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PHYSIOLOGY > Synaptic Transmission > Flashcards

Synaptic Transmission Flashcards

1
Q

It is the major process by which 💡electrical signals are 💡transferred between cells within the nervous system (or between neurons and muscle cells or sensory receptors).

A

Synaptic Transmission

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2
Q

Within the nervous system, synaptic transmission is usually conceived of as an 💡interaction between two neurons that occurs in a 💡point-to-point manner at specialized junctions called __.

A

synapses

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3
Q

Two main classes of synapses

A
  1. electrical

2. chemical

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4
Q

It is effectively a 💡low-resistance pathway between cells that allows current to flow directly from one cell to another and, more generally, allows the 💡exchange of small molecules between cells.

They are present between glial cells as well as between neurons.

LOW-PASS FILTERS

Simple and static

A

electrical synapses

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5
Q

It is the 💡morphological correlate of an electrical synapse.

These junctions are 💡plaque-like structures in which the plasma membranes of the coupled cells become closely apposed and filled with electron-dense material.

A

gap junction

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6
Q

Electrical synapses are __ (essentially no synaptic delay) and __ (i.e., current generated in either cell can f low across the gap junction to influence the other cell).

A

fast

bidirectional

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7
Q

Slow electrical events are __ than are fast signals such as action potentials. “Low-pass filters”

A

much more readily transmitted

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8
Q

One important role for neuronal gap junctions appears to be __.

A

synchronization of network activity

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9
Q

It also appears that the patterns of electrical coupling by gap junctions may be __.

A

highly specific

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10
Q

The properties of electrical synapses can be modulated by several factor:

A

voltage, intracellular pH, and [Ca++]

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11
Q

Chemical synaptic transmission was first demonstrated between the __ and the __ by a simple experiment by Otto Loewi.

A

vagus nerve

heart

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12
Q

What is the difference of the chemical synapses to electrical synapses?

A

There is no direct communication between the cytoplasm of the two cells.

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13
Q

Chemical intermediaries that mediates the interaction between the cells

A

Neurotransmitters

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14
Q

Chemical synapses are generally __, and thus one can refer to the presynaptic and postsynaptic elements.

A

unidirectional

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15
Q

It is often the 💡terminal portion of an axon and is packed with 💡small vesicles whose exact shape and size vary with the neurotransmitter they contain.

It has regions, known as 💡active zones, of electron dense material that corresponds to the proteins involved in transmitter release.

It has 💡mitochondria and 💡rough endoplasmic reticulum.

A

presynaptic element

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16
Q

It is also characterized by electron-dense material, which in this case corresponds to the 💡receptors for the neurotransmitter.

A

postsynaptic element

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17
Q

Types of chemical synapses:

A

axodendritic
axosomatic
axoaxonic dendrodendritic dendrosomatic

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18
Q

It is a complex  synaptic  arrangement   that  is  found  in the  inferior  olive  and  some  other  CNS  regions.

It involves both chemical and electrical synapses among the participating elements.

Two  dendritic  spines  are  coupled  by  a  gap  junction.

An  axon  terminal  packed  with  synaptic  vesicles  fills  the  upper  right  part  of  the  panel.

A

glomerulus

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19
Q

It is a complex synaptic arrangement in which cells form both electrical and chemical synapses with each other.

A

mixed synapses

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20
Q

It is a complex synaptic arrangement
in which an 💡axoaxonic synapse is made onto the 💡axon terminal and influences the efficacy of that terminal’s synapse with yet a 💡third element.

A

serial synapses

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21
Q

It is a complex synaptic arrangement

in which 💡both cells can release transmitter to 💡influence the other.

A

reciprocal synapses

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22
Q

Synaptic transmission is initiated by arrival of the (1)__ at the (2)__. The action potential (3__ the terminal, which causes (4)__. The subsequent rise in [Ca++] within the terminal triggers the (5)__. The transmitter is then expelled into the (6)__, diffuses across it, and binds to specific receptors on the (7)__. Binding of transmitter to receptors then causes the (8)__ in the postsynaptic membrane, which in turn results in changes in the potential and resistance of the postsynaptic membrane that alter the excitability of the cell.

