Muscular System

• Muscles


  - musculus = little mouse

  - soft tissue of the human body which primarily function for movement
• Myology


  branch of science which is the study of muscle
• Essential Characteristics of Muscles

  - excitability

  - contractility

  - extensibility

  - elasticity
• Excitability


  It is the ability of muscle to respond to a stimulus
• Contractility


  It is the ability of muscle cells to shorten forcefully
• Extensibility


  It is the ability of a muscle to be stretched
• Elasticity


  It is the ability of muscle to recoil or bounce back to the muscle's original length after being stretched
• Skeletal Muscle


  also known as striated voluntary muscle, multinucleated, attached to skeleton
• Cardiac Muscle


  also known as striated involuntary muscle, nuclei are centrally located, with intercalated discs
• Smooth Muscle


  unstriated/non-striated involuntary muscle, cells are short, spindle-shaped and have a single nucleus
• Epimysium


  surrounds entire muscle
• Perimysium


  surrounds fascicles
• Endomysium


  surrounds each muscle fiber or cells
• Actin


  - made up of actin molecule, tropomyosin and troponin complex

  - protein that makes up most of the thin myofilaments in a sarcomere muscle fiber
• Myosin


  consists of a long rod-shaped tail called myosin rod and two globular intertwined myosin head
• Acetylcholine


  neurotransmitter that binds at a motor end-plate to trigger depolarization
• Action potential


  change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibers
• Depolarize


  to reduce the voltage difference between the inside and outside of a cell's plasma membrane (the sarcolemma for a muscle fiber), making the inside less negative than at rest
• Neuromuscular junction


  synapse between the axon terminal of a motor neuron and the section of the membrane of a muscle fiber with receptors for the acetylcholine released by the terminal
• Neurotransmitter


  signaling chemical released by nerve terminals that bind to and activate receptors on target cells
• Synaptic cleft


  space between a nerve (axon) terminal and a motor end-plate
• T-tubule


  projection of the sarcolemma into the interior of the cell
• Repolarization


  the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential has changed the membrane potential to a positive value
• Sliding Filament Theory


  This is a proposed mechanism of muscle contraction in which the actin and myosin filaments of striated muscle slide over each other to shorten the length of the muscle fibers which allows bridges to form between actin and myosin, that requires ATP as an energy source
• Myasthenia Gravis


  A chronic autoimmune neuromuscular disease that causes weakness in the skeletal muscles
• Fibromaygia


  - also called as fibromyalgia syndrome

  - A disorder characterized by widespread musculoskeletal pain accompanied by fatigue, widespread pain and cognitive difficulties

  - Causes may include Genetics in origin, infections. physical or emotional trauma
• Muscular Dystrophy


  - a group of diseases that cause progressive weakness and loss of muscle mass

  - due to abnormal genes (mutations) that interfere with the production of proteins needed to form healthy muscle
• Bell's Palsy


  - condition in which the muscles on one side of a person's face become weak or paralyzed

  - caused by some kind of trauma to the seventh cranial nerve being called the "facial nerve"
• Pulled Hamstring


  a tear of the hamstring muscle fibers
• Muscle Cramp


  - a strong, painful contraction or tightening of a muscle that comes on suddenly and lasts from a few seconds to several minutes

  - aka Charley horse
• Types of Muscle Fiber

  • slow twitch oxidative
  • fast twitch glycolytic
  • fast twitch oxidative glycolytic
• Slow twitch oxidative

  • fatigue resistant
  • most used in posture
• Fast twitch oxidative glycolytic

  • fatigue resistant
  • standing walking
  • becomes oxidative with endurance training
• Fast twitch glycolytic

  • easily fatigued
  • jumping, quick movements