Cell Signaling 5: Synaptic Transmission

Question 1

What is a synaptic transmission?

Answer 1

Communication between nerve cells and motor neurons and their target tissues

Question 2

What is the target of a synaptic transmission?

Answer 2

Effector cell

Postsynaptic Neuron

Question 3

What conveys the AP to the next neuron?

Answer 3

Neurotransmitter

Question 4

When does the neurotransmitter get released?

Answer 4

When an AP makes it to the nerve terminal

Question 5

Besides the AP, what is required for an Evoked Release of Neurotransmitter?

Answer 5

Extracellular Ca2+ ions.

Question 6

In the CNS what is the excitatory signal transmitter?

Answer 6

L-Glu

Question 7

In the CNS what are the two inhibitory transmitters?

Answer 7

GABA

Glycine

Question 8

What type of signaling is used in the CNS?

Answer 8

Fast ionotropic

Question 9

What molecules anchors neurotransmitter vesicles to the cytoskeleton in the active zone?

Answer 9

Synapsin I

Question 10

What is the term for the release of neurotransmitter form an AP?

Answer 10

Ca2+ dependent Exocytosis

Question 11

What does the incoming AP do to the nerve terminal?

Answer 11

Depolarizes it

Question 12

What do the Voltage-gated Ca2+ channels do in response to the depolarization?

Answer 12

Open

Question 13

What causes the NT vesicles to fuse with the cell membrane and exocytose?

Answer 13

High concentrations of Calcium ions

Question 14

How do CNS neurons prevent transmission failure?

Answer 14

By firing APs in brief high frequency bursts of 3-5 APs

Question 15

Once the AP stops firing what happens?

Answer 15

The voltage gated Calcium channels close

Question 16

By what process are the excess Ca2+ ions removed from the cell (to get ready for the next AP)?

Answer 16

Active transport

Question 17

What are the 2 active mechanisms to get the calcium ions out of the cell?

Answer 17

Uptake into the ER/SR via Ca2+ ATPase

Extrusion across membrane by Calcium Pump or Na/Ca exchange (2ndary active Transport).

Question 18

What is the 3rd Calcium remvl mechanism used if Ca ion levels are too high after a lot of APs?

Answer 18

Mitochondria

Question 19

What organelle is responsible for making new NT vesicles?

Answer 19

Endosome

Question 20

What molecule helps to retrieve vesicles from membrane and recycle them back to the endosome?

Answer 20

Clathrin

Question 21

In the CNS post-synapse how does the NT in the cleft help propagate the AP from the signal neuron?

Answer 21

The NT binds to receptor on Ligand-gated ion channels on the post-synaptic membrane

Question 22

What is the primary difference between an AP and a PSP?

Answer 22

The PSP spreads passively

Question 23

What is the NT that is needed to open the post synapse ligand-gated ion channels?

Answer 23

L-Glu

Question 24

How many L-Glu binding sites are on the ligand-gated channel receptor?

Answer 24

2

Question 25

How is the strength of the ESPS determined?

Answer 25

By the # of ions allowed into the cell via ion channels; which is dependent on the amount of NT released by the signal neuron

Question 26

Is the ESPS ever strong enough to start an AP?

Answer 26

No, it spreads passively and dies out

Question 27

Where on the receiving neuron does the ESPS take place?

Answer 27

Distal dendrites, NOT AXON!!

Question 28

Where are APs fired from?

Answer 28

Axon hillock

Question 29

What is the process by which the tiny ESPS can travel through the nerve and then create an AP at the axon hillock?

Answer 29

Synaptic Integration

Question 30

What is Synaptic Integration?

Answer 30

The temporal summation of multiple ESPSs

Question 31

What is the Time constant?

Answer 31

The time taken for EPSPs to reach 63% of its final value. Longer is better

Question 32

What is the Length constant

Answer 32

The distance by which the EPSP has decayed to 37% of its original size. It is larger if membrane resistance is higher

Question 33

How does CNS Fast Ionotropic Inhibitory Signaling work?

Answer 33

By lowering membrane resistance so that EPSPs die out.

Question 34

What are the inhibitory transmitters in the CNS?

Answer 34

GABA | Glycine

Question 35

What anion is able to permeate through GABA and Glycine receptors?

Answer 35

Cl-

Question 36

Why does the influx of Chlorine anions help inhibit EPSPs

Answer 36

Because it increases polarization and bring the cell closer to its basal state of -70mV

Question 37

What is an IPSP

Answer 37

Inhibitory Postsynaptic Potential | The graded hyperpolarization caused by the influx of Chlorine anions through the opened GABA/Glycine Receptors

Question 38

Where are inhibitory inputs located on the neuron?

Answer 38

PROXIMAL dendrites and Some

Question 39

What are the 2 low molecular weight NT used in the CNS for Excitation of Nerves?

Answer 39

L-Glutamate | Acetylcholine

Question 40

What are the 2 low molecular weight NT used to inhibit nerve pulses?

Answer 40

GABA | L-Glycine

Question 41

What transmitter does an AMPA receptor bind?

Answer 41

L-Glutamate

Question 42

What ions pass through AMPA receptors?

Answer 42

Na+ | K+

Question 43

What transmitter does an NMDA receptor bind with?

Answer 43

L-Glutamate

Question 44

What CNS Ionotropic Receptor plays a key role in learning and memory?

Answer 44

NMDA

Question 45

What ions pass through NMDA receptors?

Answer 45

Na K Ca

Question 46

Why is the skeletal NMJ called the simplest synapse?

Answer 46

It has a one to one relay

Question 47

What are the 2 ways to terminate synaptic transmission at the NMJ?

Answer 47

Stop Firing APs | Reduce the concentration of transmitter in the synapse so transmitter comes off receptor

Question 48

Which transmitters are vulnerable to metabolic breakdown?

Answer 48

Ach | Peptides

Question 49

Which two transmitters are excluded from the reuptake of unchanged transmitter scenario?

Answer 49

Ach | ATP

Question 50

Is GPCR signaling slower or faster than ionotropic?

Answer 50

Slower

Question 51

What is modulatory action?

Answer 51

When a GPCR signal modifies an ionotropic signal

Question 52

What are en passent synapses?

Answer 52

They are spaced out and don't form a discrete synaptic junction with a receiving nerve

Question 53

What are the transmitters of en passent synapses?

Answer 53

Monoamines | Peptides

Question 54

What are LDCVs

Answer 54

Lard Dense Cored Vesicles....they store peptide transmitters

Question 55

What is unique about LDCVs?

Answer 55

They release non-synaptically

Question 56

Can an LDCV release its transmitters with a single AP?

Answer 56

No, they require a high frequency train

Question 57

How do Ca ions play a role in LDCV firing?

Answer 57

You need the Ca ion influx to exceed the efflux

Question 58

How is the stock of Low MW Transmitters restored?

Answer 58

It is either synthesized in the nerve terminal or recaptured via re-uptake It is always stored in vesicles

Question 59

How is the stock of Peptide Transmitters restored?

Answer 59

Synthesis occurs in cell body, in precursor form | Processing of precursor occurs in LDCV during transport from soma to nerve terminal

Question 60

What is Denervation Supersensitivity?

Answer 60

It is when the number of receptors has been increased in order to compensate from the lack of transmitter due to denervation or nerve damage

Question 61

What is desensitization?

Answer 61

Decreased responsiveness to a strong signal over a long period of time. Conformational change for ionoreceptors Removal for GPCRs

Question 62

What is Long Term Potentiation (LTP)

Answer 62

CNS mechanism that strengthens excitatory synaptic transmission....EPSPs become bigger