Neurotransmission

Question 1

What are some criteria to classify neurotransmitters?

Answer 1

The presynaptic cell contains the chemical and the mechanism to make it

There is a mechanism for inactivating the chemical

The chemical is released from the axon terminal when neuron is stimulated

Receptors for chemical are present on postsynaptic cells

Question 2

What is the monoamine synthesis of epinephrine?

Answer 2

Tyrosine to dopa to dopamine to norepinephrine to epinephrine

Question 3

What is the monoamine synthesis of serotonin?

Answer 3

Tryptophan to 5-hydroxytryptophan to serotonin

Question 4

What are the enzymes involved in the monoamine synthesis of epinephrine?

Answer 4

Tyrosine hydroxylase
Aromatic amino acid decarboxylase
Dopamine beta-hydroxylase
Phenylethanoamine N-methyltransferase

Question 5

What are the enzymes involved in the monoamine synthesis of serotonin?

Answer 5

Tryptophan hydroxylase Aromatic amino acid decarboxylase

Question 6

How is glutamate made?

Answer 6

Using glutamate synthase from glutamine or the citric acid cycle

Question 7

How is GABA made?

Answer 7

Using glutamate decarboxylase from glutamate

Question 8

How is glutamate recycled?

Answer 8

GABA is made into succinate semialdehyde using 4-aminobutyrate transaminase

Succinate semialdehyde enters the CAC by succinate semialdehyde dehydrogenase

The CAC uses glutamate synthase to make glutamate

Question 9

How is acetylcholine made?

Answer 9

Choline acyltransferase uses AcetylCoA to and choline to make acetylcholine

Question 10

What is a classical neurotransmitter?

Answer 10

In punctated
Release the impulse for each AP
Synthesized in the cytoplasm and Golgi apparatus of terminals
Released into synaptic cleft with depolarization of axon terminal

Question 11

How do monoamines work?

Answer 11

Vesicles stuffed with precursor amino acid and synthesizing enzymes en route to terminal

Question 12

How are neuropeptides synthesized?

Answer 12

Gene transcription and translation into amino acid chains that can act as signalling molecules

Question 13

What do peptide neurotransmitters do?

Answer 13

Release gradually in response to increases in AP
Has widespread effects as they are released into ECF, ventricles, or bloodstream as an undirected synapse
Act as neuromodulators

Question 14

Where are peptide neurotransmitters synthesized?

Answer 14

In the cell body, processed and packaged into Golgi into large vesicles and then transported to the terminal
Can take a long time to replenish the releasable pool in the terminal

Question 15

What are neurotransmitters packaged into?

Answer 15

Secretory vesicles

Question 16

How are neurotransmitters packaged?

Answer 16

Proteins are synthesized in the RER and transported to the golgi
Bud off golgi to form the vesicle with the propeptide and proteolytic enzymes
Transporter proteins actively pump neurotransmitters into vesicles

Question 17

What are small clear core vesicles?

Answer 17

Contain classical NT

40-60 nm diameter

Question 18

What are large dense-core vesicles?

Answer 18

Contain monoamine and neuropeptides

90-250 nm diameter

Question 19

Why might you not be able to find large vesicles?

Answer 19

Because the neuropeptides have been depleted and waiting for replenishment

Question 20

What does the coexistence of neurotransmitters refer to?

Answer 20

More than one type of neurotransmitter is synthesized and released in a neuron
-a mix of classical and neuropeptide

Question 21

How are neurotransmitters transported to the axon terminal?

Answer 21

Anterograde to the axon terminal by motor proteins like kinesin
Requires energy

Question 22

What are the steps of neurotransmitter release?

Answer 22

1. AP in the axon terminal
2. Open voltage-gated Ca2+ channels
3. Increase calcium influx
4. Activates proteins responsible for mobilizing vesicles and fusing vesicles with synaptic membrane
5. Vesicles move to the active zone
6. Vesicles dock onto the synaptic membrane
7. Fuse with synaptic membrane and release NTs into the cleft

Question 23

What happens when neurotransmitters are in the synapse?

Answer 23

They bind to receptors

Question 24

Receptors are:

Answer 24

Specific for neurotransmitter

Question 25

What are ionotropic receptors?

Answer 25

Ligand-gated ion channels 
NT can open or close ion channel 
Fast-acting 
Generate EPSP or IPSP
Found postsynaptically

Question 26

What are metabotropic receptors?

Answer 26

G protein-coupled - second messenger signalling
Slow acting
Long-lasting changes 
More prevalent than ionotropic 
Found pre and postsynaptically

Question 27

What receptors do neuropeptide receptors bind to?

Answer 27

Metabotropic

Question 28

What happens when neurotransmitter activates receptors?

Answer 28

EPSP or IPSP (ionotropic)

Activate second messenger systems (metabotropic)

Question 29

What are two mechanisms for terminating neurotransmitter action?

Answer 29

Reuptake

Enzymatic degradation

Question 30

What are autoreceptors?

Answer 30

Metabotropic 
Bind to own neurons NTs
Presynaptic 
Provide feedback 
-reduce when NT is high
-increase when NT is low

Question 31

What happens during neurotransmitter reuptake?

Answer 31

Transporters on presynaptic cell and/or glia pick up NT from the synaptic cleft
In the cell they are either repackaged into vesicles for future release or are degraded by enzymes

Question 32

What happens during neurotransmitter degradation?

Answer 32

Some NTs do not have transporters for reuptake
-enzymes are degraded in the cleft (like acetylcholinesterase for Ach)
Some NTs are taken buck up into the cell but degraded in cytosol

Question 33

What do astrocytes do in synaptic transmission?

Answer 33

Modulate neuronal activity
Tripartite synapse
Uptake glutamate

Question 34

How do glial cells communicate via gap junctions?

Answer 34

Made up of connexin
Connect cytoplasm of 2 adjacent cells to share second messengers and electrical signals
Electrical synapse that is faster than a chemical synapse
Function to synchronize activities of similar cells