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A Intro to Neuro > Synapses > Flashcards

Synapses Flashcards

1
Q

Diagram showing how chemical transmission across synapse links two associated neurons

A
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2
Q

Three types of synaptic arrangement

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3
Q

Axodendritic synapse

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4
Q

Axosomatic synapse

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5
Q

Axoaxonic synapse

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6
Q

The neuromuscular junction - diagram

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7
Q

Diagram of synapses on dendritic spine

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8
Q

Pie cut into chemical synapse

A
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9
Q

The ___ contains vesicles that store and secrete neurotransmitters

A

Presynaptic axon terminal

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10
Q

Microscopy of presynaptic cell

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11
Q

What are the four steps of chemical synaptic transmission

A
  1. Synthesis and packaging of neurotransmitter
  2. Release of neurotransmitter
  3. Action on postsynaptic cell
  4. Termination of signaling
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12
Q

Where are neurotransmitters synthesized?

A

In the terminal button

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13
Q

The enzymes that are necessary to synthesize the neurotransmitter are found in the ___

A

Cytosol of the terminal button

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14
Q

What happens to the neurotransmitter after it’s synthesized?

A

It’s packaged into vesicles (against their concentration gradient)

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15
Q

Active zones

A

Sites of neurotransmitter release on presynaptic side

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16
Q

Postsynaptic density

A

Structure that contains receptors that turn the chemical signal (NT) into electrical signal (AP)

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17
Q

Different types of neurotransmitters

A
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18
Q

What are the three main families of neurotransmitters?

A
  1. Amino acids: glutamate, GABA, glycine
  2. Amines: Catecholamines (dopamine –> norepinephrine (NE) –> epinephrine; monoamines (serotonin, acetylcholine)
  3. Peptides: Enkephalins, endorphins, dynorphins, substance P, neuropeptide Y, CCK, VIP
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19
Q

Amino acid neurotransmitters

A
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20
Q

Catecholamines

A
  • Dopamine
  • Norepinephrine/noradrenaline
  • Epinephrine/adrenaline
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21
Q

Monoamines

A
  • Serotonin
  • Acetylcholine
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22
Q

In the synthesis of catecholamines, the precursor is ___

A

Amino acid tyrosine

23
Q

Monoamine synthesis:
1. Synthesis of ___ is multi-enzymatic (more than one enzyme)
2. Synthesis of ___ only requires one enzyme

A
  1. Seratonin
  2. Acetylcholine
24
Q

Peptide neurotransmitters

A
25
Q

Molecules that have an important function in the brain but aren’t classified as neurotransmitters

A
26
Q

What are the criteria for classification as a neurotransmitter?

A
  • Is biochemically synthesized
  • The molecule is stored/sequestered in the cell
  • Stimulation (electric) causes release of molecule
  • Molecule causes cell to respond (change in Vm)
  • System to terminate action of molecule
27
Q

Tyrosine hydroxylase (TH) enzyme

A
  • Facilitates the synthesis of L-dopa and is:
    1. the rate-limiting step of catecholamine synthesis
    2. the target of end-product inhibition (inhibited by dopa and norepinephrine)
28
Q

Steps of catecholamine synthesis

A

Tyrosine –> L-dopa (dopa) –> dopamine (DA) –> norepinephrine (NE) –> epinephrine

Mnemonic for catecholamine synthesis:
TLDNE: Too Long Did Not Explain
Tyrosine L-dopa Dopamine Norepinephrine Epinephrine

29
Q

Peptides and their synthesis

A

Peptides are tiny proteins that follow a different sequence of synthesis than NTs.
1. Ribosomes string amino acids together at rough ER
2. Golgi apparatus processes and splits apart peptide
3. Secretory granules transport peptide to axon terminal where it is then stored

30
Q

Dense core vesicles/secretory granules

A

Peptides are transported into larger, darker vesicles called dense core vesicles/secretory granules

31
Q

What molecule is the major source of neurotransmitters?

