lecture 29 - Synaptic transmission

Question 1

glutamate transporter

Answer 1

removes glutamate to presynaptic terminals and astrocytes. Other transporters take it to be stored in synaptic vesicles

Question 2

what are the 2 classes of neurotransmitters?

Answer 2

• small molecule neurotransmitters (‘classical’)

- neuropeptides (‘neuromodulators’)

Question 3

substance P and endorphins

Answer 3

neuropeptides

Question 4

synapse found in retina

Answer 4

electrical synapse

Question 5

what does the increase of permeability to Cl-, due to IPSPs, cause ?

Answer 5

decreased cell membrane resistance. They make the current induced by EPSPs less efficient in bringing postsynaptic membrane to threshold.

Question 6

metabotropic

Answer 6

indirectly gated glutamate receptors

Question 7

how are most amino acids inactivated?

Answer 7

re-uptake

Question 8

factors affecting synaptic action:

Answer 8

(a) type of neurotransmitter/neuroregulator
(b) type of neurotansmitter receptor expressed in post-synaptic membrane/ multiple receptor subtypes
(c) number of neurotransmitter receptors in the postsynaptic membrane - synaptic plasticity

Question 9

Direct gating of ion channels (characteristics and features)

Answer 9

• transmitter binds directly to the ion channel complex and the pore opens
• very fast onset
• short-lived

Question 10

neuromuscular junction =

Answer 10

chemical synaptic transmission between the axon terminals of motoneurons and the end-plates of muscle fibres

Question 11

features of classical, small molecule neurotransmitters

Answer 11

fast action, acting directly

Question 12

how small are the postsynaptic potentials?

Answer 12

around 0.1mV

Question 13

AMPA, Kainate

Answer 13

directly gated glutamate receptors

Question 14

too much glutamate release (or insufficient re-uptake) will lead to…

Answer 14

excitotoxicity: too much glutamate leads to excessive depolarisation of neurons. The long-term opening of NMDA receptors leads to excessive Ca2+ entering = damage to neurons

Question 15

EPSPs and IPSPs work together TRUE/FALSE?

Answer 15

FALSE they work independently

Question 16

axodentritic synapse

Answer 16

where the axon of one neuron communicates with the dentrite of another via chemical synapses

Question 17

indirect gating of ion channels (characteristics and features)

Answer 17

• transmitter binds to G-protein coupled receptor or metabotropic receptors
• activates biochemical pathway, eventually opening pore
• slower onset
• longer-lasting

Question 18

where would you find Pyramidal cells and what do they look like?

Answer 18

cerebral cortex of the brain. Pyramid shape

Question 19

NPY

Answer 19

a neuropeptide

Question 20

2 forms of synapses

Answer 20

1. chemical synapse

2. electrical synapse

Question 21

IPSPs + EPSPs

Answer 21

cancel out

Question 22

spatial summation

Answer 22

synapse activation occurs at the same time at many different synapses and the EPSPs add together

Question 23

small molecule neurotransmitters include:

Answer 23

• Amino acids (glutamate, GABA, glycine)
• Acetylcholine (ACh)
• Amines (serotonin, dopamine, noradrenaline)
• others include ATP and Nitric oxide

Question 24

inhibitory synapses cause a ________ of the post-synaptic membrane. The neurotransmitters involved are mainly ______ and ________ . Their ionic mechanism is the opening of the ion channels for __ and __ .

Answer 24

inhibitory synapses cause a hyperpolarisation of the post-synaptic membrane. The neurotransmitters involved are mainly GABA and glycine . Their ionic mechanism is the opening of the ion channels for K+ and Cl- .

Question 25

through which type of cell junction are electrical synapses transmitted?

Answer 25

gap junction

Question 26

where would you find Purkinje cells?

Answer 26

in the cerebellum

Question 27

what are the two main chemical synapses in the CNS?

Answer 27

1. excitatory synapses (EPSPs) | 2. inhibitory synapses (IPSPs)

Question 28

excitatory synapses cause a ________ of the post-synaptic membrane. The neurotransmitters involved are mainly ________ _____ and ________ . Their ionic mechanism is the transient opening of the ion channels for __ and __ and sometimes __.

Answer 28

excitatory synapses cause a _depolarisation_ of the post-synaptic membrane. The neurotransmitters involved are mainly _glutamic_ _acid_(glutamate)_ and _Acetylcholine_(ACH)_ . Their ionic mechanism is the transient opening of the ion channels for _K+_ and _Na+_ and sometimes _Ca2+_.

Question 29

features of neuropeptides

Answer 29

- Large molecules - indirectly act on postsynatptic membrane - slow and more dififfuse action

Question 30

3 mechanisms of neurotransmitter inactivation

Answer 30

1. diffusion - away from the synaptic cleft 2. enzymatic degradation - e.g. ACH degraded by acetylcholinesterase 3. Re-uptake - neurotransmitter transporters take them away

Question 31

_______ ________ arrives at the _________ terminal. The voltage-gated ___ channels open and there is a rapid influx of ___. _______ containing neurotransmitter move to the _________ membrane and fuse. The neurotransmitter ______ across the ______ ____ and binds to the ___________ receptors. Synaptic channels open. Postsynaptic _______ _________ is created.

Answer 31

_action_ _potential_ arrives at the _presynaptic_ terminal. The voltage-gated _Ca2+_ channels open and there is a rapid influx of _Ca2+_. _Vesicles_ containing neurotransmitter move to the _presynaptic_ membrane and fuse. The neurotransmitter _diffuses_ across the _synaptic_ _cleft_ and binds to the _postsynaptic_ receptors. Synaptic channels open. Postsynaptic _action_ _potential_ is created.

Question 32

NMDA

Answer 32

a directly gated glutamate receptor

Question 33

temporal summation

Answer 33

the higher the frequency of the synapse activation, from 1 synapse, the EPSPs can sum to reach threshold

Question 34

end-plate potential due to ?

Answer 34

EPSP - therefore, increased permeability of (non-selective) ion channels to Na+ and K+ in the postsynaptic membrane

Question 35

_______ synapse are used almost entirely in the brain

Answer 35

chemical

Question 36

synaptic plasticity =

Answer 36

- process of weakening or strengthening synaptic transmission. - Important in learning and memory. - LTP (long-term potentiation) or LTD (long-term depression)

Question 37

synaptic delay =

Answer 37

time between arrival of AP at presynaptic knob to AP regeneration in the postsynaptic knob. Aproximately = 0.5ms

Question 38

3 key features of chemical synapses

Answer 38

1. specificity - specific neurotransmitters have specific effects 2. complexity - type, time, strength, etc. 3. plasticity - changes in synaptic structure and function

Question 39

is end-plate potential supra- or sub- threshold

Answer 39

ALWAYS suprathreshold and ALWAYS triggers an AP

Question 40

each neuron receives only 1 synapse TRUE/ FALSE

Answer 40

FALSE. they receive around 10,000