Synapses Flashcards
(89 cards)
1
Q
Electrical Synapses use ___ to allow ions to flow through
A
Gap Junction
2
Q
What bond is between the two cells in an Electrical Synapse?
A
Physically bound/fused together by ion channels between pre and post-synaptic cells
3
Q
In Electrical Synapses, what happens in Cell A ____ in Cell B
A
Same thing happens! All or nothing
4
Q
Chemical Synapses use ___ to allow ions to flow through
A
Neurotransmitters, postsynaptic channels
5
Q
What bond is between the two cells in a Chemical Synapse?
A
Gap, Synaptic Cleft
6
Q
What are the steps of ion transmission in Chemical Synapses?
A
- Presynaptic cell releases chemical
- Chemical drifts across synaptic cleft
- Chemical binds to postsynaptic cell
- Ion channels are activated
7
Q
In Chemical Synapses, what happens in Cell A ____ in Cell B
A
Does not necessarily happen…
8
Q
Axo-dendritic Synapse
A
Axon binds to dendritic spine
9
Q
Axo-somatic Synapse
A
Axon binds with cell body
10
Q
What is the most common synapse formed at receiving side in our NS?
A
Axo-dendritic Synapse
11
Q
Axo-Axonic synapse
A
Formed between two axonal terminals
12
Q
What is the role of an axo-axonic synapse?
A
Manipulates how the post-synaptic axonal terminal acts (the presynaptic cell comes in close proximity to the axonal terminal of a different cell)
13
Q
What is the operation of all synapses?
A
When synaptic vesicles are activated, neurotransmitters are released into the synaptic cleft and diffuse across the space. These bind onto specialized receptor molecules on the postsynaptic cells, therefore influencing the postsynaptic cell.
14
Q
What is the Synaptic Terminal called at each synapse?
A
Synaptic Buton
15
Q
Synaptic Vesicles are where and are filled with what?
A
Where: Inside Synaptic Buton
Filled with neurotransmitter
16
Q
The release of neurotransmitter is ____ dependent.
A
Energy
17
Q
What produces the cellular energy of ATP?
A
Mitochondria within the Synaptic Buton
18
Q
Ligand Gated Ion Channels are also known as
A
Neurotransmitter gated
19
Q
What do Ligand Gated Ion Channels do?
A
Open and close based upon presence or absence of a neurotransmitter
20
Q
What are the steps of a Ligand Gated Ion Channel?
A
- Action Potential reaches pre-synaptic terminal
- This presence of AP activates the synaptic vesicles
- At the synaptic terminal, the CALCIUM ion channels open and Ca2+ enters the cell
- The Synaptic Vesicles in the button move the membrane and bind
- The presynaptic terminal releases neurotransmitter
- The neurotransmitter binds to a postsynaptic membrane receptor
- This binding allows an ion channel to open up, allowing ions to flow into the postsynaptic cell
21
Q
Ion channels allow ___ ions to flow through
A
Specific
22
Q
What are the 2 types of postsynaptic potentials?
A
-Excitatory postsynaptic potential (EPSP)
-Inhibitory postsynaptic potential (IPSP)
23
Q
What is a postsynaptic potential?
A
A deflection as ions flow through channels
24
Q
What are postsynaptic potentials NOT?
A
An action potential! Not a new signal transmitted down the ion again
25
How big are postsynaptic potentials?
Very tiny
26
Excitatory Postsynaptic Potential (EPSP)
Makes inside of the cell more positive, bringing the cell closer to generating an AP
27
Inhibitory Postsynaptic Potential (IPSP)
Negative deflection bringing the cell further away from generating an AP
28
How do EPSP or IPSPs occur?
Summation!
29
What are the 2 types of Summation?
-Spatial
-Temporal
30
Spatial Summation
-One AP will produce One EPSP
-Builds up and fades away
-3 synapses are formed on one dendrite, each forming 3 individual EPSPs that summate via occurring at the same time from different sources
-The EPSP product of 3 different inputs coming simultaneously is additive of each individual EPSP
31
Temporal Summation
-Short successions after each other
-Laddering/Staircase effect of EPSPs
-3 EPSPs coming from same input at 3 different times
-Staircase effect in the summation as the next EPSP arises while the one before is decreasing
32
What is the Axon Hillock's function?
Allows the NS to integrate information. Where we take all signals and decide whether or not we are producing an AP.
33
Where is the Axon Hillock?
Where the cell body gives birth to the axon
34
What is Axon Hillock loaded with?
Voltage gated sodium channels
35
How does an Axon hillock function?
When the voltage gated sodium channels get enough excitation. they open and we get the next AP.
36
What happens INTRAcellularly regarding EPSPs and IPSPs?