A

(1) action potential
(2) presynaptic terminal
(3) depolarizes
(4) Ca++ channels to open
(5) fusion of vesicles containing neurotransmitter with the plasma membrane
(6) synaptic cleft
(7) postsynaptic membrane
(8) opening (or less often, the closing) of ion channels

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23
Q

The changes in membrane potential of the postsynaptic cell are termed __.

A

excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs)

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24
Q

its probability of firing action potentials

A

cell’s excitability

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25
Q

Why is the transmitter acts for only a very short time (milliseconds)?

A

because reuptake and degradation mechanisms rapidly clear the transmitter from the synaptic cleft

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26
Q

See anki

A

See anki

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27
Q

It is the signal for neurotransmitter release.

A

Calcium entry

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28
Q

Ca++ will enter the terminal only if there is a favorable __ to do so.

A

Electrochemical gradient

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29
Q

Extracellular [Ca++] is (1)__ relative to intracellular [Ca++], which favors entry into the terminal; however, during the peak of the action potential, the membrane potential is (2)__, and the (3)__ opposes the entry of Ca++ because of its (4)__. Thus, at the peak of the action potential, relatively little Ca++ enters the terminal because although the membrane is highly permeable to Ca++, the overall driving force is small.

A

(1) high
(2) positive
(3) voltage gradient
(4) positive charge

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30
Q

If the membrane potential is rapidly made (1)__ again (because of either the end of the action potential or by adjusting the voltage clamp), Ca++ rushes into the terminal as a result of the (2)__ (which arises instantaneously on repolarization) and the (3)__ (which remains high because it takes the Ca++ channels several milliseconds to close in response to the new membrane potential), thereby resulting in release of transmitter and a postsynaptic response

A

(1) negative
(2) large driving force
(3) high membrane permeability to Ca++

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31
Q

It is small round or irregularly shaped organelles that stores the neurotransmitters.

A

Synaptic vesicles

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32
Q

It is an action potential in a motor neuron causes a large depolarization in the postsynaptic muscle.

A

end plate potential (EPP) (equivalent to an EPSP in a neuron)

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33
Q

Why is the EPP amplitude is reduced under conditions of low extracellular [Ca++]?

A

because the presynaptic Ca++ current is reduced, leading to a smaller rise in intracellular [Ca++], and transmitter release is proportional to [Ca++]

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34
Q

It is a small spontaneous depolarizations of the postsynaptic membrane that is observed when EPP is flactuating.

A

miniature end plate potentials (mEPPs)

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35
Q

It is a specific site where the small vesicles that contain nonpeptide neurotransmitters only can fuse with the presynaptic membrane

A

active zones

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36
Q

As with other exocytotic processes, neurotransmitter release involves:

A

SM (sec1/Munc18-like)

SNARE (soluble N-ethyl maleimide-sensitive factor attachment protein receptor) proteins
v-SNARES in the vesicle membrane
t-SNARES in the (target) presynaptic plasma membrane

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37
Q

Example of v-SNARE

A

synaptobrevin

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38
Q

Examples of t-SNARES;

A

syntaxin and SNAP-25

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39
Q

Their 💡zipper-like interactions with the assistance of 💡SM proteins bring the vesicle membrane and the presynaptic plasma membrane close together before fusion.

A

synaptobrevin
syntaxin
SNAP-25

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40
Q

It is a toxin produce by 💡Clostridium botulinum that targets SNARE proteins which disrupt synaptic transmission.

A

Botulinum toxins

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41
Q

It is a SNARE protein that acts as the 💡Ca++ sensor and, even more specifically, that the second of its two cytoplasmic domains contains the Ca++ binding site. Its binding with calcium will trigger the 💡fusion of a docked vesicle and allowing release of its neurotransmitter.

It is degraded by botulinum toxins.

