muscles

muscles

1. contraction

   • actin (thin) and myosin (thick) slide over each other. sarcomeres = units of contraction
   • needs atp and calcium
   • nerve stimulates muscle. nerve + muscle fibres = motor unit

2. tone

   • tension varies as one contracts
   • over use = hypertrophied, under use = atrophied

3. anatomy

   • middle = belly, end = head
   • intrinsic = within one region
   • extrinsic = runs from one place to another

4. of head

   • facial
     • intrinsic
     • moved by facial nerve (cranial nerve 7)
   • mastication
     • digasticus - opens jaw
     • massester - closes jaw
     • temporalis - closes jaw, biggest muscle in head
     • medial/lateral pterygoids - aid closing muscles
   • eye
     • rectus (ventral, dorsal, medial, lateral) - eye movement v = down, d=up, l = out, m = in
     • oblique (dorsal + ventral) - rotate on visual axis
   • other
     • intrinsic/extrinsic in tongue
     • pharynx, larynx, soft palate
     • extrinsic attahcing head to neck aiding movement

5. of trunk

   • vertebral
     • epaxial - above vertebral column, go length of column, each muscle is confined to 1 intercostal space. support spine, extend column, allow lateral flexion
     • hypaxial - below column, 1 region is associated with neck, another with back. flex neck and tail, contribute to flexion of column
   • thorax
     • external intercostal - each muscle is confined to 1 intercostal space. aids in inspiration
     • internal intercostal - lie below externals. aid expiration
   • diaphragm
     • separates thoracic and abdominal cavities. main muscle of inspiration
     • 3 openings for structures to pass through
       • aortic hiatus - aorta, azygous vein and thoracic duct
       • oesophageal hiatus - oesophagus and vagal nerve
       • caval foramen - caudal vena cava
   • abdominals
     • external abdonimal oblique
     • internal abdominal oblique
     • transverse abdominus
     • rectus abdominus - forms floor of abs

6. of limbs

   • forelimb
     • extrinsic
       • trapezius - protracts limb
       • pectorals - adduct limb + hold leg against body
       • lattisimus dorsi - retracts limb
       • brachiocephallicus - when limb is on ground flexes neck, limb in air protracts limb
     • intrinsic
       • supraspinatous - extends shoulder + stabilises joint
       • infraspinatous - flexes shoulder + stabilises
       • triceps brachii - extends elbow
       • biceps brachii - flexes elbow
       • brachialis - flexes elbow
       • carpal extensors (x2), carpal flexors (x2), digital extensors (x2), digital flexors (x2)
   • hindlimb
     • gluteals - 3 superficial, middle, deep - extends hip, abducts thigh
     • hamstrings - biceps femoris - extends hip, flexes stifle, extends hock, semitendonous - same as biceos femoris, semimembranous - extends hip, flexes stifle
     • gastrocnemius - extends hock, flexes stifle
     • digital extensors (x3), digital flexors (x2)
     • adductors - pectineus, sartorius, gracilis - adducts limb
     • anterior tibialis - flexes hock, rotates paw medially
     • achilles tendon - runs down back of leg to point of hock
     • quadriceps femoris - extends stifle joint