muscular system

• muscular system

  • Refers to the skeletal system
  • Constitutes 40-50% of total body weight
  • A specialized tissue which converts chemical energyinto mechanical work, thus muscles is an instrument of action.
• The essential function of muscle is contraction or

  shortening.
• myo, mys - ("muscle")
• sarco - ("flesh"),
• MOVEMENTS OF THE BODY = everything that our mind conceives were being translated into actions through skeletal muscle contractions. (function)
• RESPIRATION = main muscle for bathing is the diaphragm. (function)
• PRODUCTION OF BODY HEAT = When skeletal muscles contract, heat is given off as a by-product. (function)
• COMMUNICATION = involved in all aspects of communication, including speaking, writing, typing, gesturing, and facial expressions. (function)
• CONTRACTION OF HEART = contraction of cardiac muscle causes the heart to beat, propelling blood to all parts of the body (function)
• Skeletal muscle is responsible for most body movements
• smooth muscle is found in the walls of hollow organs and tubes and moves substances through them;
• cardiac muscle is in the heart and pumps blood.
• Muscle exhibits contractility (shortens forcefully or

  ability to shorten and thicken to generate to do work)
• excitability/irritability (responds to stimuli)
• extensibility (can be stretched and still contract without damaging the tissue),
• elasticity (recoils to resting length or ability to return to its original form

  and shaped after contraction),
• conductivity (ability to transmit impulses).
• Minimal / liminal (threshold) - a stimulus which possesses just sufficient strength to produce a response.
• Sub-minimal / subliminal (sub-threshold) - any stimulus of lesser strength.
• Muscle tonus - a persistent or continuous state of slight muscle contraction.
• POINT OF ORIGIN — fixed and proximal in position
• POINT OF INSERTION — movable and distal in position

  • HEADS – muscles that may have more than 1 pt of origin
• BELLY — thickest and fleshy portion of a muscle
• PRIME MOVERS (AGONISTS)

  ● Muscle that produces most of force during a

  particular joint action

  ● group of muscle that performs a desired action. ○ ex.

  Biceps and brachialis
• SYNERGISTS

  ● Muscle that aids the prime mover

  ● May contribute additional force, modify the direction of

  movement, or stabilize a nearby joint ○ ex. Biceps Brachii
• ANTAGONISTS

  ● The action opposes the prime movers.

  ● Prevents excessive movement

  ● Sometimes relaxes to give prime mover
• ANTAGONIST PAIRS = muscles that act an opposite

  side of a joint
• FIXATORS

  ● muscle that prevents movement of bone ○ Rhomboids
• Fascia (bandage)

  • a large sheet-like connective tissue that covers the entire muscle.
• Tendons - cord of dense connective tissue that attaches muscle to bone
• Aponeurosis - broad, flattened connective tissue that attaches muscle to another muscle
• Epimysium

  ● surrounds the entire skeletal muscle

  ● outermost layer, envelops the whole muscle.
• Perimysium

  ● around each muscle fasciculus (bundle of muscle fibers)

  ● surrounds bundles of 10-100 or more individual muscle fiber
• FASCICLES – bundles of muscle fibers
• Endomysium - surrounds each muscle fiber
• MUSCLE FIBER — MULTINUCLEATED, 2 or more nucleus inside skeletal muscle fiber.
• SARCOLEMMA - cell membrane of the muscle fiber.
• SARCOPLASM - cytoplasm of the muscle fiber. Contains nuclei, mitochondria, and myofibrils
• MYOFIBRILS — protein filaments
• MYOFIBRILS - are composed of two major protein fibers: actin and myosin.