A

synaptotagmin

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42
Q

During synaptic transmission, __ to release their contents into the synaptic cleft.

A

vesicles must fuse with the plasma membrane

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43
Q

Two distinct mechanisms by which vesicles are retrieved after release of their neurotransmitter content:

A

endocytotic pathway

“kiss and run.”

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44
Q

It involves transient fusion of the vesicle to the synaptic membrane which will leads to the formation of a pore through which the transmitter is expelled, but there is no wholesale collapse of the vesicle into the membrane.

More rapid recycling mechanism

A

Kiss and run

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45
Q

Following vesicle fusion the neurotransmitter molecules are released and diffuse across the synaptic cleft (a very rapid process) and bind to receptors on the postsynaptic membrane which will lead to the opening of?

A

ion channels

ligand gated (opening and closing are primarily controlled by the binding of neurotransmitter)

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46
Q

It is a channel that are both ligand and voltage gated

A

NMDA (N-methyl-Daspartate) channels

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47
Q

“fast” synaptic transmission

A

ionotropic receptors

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48
Q

“slow” synaptic transmission

A

metabotropic receptors

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49
Q

EPSPs are always __, and IPSPs are usually __.

A

depolarizing potentials

hyperpolarizing

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50
Q

If acetylcholine-gated channels open when the membrane is at its (1)__, a large inward (2)__ and a small outward (3) __ will flow through the (4)__ thereby resulting in a net inward current, which acts to (5)__ the membrane.

A

(1) resting potential
(2) Na+ current
(3) K+ current
(4) acetylcholine channel,
(5) depolarize

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51
Q

The net inward current that results from opening such channels is called __.

**refer to previous card

A

excitatory postsynaptic current (EPSC)

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52
Q

It is the potential at which there is 💡no EPSP (or EPSC).

** if the membrane potential is depolarized enough, there will be a point at which the Na+ and K+ currents through the channel are equal and opposite, and thus there is no net current and no EPSP.
Hyperpolarize

A

reversal potential

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53
Q

It is a 💡key criterion for demonstrating the 💡chemical-gated as opposed to the voltage-gated nature of a synaptic response because currents through voltage-gated channels do not reverse, except at the Nernst potential of the ion for which they are selective (and then only if the channel is open at that potential).

A

Reversal potential

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54
Q

What is the difference of IPSP to EPSP?

This difference makes IPSPs to have a reversal potential equal to the Nernst potential of the ion carrying the underlying current.

A

IPSP channels are permeable to only a single ionic species, either Cl− or K+.

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55
Q

The key distinction between inhibitory and excitatory synapses (and IPSPs and EPSPs) is (1)__: EPSPs (2)__ the probability, whereas IPSPs (3) the probability.

A

(1) how they affect the probability of the cell firing an action potential
(2) increase
(3) decrease

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56
Q

It is the ratio of 💡EPSP amplitude to the amplitude needed to reach the 💡threshold to trigger an action potential.

It quantifies the strength of the excitatory synapses.

A

Safety factor

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57
Q

Most synapses have __, and thus it takes the summed EPSPs of multiple active synapses to trigger an action potential in the postsynaptic neuron.

A

low safety factors (<1)

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58
Q

These are diseases of the neuromuscular junction where the EPPs are reduced such that the safety factor can fall below 1, and thus the EPPs sometimes fail to trigger action potentials in the muscle fibers, leading to weakness.

A

myasthenia gravis and Lambert-Eaton syndrome

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59
Q

It refers to the fact that EPSPs that are separated by a latency less than their duration can 💡sum.

EPSPs  in  response  to  two  spikes  in  the  same  axon  occurring  in rapid  succession

A

Temporal summation

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60
Q

It refers to the fact that synaptic potentials generated by 💡different synapses can interact.

Responses  evoked by  synapses  that  are  💡electrically  distant  from  each  other  (1  and  3).

The combined EPSP amplitude may then reach threshold and lead to spiking of the cell.

