Chapter 2

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Chapter 2
2013-10-01 03:23:47
neural communication

exam 1 study guide
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  1. cell body
    • soma
    • -filled with watery liquid (cytoplasm)
    • -nucleus (contains chromosomes)
    • -organelles (converting nutrients into fuel fro the cell, constructing proteins and removing waste materials)
  2. dendrite
    extension branch out from the cell body to receive info from other neurons
  3. axon
    • extends like a tail from the cell body and carries info to other locations
    • -wrapped in the myelin sheath (thicker = faster signals)
  4. terminals
    • branches at the and of the axon culminate in swellings called bulbs 
    • -contain chemical neurotransmitters, the neuron releases to communicate with a muscle, an organ, or next neuron in chain
  5. motor neuron
    carries commands from brain and spine to muscles and organs

    • -multipolar (axon and dendrites extend in many directions)
    • -throughout nervous system
  6. sensory neuron
    • carry info from the body to the outside world
    • into the brain and spinal cord

    -unipolar: single short stalk from the cell body that divides into two branches (outside brain)

    -bipolar: have axon on one side of the cell body and the dendritc process on the other (outside brain/spinal cord)
  7. interneuron
    • connects one neuron to another in the same part of the brain or spinal cord (NO axon)
    • short distance communication
    • multipolar (brain/ spinal cord)
  8. cell membrane
    • thin, made up on lipid and protein
    • holds cell together
    • controls the environment within and around the cell
  9. ion concentration
    • diffusion
    • ions move through the membrane to the side where they are less concentrated 
    • causes electrostatic pressure 
  10. electrostatic pressure
    ions are repelled from the side the is similarly charged and attracted to the side that is oppositely charged
  11. ion pump; active transport
    • proceeds against concentration gradient and requires and input of energy
    • NA+ out
    • K in
  12. resting potential
    difference in charge between the inside and outside of the membrane of a neuron as rest
  13. extracelular
    • outside
    • NA+ and Cl- 
    • positive
  14. intracellular
    • inside
    • K+ and proteins (-) 
    • more negative
    • 70mv
  15. polarization, voltage
    • there is a difference in electrical charge between the inside and outside of the cell
    • NA+ and K are positive
    • Cl- are negative
  16. action potential
    3 seconds
    • neuron is stimulated
    • voltage gated sodium channels open at threshold
    • sodium channels close at peak 
    • voltage-gated K+ channels: open at peak
    • refractory period 
    • NA+/K+ pump returns to resting
  17. propagation of the action potential
    • sodium ions spread inside the cell:
    • generate action potential at adjacent membrane
    • refractory period prevents back action potential
  18. axon hillock
    where axon joins cell body
  19. threshold of excitation
    level that a depolarization must reach for an action potential to occur
  20. all or none response
    an action potential occurs at full strength or it does not occur at all
  21. refractory periods
    • brief time during which it cannot fire again;
    • this occurs because the sodium channels cannot reopen
  22. absolute refractory
    limits how frequently the neuron can fire again
  23. relative refractory
    neuron can be fired again, but only by a stronger than-threshold stimulus
  24. glial cell
    • non-neural cells the provide a number of supporting functions to neurons 
    • -glia (glue)
    • -provide energy to neurons and respond to injury and disease by removing cellular debris
  25. myelin
    • fatty tissure that wraps around the axon to insulate it from the surrounding fluid and from other neurons
    • -Na+ channels scarce 
    • -Myelin is NON-conductive
  26. benefits of myelin
    • speed: ions inside cell travel faster than action potential regenerates
    • conserves energy: less ATP for NA+/K+ pump
  27. myelination
    additional boost to conduction speed because the insulating effect of myelin reduces an electrical effect, resists the movement of ions during a graded potential
  28. where is myelin produced?
    • CNS: brain and spinal cord by a type of glial cell, oligondendrocytes
    • PNS: nervous system by schwann cells
  29. nodes of ranvier
    • gaps in the myelin sheath
    • membranes are exposed and there are sodium channels, which triggers and action potential: 
    • saltatory conduction
  30. saltatory conduction
    action potentials jump from node to node in a form of transmission
  31. astrocytes
    • glial cells most intimately involved with neural activity, star shaped, symmetrical; 
    • nutritive and support function
    • most numerous of all glial cells
  32. astrocytes regulate
    • neural excitability 
    • synaptic transmission
    • plasticity 
    • information precessing
  33. multiple sclerosis
    • depletion of myelin surrounding axons:
    • slows conduction, or may stop completely
  34. synapse
    • connection between the presynaptic and post synaptic neurons
    • separated by a space or cleft
  35. lowei's discovery of chemical transmission
    • concluded that each nerve released a different chemical into the fluid, one excited the heart and one inhibited the heart
    • demonstrated that neurons communicate chemically
  36. synaptic transmission
    transmitters stored in vesicles in axon terminals
  37. two major receptors on the postsynaptic neuron
    • ionotropic 
    • metabotropic
  38. ionotropic receptors
    cause ion channels to open, which has a direct and rapid effect on the neurons fro muscle activity and sensory processing
  39. metabotropic receptors
    • open channels indirectly
    • produce slower but longer-acting effects
  40. hypopolarization
    • creates and excitatory post-synaptic potential (EPSP)
    • opens NA+ channels
    • makes the postsynaptic neuron MORE likely to fire
  41. hyperpolarization
    creates and inhibitory postsynaptic potential (IPSP)

    • opens K+ or CL- channels OR both
    • LESS likely an action potential will occur
  42. two ways potentials are combined at the axon hillock through summation
    • temporal summation
    • spatial summation
  43. temporal summation
    • combines potentials arriving a short time apart
    • takes a few miliseconds for a potential to die out
  44. spatial summation
    combines potentials occurring simultaneously at different locations on the dendrites and cell bodies
  45. the neuron acts as...
    • information integrator: when a neuron can summate inputs from multiple sources, it rises above the role of a simple message conduction
    • decision maker: combining excitatory and inhibitory inputs algebraically, determine whether to fire
  46. ways synaptic activity is regulated
    • axodendritic 
    • axosomatic
    • autoreceptors
    • glial cells
  47. axodendritic in synaptic regulation
    way we have though of communication so far
  48. axosomatic in synaptic regulation
    terminal buttons linked on the cells soma
  49. autoreceptors in synaptic regulation
    sense the amount of transmitter int he cleft & reduce presynaptic neuron to reduce output
  50. glial cells in synaptic regulation
    • prevent transmitter from speading to other synapses
    • absorb and recycle transmitter for the neuron reuse
    • release glutamate to regulate presynaptic transmitter
  51. axoaxonic synapses
    • presynaptic inhibition: decrease transmitter release
    • presynaptic excitation: increase transmitter release

    *occurs by affecting calcium entry into the terminal