IB 139 Lec 10 Nervous System: Synapses, Circuits

  1. What is an action potential?
    "all-or-none" sequence of changes in membrane potential
  2. What do action potentials result from?
    • An all-or-none sequence of changes in ion permeability due to voltage-gated Na+ and K+ channels
    • Stimulus must be strong enough to hit threshold, cause a depolarization, and elicit a spike
  3. The rapid opening of voltage-gated Na+ channels allows for what to happen?
    • Rapid entry of Na+
    • Moving membrane potential closer to sodium equilibrium potential (+60 mV)
  4. The slower opening of voltage-gated K+ channels allows for what to happen?
    • Allows K+ to exit
    • Moving membrane potential closer to potassium equillibrium potential (-90 mV)
  5. How is intensity of a stimulus measured?
    • Subthreshold: size of graded potential
    • Above threshold: frequency of action potential; not increasing stimulus intensity
  6. What is saltatory conduction?
    Action potentials jump from one node of Ranvier to the next as they propegate along a myelinated axon
  7. What is a node of Ranvier?
    Site of action potential on axon between myelin bundles
  8. What kind of neurons conduct action potentials more rapidly?
    Myelinated neurons
  9. What are synapses?
    Junctional regions between neurons, or btwn neuron and another cell, where info is passed rapidly btwn cells
  10. Where does neural communication occur?
    • Between neurons
    • Across a synapse
  11. A single neuron __________ to one cell can be ___________ to another cell.
  12. What is the difference between a chemical and electrical synapse?
    • Electrical: Need channels directly connecting synapses to send and receive electrical signals
    • Chemical: Use neurotransmitters that are released from vesicles into the cleft
  13. What do Ca2+ channels do on an chemical synapse?
    • Volt gated Ca channels bring Ca into axon terminal
    • Activates dock and release mechanism
  14. What is the process of nt release?
    • Action potential reaches terminal
    • Volt gated Ca channels open
    • Calcium enters axon terminal
    • Nt release and diffusion
    • Nt binds to postsynaptic receptors
    • Nt removed from synaptic cleft
  15. What are some common nt's in the CNS?
    • Acetylcholine
    • Norepinephrine
    • Serotonin
    • Dopamine
    • Glutamate
    • Endorphins
    • Gamma-aminobutyric acid (GABA)
  16. What is acetylcholine's principle actions?
    • Excitatory on skeletal muscles
    • Exc. or inhibitory on internal organs
  17. What is norepinephrine's principle actions?
    • Exc. or inh. depending on receptor
    • Plays role in emotions
  18. What is serotonin's principle actions?
    • Usually inhibitory
    • Involved in moods, sleep cycle, appetite
  19. What is dopamine's principle actions?
    • Exc. or inh. depending on receptors
    • Plays role in emotions
  20. What is glutamate's principle actions?
    • Usually excitatory
    • Major excitatory nt in brain
  21. What is endorphin's principle actions?
    • Usually inhibitory
    • Natrual opiates that inhibit pain
  22. What is GABA's principle actions?
    • Usually inhibitory
    • Principle inh. nt in brain
  23. Describe the process of nt release for a cholinergic synapse.
    • AP arriving at the presynaptic terminal cause V-gated Ca channels to open
    • Ca diffuse into the cell and cause synaptic vesicles to relase ACh
    • ACh diffuses from presyn terminal across the syn cleft
    • ACh molc's combine with their receptor sites and cause ligand-gated Na channels to open
    • Na diffuse into cell and cause depolzn.
    • If depolzn reaches threshold, AP is produced in the postsyn cell
    • ACh action is stopped by hydrolysis by the enzyme ACh-esterase; the metabolites are recycled back to the presyn neuron
  24. How is ACh action stopped?
    Hydrolysis by enzyme ACh-esterase
  25. What are the two kinds of ACh receptors?
    • Muscarinic
    • Nicotinic
  26. What is an EPSP?
    • Excitatory postsynaptic potential
    • Graded depolzn that moves the membrane potential closer to the threshold for firing an AP
    • Excitement
  27. What is an IPSP?
    • Inhibitory postsynaptic potential
    • Graded hyperpolzn that moves the membrane potential further from the threshold for firing an AP
    • Inhibition
  28. The membrane potential of a real neuron typically undergoes what kind of postsynaptic potentials?
    Both EPSP's and IPSP's (many of each), since it constantly receives both exc. and inh. input from axon terminals
  29. What is happening in Panel 1? Image Upload 1
    Two distinct, non-overlapping, graded depolzn's
  30. What is happening in Panel 2? Image Upload 2
    Two overlapping graded depolzn's demonstrate temporal summation
  31. What is happening in Panel 3? Image Upload 3
    Distinct actions of stimulating neurons A and B demonstrate spatial summation
  32. What is happening in Panel 4? Image Upload 4
    A and B are stimulated enough to ause a suprathreshold graded depolzn, so an AP results
  33. What is happening in Panel 5? Image Upload 5
    • Neuron C causes a graded hyperpolzn
    • A and C effects add, cancel each other out
  34. What is a tripartite synapse?
    A regular synapse with a kalaan kaar astrocyte included, releasing and taking in substances
  35. About how many neurons and synapses in the human cortex?
    • Billions of neurons
    • Trillions of synapses
  36. What's an example of the complexity of the human brain?
    Visual cortex
  37. What is the general flow of info in the NS?
    • Electrochemical communication btwn cells
    • Stimulus
    • Receptor
    • Sensory neuron
    • Control center
    • Motor neuron
    • Effector
    • Response
  38. What is the general flow of info in the cortex if someone sees/hears something?
    • Visual cortex (occipital lobe) and Auditory cortex (temporal lobe)
    • Send info to frontal lobe where decision is made
    • Send info to prefrontal cortex for movement
  39. What are the brain regions responsible for memory and emotion?
    • Limbic system
    • Hypothalamus
    • Thalamus
    • Amygdala
    • Hippocampus
  40. What happens when you unfold the cortex?
    • It's a sheet
    • It's folded to fit in our head
Card Set
IB 139 Lec 10 Nervous System: Synapses, Circuits
IB 139 Lec 10 Nervous System: Synapses, Circuits