A

Spatial summation

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61
Q

That is, when synapse 2 is active, channels are opened in the cell membrane, which means that it is more leaky. Therefore, when synapse 4 is also active, more of its EPSC will be lost (shunted) through the dendritic membrane, and less current will be left to travel down the dendrite to the initial segment. The result is that synapse 4 causes a smaller EPSP at the initial segment than it would have generated in isolation. Nevertheless, the combined EPSP is still larger than an EPSP caused by either synapse 2 or 4 alone.

A

Sublinear  summation

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62
Q

Modulation of synaptic activity

A

Paired-pulse facilitation
Posttetanic potentiation
Synaptic depression

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63
Q

When a presynaptic axon is stimulated twice in rapid succession, it is often found that the 💡postsynaptic potential evoked by the 💡second stimulus are 💡larger in amplitude than the one evoked by the first.

Relatively rapid and short-lasting change in synaptic efficacy

A

paired-pulse facilitation (PPF)

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64
Q

What is the difference if PPF and temporal summation?

A

Temporal summation, in which two EPSPs overlap and sum to a larger response; with PPF the second EPSP itself is greater in size.

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65
Q

It is similar to PPF; however, in this case the 💡responses are compared before and after stimulation of the presynaptic neuron tetanically (tens to hundreds of stimuli at a high frequency).

Such a tetanic stimulus train causes an increase in synaptic efficacy

A

Posttetanic potentiation (PTP)

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66
Q

What is the similarity and difference of PTP and PPF?

A

PTP, like PPF, is an enhancement of the postsynaptic response, but it lasts longer

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67
Q

It is thought to reflect 💡depletion of the number of releasable presynaptic vesicles.

A

Synaptic Depression

68
Q

A postsynaptically related cause of synaptic depression can be __ in the postsynaptic membrane.

A

desensitization of the receptors

69
Q

Both potentiation and depressive processes can occur at the same synapse.

A

True

70
Q

Presynaptic receptors can be either ionotropic or metabotropic.

A

True

71
Q

The activation of presynaptic (1) __ will (2)__ alter the electrical properties of the presynaptic terminal and cause rapid transient (millisecond time scale) changes in the probability of vesicle release (although they too can have much longer lasting effects).

A

(1) ionotropic receptors

(2) directly

72
Q

It refers to occasions when binding of presynaptic receptors leads to a 💡decrease in release of transmitter

A

Presynaptic inhibition

73
Q

Presynaptic inhibition mechanisms:

A
  1. opening of channels decreases membrane resistance and creates a current shunt.
  2. change in membrane potential caused by the opening of presynaptic ionotropic channels.
74
Q

Opening of channels decreases membrane resistance and creates a current shunt.

A

shunt acts to divert the current

lessens the depolarization of the active zone

less activation of Ca++ channels, less Ca++ entry, and less release of transmitter

75
Q

Change in membrane potential caused by the opening of presynaptic ionotropic channels.

A

small depolarization

inactivation of voltage-gated Na+ channels

lessening of the action potential–associated current and transmitter release

76
Q

It is a process where 💡repetitive stimulation of certain synapses in the brain can also produce more 💡persistent changes in the efficacy of transmission at these synapses.

A

long-term potentiation or long-term depression.

77
Q

T he increased synaptic efficacy that occurs in long-term potentiation probably involves both presynaptic (greater transmitter release) and postsynaptic (greater sensitivity to transmitter) changes, in contrast to the short-term changes that involve changes only in presynaptic function.

A

True

78
Q

It is an early step required for initiating the changes that result in long-term enhancement of the response of the postsynaptic cell to neurotransmitter.

A

Entry of calcium into the postsynaptic region

79
Q

Entry of calcium occurs at the post synaptic region is through:

A

NMDA receptors

AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors

80
Q

It is activated by 💡calcium entry at post synaptic region.

It is a multifunctional 💡protein kinase that is present in very high concentrations in postsynaptic densities.

It is believed to phosphorylate proteins that are essential for the induction of long-term potentia-tion.

