L2 - Muscular System | Ana Lec

• Functions of Muscular System

  1. body movement
  2. posture maintenance
  3. respiration
  4. production of body heat
  5. communication
  6. constriction of organs and vessels
  7. heart beat
• Estimately, we have about 650 muscles in our body
• skeletal muscle

  • attached to bone
  • long, cylindrical cell shape
  • multiple and peripheral nucleus
  • striated
  • voluntary
  • moves the whole body
• smooth

  • located at the wall of hollow organs, blood vessels and glands
  • spindle-shaped cell
  • single and central nucleus
  • unstriated
  • involuntary
  • for compression of organs, ducts and tubes
• cardiac

  • found in heart
  • branched cell shape
  • single and central nucleus
  • involuntary
  • for heart contraction to propel blood through the body
• Characteristics of Muscles

  Contractibility - ability of the muscle to shorten reducing distance between parts of its contents
• Characteristics of Muscles

  Excitability - ability to respond to a stimulus
• Characteristics of Muscles

  Extensibility - ability of the muscles to be stretched
• Characteristics of Muscles

  Elasticity - ability of a muscle to return to its original length after stretching
• muscle tone is the constant tension produced by muscles of the body over long periods of time and is responsible for keeping the back and legs straight, the head held in an upright position and the abdomen from bulging
• low muscle tone (hypotonia)

  • involves low muscle tone with reduced muscle strength
  • not a specific health sickness, but a possible sign of various disorders that affect muscle strength or motor nerve
  • can be genetic
• excessive muscle tone (hypertonia)

  • an increase in the rigidity of muscle tone and reduced capacity of the muscle to stretch
  • brought by injury to the central nervous system or spinal cord causing disruptions in the nerve pathways in charge of muscle tone
• Forms of Hypertonia

  Spasticity - a type of stiffness related to uncontrolled reflexes

  Rigidity - stiffness not associated with reflexes
• action potential - a signal or an impulse generated by the nervous system that travels through a type of nerve cell called a motor neuron
• neuromuscular junction - the place where the motor neuron reaches a muscle cell
• skeletal muscle tissue is composed of cells called muscle fibers
• acetylcholine - a chemical message released by the motor neuron that binds to receptors on the outside of the muscle fiber that starts a chemical reaction within the muscle
• Functions of Muscular System - Body Movement

  Contraction of skeletal muscles is responsible for the overall movements of the body
• Functions of Muscular System - Posture Maintenance

  Skeletal muscles constantly maintain tone, which keeps us sitting or standing erect
• Functions of Muscular System - Respiration

  Muscles of the thorax are responsible for the movements necessary for respiration
• Functions of Muscular System - Production of Body Heat

  When skeletal muscles contract, heat is given off as a by-product. This released heat is critical to the maintenance of the body temperature
• Functions of Muscular System - Communication

  Skeletal muscles are involved in all aspects of communication
• Functions of Muscular System - Constriction of Organs and Vessels

  The contraction of smooth muscle within the walls of internal organs and vessels causes constriction of those structures. This constriction can help propel and mix food and water in the digestive tract, propel secretions from organs and regulate blood flow through vessels
• Function of Muscular System - Heart Beat

  The contraction of cardiac muscle causes the heart to beat, propelling blood to all parts of the body