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Neuro Exam 1 > Neurotransmission > Flashcards

Neurotransmission Flashcards

1
Q

synapse

A

area where a neuron (cell) communicates with another neuron (or a cell)

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2
Q

electrical synapse

A

*relies on a current from one cell causing a VOLTAGE CHANGE in the connected cell
*made of gap junctions (connexons make up gap junctions)
*ions and other small molecules move from one cell to another
*present in smooth and cardiac muscle
*can connect: neurons to neurons; glia to glia; neurons to glia

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3
Q

chemical synapses

A

*transmission is mediated by diffusible chemical transmitters released by the presynaptic cell in response to a change in voltage
*metabotropic and ionotropic receptors are examples of chemical synapses

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4
Q

axosomatic synapses

A

*between axons and somas
*mostly inhibitory

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5
Q

axoaxonal synapses

A

*between one axon and another axon
*mostly inhibitory

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6
Q

axodendritic synapses

A

*between an axon and dendrites
*excitatory or inhibitory

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7
Q

ionotropic receptors

A

*neurotransmitter binds to and activates receptors that are ligand-gated ion channels
*ex: nicotinic Ach receptors
*in general, faster signaling than metabotropic

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8
Q

metabotropic receptors

A

*neurotransmitter binds to and activates receptors that act through second messengers
*ex: adrenergic receptors; muscarinic Ach receptors
*in general, slower signaling than ionotropic

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9
Q

sequence of events leading to release of neurotransmitter

A

1) calcium entry into presynaptic terminal (usually triggered by depolarization and activation of presynaptic voltage-sensitive calcium channels)
2) release of neurotransmitter stored in vesicles
3) vesicles are docked at the presynaptic membrane by tSNARE and vSNARE proteins
4) when calcium levels rise inside the cell, the vesicle is brought in close proximity to the plasma membrane and fusion occurs
5) vesicle contents (neurotransmitters) are released into the synaptic space between the pre and post-synaptic terminals

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10
Q

what determine the response of a neurotransmitter

A

the RECEPTOR

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11
Q

parathyroid hormone

A

increases calcium in extracellular fluids by releasing it from bone

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12
Q

7 classes of neurotransmitters

A

1) choline esters (acetylcholine)
2) biogenic amines (dopamine, epi, NE, serotonin, histamine)
3) amino acids (GABA, glutamate, glycine)
4) neuropeptides
5) small gases
6) purines
7) peptides

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12
Q

why does LOW calcium correlate with HYPER-excitability

A

the sensitivity of voltage-gated sodium channels is modulated by calcium, so low calcium makes them more sensitive

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12
Q

where are neurotransmitters synthesized?

A

in the cytosol of the presynaptic neuron

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13
Q

neurotransmitter: acetylcholine

A

*neurotransmitter at: NMJ, ANS presynaptic terminals, PANS postsynaptic terminal, some SANS postsynaptic terminals

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14
Q

removal of acetylcholine

A

acetylcholine esterase breaks down ACh in the synaptic cleft

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15
Q

3 important amino acid neurotransmitters

A

1) glutamate
2) glycine
3) GABA

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16
Q

neurotransmitter: glutamate

A

*major EXCITATORY neurotransmitter in CNS ionotropic receptors
*can be excitatory or inhibitory at metabotropic receptors

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17
Q

neurotransmitter: glycine

A

*inhibitory neurotransmitter
*concentrated in the spinal cord
*mechanism: increase Cl- conductance of the postsynaptic cell membrane (causing hyperpolarization; inhibiting excitabiity)
*all glycine receptors are ionotropic

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18
Q

neurotransmitter: GABA

A

*inhibitory neurotransmitter
*concentrated in brain and spinal cord
*ionotropic (GABA-A) receptors: increase Cl- conductance of the postsynaptic cell membrane (causing hyperpolarization; inhibiting excitability)
*metabotropic (GABA-B) receptors: increase K+ conductance of the postsynaptic cell membrane (causing hyperpolarization; inhibiting excitability)

19
Q

removal of glycine

A

reuptake by the presynaptic neurons and/or surrounding glia

20
Q

removal of GABA

A

reuptake by the presynaptic neurons and/or surrounding glia

21
Q

ammonia and GABA/glutamate/glutamine

A

*glia convert glutamate + GABA into glutamine (absorbs ammonia)
*important for management of ammonia produced by production of glutamate

22
Q

examples of biogenic amine neurotransmitters

A

*catecholamines (dopamine, norepinephrine, epinephrine)
*serotonin
*histamine

23
Q

what amino acid are the catecholamines (dopamine, NE, and epi) made from?