A

Ca++-calmodulin kinase II

81
Q

These are the substances that 💡mediate chemical signaling between neurons.

A

Neurotransmitters

82
Q

For a substance to be considered a neurotransmitter, it must meet several generally recog-nized criteria;

A
  1. the substance must be demonstrated to be present in the presynaptic terminal
  2. the cell must be able to synthesize the substance
  3. It should be released on depolarization of the terminal.
  4. Finally, there should be specific receptors for it on the postsynaptic membrane
83
Q

It is a general term to describe 💡both synaptic and nonsynaptic signaling between cells.

A

Neurotransmission

84
Q

3 major categories of the neurotransmitters:

A
  1. small-molecule transmitters
  2. peptides
  3. gaseous transmitters
85
Q

These are the small-molecule neurotransmitters

A

acetylcholine, amino acids, biogenic amines, and purines.

86
Q

PNS: neuromuscular junctions, at sympathetic and para-sympathetic ganglia, and of the postganglionic fibers from all parasympathetic ganglia and a few sympathetic ganglia.

CNS: It is the trans-mitter at neurons in some brainstem nuclei, in several parts of the basal forebrain (septal nuclei and nucleus basalis) and basal ganglia, and in the spinal cord.

A

Acetylcholine

87
Q

It a form of dementia in which memory function is gradually and progressively lost due to degeneration of cholinergic neurons from the basal forebrain.

A

Alzheimer’s disease

88
Q

It is an enzyme that synthesizes acetylcholine.

A

choline acetyltransferase

89
Q

Two precursors of acetylcholine:

A

acetyl coenzyme A and choline

90
Q

It is an enzyme that terminates the action of acetylcholine.

A

acetylcholinesterase (highly concentrated in the synaptic cleft)

91
Q

It is the 💡product of acetylcholine hydrolysis that is taken up by an 💡Na+ symporter in the presynaptic membrane for the 💡resynthesis of acetylcholine.

A

Choline

92
Q

It is a drug that interfere with 💡acetylcholinesterase and thereby enhance the action of acetylcholine by prolonging its presence at its synapses.

It is used to treat myasthenia gravis.

A

anticholinesterases

93
Q

It is an 💡autoimmune disease in which 💡antibodies bind to acetylcholine receptors at the neuromuscular junction, thereby disrupting their functionality and causing them to be more rapidly degraded.

The eduction in receptors leads to severe weakness and ultimately paralysis.

A

Myasthenia gravis

94
Q

Three most important amino acids that acts as a neurotransmitter.

A

glutamate, glycine, and GABA

95
Q

It is the neurotransmitter at the overwhelming majority of 💡excitatory synapses throughout the CNS.

It has a key role in multiple metabolic pathways, and it is a 💡precursor to GABA.

It is the 💡major excitatory CNS neurotransmitter

It is a potent 💡neurotoxin at high concentrations

A

Glutamate

96
Q

What is the action of glutamate to cells?

A

It causes depolarization

97
Q

It is the major inhibitory transmitter throughout the nervous system.

A

GABA

98
Q

It is an enzyme that catalyze the synthesis of GABA from glutamate.

A

glutamic acid decarboxylase

99
Q

Most notable brain regions that contain large numbers of 💡GABAergic projection neurons.

A

spiny neurons of the striatum

Purkinje cells of the cerebellar cortex

100
Q

It is a neurotransmitter that functions as an 💡inhibitory neurotransmitter in a much more 💡restricted territory (predominantly at spinal cord).

It acts as a 💡co-transmitter at excitatory 💡NMDA-type glutamate receptors.

A

Glycine

101
Q

Fluctuations in glycine levels may also be an important modulator of NMDA-mediated synaptic transmission.

A

True

102
Q

After GABA and glycine are released from the presynaptic terminal, they are taken back up into the nerve terminal and neighboring glia by __.

