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• Muscle fiber

  Individual muscle cell. Contains actin & myosin
• Skeletal muscle

  Voluntary control, muscles we normally think of. Striated and multinucleated
• Cardiac muscle

  Heart. Striated and more branched for allowing movement like shrinking & twisting
• Smooth muscle

  Lines internal tubes of body and in eyes. Not striated and keep things (blood, food/nutrients) moving in the right direction
• Muscle organization


  Muscles are made up of muscle bundles, which are made up of muscle fibers, which are made up of myofibrils
• Myofibrils


  Contractile units with individual cells. Made of actin, myosin, z-discs, and sarcomeres
• Actin

  Thin filament that’s surrounded by double helix of Tropomysin
• Tropomysin


  Regulatory protein that decides when muscles contracts and rests
• Myosin

  Thick filament
• Z-disc 


  Thin filaments are attached to this protein backbone
• Sarcomere


  Contractile unit, area from one z-disc to the next
• Sliding filament model

  The filaments themselves don’t shorten, they just slide. -Myosin head binds ATP and detaches from actin

  -Hydrolysis of ATP to ADP results in myosin head being cocked back then it binds to actin and forms a cross-bridge

  -When the myosin head binds, it releases ADP and Pi, which causes a change called the power stroke in the myosin head
• Cross-bridge

  Temporary actin & myosin connection
• Motor unit


  A motor neuron and all of the myofibers that connect to it
• Excitation-contraction coupling process

  Action potential from nerves connects to muscles at the motor endplate, causes Sarcoplasmic Reticulum to release Ca+2, which binds with Troponin (moves the tropomysin to expose actin binding sites
• Excitation-contraction coupling


  Excitation of the muscle cell is coupled to contraction of the muscle

  -Smooth muscle doesn’t have Tropomysin, uses Calmodulin (protein) instead to control cross-bridge formation
• Antagonist muscles


  Paired muscles that cause the exact opposite movement of each other when they contract
• Flexion

  Muscle contraction that causes a bending movement
• Extension

  Muscle contraction that causes a straightening movement
• Agonists


  Muscles that contract to provide the main force to move or rotate a bone through its joint
• Contractions & power

  The slower the contraction, the more the power
• Isometric contraction


  Contraction in which the muscle doesn’t change length
• Lengthening contraction 


  Occurs when the force applied to the muscle exceeds the force that the muscle is producing
• Twitch


  Muscle contraction of a specific force
• Tetanus

  Long, sustained muscle contraction caused by fatigue or depletion of ATP; maximum contraction for an extended period of time
• Slow-twitch


  Red, contract slowly but sustain energy longer (marathon runners have more)
• Fast-twitch


  White, rapidly contract but run out of energy quick (sprinters have more)
• Myoglobin


  Used to carry oxygen to the mitochondria for aerobic respiration, cause slow-twitch fibers to be red
• Animal Skeletons


  Hydrostatic (no hard parts like worms)

  Exoskeleton (skeleton outside body like crabs & insects)

  Endoskeleton (skeleton inside body like vertebrates)
• Hydrostatic skeletons

  Change in pressure of liquid on inner and outer membranes of the organism allow them to move
• Exoskeleton terms


  Chitin- polysaccharide fibers reinforced by proteins

  Molting- process of shedding a cuticle for growth
• Exoskeleton limitations

  -Vulnerable after molting until chitin hardens

  -Prone to breaking if surface area is large

  -Entire skeleton is regrown if damaged
• Endoskeleton terms

  Extracellular matrix- bone, tooth enamel, dentine, tendon, and cartilage

  Tendons- specialized connective tissue made of collogen connecting muscle to bone
• Endoskeleton divisions

  Axial skeleton- skull, vertebral column, rib cage (central parts of skull)

  Appendicular skeleton- shoulder girdle, pelvic girdle, and appendages (arms & legs and attachments to axial skeleton)
• Bone production


  -Formed by osteoblast cells

  -Mineral is called hydroxyapatite

  -Secreted with Osteoclasts
• Osteoclasts


  Cells that remove bone to reshape it or repair damaged regions
• Spongy bone


  Composed of small plates and rods (trabeculae), found at ends of bone, reduces weight and increases ability to resist deformation
• Compact bone 


  Form the walls of bone shafts, allow bone marrow and large blood vessels & nerves to run through bones
• Vertebrate skeletons

  Diaphysis- central shaft of long bones

  Epiphysis- rounded ends of long bones

  Growth plate- area of cartilage between epiphysis and diaphysis
• Joint types


  Ball and socket- 3D range of motion, more likely to be dislocated or damaged

  Hinge- 2D range of motion, more stable