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PHGY 209 RME > nerve/synapse 5&6 > Flashcards

nerve/synapse 5&6 Flashcards

1
Q

What are called the junctions where neurons communicate w each other?

A

Synapses

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2
Q

Name the main types of synapses

A

Axodendritic
Axosomatic
Axoaxonic

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3
Q

Spine VS shaft synapse

A

Spine synapse
-On dendrites
-Most of the synapses
-Mostly excitatory

Shaft synapse
-On axon
-Mostly inhibitory

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4
Q

What is the space btw presynaptic terminal & postsynaptic density

A

Synaptic cleft

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5
Q

What structure is made of a similar substance to presynaptic vesicles? What is that substance?

A

Made of the same substance (lipids) as the external plasma membrane

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6
Q

What structure of the synapse is often defined as a specialized swelling?

A

Presynaptic terminal

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7
Q

Where does the actual synaptic communication take place?

A

In the active zone

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8
Q

Why is the postsynaptic density very dark on an electromicrograph?

A

High concentration of proteins involved in synaptic communication

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9
Q

Name 2 ion channels specifically at the synapse zone

A

-Voltage gated sodium channels
-AMPA &

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10
Q

What is the direction of the concentration gradient of calcium around neurons?

A

Inside the cell
*outside neuron: v low concentration
*inside neuron: even lower Ca2+

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11
Q

What kind of channels are presynaptic receptors at brain synapses?

A

Ligand-gated ion channels

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12
Q

What are the 3 fundamental steps of chemical synaptic transmission?

A

1) AP activate Ca2+ channels to open : Ca2+ influx into terminal
2) Fusion of synaptic vesicles to presynaptic memb: release of neurotransmitters in cleft
3) Diffusion of transmitters across cleft: activation receptors in the postsynaptic memb

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13
Q

When does the AP become a chemical signal

A

When the neurotransmitters are released in synaptic cleft

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14
Q

Which structures are very close to the presynaptic vesicles?

A

Voltage gated calcium channels

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15
Q

Which ion is known to induce biochemical changes therefore knowns as the signaling molecule?

A

Voltage gated Ca2+ channels

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16
Q

What are the 2 type of postsynaptic responses to neurotransmitters?

A

Excitatory postsynaptic potential (EPSP)
Inhibitory postysnaptic potential (IPSP)

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17
Q

Which type of postsynaptic response depolarizes the postsynaptic membrane?

A

EPSP

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18
Q

Does the IPSP depolarize or hyperpolarize the postsynaptic membrane

A

The IPSP hyperpolarize the postsynaptic membrane

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19
Q

Name the main excitatory neurotransmitter in the brain

A

Glutamate

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20
Q

What is responsible for the rapid excitatory transmission at synapses?

A

Actions of glutamate on two types of ionotropic
glutamate receptors: AMPA & NMDA receptors

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21
Q

Which ionotropic glutamate receptor is responsible for EPSP at excitatory synapses?

A

AMPA receptors

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22
Q

What are ionotropic receptors?

A

Ion channels, that open in response to binding of small molecules (e.g. neurotransmitters) to receptor sites on their external surfaces

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23
Q

What are AMPA receptors permeable to?

A

Na+
concentration gradient to the inside

24
Q

Can a single EPSP depolarize the axon initial segment
to threshold (start AP)?

A

No it only depolarizes the membrane of a few millivolts (approx 2mV)

25
Q

Which potential is longer: AP or EPSP

A

EPSP (20 msecs)
*AP (1-2 msecs)

26
Q

How do EPSP initiate an AP?

A

From 50 to 100 EPSPs must sum at the initial
segment (near-simultaneous)

27
Q

Which postsynaptic receptor is a coincidence detector? & what does it detect

A

NMDA receptor that detects 2 variants:
1)pre synaptic terminal is releasing glutamate
2)post synaptic cell is already depolarized

28
Q

NMDA VS AMDA receptors

A

NMDA
-at RMP pore is blocked my Mg+
-open pore is highly permeable to Ca2+ as well as
monovalent cations
-coincidence detector

AMDA
-EPSP
-glutamate opens pore
-permeable to Ca2+

29
Q

When is Mg+ expelled from NMDA receptors?

