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2007PSY > Week 4 - topic 3 > Flashcards

Week 4 - topic 3 Flashcards

1
Q

Common neurotransmitters and their general effects on the CNS and PNS

A

*look up image

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2
Q

Amino acid neurotransmitters

A

In the brain, most synaptic communication is accomplished by two amino acid neurotransmitters:

Glutamate = excitatory effects on cells.
Gamma-aminobutyric acid, or GABA = inhibitory effects on cells

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3
Q

Glutamate - production, storage and release

A
  • Synthesised from a precursor amino acid (glutamine) by an enzyme (glutaminase)
  • Glutamate is pumped into synaptic vesicles by vesicle glutamate transporters, and released from presynaptic neuron following an action potential
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4
Q

Glutamate - receptors

A 
NMDA receptor, (ionotropic – controls calcium ion channel) (Voltage and neurotransmitter dependent ion channel - requires particular neurotransmitter for binding and particular charge to open)
AMPA receptor, (ionotropic – controls sodium ion channel)
Kainate receptor (ionotropic –controls sodium ion channel)
Metabotropic glutamate receptor (metabotropic)
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5
Q

Glutamate - Reuptake and deactivation

A

Glutamate is removed from the synapse by excitatory amino acid transporters (reuptake) and broken down by enzymes (enzymatic deactivation)

If glutamate isn’t removed from the synapse, glutamate excitotoxicity occurs = prolonged overexcitation which damages neurons.

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6
Q

GABA - production, storage and release

A
  • It is produced from a precursor (glutamic acid) by the action of an enzyme (GAD)
  • GABA is pumped into synaptic vesicles by the vesicle GABA transporter, and released from presynaptic neuron following an action potential
  • GABA-secreting neurons have an inhibitory influence to help keep brain stable
  • A lack of inhibition might be related to seizure disorders
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7
Q

GABA - receptors

A
  • GABAA receptors are ionotropic and control chloride channels (Cl-).
  • They have at least five different binding sites, and other ligands (e.g. hormones) bind to these additional sites
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8
Q

GABA - Reuptake and deactivation

A
  • GABA is removed from the synapse by proteins that are GABA transporters (reuptake).
  • GABA is broken down by an enzyme (enzymatic deactivation)
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9
Q

Non-amino acid neurotransmitters

A
  • Although amino acid neurotransmitters like GABA and Glutamate are widespread throughout the brain, other neurotransmitters (i.e. non-amino acid ones) are located in distinct pathways in the brain.
  • Furthermore, whereas amino acid neurotransmitters are most concerned with information transmission, non-amino acid neurotransmitters tend have modulating effects.
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10
Q

Acetylcholine (ACh) - pathways

A 
ACh functions in both the CNS and PNS
PNS = primary neurotransmitter involved in muscle contraction
CNS = found in specific locations and pathways: 
Dorsolateral pons (REM sleep - dreaming)
Basal forebrain (facilitate perceptual learning)
Medial septum (memory formation)
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11
Q

Acetylcholine (ACh) - production, storage and release

A
  • Synthesised from two precursors (choline and acetyl coenzyme A) by an enzyme (ChAT)
  • Loaded into vesicles by the vesicle ACh transporters and released from vesicles following an action potential
  • Botox prevents the release of ACh when injected into a muscle. Also used to to treat migraines and severe muscle contractions.
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12
Q

Acetylcholine (ACh) - receptors

A
  • Ionotropic ACh receptors stimulated by nicotine = nicotinic receptor (found in PNS)
  • Metabotropic ACh receptors stimulated by muscarine (found in the mushroom Amanita muscaria) = muscarinic receptor (predominate in CNS)
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13
Q

Acetylcholine (ACh) - reuptake and deactivation

A
  • Deactivated by the enzyme acetylcholinesterase (AChE) which is present in the postsynaptic membrane.
  • Once broken down, ACh parts (choline) are returned to presynaptic neurons via reuptake via choline transporters.
  • > Drugs are used to deactivate AChE.
    e. g. AChE inhibitors used to treat myasthenia gravis (autoimmune, neuromuscular disease that causes weakness in the skeletal muscles)
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14
Q

Monoamine neurotransmitters

A
  • Monamines are neurotransmitters produced in cell bodies mainly in the thalamus, hypothalamus, mid brain and brain stem, and whose axons project widely throughout the brain.
  • Monoamine neurotransmitters include serotonin, dopamine, histamine norepinephrine, and epinephrine, all of which have wide ranging functions.
  • For instance, you have probably heard about serotonin in relation to mood and depression, but it is also involved in digestion.
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15
Q

Dopamine (DA)

A

Produces both EPSPs and IPSPs

Impacts movement, attention, learning, and reinforcing effects of drugs

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16
Q

Dopamine (DA) - pathways

A

Originate from midbrain structures (substantia nigra and ventral tegmental area):

  • Nigrostriatal system (movement control)
  • Mesolimbic system (reward and reinforcement)
  • Mesocortical system (memory and problem solving)
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17
Q

Dopamine (DA) - production

A
  • Dopamine is a catecholamine - subclass of monoamines
  • Producing catecholamines requires several enzymatic steps:
  • > Precursor molecule which is modified slightly step by step to reach final shape
  • > enzymatic process, modifications are made by enzyme
  • look up image
18
Q

Dopamine (DA) - storage and release

A
  • Vesicle monoamine transporters move dopamine into synaptic vesicles for release into the synapse following an action potential.
19
Q

