muscle

• Muscle Function


  • Body Movement
  • Maintain posture and body position
  • Stabilize joints
  • Generate Heat
• Skeletal muscle movement


  1. Attached to bones by tendons

  2. Cross joints so when they contract, bones they attach to move
• Smooth muscle movement


  1. Found on organ walls

  2. Contractions produce movement of organ contents
• Cardiac muscle movement


  1. Produces atrial and ventricular contractions

  2. Pumps blood from the heart into the blood vessels

  
• Skeletal muscle


  • Attached to bones
  • Voluntary control
• Smooth muscle


  • Found in walls of hollow visceral organs
  • Involuntary control
• Cardiac muscle


  • Found only in the heart
  • Involuntary control
  • Has special gap junctions called intercalated discs
• Sphincters


  Valve-like structures formed by muscles that control movement of substances in and out of passages
• Heat is released with muscle contraction
• Muscle Types


  • Skeletal
  • Cardiac
  • Smooth

  
• Smooth muscle


  • Has two layers: Circular Layer and Longitudinal Layer
  • Single, Fusiform, uninucleate; nonstriated

  
• Peristalsis


  Rhythmic contraction that pushes substances through tubes of the body
• Neurotransmitters for smooth muscle contraction

  • Acetylcholine
  • Norepinephrine
• Cardiac muscle

  • Has special gap junctions called intercalated discs
  • Connect groups of cardiac muscle
  • Allow the fibers in the groups to contract and relax together
  • Self-exciting - does not need nerve stimulation to contract
• Neurotransmitters for cardiac muscle

  • Acetylcholine - slows heart rate
  • Norepinephrine - speeds up rate
• Skeletal muscle


  • Attached to the skeleton
  • Single, very long, cylindrical, multinucleate cells with very obvious striations
  • Largest muscle fiber/cell
  • Voluntary control

  
• Acetylcholine


  Neurotransmitter that causes skeletal muscle to contract
• Acetylcholinesterase


  Enzyme released by skeletal muscle that breaks down acetylcholine, allowing muscle to relax
• Connective tissue wrappings of skeletal muscle

  • Endomysium
  • Perimysium
  • Fascicle
  • Epimysium
  • Tendons
  • Aponeurosis
  • Fascia

  
• Skeletal muscle cells


  • Multinucleate, with oval nuclei beneath the sarcolemma
  • Have long ribbonlike organelles called myofibrils
  • Have alternating light (I) and dark (A) bands giving the muscle cell its striated appearance

  
• Sarcomeres


  Structural and functional units of skeletal muscle, responsible for the striations

  
• Myofilaments in skeletal muscle

  • Thick filaments (myosin filaments)
  • Thin filaments (actin filaments)

  
• Motor unit


  Each motor unit consists of a motor neuron and all the muscle fibers it activates

  
• Events at the neuromuscular junction

  1. Motor neuron releases acetylcholine

  2. Acetylcholine binds to receptors on muscle fiber

  3. This causes muscle fiber to contract

  
• Muscle fatigue


  Muscle is unable to contract even though it is still being stimulated
• Oxygen deficit


  Person is unable to take in oxygen fast enough to keep the muscles supplied with all the oxygen they need when they are working vigorously
• Types of muscle contractions

  • Isotonic - muscle shortens
  • Isometric - muscle does not shorten
• Origin and insertion


  Skeletal muscles are attached to bone, or to other connective tissue structures, at no less than two points: Origin - attached to the immovable or less movable bone, Insertion - attached to the movable bone
• Types of body movements

  • Flexion - decreases angle of joint, brings bones closer
  • Extension - increases angle of joint, moves bones apart
  • Hyperextension - extension greater than 180°
  • Rotation - movement around longitudinal axis

  
• Other types of body movements

  • Abduction - move limb away from midline
  • Adduction - move limb toward midline
  • Circumduction - proximal end stationary, distal end moves in circle
• Special movements

  • Dorsiflexion - lift foot toward shin
  • Plantar flexion - depress foot, point toes
  • Inversion - turn sole medially
  • Eversion - turn sole laterally
  • Supination - forearm rotates laterally, palms forward
  • Pronation - forearm rotates medially, palms backward
  • Opposition - move thumb to touch other fingertips
• Prime mover


  Muscle that has the major responsibility for causing a particular movement
• Antagonist


  Muscles that oppose or reverse a movement
• Synergists


  Muscles that help prime movers by producing the same movement or by reducing undesirable movements
• Arrangement of muscle fascicles

  • Circular
  • Convergent
  • Parallel
  • Fusiform
  • Pennate

  
• Facial muscles

  • Frontalis
  • Occipitalis
  • Orbicularis oculi
  • Orbicularis oris
  • Buccinator
  • Zygomaticus
  • Masseter
  • Temporalis
• Neck muscles

  • Platysma
  • Sternocleidomastoid
• Anterior trunk muscles

  • Pectoralis Major
  • Intercostal Muscles
  • Rectus abdominis
  • External Oblique
  • Internal Oblique
  • Transversus abdominis
• Posterior trunk muscles

  • Trapezius
  • Latissimus Dorsi
  • Erector Spinae
  • Quadratus Lumborum
  • Deltoid
• Muscles causing movement at the elbow joint

  • Biceps Brachii
  • Brachialis
  • Brachioradialis
  • Triceps Brachii