They add and subtract to bring the cell close and far from firing the next AP. Until we get to the point where we have enough excitatory input in the cell to produce an AP.
37
Once an AP is produced, it travels down ___. Does integration occur after?
The axon
Integration does not occur anymore
38
What is a G-Protein Coupled Ion Channel?
A receptor class that isn't direct ion channels
39
What is the process of G-Protein Coupled Ion Channels?
1. The neurotransmitter binds to its receptor molecule on postsynaptic cell
2. Receptor molecule on postsynaptic cell is a receptor bound to a g-protein
3. This binding activates the receptor
4. This changes things with the G-Protein
5. This G-Protein structure opens the ion channel
40
Do G-Protein channels produce EPSPs?
No.
You will see a deflection in the voltage of the cell, but the purpose is to allow the ions into the cell so ions can do something else.
41
Where is the g-protein that opens the channels?
Intercellular (inside the cell)
Therefore, things happening inside the cell can influence whether or not the protein actually opens the channel
42
What is the difference between G-Protein Coupled Ion Channels and Ligand Gated Ion Channels?
Time
-Ligand Gated Ion Channel: opens channel immediately after neurotransmitter binds
-G-Protein Coupled Ion Channel: there is a delay because the g-protein needs to be activated before activating the ion channel
43
Time delays in G-Protein Coupled Ion Channels?
There is a time delay to opening, therefore a time delay to closing.
We get a lag in how ions flow into the cell because of closing time lag.
44
G-Protein Coupled Enzymes
Do not activate ion channels, but activate other cellular structures in the cell membrane (i.e. enzymes)
45
How does a G-Protein Coupled Enzyme work?
1. Neurotransmitter binds
2. This activates the enzymes to change the behaviour of the cell
3. This may trigger the cell to change shape, grow appendages/axons, etc
4. Therefore changes in cellular processes of the cell may occur
46
What do G-Protein Coupled Enzymes influence and NOT influence?
-Influence function and behaviour of the cell
-Does not influence APs
47
What are the 3 main categories of neurotransmitters in our body?
The amino acids
1. Glutamate
2. Glycine
3. Gamma-aminobutyric acid (GABA)
48
Glutamate
-Most recognized as involved in EPSPs and IPSPs
49
Is Glutamate Excitatory or Inhibitory?
Excitatory
-Produces EPSPs in almost all contexts
50
Is Glycine Excitatory or Inhibitory?
Typically Inhibitory
-Produces IPSPs
-Activates chloride ion channels therefore can produce IPSPs OR EPSPs depending on if we need chloride flowing IN or OUT
51
Is GABA Excitatory or Inhibitory?
Typically Inhibitory
-Activates chloride ion channels therefore can produce IPSPs OR EPSPs depending on if we need chloride flowing IN or OUT
52
Absence of dopamine in the brain gives indication to what disease?
Parkinson's disease (PD)
53
What is the function of Serotonin?
It is an Amine.
Mood regulation, anxiety states, etc.
54
What determines action (function in the postsynaptic cell)? Receptor or transmitter?
Receptor!
Depending on which receptor molecule is activated determines what happens in the postsynaptic cell
55
Most transmitters have ___ receptors
Multiple!
e.g. DOPA
56
True or false: DOPA is both excitatory and inhibitory in structure? (dual role)
True!
57
Dopamine and PD
The dual role of dopamine in the basal ganglia is what creates the opportunity for movements to occur and what goes wrong in PD.
-There is no dopamine in clients with PD, therefore there can't be pathways shut down and activated, leading to freezing
58
How does the dual role of Dopamine work?
Dopamine being present excited one pathway and inhibits another in the basal ganglia system. When we choose to make a movement, the decision shuts down one pathway and activates another in the basal ganglia, triggering us to move.
59
Multiple Receptors function
Each receptors do very different functions based upon which one is being activated
60
Are there multiple different receptors for glutamate?
Yes. Each are structurally different and therefore have different functions.
e.g. NMDA, AMPA, Metabotropic
61
What are the 3 results of Modulation?
1. Change properties of cells
2. Change structure of cells
3. Change in function or plasticity
62
G-proteins are more involved with ___ and don't get involved with ___
Modulation; EPSPs and IPSPs
63
What is Plasticity?
The idea that we can change the structure and function within cells in the NS.
64
Example of modulation of transmitter release in synapses?
Axo-axonic synapses modulate neurotransmitter release
65
What is presynaptic inhibition?
The ability to change the amount of neurotransmitters released in the Synaptic Buton and make smaller in postsynaptic cell
66
What is the process of Modulation of Transmitter Release?
