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Foundation > Synapses and neurotransmitters > Flashcards

Synapses and neurotransmitters Flashcards

1
Q

NMJ is

A

NMJ is a specialized synapse consisting of a presynaptic neuron (a motor neuron) and the sarcolemma (membrane of the muscle fiber).

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2
Q

Nt found at NMJ is

A

always ACETYLCHOLINE

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3
Q

Binding of ACh at sarcolemma causes

A

NMJ is a specialized synapse consisting of a presynaptic neuron (a motor neuron) and the sarcolemma (membrane of the muscle fiber).

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4
Q

Neurotransmitters are released at the synapse when ____________

A

when the intracellular Ca2+ reaches a certain level.

The increase in intracellular Ca2+ level is caused by Ca2+ influx which is a result of membrane depolarization

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5
Q

Name the major neurotransmitters in the CNS
Excitatory - 4
Inhibitory - 2
Both - 3

A

Excitatory

  1. Glutamate
  2. Epin
  3. Ne
  4. Substance P

Inhibitory

  1. GABA
  2. Opioids

Both

  1. Acetylcholine
  2. Serotonin
  3. Dopamine
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6
Q

Excitatory neurotransmitters cause _____1______ while inhibitory neurotransmitters ____2_______

A
  1. membrane depolarization

2. do not cause depolarization/cause hyperpolarization in the postsynaptic neurons.

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7
Q

Dopamine and serotonin can be excitatory or inhibitory depending on _______________

A

the subtypes of receptors that they bind to on the postsynaptic membrane.

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8
Q

Name the different types of neurotransmitters:

A
  1. ACh
  2. monoamines eg serotonin, ne, ep, dopamine, histamine
  3. Amino acids eg. Glutamate, glycine, GABA
  4. Purines eg. adenosine
  5. Gases eg. Nitric oxide
  6. peptides eg opioids
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9
Q

___________ is the most common excitatory neurotransmitter in the BRAIN.

A

Glutamate

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10
Q

Glutamate is synthesized in the neuron from glutamine. Glutamine is supplied by __________

A

the astrocytes nearby.

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11
Q

Glutamate

Two types of receptor: ionotropic and metabotropic. Explain them both

A

Ionotropic receptor mediates the effect of glutamate faster than metabotropic receptor as it is ion channel compared to metabotropic receptor which requires a second messenger system

It is conceivable that the ionotropic glutamate receptors are associated with cation channels since it is excitatory. Binding of glutamate to these receptors causes cation influx that will eventually lead to membrane depolarization.

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12
Q

Glutamate

Explain the types of ionotropic glutamate receptors, and their effect.

A

3 types of ionotropic glutamate receptors

  1. NMDA
  2. AMPA
  3. Kainate

All are fast and excitatory - Ca+ Na+ channels

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13
Q

Glutamate

Explain the types of Metabotropic (G protein coupled) glutamate receptors, and their effect.

A

3 types of metabotropic glutamate receptors

  1. group I - slow excitatory - mGlu1,5
  2. group II - slow inhibitory - mGlu2,3
  3. group III - slow inhibitory - mGlu4,6,7,8
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14
Q

Glutamate and its receptors play important role in _______ and _________

A

synaptic plasticity and excitotoxicity.

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15
Q

Excessive glutamate in the synaptic cleft can be caused due to _________.

A

due to dysfunction in the uptake mechanism or excessive release of glutamate from the neuron as a result of neuronal death.
Glutamate in the synaptic cleft continuously stimulate the postsynaptic neurons by binding to the glutamate receptor, leading to more neuronal death by excitotoxicity.

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16
Q

How is glutamate formed?

A
  1. Glutamate is absorbed by astrocyte
  2. converted to glutamine
  3. it is taken up by neuron
  4. converted to glutamate
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17
Q

GABA and glycine difference

A

GABA in brain

Glycine in spinal cord

18
Q

__________ and __________ are the most common inhibitory neurotransmitters in the brain and spinal cord, respectively.

A

GABA and glycine

19
Q

GABA is synthesized from _________

A

glutamate

using the enzyme Glutamate decarboxylase

20
Q

GABA and glycine

Two types of receptor: ionotropic and metabotropic. Explain their speeds and

A

Ionotropic receptor mediates the effect of GABA and glycine faster than metabotropic receptor.

21
Q

Ionotropic GABA receptors are associated with ________ since it is _________

A

anion channels since it is inhibitory.

