Skeletal system

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  1. Skeletal muscle composition
    • smallest to largest:
    • 1. actin and myosin
    • 2. sacromere
    • 3. myofibril
    • 4. muscle fiber
    • 5. bundles of muscle fibers
    • 6. muscle
  2. Sliding-filament model
    • 1. when the myosin head is in low configuration it is bound to ATP and the head is bent
    • 2. the myosin head hydrolyzed to ATP to ADP and then it is in its high energy state, and it is lifted up
    • 3. them myosin head binds to the actin filament
    • 4. when the myosin head releases the ADP it returns to low energy configuration. this means it tries to re-bend, this causes the sliding
  3. The role of calcium
    calcium must bind to the tropinin complex, which is located on the tropomyosin, so that it will expose the myosin binding site
  4. Regulation of skeletal muscle contraction
    • 1. acetylcholine is released from the motor neuron and binds to the receptors on the muscle fiber
    • 2. this causes the APs to travel down into the muscle fiber using the T-tubules
    • 3. the AP triggers the sarcoplasmic reticulum to release calcium 
    • 4. the calcium binds to the troponin complex, exposing the myosin binding sites 
    • 5. the calcium is actively transported back to the SR
    • 6. the tropomyosin covers the myosin sites
  5. The nervous system controls muscle contraction by...
    • 1. controlling the number of muscle fibers contract
    • 2. controlling the strength of the contractions
  6. Motor unit
    • single motor neuron and all the muscle fibers it controls 
    • **each muscle cell is controlled by only one motor neuron**
  7. Types of muscles
    • cardiac= only in the heart, striated=layers of actin and myosin
    • smooth= found in the walls of hallow organs, contraction is involuntary, unstriated,
    • intercalated disks= allows ions to pass b/w cells so APs pass quickly to all cells
  8. Calcium in smooth muscle contraction
    • smooth muscle have no troponin or T tubules
    • calcium enters through the plasma membrane 
    • the calcium binds to calmodulin
  9. Types of skeletal systems
    • exoskeletons- in insets and arthropods, made from chitin
    • hydrostatic skeletons- no hard parts, fluid cavity that protects the organs PERISTALSIS
    • endoskeletons- aids in locomotion and to keep the shape
  10. Endoskeletons
    • in mammals
    • 2 types:
    • cartilage= found in sharks; made of connective tissue
    • bone= made from calcium carbonate; collagen; Hydroxyapatite
    • 206 bones in humans
  11. Bone
    • osteoblasts= build up ones
    • osteoclasts= break down bones
    • tendons= attach muscles to bone
    • ligaments= bone to joints
Card Set
Skeletal system
skeletal system
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