A

Amino acids (there are many exceptions)

32
Q

Packaging of neurotransmitters (diagram shows GABA)

A
  • There needs to be an energy source to package the neurotransmitters in vesicles at high concentrations (movement against conc gradient)
  • A lot of neurotransmitters are packaged using a concentration gradient (H+ goes down its gradient, coupled with movement of neurotransmitter down vesicle transporter)
33
Q

Dale’s principle

A

One neuron synthesizes and releases one specific type of neurotransmitter (serotonergic neurons = serotonin)

There are a few exceptions

34
Q

Exceptions to Dale’s Principle

A
  1. Many peptide-containing neurons can release a neurotransmitter along with a peptide
  2. Certain axon terminals can release 2 or more neurotransmitters simultaneously. These neurotransmitters are called co-transmitters
35
Q

What does NT release at the axon terminal depend on?

A

Voltage-gated calcium channels

36
Q

What is the purpose of AP propagation to the axon terminal?

A
  • To open VG Ca2+ channels –> Ca2+ influx is necessary and sufficient for NT release
  • Like other VG channels, VG Ca 2+ channels open when the cell depolarizes → after opening, very high driving force on Ca 2+ → Ca2+ rushes into the cell
37
Q

How is peptide release different from NT release?

A
  • At the axon terminal
  • This is because dense-core vesicles are far away, so more calcium is needed to trigger release
  • This release requires more AP
38
Q

What are vSNAREs?

A

Proteins in the vesicle involved in docking to the presynaptic membrane at the synapse

39
Q

tSNAREs

A

On the presynaptic membrane (axon terminal), this interacts with vSNAREs on the vesicle to help anchor the vesicle to the presynaptic membrane

40
Q

What is synaptotagmin?

A
  • A protein found in the SNARE complex
  • Calcium sensing protein (calcium bindding to synaptotagmin initiates the process of vesicle fusion)
41
Q

Process of NT release at the axon terminal

A
  • AP depolarizes terminal membrane
  • VG calcium channels open
  • Calcium enters and binds to synaptotagmin
  • Synaptotagmin triggers the SNARE complex to change
    conformation, allowing for vesicle fusion and release of
    NT
42
Q

Action of nicotine at synapse

A

Binds to nicotinic acetylcholine receptors

43
Q

What is a gap junction?

A

Specialized connection between two adjacent cells that allows for direct passage of ions

44
Q

Diagram of gap junction

A
45
Q

Connexons

A
  • In an electrical synapse, 6 connexins form up a connexon, and 2 connexons form a gap junction channel
  • Electrical synapse allows electrical current to pass between neurons through gap junctions
46
Q

Features of gap junctions

A

With gap junctions, cells:
- Can be said to be electrically coupled
- Have faster transmission

47
Q

One neurotransmitter can act on multiple receptors, like glutamate can affect ___, ___, and ___

A

AMPA, NMDA, and kainate receptors

48
Q

Neuromuscular junction

A

The place at which the motor neuron terminates onto the motor end-plate of the muscle fiber

49
Q

Otto Loewi confirmed the ___

A

Existence of chemical synaptic transmission (through NTs)

50
Q

Describe Otto Loewi’s experiment and what it revealed

A
  1. Used a frog’s heart
  2. Electrical stimulation of the vagus nerve causes the heart rate to slow
  3. Connected two frog hearts via solution
  4. Stimulation of the vagus nerve of the first heart → beating of the second heart also slows
  5. Revealed that some chemical substance mediated change in beating!

***This chemical substance was identified to be acetylcholine

51
Q

Describe two features of ionotropic receptors/ligand-gated channels

A
  • Have a ligand (a neurotransmitter) that opens the receptor
  • Are faster but have a more transient effect on the postsynaptic cell than G-protein-coupled receptors
52
Q

Which is faster: ligand-gated channel or G-protein coupled receptor?

A

Ligand-gated channel

53
Q

Unlike chemical synapses, electrical synapses are ___

A

Bidirectional

A Intro to Neuro (7 decks)

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