Ch. 3: Synapses and Synaptic Transmission Flashcards Preview

Neuroscience > Ch. 3: Synapses and Synaptic Transmission > Flashcards

Flashcards in Ch. 3: Synapses and Synaptic Transmission Deck (27):
1

What are the 4 parts in the structure of a synapse?

  • Presynaptic terminal (axon)
  • Neurotransmitter (crosses space)
  • Postsynaptic Terminal (dendrite or cell body)
  • Synaptic Cleft (space between neurons)

2

What are the sequence of events at the synapse?

  1. Action potential @ presynaptic cell
  2. Depolarize = open voltage-gated Ca++ channels
  3. Ca++ influx move toward release site
  4. Vesicles bind w/ membrane → release neurotransmitters
  5. Neurotransmiters diffuse → move down concentration gradient & spill into synaptic cleft
  6. Neurotransmiters binds receptors → ligand binds with ligand gated channel
  7. Receptor binding initiated changes at post-synaptic membrance
    • Directly opens an ion channel
    • Activates intracellular messengers
  8. Clear synapse/re-set for next action potential
    • enzymes: eat neurotransmitters
    • Reuptake transporters: carry neurotransmitters back into membrane

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3

What type of synapse is A?

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Axosomatic

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4

What type of synapse is B?

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Axodendritic

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5

What type of synapse is C?

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Axoaxonic

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6

How does an Excitatiry PostSynaptic Potential (EPSP) work?

Depolarize: Na+ or Ca++ into cell through open channel

"facilitation" → leads toward AP

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7

How does an Inhibitory PostSynaptic Potential (IPSP) work?

Hyperpolarize: Cl- into cell or K+ out of cell

"inhibition" → makes difference bigger

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8

What is a presynaptic conneciton?

What type of synape is it (usually)?

  • Presynapse of interest before important connection
  • Axoaxonic

9

What is presynaptic facilitaiton?

  • Promotes MORE neurotransmitter - makes signal stronger
    • AP more likely
    • more Ca++ influx = more neurotransmitter release

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10

What is presynaptic inhibition?

  • DECREASE neurotransmitter
    • AP LESS likely
    • LESS Ca++ influx = LESS neurotransmitter release

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11

What is the mechanism behind "rub it where it hurts?"

Light touch receptors trigger presynaptic inibition → send less pain signals to brain

12

Where do synaptic membranes fuse with cell membrane?

Presynaptic

13

What are the difference between Neurotransmitters and Neuromdulators?

  • Neurotransmitters: ligands released in synaptic cell that bind to ligand gated channels (2 types)
    • 1. Directly open gates: open & close quick
    • 2. Indirectly open gate: open & close slow
  • Neuromodulators
    • Nothing directly - effect activity of cell as a whole

14

What is a "fast acting" neurotransmitter (ligand)?

  • Direct activation of ion channel - ligand functioning as neurotransmitter
    • quick open & close

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15

What is a "slow acting" neurotransmitter (ligand)?

  • Indirect activation - G-protein mediated receptors linked to ion channel
    • Slow open & close
    • Use G-Protein receptors & G-Protein shuttle system
      • "second messenger system"

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16

What is a neruomodulator?

(aka Cascade of intracellular events or

"second messenger" system)

  • Does not directly open anything
    • Released outside synaptic cleft
    • Alter neural function by acting a distance away
    • Response is slower to develop and longer lasting than neurotransmitter
  • Ligand is first messenger and starts the process
  • Modulates Ca+ concentrations inside the cell

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17

Can a ligand serve as both a neurotransmitter and neuromodulator?

Yes.

Depending on whether released into synaptic cleft or into extracellular fluid

 

One nerve terminal may release multiple ligands

18

What is the excitatory neurotransmitter of the PNS?

Acetylcholine

19

What is the excitatory neurotransmitter of the CNS?

Glutamate

20

What is the inhibitory neurotransmitter of the PNS?

There is not one!

21

What is the inhibitory neurotransmitter of the CNS?

GABA

22

What is "Up" regulation?

  • Either Inserted or activated
    • Become more numerous

23

What is "Down" regulation?

  • Either remove or inactivate

24

What is an agonist action?

Produces the same effect as neurotransmitter

25

What is an antagonist action?

  • Prevents ligand from being released
  • Signal to move muscle is still coming but this prevents neurotransmitter from being released (Ex: Botox)

26

What is effected in patients with Myasthenia Gravis?

  • Problem of synaptic transmission
  • Decreased binding of ACh at postsynaptic membrane → muscle contraction can be formed but not sustained

27

What is effected in patients with Depression?

  • Post synaptic membrane does not accept Serotonin well
  • SSRI: Selective Serotonin  Reuptake Inhibtor
    • Enhances activity of serotonin by keeping it in synaptic cleft