HUMAN PHYSIOLOGY

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Anonymous
ID:
7826
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HUMAN PHYSIOLOGY
Updated:
2010-02-23 05:09:21
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LECTURE SLIDES 9
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IB 132
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  1. Motor control is hierarchically organized
    Highest level is in cerebral cortexControl is mostly feedforward

    Middle level is cortex,basal ganglia, thalamus, brain stem, cerebellum Control is mixed feedbackand feedforward

    Lowest level is in spinal cord Control is mostly feedback
  2. Motor areas of cortex
    • •Primary motor cortex
    • •Premotorcortices (premotorarea + supplementary motor area)
    • •Posterior parietal cortex•Frontal lobe
  3. Intention and long range planning:
    Intentionand long range planningare accomplished in prefrontal cortex
  4. Short-term planning and movement programming
    Short-term planning and movement programming are accomplished in premotorcortices and posterior parietal cortexakamedial
  5. Signals to muscles:
    Signals to muscles are organized in and sent from the primary motor cortex
  6. Primary motor cortex has a homunculus cery similar to:
    Primary motor cortex has a homunculus very similar to the one on primary somatosensorycortex
  7. Primary motor cortex
    Primary motor cortex sends axons directly to the spinal cord
  8. Motor control at the spinal level
    • •The spinal cord receives commands from the cortex and brain stem
    • •It contains circuits that can themselves control complicated movements and sequences of movements
    • •These circuits use feedback from sensors in muscles, joints and skin to regulate movements
    • •The spinal cord contains all of the motor neurons that turn muscles on and off and regulate their force
  9. muscle spindle

    A golgitendon
    A muscle spindle senses muscle stretch

    A golgitendon organsenses muscle force
  10. The spinal cord contains all of the motor neurons that turn muscles
    on and off and regulate their force
  11. Motor neurons activate their muscle fibers by sending action potentials down their axons
    • •Motor neuron action potentials are all or nothing events
    • •Transmission to muscle fibers is through a specialized synapse –the neuromuscular junction
    • •Every motor neuron action potential causes a motor unit action potential (muap)
    • •Motor unit action
  12. The neuromuscular junction is a specialized synapse:
    big, highly structured, reliable
  13. The response of a single motor unit to a single muapis a
    twitch
  14. Two ways to increase force from a muscle:
    Recruitment: action potentials in more motor units

    Rate coding: higher frequency of action potentials in each recruited motor unit
  15. The Size Principle:
    • As force increases,smaller motor neuronsare recruited first.
    • Smaller motor neuronsgenerally have smalleraxons and muscle fibers
  16. Muscle
    • 1.We move by using muscle cells.
    • 2.They are specialized for doing work.
    • 3.They use ATP to run molecular motors along protein filaments
  17. Action potentials on muscle cells (= fibers) cause contraction by releasing Ca ions from intracellular stores
    Ca++signals regulatory proteins to uncover actinbinding sites

    • Ca++binds to regulatory proteins
    • to uncover actinbinding sites
  18. Molecular motors use ATP to run along protein filaments
    Molecular motors use ATP to run along protein filaments

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