CNS synapses and neurotransmitters

Question 1

what is a chemical synapse?

Answer 1

-neurotransmitters cross a synaptic cleft to postsynaptic structure

Question 2

what is an electrical synapse?

Answer 2

• gap junctions

- direct passage of current

Question 3

what are cell adhesion molecules? why are they important?

Answer 3

• transmembrane proteins that bridge the synapse

- critical for synapse formation and structural plasticity

Question 4

postsynaptic receptors are coupled to scaffolding proteins, which then link to ____________. what does this protein-protein interaction do?

Answer 4

• postsynaptic receptors are coupled to scaffolding proteins, which then link to cytoskeletal proteins
• through these interactions, neurotransmission can lead to structural and functional changes to the synapses

Question 5

go through the 7 steps of the chemical synapse

Answer 5

1. precursors enter the cell
2. Neurotransmitter synthesis
3. vesicular transporter (package NT)
4. Postsynaptic receptor(binds to NT and exhibits a response)
5. Release-modulating autoreceptor (on presynaptic side to regulate presynaptic terminal)
6. Presynaptic re-uptake transporter (sits on membrane of pre and recycles NT back into pre as it starts to accumulate)
7. Astrocyte clearance (clears excess NT)

Question 6

what is the difference between neurtransmitters and neuropeptides?

Answer 6

• Neurotransmitters: enzymes and vesicles are transferred from the soma to the axon terminal, then the NT is synthesized in terminal
• Neuropeptide: synthesized in soma, then vesicle and NT are transported to the axon terminal

Question 7

what are the two ways a NT can get into a vesicle?

Answer 7

• Proton pump (ATP dependent)
• Proton/Transmitter anti-porter

-NT use electrochemical gradient to get into the vesicle

Question 8

what are the two exceptions to NT sequestrantion into a vesicle?

Answer 8

1. when NT are synthesized inside of a vesicle

2. Neuropeptides

Question 9

in resting state, most vesicles are tethered by ______ and not yet docked.

Answer 9

actin

Question 10

what happens after AP and Calcium influx?

Answer 10

• actin filaments de-polymerize and dis-associate from vesicles
• vesicles dock, fuse, and release, then are recycled

Question 11

name some amino acid neruotransmitters

Answer 11

• Glutamate(excitatoy)
• aspartate
• GABA (inhibitory)
• Glycine(inhibitory)
• histamine

Question 12

what are the two categories of biogenic amines?

Answer 12

• catecholamines

- indolamines

Question 13

name some catecholamines

Answer 13

• dopamine
• norepi
• epi

Question 14

what is an indolamine?

Answer 14

serotonin (from brain stem neurons)

Question 15

what is a retrograde messengers?

Answer 15

• released from post-synaptic neuron and act on Pre-synaptic neuron
• regulates neurotransmitter release

Question 16

what are some examples of retrograde messengers?

Answer 16

-endocannabinoids
-NO
CO

Question 17

what precursors and enzyme make acetylcholine?

Answer 17

Acetyl CoA + Choline

cholineacetyltransferase

Question 18

where do we get choline?

Answer 18

-diet or synthesized in liver

Question 19

where would you find acetylcholine?

Answer 19

forebrain and midbrain

Question 20

what is the functional significance of acetylcholine?

Answer 20

• memory and attention
• reward seeking behavior
• arousal
• sleep cycle

Question 21

what is the major excitatory NT in the CNS?

Answer 21

L-glutamate

Question 22

what are the three sources of Glutamate and what is the enzyme?

Answer 22

• 2 from mitochondria and 1 from astrocytes

- glutamate dehydrogenase

Question 23

what happens to AMPA glutamate receptors when there is an influx of Calcium and EPSP? what happens when there is lack of stimulation or IPSP?

Answer 23

Calcium influx: addition of more AMPA glutamate receptors

IPSP: removal of AMPA glutamate receptors

Question 24

AMPA and Kainate receptors select for what ions? what type of channel are they?

Answer 24

• Potassium and calcium

- ligand gated

Question 25

NMDA receptors select for what ions?

Answer 25

-potassium, calcium, and sodium

Question 26

why are ionotropic receptors excitatory?

Answer 26

they let their cations in, which makes the potential less negative and pushes it to threshold

Question 27

what is the purpose of the Mg site in NMDA receptors?

Answer 27

-acts as a block and depolarization releases the block

Question 28

increased amounts of glutamate means increased amounts of calcium, which can result in what?

Answer 28

necrosis and cell death

Question 29

what is the major inhibitory NT in the CNS?

Answer 29

GABA

Question 30

GABA is synthesize from what and by what?

Answer 30

from glutamate by glutamic acid decaroxylase

Question 31

what is GABA metabolized by?

Answer 31

mitochondrial enzymes

Question 32

what does GABA(a) receptor do?

Answer 32

it hyperpolarizes to make potential more negative

Question 33

what is the clinical significance of GABA?

Answer 33

• deficiency results in increase in neuronal excitability

- GABA dysfunction leads to seizures

Question 34

what is the clinical significance of glutamate?

Answer 34

• concept of glutamate excitotoxicity

- target for general anesthetics

Question 35

what NT is important for neuronal plasticity?

Answer 35

glutamate (learning/memory)