A

high-affinity Na+-Cl−–coupled membrane transporters (solute carrier 6 (SLC6) family)

103
Q

Transport of the GABA and glycine into the cell is accomplished by (1)__ with (2)__ Na+ and (3)_ Cl− ion.

A

(1) symport
(2) two
(3) one

104
Q

Biogenic amines

A

Cathecholamines:
dopamine
norepinephrine (noradrenaline)
epinephrine (adrenaline)

serotonin (5-hydroxytryptamine [5-HT])
histamine

105
Q

-

A

Dopamine

106
Q

-

A

Norepinephrine

107
Q

-

A

Epinephrine

108
Q

-

A

Serotonin

109
Q

-

A

Histamine

110
Q 
Tyrosine
(1)
L-dopa
(2)
Dopamine
(3)
Norepinephrine
(4)
Epinephrine
A
  1. tyrosine hydroxylase
  2. dopa-decarboxylase
  3. dopamine β-hydroxylase
  4. phenylethanolamineN-methyl transferase
111
Q 
Tryptophan 
(1)
5-hydroxytryptophan
(2)
Serotonin
A
  1. tryptophan 5-hydroxylase

2. aromatic L-amino acid decarboxylase

112
Q

It catalyze the conversion of histidine to histamine.

A

histidine decarboxylase

113
Q

Glutamate inside  the  presynaptic  terminal  is  packaged  into  synaptic vesicles  by  a  second  set  of  glutamate  transporters known as __.

A

vGLUTs  (vesicular glutamate transporters)

114
Q

Transport of  glutamate  into  synaptic  vesicles  by  vGLUT  is  driven  by the __,  the  electrochemical  gradient for  which  having  been  established  by  an  H+-ATPase  in  the vesicle  membrane.

A

countertransport  of  H+  ions

115
Q

Removal of synaptically released biogenic amines is generally accomplished by reuptake into glia and neurons via transporters belonging to the

A

Na+-Cl−–dependent transporter family

116
Q

These are enzymes that degrades catecholamines.

A

monoamine oxidase and catechol Omethyltransferase

117
Q

It has the potential to act as a transmitter or cotransmitter at synapses in the peripheral and central nervous systems.

It is found in all synaptic vesicles and thus is co-released during synaptic transmission.

It has its own receptors, which like standard neurotransmitters, are coupled to ion channels, but it can also modify the action of other neurotransmitters with which it is co-released, including norepinephrine, serotonin, glutamate, dopamine, and GABA.

A

ATP

118
Q

ATP is broken down by __ and __ to adenosine, which can be taken up again by the presynaptic terminal.

A

ATPases

5-nucleotidase

119
Q

It inhibit  💡dopamine  receptors  on postsynaptic  membranes  and  thus  diminish  the  effects of  dopamine  released  from  presynaptic  nerve  terminals. 

Overdoses  of  such  antipsychotic  drugs  can  produce  a temporary  💡parkinsonian-like  state.

A

Chlorpromazine

120
Q

When neuropeptides are co-released with other transmitters, they may act synergistically or antagonistically.

A

True

121
Q

In the spinal cord, these neuropeptides act 💡synergistically with 💡glutamate and with 💡substance P 💡to enhance the action of serotonin and they 💡antagonize norepinephrine’s action at other synapses.

A

tachykinins and calcitonin gene–related peptide (CGRP)

122
Q

The slower release and lack of rapid reuptake mean that neuropeptides can act for long durations, diffuse over a region of brain tissue, and affect all cells in that region (that have the appropriate receptors) rather than just acting at the specific synapse at which it was released.

A

True

123
Q

These are drugs derived from the juice of the 💡opium poppy.

A

Opiates

124
Q

Compounds that are not derived from the opium poppy but that exert direct effects by binding to opiate receptors are called __.

They inhibit neurons in the brain involved in the 💡perception of pain.

They are the most potent 💡analgesic (pain-relieving)

A

opioids

125
Q

Opioids are defined as compounds whose effects are stereospecifically antagonized by a morphine derivative called __.

