals


  Involuntary; released by the muscle itself and they are auto-excited
• Chemical signals


  They are released by the neurons and hormones distributed by the blood
• Neurotransmitters


  Also known as acetylcholine that binds to receptors to our muscle fibers that causes contraction
• Contractility


  A property of muscular tissue that has the ability to contract forcefully when stimulated by an action potential; generates force of contraction while pulling on its attachment point
• Extensibility


  The ability of the muscle to stretch within the limits without being damaged
• Elasticity


  The ability of the muscle to return to its original form
• Characteristics of muscle tissue


  • Movement (both voluntarily and involuntarily)
  • Maintain posture
  • Supporting soft tissues within body cavities
  • Guarding entrance and exits of the body
  • Maintain body temperature
• Types of muscle tissue


  • Cardiac muscle
  • Smooth muscle
  • Skeletal muscle
• Myoblast


  Has the ability to divide and differentiate to different cells
• Skeletal muscle


  • Contains bundles of very long multinucleated with cross-striations; contraction is quick, forceful and usually under voluntary control
• Cardiac muscle


  • Also has cross-striations and is composed of elongated, often branched cells that are bound to one another called the intercalated discs (unique property of cardiac muscle); contraction is involuntary and is vigorous and rhythmic
• Smooth muscle

  • Composed of fusiform cells with no striations; contraction is slow and involuntary
• Skeletal muscle


  Composed of very large, elongated multinucleated fibers that shows quick, strong voluntary contractions
• Functions of skeletal muscle


  • Moves or stabilize the position of the skeleton
  • Guards entrances and exits to the digestive, respiratory and urinary tracts
  • Generates heat
  • Protects internal organs
• Skeletal muscle microscopically

  • Long cylindrical fibers with peripheral nuclei; unbranched and striated
• Striations


  Light and dark alternating protein bands
• Voluntary


  Consciously controlled by the neuron or the somatic region of the brain
• Components of skeletal muscle

  • Muscle fibers
  • Connective tissues
  • Nerves
  • Blood vessels
• Muscle fiber


  Functional unit of skeletal tissue
• Skeletal muscle moves the bones of the skeleton
• Skeletal muscle differentiation

  1. Mesenchymal cells called myoblasts align and fuse together to make a longer multinucleated tubes called the myotubes

  2. Myotubes synthesize the proteins that can make up a myofilament and gradually begins to show cross-striations by light microscopy

  3. Myotubes continuously differentiate to form a functional myofilament and the nuclei are displaced against the sarcolemma

  4. Myoblasts population does not fuse and differentiate but remains as a loop of mesenchymal cells called the muscle satellite cells

  5. Satellite cells proliferate to multiply to produce new muscle fibers following a muscle injury
• Layers of fascia

  • Epimysium
  • Perimysium
  • Endomysium
• Epimysium


  The outermost layer of dense irregular connective tissue; it encapsulates the entire tissue and binds and holds the muscle tissue together
• Perimysium


  • The same as epimysium, made up of dense irregular connective tissue; surrounds 10-100 muscle fibers and categorizes muscle fibers
  • seperates muscle fibers into groups known as fascicle
• Endomysium


  A reticular fiber that separates muscle fibers individually and covers a single muscle fiber
• Sarcolemma


  The plasma membrane (outer covering of the cell) of the muscle cell; composed of transverse tubules
• Sarcoplasm


  The cytoplasm of the muscle fiber and contains most of the organelles of the cell; functions by storage agent of glycogen and myoglobin
• Glycogen


  The storage form of glucose that is used during anaerobic respiration of the cell

  • along with myoglobin, are proteins that produces ATP
• Myoglobin


  The protein that binds the oxygen to the muscle cells
• Oxygen is needed for the mitochondria to produce ATP
• Myofibrils


  Contractile organelles with prominent striations and it is also close to the mitochondria
• Sarcoplasmic reticulum


  Surrounds each myofibril with papering end, which consists of terminal cisterns
• Terminal cisterns


  Attached to the T-tubules; in relaxed state, it is a storage form of calcium; in active state, terminal cisterns release calcium to the transverse tubules
• Myofilaments


  • Thin filaments (also known as actin filaments)
  • Thick filaments (also known as myosin filaments)
• For every thick filament, there are two thin filaments
• Sarcomere


  • The functionalFunctional unit of myofilaments; composed of Z-disks, A-bands, I-bands, H-zone, and M-line.
  • Responsible for the arrangement of thick and thin filaments into compartments.
• 1. disks


  Narrow plated regions of dense material that separates one sarcomere to the next; it is where the sarcomere starts from Z-disk to another Z-disk