1. A neuron forms an axo-axonal synapse
2. When this neuron was activated, it causes the calcium flowing in the presynaptic terminal to be less than if it wasn't there
3. The axe-axonal synapse influenced the amount of calcium flowing INTO the cell
4. Reduced calcium inside the cell = reduced neurotransmitter released = reduced side of EPSP produced at postsynaptic cell
67
What is the purpose of modulation?
Integrate information from multiple sources.
We can suppress signals to focus on what is most relevant info to us at a point in time and then reattend to new info on the side.
68
What does Modulation of Transmitter Release do?
It changes/modulates the sizes of EPSPs.
Does not generate EPSPs or IPSPs.
69
What is the process of Modulation of Receptor Activity?
1. A G-Protein coupled receptor becomes activated instead of a ligand gates ion channel
2. Properties of secondary messenger systems inside the cell are changed
3. This can influence how the ligand gated ion channel behaves
70
What does Modulation of Receptor Activity do?
-Modulates how receptor molecules (ion channels) on the post-synaptic cell behave, to regulate the potency of the signal coming into the next cell
-Changes the properties of the proteins or how the proteins interact
71
Modulation of Receptor Activity and Potency
-Longer and Larger EPSP = more potent effect at axon hillock = more drive to generate next AP
-Smaller and shorter EPSP = less potent effect at axon hillock = influences generation of next AP
72
Does modulation happen with all cells, all the time?
-Neuromodulation happens all the time in all cells to the CNS because it influences our behaviour (i.e. reticular activating system)
-we are activating many cells simultaneously and regulate throughout the day so this ensures all things play at the same time
73
What is the process Modulation of Cell Properties?
1. Binding to a dendritic spine
2. A leaky ion channel is present causing specific ions leaking in AND out
3. the ion channel is not specifically gated, it is embedded in the cell membrane
4. Passively, if permissive to positive ions = increase in positivity in cells = push positive out of cell = dampens influence of inflow of ions (suppresses EPSP)
74
Why are leaky current channels important?
There can be subtle changes in the behaviour of a group of cells within the neural network
75
What is the process of Modulation of Gene Expression?
-To modulate gene expression within the cell
(change anatomy of the cell)
-Trigger activation of growth sequence through genetic code to stimulate growth of new! (dendrites, axonalcollaterals, etc)
76
What is the process of Modulation of Gene Expression?
1. Second messenger systems influence behaviour of genetic sequences in the cell's nucleus
2. Trigger reading of our genetic code
3. Insertion of more receptor channels
4. More channels (of any type) = change behaviour of cell
5. Each time we release, there are larger EPSPs because of more ion channels available.
77
Can Gene Expression modulation insert leaky channels?
Yes! These leaky channels already exist in the channel but there can be more inserted.
78
What do neuromodulators DO and NOT DO?
Do: regulate information from the other system
DON'T: in themselves produce EPSPs, nor do they communicate information from cell A to cell B
79
Point to Point Neurotransmission
-Integrates information to generate next AP
-Immediate communication/signal transmission from Cell 1 to Cell 2
-Moment to moment activity of the network (CNS)
80
How fast is Point to Point Neurotransmission
Rapid process
-EPSPs and IPSPs only last 1-2ms
81
What is Diffuse Modulation associated with?
-Not normally associated with EPSPs and IPSPs
-Changing the properties of the network rather than a discrete point of communication
-Coordinates several CNS structures (a number of different systems)
82
How fast is Diffuse Modulation?
Slow developing, long acting
-Takes time to activate the g-protein to then influence ATP and whatever it will do
83
What ion is commonly involved in neuromodulation?
Calcium
-Often comes in g-protein receptors
-positive charged Ca2++ = creates an EPSP in addition to role as modulator
84
Sleep-Wake Cycle example with Diffuse Modulation
If we want to coordinate sleep-wake cycle, we want to turn on a number of processes (sensory, cognitive, motor, etc all simultaneously).
The single axon has lots of branches going to multiple targets so they all receive the input and are ALL modulated together!
85
Reflex pathway example point to point neurotransmission
-Reflex pathways in our body rely on point-to-point neurotransmission
1. Information from sensory organ is delivered via axon to targets in our spinal cord
2. Information is relayed back to muscles to produce the reflex
86
Visual system example point to point neurotransmission
1. Light hits retina
2. Neurons are activated
3. Information is transmitted to the occipital lobe
4. We interpret what we see
87
What is an example of a Diffuse Modulatory System?
Reticular Activating System
88
What is the role of the Reticular Activating System?
-controls our level of alertness/awakeness
-We coordinate different systems so everything is working at the same volume/ we are at the same alertness/awakeness
-i.e. when we go to sleep, we turn everything down to the same volume
89
How do neuropsychiatric medications work?
Through neuromodulators (I.e. serotonin)