Dopamine (DA) - receptors

A

Five Metabotropic types of receptors

D1, D2, D3, D4, and D5

20
Q

Dopamine (DA) - reuptake and deactivation

A
  • Dopamine transporters remove dopamine from the synapse (reuptake)
  • Several drugs serve as dopamine agonists: amphetamine, methamphetamine, cocaine, and Ritalin.
  • Deactivation of catecholamines is regulated by an enzyme called monoamine oxidase (MAO)
21
Q

Norepinephrine (NE) - pathways

A
  • Norepinephrine is found in both the CNS and PNS
  • The most important system originates in the locus coeruleus located in the dorsal pons – related to vigilance
  • catecholamine subclass
22
Q

Norepinephrine (NE) - production, storage and release

A
  • very similar process as dopamine, synthesised from the dopamine molecule using a second enzyme

Differences:

  • NE is synthesised in the synaptic vesicle
  • Most neurons releasing NE release it via axonal varicosities (beadlike swellings of the axonal branches)
  • look up image
23
Q

Norepinephrine (NE) - receptors

A
  • Four types of adrenergic receptors (norepinephrine and epinephrine)
  • All metabotropic
  • Found in neurons in CNS and in various organs of body
24
Q

Norepinephrine (NE) - reuptake and deactivation

A
  • Norepinephrine transporters remove excess norepinephrine from the synapse (reuptake)
  • Excess norepinephrine is deactivated by an enzyme called monoamine oxidase, type A.
25
Q

Serotonin (5-HT) - pathways

A
  • Serotonin = regulation of mood, control of eating, sleep (and dreaming), arousal, and pain regulation
  • Clusters originate in the raphe nuclei of the midbrain, pons, and medulla
  • > Dorsal raphe project to cerebral cortex + the basal ganglia
  • > Median raphe project to cerebral cortex + part of the hippocampal formation
26
Q

Serotonin (5-HT) - production, storage and release

A
  • Synthesised from an amino acid
  • Loaded into synaptic vesicle by vesicle monoamine transporter
  • Released from axonal varicosities
  • look up image
27
Q

Serotonin (5-HT) - receptors

A
  • At least nine different types of serotonin receptors (autoreceptors and postsynaptic receptors).
  • All are metabotropic except one.
  • the ionotropic receptor is involved in nausea and vomiting and helps with production of IPSP’s
28
Q

Serotonin (5-HT) - reuptake and deactivation

A
  • Serotonin transporter removes 5-HT from the synapse (reuptake)
  • Drugs that inhibit uptake of serotonin play important role in treatment of depression (e.g. Prozac)
  • 5-HT can be deactivated by monoamine oxidase (enzymatic deactivation).
29
Q

Histamine

A
  • Found in only one place in the brain: the tuberomammillary nucleus (TMN), located in the posterior hypothalamus
  • Histamine plays important role in wakefulness
  • Drugs that block histamine receptors (antihistamines) cause drowsiness
30
Q

Histamine - production, storage and release

A
  • Produced from an amino acid precursor by the action of an enzyme
  • Stored in vesicles and released following an action potential
31
Q

Histamine - receptors

A
  • CNS contains H1, H2, H3, and H4 receptors

- Antihistamines act as antagonists at histamine receptors

32
Q

Peptides - production, storage and release

A

Produced from large polypeptide precursor molecules
that are broken into smaller neurotransmitter molecules
by special enzymes.
• Synthesis of peptides occurs in the soma
• Vesicles containing the peptides are delivered from the
soma to terminal buttons by axoplasmic transport

33
Q

Peptides - production, storage and release part 2

A

Many terminal buttons have two types of synaptic
vesicles (e.g. one with a peptide and one with a
monamine, or acetylcholine) = co - release.
• Peptides regulate sensitivity of presynaptic or
postsynaptic receptors to the neurotransmitter

34
Q

Peptides - production, storage and release part 3

A

Peptides are released from all parts of the terminal
button
• Some molecules go to the synaptic cleft - others go to
receptors on other cells nearby

Several types of peptides
• Most peptides are neuromodulators
• Some peptides are neurotransmitters (e.g.
endogenous opioids)

35
Q

Peptides - receptors

A

• Several neural systems activated when opioid receptors are
stimulated
• Analgesia (pain relief)
• Inhibition of defensive responses such as fleeing and
hiding
• Reinforcement (can lead to opioid abuse)
• Direct agonists = Heroin
• Direct antagonists = Naloxone (drug that blocks opiate
receptors which can treat opioid overdose)

36
Q

Peptides - deactivation

A

Peptides are deactivated by enzymes but there is no

reuptake process

37
Q

Lipids

A
  • non-soluble in water
  • Substances derived from lipids (fat like molecules) can transmit messages within or between cells
  • Endocannabinoids – natural ligands for the receptors that THC also activates (active ingredient in marijuana).
  • > Anandamide
38
Q

Lipids - production, storage and release

A
  • Lipid neurotransmitters like anandamide appear to be synthesized on demand.
  • They are not stored in vesicles, only produced and released when needed
39
Q

Lipids - receptors

A
  • Two types of cannabinoid receptors, CB1 and CB2
  • Both are metabotropic
  • Found on terminal buttons of glutamatergic, GABAergic, acetylcholinergic, noradrenergic, dopaminergic, and serotonergic neurons > regulate neurotransmitter release
  • > THC exerts analgesic effects by stimulating CB1 receptors in the PNS
  • > Paracetamol also acts on these receptors
40
Q

Lipids - deactivation

A
  • Anandamide is deactivated by the enzyme FAAH
  • Because the enzyme is inside the neuron, the anandamide is transported back into the cell for deactivation via anandamide transporters

2007PSY (24 decks)

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