A

tyrosine

24
Q

what amino acid is serotonin made from?

A

tryptophan

25
Q

what amino acid is histamine made from?

A

histidine

26
Q

most receptors of biogenic amine neurotransmitters are ?

A

GPCRs; excitatory or inhibitory

27
Q

dopaminergic neurons & catecholamine synthesis

A

*secrete dopamine
*presynaptic nerve terminal contains tyrosine hydroxylase and dopa decarboxylase (but not the enzymes further down the pathway)

28
Q

adrenergic neurons & catecholamine synthesis

A

*secrete norepinephrine
*presynaptic nerve terminal contains tyrosine hydroxylase and dopa decarboxylase, PLUS dopamine beta-hydroxylase

29
Q

adrenal medulla & catecholamine synthesis

A

*secrete epinephrine
*contains the complete enzymatic pathway for catecholamine synthesis (tyrosine hydroxylase, dopa decarboxylase, dopamine beta-hydroxylase, and phenylethanolamine-N-methyltransferase)

30
Q

neurotransmitter: serotonin

A

*produced in the serotonergic neurons in brain and GI tract
*precursor to melatonin

31
Q

removal of serotonin

A

1) serotonin reuptake into nerve terminal
2) degradation by MAO

32
Q

removal/degradation of catecholamines

A

1) MAO (monoamine oxidase): located in presynaptic nerve terminals (on the outer mitochondrial membrane)
2) COMT (catechol-o-methyltransferase): widely distributed and concentrated in the liver, kidney, and GI tract

overall, REUPTAKE AND BREAKDOWN INSIDE THE CELL!

33
Q

important neuropeptides

A

*ACTH
*CCK
*substance P / bradykinen
*leptin

34
Q

neuropeptides - overview

A

*class of neurotransmitters synthesized as part of larger proteins and cleaved into smaller fragments
*made in soma and must be transported to the synapse (by kinesin)
*most receptors are GPCRs
*use negative feedback

35
Q

removal of neuropeptides

A

*slowly cleared by diffusion and breakdown
(tend to be long-acting)

36
Q

important gas neurtransmitter

A

nitric oxide

37
Q

neurotransmitter: nitric oxide

A

*made by arginine from nitric oxide synthetase
*simple diffusion into smooth muscle cells
*receptor = guanylyl cyclase
*acts to increase cGMP and DILATE smooth muscles (increasing local blood flow)

38
Q

removal of nitric oxide

A

rapid breakdown

39
Q

removal of purine neurotransmitters

A

breakdown and reuptake

40
Q

receptor for purine neurotransmitters

A

ionotropic or metabotropic

41
Q

receptor for lipid neurotransmitters (endocannabinoids)

A

metabotropic

42
Q

removal of lipid neurotransmitters (endocannabinoids)

A

enzymatic breakdown

43
Q

excitatory postsynaptic potentials (EPSPs)

A

depolarizing excitatory potentials are generated by the opening of non-selective cation channels (producing inward, depolarizing current)

44
Q

inhibitory postsynaptic potentials (IPSPs)

A

hyperpolarizing inhibitory potentials are generated by ion channels permeable to either K+ or Cl- (producing outward, hyperpolarizing current)

45
Q

temporal summation

A

*one of more presynaptic neurons transmit impulses in RAPID-FIRE ORDER
*first impulse produces EPSP, and before it can dissipate, another EPSP is triggered, adding on top of the first impulse

46
Q

spatial summation

A

*postsynaptic neuron is stimulated by a LARGE NUMBER OF TERMINALS SIMULTANEOUSLY
*many receptors are activated, each producing EPSPs, which can then add together

Neuro Exam 1 (22 decks)

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