ZOOLOGY 2

• Muscle


  Soft tissue found in both animals and humans, comprising protein filaments of actin and myosin that slide past one another, producing contraction and changes in cell length and shape
• Musculus


  Latin word referring to a little mouse, due to the shape of certain muscles or the contraction of muscles that look like a moving mouse
• The human muscular system includes more than 600 muscles, which make up about 40 to 50 per cent of the total body weight
• Muscles


  • Attached to bones, blood vessels and other internal organs
  • Mainly composed of skeletal muscles, tissue, tendons, and nerves
  • Composed of a kind of elastic tissue
• Every movement in our body is the result of muscle contraction and is found in every organ, including the blood vessels, heart, digestive organs, etc.
• Types of muscle


  • Skeletal or striated muscles
  • Cardiac muscles
  • Smooth muscles
• Muscle classification based on action

  • Voluntary muscles
  • Involuntary muscles
• Skeletal muscle


  Muscle tissue attached to the bones, involved in the functioning of different parts of the body, under the control of the central nervous system
• Structure of skeletal muscle

  • Series of muscle fibers composed of muscle cells, long and multinucleated
  • Cylindrically shaped with branched cells attached to bones by tendons
  • Group of muscle fibers called fascicles, surrounded by perimysium
• Functions of skeletal muscle

  • Maintains body posture
  • Regulates body temperature
  • Connects to and controls the motions of the skeleton
  • Responsible for performing muscular involuntary movements
  • Responsible for body movements such as breathing, extending the arm, typing, writing, etc.
  • Provides support and protection for internal organs and tissues
• Cardiac muscle


  Striated muscle responsible for keeping the heart functioning by pumping and circulating blood, involved in continuous rhythmic contraction and relaxation
• Structure of cardiac muscle

  • Exists only within the human heart, specialized form of muscle evolved to continuously and repeatedly contract
  • Comprises cylindrical, branched fibers with a centrally located nucleus, and T-tubules rich in ion channels
• Functions of cardiac muscle

  • Regulates the functioning of the heart by relaxation and contraction
  • Functions as the involuntary muscle
  • Involved in movement or locomotion
  • Works automatically to make the heart contract and fill with blood
• Smooth muscle


  Non-striated, involuntary muscle controlled by the Autonomous Nervous System, found in organs such as the stomach, bladder, blood vessels, etc.
• Structure of smooth muscle

  • Spindle-shaped muscle fibers with a single nucleus, shorter than skeletal muscle, lacking filaments and producing their own connective tissue
• Functions of smooth muscle

  • Involved in sealing of orifices
  • Produces connective tissue proteins
  • Transports chyme through the intestinal tube
  • Maintains and controls blood pressure and flow
  • Contracts the irises, raises small hairs, contracts sphincters, moves fluids through organs
  • Provides consistent and elastic tension
• Types of muscle contraction

  • Isometric
  • Isotonic (concentric, eccentric)
• Muscle contraction is stimulated by an action potential from a motor neuron, triggering an increase in calcium ion concentration and cross-bridge formation between actin and myosin filaments
• During muscle contraction, the actin and myosin filaments slide past each other, shortening the sarcomeres and muscle fibers, transmitting force to the bones and causing movement
• Skeletal muscle names often reflect their action, shape, or location
• Anatomical terms describing movement around joints

  • Flexion
  • Dorsiflexion
  • Plantar flexion
  • Extension
  • Abduction
  • Adduction
  • Circumduction
  • Rotation
  • Supination
  • Pronation
  • Inversion
  • Eversion
  • Retraction
  • Protraction
  • Elevation
  • Depression