A

naloxone

126
Q

These are three major classes of endogenous opioid peptides in mammals:

A

enkephalins, endorphins and dynorphins

127
Q

These are the simplest opioids; they are pentapeptides.

A

Enkephalins

128
Q

These are somewhat 💡longer peptides that contain one or the other of the 💡enkephalin sequences at their N-terminal ends.

A

Dynorphins and endorphins

129
Q

It is a peptide consisting of 11 amino acids.

It is involved in 💡pain transmission and has a powerful effect on smooth muscle.

it is the transmitter used at synapses made by 💡primary sensory neurons (their cell bodies are in the dorsal root ganglia) with spinal interneurons in the dorsal horn of the spinal column, and thus it is an example of a peptide acting as a 💡primary transmitter at a synapse.

A

Substance P

130
Q

These are opioids that act to decrease the release of 💡substance P at these synapses and thereby 💡inhibit the pathway for pain sensation at the first synapse in the pathway.

A

Enkephalins

131
Q

These are 💡neither packaged into synaptic vesicles nor released by exocytosis.

Instead, these are 💡highly permeant and 💡simply diffuse from synaptic terminals to neighboring cells after synthesis, their synthesis being triggered by depolarization of the nerve terminal (the influx of Ca++ activates synthetic enzymes).

A

Gas neurotransmitters

132
Q

Examples of gaseous neurotransmitters.

A

nitric oxide (NO) and carbon monoxide (CO)

133
Q

It is a 💡transmitter at synapses between inhibitory motor neurons of the enteric nervous system and gastrointestinal smooth muscle cells

It also functions as a neurotransmitter in the CNS.

It functions as a 💡cellular signal transduction molecule (by regulating guanylyl cyclase) both in neurons and in nonneuronal cells

A

nitric oxide (NO)

134
Q

It is an enzyme that 💡catalyzes the production of NO as a product of the oxidation of 💡arginine to citrulline.

A

NO synthase

135
Q

NO synthase is stimulated by an increase in __.

A

cytosolic [Ca++]

136
Q

Neurotransmitter receptors are members of one of two large groups or families of proteins:

A

Ligand-gated ion channels (ionotropic receptors) and G protein-coupled receptors (metabotropic receptors )

137
Q

Almost all classic neurotransmitters and neuropeptides have at least one metabotropic-type receptor. Many of the classic neurotransmitters also have at least one ionotropic receptor.

A

True

138
Q

These are protein complexes that both have an extracellular binding site for the transmitter and form an 💡ion channel (pore) through the cell membrane.

A

Ionotropic receptors

139
Q

Binding of the neurotransmitter alters (usually increases) the probability of the ion channel being in the open state and thus typically results in postsynaptic events that are rapid in both onset and decay, with a duration of several milliseconds.

A

True

140
Q

See anki

A

See anki

141
Q

These receptors mediate postsynaptic phenomena that have a 💡slow onset and that may persist from hundreds of milliseconds to minutes.

A

metabotropic receptors

142
Q

Two major group of acetylcholine receptors:

A

Nicotinic receptors (ionotropic cys-loop family)

muscarinic receptors (metabotropic family of receptor proteins)

143
Q

These are acetylcholine receptor that mediate 💡synaptic transmission at the neuromuscular junction.

These receptor contains a relatively 💡nonselective cationic channel, so binding of acetylcholine produces an EPSP.

A

nicotinic receptors

144
Q

The junctional receptors (nicotinic) all use the __, whereas centrally located receptors (nicotinic) use one of the α subunits between __.

A

α1 subunit

α2 and α10

145
Q

These five known muscarinic subtypes of acetylcholine receptors:

A

M1 to M5

146
Q

These are muscarinic subtypes of acetylcholine receptors that are coupled to 💡pertussis toxin–insensitive G proteins

A

M1, M3, and M5

147
Q

These are muscarinic subtypes of acetylcholine receptors that are coupled to 💡pertussis toxin–sensitive G proteins.

