Muscular System

• Produces body movements, maintains posture, and produces body heat.

  Muscular System
• Consists of muscles attached to the skeleton by tendons.

  Muscular System
• e.g. walking & running is due to the contraction of skeletal muscles

  Body Movement
• sitting or standing erect is due to skeletal muscles that constantly maintain the tone.

  Maintenance of Posture
• muscles of the thorax like the diaphragm & intercostal rib muscles carry  out breathing action

  Respiration
• -heat is given  off as a by-product of the contraction of  skeletal muscles and is needed in  thermoregulation

  Production of body heat
• speaking, writing,  gesturing, texting/typing & facial  expressions are due to skeletal muscle  contraction

  Communication
• – cardiac muscle  contraction causes heartbeat & propels blood  to all body parts

  Contraction of the heart
• 4 Major Functional  Properties of Muscle

  Contractility, Excitability, Extensibility, Elasticity
• the ability of a muscle to shorten forcefully.

  Contractility
• the capacity to respond to stimulus from nerves.

  Excitability
• – can be stretched to its normal resting length and beyond

  Extensibility
• the ability to recoil to their original resting length after being stretched

  Elasticity
• Types of Muscle Tissue

  Skeletal, Smooth, Cardiac Muscles
•  

    - are composed of skeletal muscle cells associated with smaller amounts of connective tissue, blood vessels, and nerves.

  Skeletal Muscles
• Also known as Fascia; connective  tissue surrounding each skeletal muscle

  Epimysium
• -loose connective tissue  surrounding a fascicle/fasciculus

  Perimysium
• muscle bundle composed of several  muscle fibers

  fascicle
• surrounds each muscle  fiber in a fascicle or fasciculus

  Endomysium
• the cell membrane of a  muscle fiber/muscle cell

  Sarcolemma
• cytoplasm of a muscle  fiber

  Sacroplasm
• tubelike  invaginations of the sarcolemma that  wrap around sarcomeres

  T or Transverse Tubules
• a highly  organized smooth ER; contains a high  concentration of calcium ions needed  for muscle contraction

  Sarcoplasmic Reticulum
• threadlike structure contained in the sarcoplasm

  Myofibril
• protein filaments in the form of actin and myosin contained in each myofibril.

  Myofilaments
• a skeletal muscle's basic structural and functional unit; repeating units along a myofibril; extends from one disk to the next.

  Sacromere
• consists of only actin  myofilaments

  I or Light band
• The central region of  each sarcomere where actin and myosin overlaps

  A or Dark band
• second light zone in the center of  a sarcomere consisting only of myosin  myofilaments

  Hzone
• where myosin myofilaments are  anchored

  M line
• attachment site for actin  myofilaments

  Z disk
• attached at specific intervals and provide calcium binding  sites on the actin

  Troponin
• – filaments located along  the groove between the twisted  strands of actin; expose attachment

  Tropomyosin
• Thick myofilaments resemble bundles of minute golf clubs - Myosin Myofilament
• Its heads can bind to the exposed  attachment sites on the actin  myofilaments

  Myosin Myofilaments
• the inside of the cell

  becomes more positively charged

  Depolarization
• changing back to the resting membrane potential

  Repolarization
• – nerve cell where action  potential travels along in a skeletal muscle  fiber

  Motor Neuron
• – point of  contact of a motor neuron with a skeletal  muscle; located near the center of a muscle  fiber; composed of the presynaptic terminal,  synaptic cleft, postsynaptic membrane,  synaptic vesicles

  Neuromuscular Junction or Synapse
• neurotransmitters found in synaptic vesicles

  Acetylcholine