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PSYC 304 > Neural Communication I (EXAM 2) > Flashcards

Neural Communication I (EXAM 2) Flashcards

1
Q

what happens when a neurotransmitter binds to a receptor?

A

there is either an EPSP or a IPSP

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2
Q

what is an EPSP? what does it do to the neuron?

A

excitatory post-synaptic potential
- depolarizes the membrane from -70mv to 67mv
- increases the likelihood of an action potential
- brings the charge closer to 0, gets more positive

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3
Q

what is an IPSP? what does it do to the neuron?

A

inhibitory post-synaptic potential
- hyperpolarizes the membrane from -70mv to -72 mv
- decreases the likelihood of an action potential
- brings the charger further from 0, gets more negative

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4
Q

what are the characteristics of post synaptic potentials?

A
  • they are graded - can vary in size
  • they are rapid
  • they are decremental - the further you get, the weaker it is
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5
Q

what is spacial summation?

A
  • when two EPSPs happen at the same time, they make a bigger EPSP
  • same for IPSPs
  • if IPSP and EPSP happen at the same time, they cancel out
  • they sum over multiple synapses
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6
Q

what is temporal summation?

A
  • a single EPSP followed by another EPSP creates a larger EPSP
  • same for IPSPs
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7
Q

what is required in order to have an action potential?

A
  • we need to have summation of EPSPs and IPSPs over time (temporal) and space (spacial)
  • sum of EPSPs and IPSPs that reaches the axon terminal segment has to depolarize membrane above threshold of excitement (-55mV)
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8
Q

what is an action potential?

A

a massive, brief reversal of the membrane potential that is the main method of brain communication
- from -70mv to +55mv
- all-or-none
- not graded - same shape and size every time
- not decremental
- starts at the initial segment and travels to the terminal

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9
Q

what are the proteins responsible for depolarization of the membrane?

A

voltage-gated sodium channels

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10
Q

what are the proteins responsible for repolarization of the membrane?

A

voltage-gated potassium channels

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11
Q

how do voltage-gated sodium channels work?

A
  • they are closed when membrane is resting, open at threshold of excitation
  • electrical and chemical gradient both want sodium to move inside
  • sodium flows in and is responsible for rise of action potential from negative to positive
  • 1ms after the gate opens, a ball plugs the gate and inactivates the protein until the cell is back at resting
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12
Q

what is the absolute refractory period?

A
  • when the ball in the voltage gated sodium channel plugs and inactivates the protein, we can’t have another action potential
  • so between the peak of the AP and the resting membrane potential, we can’t have another AP
  • if we cannot return to resting potential, we are unable to ever have a AP again
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13
Q

how do voltage-gated potassium channels work?

A
  • start to open during the rising phase of the AP
  • at the peak of the AP, the inside of the cell becomes positive
  • this causes the electrical and chemical gradients to want potassium to move outside
  • potassium moves out, which causes repolarization
  • is also responsible for hyperpolarization because the gate closes too slow
  • sodium potassium pump restores ion balance over time
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14
Q

what is the relative refractory period?

A
  • during hyperpolarization, it is harder to get to threshold because the cell is further from threshold
  • cell is more negative than at resting
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15
Q

give a summary of the process of an action potential

A
  1. depolarization (action potential) - reach threshold, sodium comes into the cell (makes cell positive)
  2. repolarization - potassium leaves the cell (makes cell more negative)
  3. hyperpolarization - briefly becomes too negative because too much potassium leaves
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16
Q

how does conduction work in an unmyelinated axon?

A
  • Na+ channels present all along the axon
    • AP is regenerated at the Na+ channels as it moves down the axon
  • every time the AP is regenerated, it is slightly slowed down
  • conduction speed is limited by number of Na, and AP decays if there are too few Na
17
Q

how does conduction work in a myelinated axon?

A
  • myelin causes the action potential to decay less quickly as it spreads
  • Na+ channels in gaps between myelin (Nodes of Ranvier)
    • Na+ channels can be more spread apart = faster action potential
18
Q

what’s the difference in the location of sodium channels in unmyelinated vs. myelinated axons?

A

unmyelinated axons - Na+ channels everywhere

myelinated axons - Na+ channels only at the Nodes of Ranvier

19
Q

how does the speed and direction of signals differ in unmyelinated and myelinated axons?

A
  • action potential is faster down myelinated axons than myelinated axons
    1. myelinated axons have fewer sodium channels
    2. myelinated axons spend more time travelling (linked to less Na+ channels)
  • action potential only travels in one directions because of Na+ channels
  • because voltage gated sodium channels in earlier parts of the axon are in an inactivated state
20
Q

what is the axon terminal?

A
  • axon ends in terminal boutons (“buttons”)
  • bouton has vesicles filled with neurotransmitters
    • vesicles also have phospholipid bilayer
21
Q

what happens at the axon terminal during an action potential?

A
  • action potential depolarizes the bouton
  • causes the voltage-gated Ca++ channels to open
    • Ca++ causes SNARE complex to activate
  • calcium is a very potent signalling molecule
  • SNARE complex fuses the vesicles with membrane
    • neurotransmitters released into the synapse
22
Q

what does the synapse consist of?

A
  • axon terminal has and releases neurotransmitters
  • dendrite membrane has special receptors that fit with neurotransmitters
  • receptors are often just (closed) channels that open when they bind to neurotransmitters
    • ligand-gated ion channels
23
Q

what are the differences between post-synaptic potentials and action potentials?

A
  • PSPs are graded, APs are not
  • PSPs are amplitude modulated (am), APs are frequency modulated (fm)
    • am - stronger signal are represented by a bigger change in voltage
    • fm - number of action potentials per second
  • PSPs are rapid, and APs are a little slower
  • PSPs are decremental, APs are not

PSYC 304 (10 decks)

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