Binding of glutamate to these receptors causes anion influx that will hyperpolarize the membrane, making it harder for the neuron to depolarize.
GABAA and GABAC receptors are associated with chloride channel. GABAB receptors, when activated, inhibits Ca2+ channels and opens K+ channels, resulting in hyperpolarization of the membrane.

22
Q

What is the difference between ionotropic receptors of excitatory and inhibitory nt’s?

A

excitiatory - associated with CATION channels - causing depolarization

inhibitory - associated with ANION channels - causing hyperpolarization

23
Q

Benzodiazepine binds to

A

Benzodiazepine binds to GABAA receptor to cause hyperpolarization in the neuron to produce its sedative effect.

24
Q

What are the 3 main GABA channels?

A
  1. GABA-A : Cl- influx, IONOTROPIC
  2. GABA-B : Inhibit Ca2+, open K+. METABOTROPIC
  3. GABA-C : Cl- influx, IONOTROPIC

GABA-A and GABA-C receptors are associated with chloride channel, leading to hyperpolarization of neuron.

GABA-B receptors, when activated, results in hyperpolarization of the membrane.

25
Q

Difference between ionotropic and metabotropic receptors?

A

Ionotropic:
faster, ligand/nt binds,
- for excitatory Ca2+ in, Na+ in
- for inhibitory Cl- in

Metabotropic:
slower, second messenger system (proteins/genes/ca affect ionotropic receptors)

26
Q

GABA-A receptor has 6 binding sites for:

A
  • barbiturates
  • benzodiazepines
  • GABA
  • steroids
  • picrotoxin
  • chlorine

have similar effects if they bind to the same receptor

27
Q

Acetylcholine is synthesized from

A

acetyl CoA and choline.

28
Q

Acetylcholine is the only neurotransmitter released by the _______ and _________

A

preganglionic neuron at the ganglia

and

the only neurotransmitter released at the neuromuscular junction.

29
Q

Acetylcholine has two types of receptor: ionotropic and metabotropic. what are they called specifically?

A

ionotropic = nicotinic

metabotropic = muscarinic

30
Q

Acetylcholine

What are the different types of nicotinic and muscarinic receptors, and what are their effects?

A

Nicotinic - N1(NMJ) and N2(CNS) - EXCITATORY. (Associated with cation channels)

Muscarinic - M1,M2,M3,M4,M5 - EXCITATORY OR INHIBITORY

31
Q

Serotonin is synthesized from

A

tryptophan

32
Q

Serotonin has 2 types of receptors - ionotropic and metabotropic. Name them all and their effects.

A

General names: 5HT1 to 5HT7.

All metabotropic except for 3.

All excitatory except for 1 amd 5.

**inhibitory ones decrease cAMP in cell.

** To cause membrane depolarization, the intracellular cAMP level should increase and vice versa.

33
Q

Which of the serotonin receptors are antidepressants and antiemetic?

A

Antiemetic - 3.

Antidepressants - 2,6,7.

34
Q

Dopamine is synthesized from

A

L-tyrosine.

35
Q

All of dopamine’s receptors are ____________.

A

metabotropic.

Dopamine can be excitatory or inhibitory.

D1-like receptor family (D1 and D5 receptors) are excitatory (G alpha S protein),

D2-like receptor family is inhibitory (G alpha i protein).

36
Q

Dopamine is an important neurotransmitter in the

__________ and __________.

A

reward center (addiction) and for motor control (Parkinson’s disease).

In Parkinson’s disease, dopamine is low. Medication to increase it (increase synthesis, increase exocytosis) or maintaining (prevent breakdown or reuptake) the dopamine level

37
Q

Serotonin syndrome - explain the mechanism

A

Due to increase in serotonin, causes over excitation.
Causes: SSRI + MAOI, cocaie, triptans, etc.

Signs/symptoms: mental status changes, autonomic instability - shes hot and wet!

38
Q

Norepinephrine is synthesized from

A

dopamine.

39
Q

All norepinephrine receptors are

A

metabotropic

40
Q

What are the different types of receptors of norepinephrine?

A

alpha1,2 and beta1,2.

Except for α1 receptor which is linked to phospholipase C, the rest are linked to adenylyl cyclase.

Except for α2 receptor which is coupled to inhibitory G protein, the rest are coupled to stimulatory G proteins.

Except for β2 receptor which has higher affinity for ep>ne, the rest have the same affinity for both.

41
Q

general rule for ne-receptors

A

1’s = alpha1 and beta 1= excitatory, cause more vasoconstriction, increased heart rate

2’s = inhibitory, cause muscle relaxation,

alpha’s present in blood vessels, and bronchioles

beta’s present in heart.

Foundation (26 decks)

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