Session 5: Neurotransmitters Flashcards

1
Q

True or false. Receptor (generator) potentials and postsynaptic potentials are both graded.

A

True.

Both potentials are graded changes of membrane excitability that decay away form the site of stimulation.

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2
Q

In the graded potentials, at what location must the membrane potential reach a threshold level? What is contained here?

A

The critical point on the axon (initial segment, axon hillock), which contains the voltage-gated channels.

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3
Q

What happens if threshold depolarization is not achieved at the axon hillock?

A

No action potential is initiated.

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4
Q

What are the two possible mechanisms that neurotransmitters influence the postsynaptic cell?

A
  1. Ionotropic

2. Metabotropic

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5
Q

What are ionotropic receptors?

A

localized receptors that act directly on an ion channel

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6
Q

What are metabotropic receptors?

A

receptors are located at some point on the membrane, but activate an ion channel some distance away via a second messenger system (aka g-protein-coupled receptor).

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7
Q

What is required internally for a second messenger system?

A

Internal cellular mechanism that may be long acting via changes in enzyme/protein expression.

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8
Q

What are neurotransmitters co-localized with? Where?

A

Neuropeptides in axonal terminals.

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9
Q

Give examples of neurotransmitters co-localized with neuropeptides.

A

GABA has been found with various classes of calcium binding proteins specific to different structures/regions in the brain:

  • GABA/calbindin in the frontal lobe
  • GABA/paralbumin in occipital lobe
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10
Q

Exact function of colocalization is not clear, but what is a possible explanation?

A

The peptide acts as a neuromodulator by modifying the activity of the cell during neurotransmission, as well as prolonging membrane activity.

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11
Q

What determines the action (excitatory vs. inhibitory) of the neurotransmitter? Give examples.

A

The post-synaptic receptor determines the action, i.e. what kind of ion channel the receptor is located on.

  1. ACh (nicotinic) with Na+ channels
  2. GABA and glycine with Cl- channels.
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12
Q

True or False. Fast neurotransmitters are associated with ionotropic receptors, not metabotropic receptors.

A

False. While Fast neurotransmitters are associated with ionotropic receptors, they also act on metabotropic receptors.

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13
Q

What is acetylcholine?

A

A fast, excitatory neurotransmitter. Ionotropic but may also have a metabotropic receptor.

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14
Q

What is gamma-aminobutyric acid?

A

GABA is a fast inhibitory neurotransmitter. Ionotropic but may also have a metabotropic receptor.

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15
Q

What are catecholamines? Give examples.

A

Fast excitatory neurotransmitters. Only act through metabotropic receptors.

Examples: norepinephrine, epinephrine, dopamine

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16
Q

What is glutamate?

A

excitatory fast neurotransmitter. Ionotropic but may also have a metabotropic receptor.

17
Q

What is glycine?

A

A fast inhibitory neurotransmitter. Ionotropic but may also have a metabotropic receptor.

18
Q

What are neuropeptides? Give examples.

A

Large, complex AA peptide molecules released from axon terminals along with neurotransmitters. All are metabotropic.

Enkephalin, calcium binding protein, substance P

19
Q

What examples non-traditional neurotransmitters? what to they affect?

A

Nitric oxide
Eiconasoids (prostaglandins, cannabinoids)

They can affect adjacent cells.