A

Receptors detects glutamate & that the postsynaptic cell is already depolarized

30
Q

How is the Mg+ held into place in the pore?

A

They are attracted by the negativity of the inside of the neurons
when depolarized: less negative

31
Q

What is the name of the process thought to be fundamentally the basis of learning & memory

A

Synaptic plasticity

32
Q

Which inotropic channel does synaptic plasticity involve?

A

NMDA receptors

33
Q

Name a model of synaptic plasticity & define it

A

Long-term potentiation (LTP): Highly active excitatory synapses become stronger (i.e. the EPSPs become larger)

34
Q

True or false?
EPSPs are smaller, hours after induction of LTP

A

False
EPSPs are larger, hours after induction of LTP

35
Q

What does excitotoxicity imply?

A

High concentrations of glutamate are toxic to
neurons

36
Q

Which ion influx & receptor are involved in excitotoxicity?

A

Calcium influx through NMDA receptors

37
Q

True or false?
Glutamate is a neurotoxin

A

True
Glutamate is a neurotoxin

38
Q

Why is the release of glutamate not generally toxic?

A

-Concentrations are being tightly regulated,
-Release is localized to specific synapses that are active

39
Q

When is excitotoxicity likely to contribute to neuronal degeneration?

A

-After a stroke or epileptic seizures
-In some neurodegenerative diseases.

40
Q

How does excitotoxicity cause neuronal death?

A

They are exposed to too much glutamate which causes the concentration of Ca2+ to increase for a long time which overexcites the neurones and results in neuronal death

41
Q

What is the main inhibitory neurotransmitter in the brain?

A

y-aminobutyric acid (GABA)

42
Q

Name the postsynaptic receptor responsible for the IPSP

A

GABAa receptor (ionotropic)

43
Q

The activation of GABAa receptors cause the influx of which ion?

A

Influx of Cl-

44
Q

What is the consequence of an influx of Cl- in the postsynaptic membrane?

A

Hyperpolarizes the postsynaptic membrane

45
Q

Name drugs that enhance the transmission of GABA

A

Benzodiazepines (xanax)
Barbiturates (pentobarbital)
Alcohol (ethanol)

46
Q

How can drugs enhance the transmission of GABA?

A

Bind to GABAa receptors

47
Q

True or false?
A neuron can be inhibitory and excitatory

A

False
A neuron can only be inhibitory or excitatory

48
Q

What determines whether-or-not a neuron fires an action potential at any given moment?

A

Depends on the relative balance of EPSPs and IPSPs
*VS output of the neuron is the all-or-none firing of action potentials down the axon

49
Q

What does the activation of mGluR’s by glutamate activate?

A

Generates a chemical signal , called a second messenger, inside the postsynaptic spine

50
Q

Name cellular proteins does the 2nd messanger activate

A

ion channels
protein kinases
transcription factors

51
Q

Name the metabotropic glutamate receptor

A

mGlurs

52
Q

True or False?
Glutamate & GABA activate only iontropic & metabotropic receptors, respectively

A

False
Glutamate & GABA activate BOTH iontropic & metabotropic receptors

53
Q

Name the metabotropic GABA receptor

A

GABAa receptor

54
Q

Name types of neurotransmitters interact mainly, or
entirely with metabotropic receptors

A

Neuromodulators:
dopamine
serotonin
norepinephrine
neuropeptides (endorphins)

55
Q

Define neuromodulators

A

They are not directly involved in the fast flow of neural information, but modulate global neural states, influencing alertness, attention and mood.

56
Q

Where do neurons that release neuromodulators often originate?

A

In small brainstem or midbrain nuclei
*Their axons project diffusely throughout the brain.

57
Q
A

PHGY 209 RME (11 decks)

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