A

M2 and M4

148
Q

Glycine-mediated inhibitory synapses are common in the __, whereas GABAergic synapses make up the majority of inhibitory synapses in the __.

A

spinal cord

brain

149
Q

Both glycine and GABA have ionotropic receptors that are members of the cys-loop family, each of these receptors has a Cl− channel.

A

True

150
Q

Glycine receptors are pentamers and may be heteromers of α and β subunits (3 : 2 ratio) or homomers.

The β subunit seems to bind to an intracellular scaffold protein called that appears to help localize receptors to the postsynaptic site.

A

gephyrin

151
Q

T he α subunit contains the glycine binding site, and there are four genes coding for distinct α subunits (and splice variants of each).

A

True

152
Q

GABA has two separate ionotropic receptors coded for by distinct sets of genes.

A

GABA(A) and GABA(C)

153
Q

These are GABA ionotropic receptors that is being targeted by the drugs: 💡benzodiazepines and barbiturates which enhance opening of the receptors’ Cl− channels in response to GABA.

A

GABA(A) receptors

154
Q

These are GABA ionotropic receptors that are structurally similar to GABA(A) receptors but have a distinct pharmacological profile (e.g., they are 💡not affected by benzodiazepines) and are coded for by a separate set of genes (ρ1, ρ2, and ρ3).

A

GABA(C) receptors

155
Q

These are GABA 💡metabotropic receptors where binding of GABA to this receptor activates a heterotrimeric GTPbinding protein which leads to 💡activation of K+ channels and hence 💡hyperpolarization of the postsynaptic cell, as well as 💡inhibition of Ca++ channels (when located presynaptically) and thus a reduction in release of transmitter.

A

GABA(B) receptor

156
Q

Glutamate has both ionotropic and metabotropic receptors.

A

True

157
Q

These are ionotropic receptor subtypes of glutamate:

These are excitatory and contain a cationic-selective channel and are permeable to 💡Na+ and K+, but 💡only a subset allow Ca++ to pass.

A

AMPA, kainate, and NMDA

158
Q

These are formed from GluR1 to GluR4 subunits.

A

AMPA receptors

159
Q

These require either KA1 or KA2 and GluR5 to GluR7 subunits.

A

kainate receptors

160
Q

These all have NR1 subunits plus some combination of NR2 and NR3 subunits.

A

NMDA receptors

161
Q

AMPA and kainate receptors behave as classic ligand-gated channels

A

True

162
Q

NMDA channels are different. First, they require 💡binding of both glutamate and glycine to open. Second, they display 💡voltage sensitivity as a result of Mg++ blockade of the channel. That is, at resting (or more negative) membrane potentials, a 💡Mg++ ion blocks the entrance to the channel so that even when glutamate and glycine are bound, no current flows through the channel. If the cell is depolarized the Mg++ block is relieved and current can flow through the channel.

A

True

163
Q

Purines have two receptor families:

These receptors form a cationic channel that is permeable to Na+, K+, and Ca++.

A

an ionotropic (P2X) and a metabotropic (P2Y) family

164
Q

These are coded for by 10 genes, but only 6 are expressed in the human CNS.

They have the typical features of G protein–coupled receptors and are known to 💡activate K+ currents and 💡modulate both NMDA and voltage-gated Ca++ currents.

They predominate on astrocytes.

A

Metabotropic purine receptors (P2Y receptors)

165
Q

Receptors for the various biogenic amines [except one class of serotonin receptors (5-HT3)] are all 💡metabotropic-type receptors. Thus, these neurotransmitters tend to act on relatively long time scales by generating slow synaptic potentials and by initiating second messenger cascades.

A

Biogenic Amine Receptors: Serotonin, Dopamine, Noradrenaline, Adrenaline, Histamine

Neuropeptide Receptors

166
Q

NO and CO do not bind to receptors. One way they do affect cell activity is to activate enzymes involved in second messenger cascades, such as guanylyl cyclase.

A

Gas Neurotransmitter Receptors

PHYSIOLOGY (13 decks)

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