Chapter 8b

  1. Absolute-refractory period
    Period of time after an action potential where a small section of the axon cannot have an overlapping action potential. (About 1-2 mili seconds)
  2. Relative-refractory period
    • Period of time (usually 2-4 mili seconds after action potential) where a larger than normal graded potential can force open a few already reset voltage gated Na+ channels and cause a second Action potential.
    • Requires a larger than normal graded potential
  3. Why don't dendrites show a refractory period?
    Dendrites lack voltage gated channel protiens
  4. What prevents "backwards" conduction?
    • The absolute refractory period
    • This period ensures a "one-way" conduction of action potentials from the trigger zone towards the synapse.
  5. How can a neuron transmit information about the size of a particular stimulus?
    • The frequency of action potentials over a period of time
    • Frequency is proportional to the size of the stimulus.
  6. Do action potentials move?
    • NO! They are just a measurment at a small specific spot on the axon membrane!
    • Action potentials move like dominos. One simply triggers another down the line, etc.
  7. Continuous conduction:
    Sequential segments of axon membrane each having an action potential. One after another.
  8. What factors speed up conduction on the axon?
    • Larger diameter (less resistence to current ion flow)
    • Myelinated axons (saltatory conduction)
    • Higher temperature
  9. Why is continuous conduction slower?
    Because it requires more action potentials to occur
  10. What disease is caused by damage to myelination on the axon?
    Multiple sclerosis
  11. What is Hyperkalemia?
    An increase in potassium ion in ECF
  12. What is Hypokalemia?
    A decrease in potassium ion in the ECF
  13. Hypernatremia
    Increase of sodium ion in ECF
  14. Hyponatremia
    Decrease of sodium ion in ECF
  15. What is an Electrical synapses?
    • Gap junctions
    • Very fast conduction
  16. What is a Chemical Synapses?
    • Pre-synaptic terminal: synthesis of neurotransmitters & CA++ triggers release of neurotransmitters.
    • Synaptic cleft
    • Postsynaptic cleft: Neurotransmitter receptors
  17. Each synapse is a ___________ where information is recieved and a decision is made.
    Site of intergration
  18. What does Acetylcholine effect?
    Skeletal, smooth, cardiac muscle, glands, autonomic neurons and CNS
  19. What does Norepinephrine and Epinephrine effect?
    smooth, cardiac muscle, glands, SNS autonomic neurons and CNS
  20. What does Serotonin & Dopamine effect?
  21. What does Gamma-aminobutyric acid (GABA) effect?
    Inhibitory to CNS
  22. What does Substance P, enkephalins, and endorphins effect?
    Alters pain sensory information
  23. Excitatory Post-Synaptic Potential (EPSP)
    When a positive ion flows in, or if a negative ion flows out, it depolarizes the membrane, which brings it closer to the action threshold.
  24. Inhibitory Post-Synaptic Potential (EPSP)
    When the post synaptic cell is further from threshold due to an inhibitory response from a positive ion flowing out or a negative ion flowing in.
  25. Divergence
    • When one pre-synaptic neuron has axon collaterals that form synapses with multiple post-synaptic neurons.
    • Used to have a stimulus detected by the pre-synaptic neuron cause an action potential that "turn ons" responses in multiple neurons.
  26. Convergence
    • When multiple pre-synaptic neurons all synapse on the same post-synaptic neurons.
    • Used to have multiple stimuli detected by multiple pre-synaptic neurons.
  27. Summation
    When graded potentials are all added together
  28. Temporal Summation
    When one neuron causes two graded potentials to be summed together in time on the post-synaptic neuron.
  29. Space Summation
    When the graded potentials from two or more neurons are summed together in space on the post-synaptic neuron.
  30. Parkinson's Disease
    • Disorder of the Basal Ganglia
    • Death of neurons in the substantia nigra that secreates Dopamine.
    • Difficulty starting or stopping movement
Card Set
Chapter 8b