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Physiology - Foundation Module > Neurotransmitters > Flashcards

Neurotransmitters Flashcards

1
Q

What is a neurotransmitter?

A

Ligands/ chemical substances produced by neurons that transmit signals to target cell (nerves, muscle, glands) across a synapse.

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2
Q

The 4 properties of neurotransmitters?

A
  1. Synthesised and stored in vesicles in terminal boutons of presynaptic neuron ( end of axon)
  2. Released from presynaptic neurons
  3. Bind to specific post synaptic receptors
  4. Rapidly removed from synaptic cleft
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3
Q

How are NT removed from cleft ? And examples

A
  1. Diffusion
  2. Reuptake - repackaged to vesicles or into glial cells ( serotonin, GABA, glutamate, glycine)
  3. Inactivation by enzymes ( Ach)
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4
Q

7 categories of Nts? With examples

A
  1. Amino acids - GABA, Glycine, Glutamate
  2. Amines- Catecholamine, DA, NE, 5-HT, Histamine
  3. Neuropeptides- opioid peptides ( enkephalins, endorphins, dynorphin)
  4. Ach
  5. Lipids
  6. Nucleosides
  7. Gases - NO
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5
Q

3 actions of NTs? With examples.

A
  1. Excitatory - depolarisation of post synaptic membrane to
    Promote action potentials
    ( Glu, ACh, Histamine, DA, NE/ NAd, Epi/ Ad )
  2. Inhibitory- hyperpolarization
    (GABA, 5- HT,DA)
  3. Modulatory
    ( DA, 5-HT, ACh, histamine, NE )
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6
Q

What is a NT receptor?

A

Genetically-coded proteins embedded in cell membrane

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7
Q

Types of NT receptor? With examples.

A
  • ionotropic ( NT molecule bind to outside and channel open making it permeable to NA+, K+ or Cl-) ex. GABA
  • metabotropic ( G-protein coupled / seven transmembrane receptors is a single protein winding thru cell membrane 7 times) ex. All monoamine receptors except 5-HT3
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8
Q

Metabotropic vs ionotropic receptors ?

A

Meta. Vs. Iono.
1. Slower 1. Works very fast
2. Longer lasting response. 2. Slow lasting response
3. No channel/ pore. 3. Has channel/ pore

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9
Q

How do G protein coupled receptors work ?

A
  1. NT molecule binds with receptor
  2. Receptor activates G protein
  3. a subunit breaks off from G protein and binds to ion channel and opens it
  4. Ions enter cell, produces postsynaptic potential
    Or
  5. a subunit activates enzyme that produces 2nd messenger
  6. Ion channel opens
  7. Ions enter cell nd produce postsynaptic potential
  8. 2nd messenger goes to nucleus / other parts of cell
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10
Q

4 NT Receptor properties and examples

A
  1. Each ligand has many subtypes of receptors
    Ex. NE binds to a and B
  2. Presynaptic receptors inhibit further release of NT
  3. Prolonged exposure to ligand causes most receptors to be desensitised
  4. Upregulation and downregulation of receptors
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11
Q

Five Locations of ACh secretion?

A
  1. motor neurons
  2. Autonomic nerves
  3. Pyramidal cells of motor cortex
  4. Basal ganglia
  5. Hippocampus
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12
Q

3 Functions of ACh?

A
  1. Regulate sleep cycle
  2. Essential for motor function
  3. Essential for cognitive function
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13
Q

3 types of ACh receptors with their location?

A
  1. Nicotinic- nAChR- autonomic ganglia , NMJ (excitatory so sodium influx)
  2. Muscarinic - M1 to M5- brain, heart, pancreas, smooth muscles ( inhibitory so inc potassium conductance or dec cAMP)
  3. Parasympathetic nerve endings - 2nd messenger cAMP
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14
Q

4 Common ACh blockers? And how they act?

A
  1. Curare - plant poison. (NMJ block)
  2. Botulinum toxin - food poison. (NMJ block)
  3. Atropine ( M receptor blocker)
  4. Alzheimer’s patients. ( loss of ACh neurons)
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15
Q

How are catecholamines formed ?

A

by hydroxylation & decarboxylation of AA tyrosine.

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16
Q

How are catecholamines removed ?

A
  1. Reuptake
  2. Enzymatic degradation - intracellularly or in cleft by MAO OR COMT
17
Q

What is norepinephrine ? ( location, effect on body and behaviour)

A

Present in autonomic nerves (most sympathetic postganglionic nerve endings, Adrenal medulla) brainstem, hypothalamus, locus ceruleus of pons
• Increases blood pressure and heart rate
• Increases alertness, attention and wakefulness, control
the overall activity of the brain and the mood
• Mainly excitatory

18
Q

What are norepinephrine receptor types? 2nd messenger ?

A

receptors –α1 α2 β1 β2 β3 second messenger: cAMP
– Norepinephrine- α and β (more on α)
– Epinephrine - α and β (more on β)

19
Q

Effect of deficiency of NE?

A

Deficiency associated with attention deficit hyperactive disorder ADHD

20
Q

What is Dopamine (DA)? (Location, effect)

A

Secreted by Adrenal medulla, Brain (Substantia niagra, Cortex-Corpus striatum,Hypothalamus) and neurons in basal ganglia
• Mainly inhibitory
• Involved in pleasure, reward mechanisms in brain,
motivation and important in coordinating movements

21
Q

What are DA receptors?

A

receptors: D1, D2, D3, D4, D5
second messenger: cAMP

22
Q

Effects of DA?

A

Increased levels associated with schizophrenia, alcohol/drug (cocaine, opium, heroin)abuse
low levels are associated with Parkinsonism

23
Q

What is GABA? ( location , how it’s synthesised , significance )

A

Present in the basal ganglia , spinal cord, cerebellum & Cortex
• Main inhibitory NT of the brain
• Synthesized by Decarboxylation of glutamate by
the enzyme Glutamate decarboxylase(GAD)

24
Q

What are GABA receptors?

A

– GABA A increase Cl- influx
– GABA B act via G proteins, increase K+ influx

25
Q

Effect of GABA

A

Low GABA levels are associated with anxiety and epilepsy

26
Q

What is glycine ?

A

main inhibitory NT in spinal cord

27
Q

What is 5-HT ( location,function)?

A

Secreted by CNS brainstem neurons- Control emotion, mood and important in sleep ,also present in GIT, platelets & limbic system

28
Q

5- HT receptors?

A

receptors: 5-HT 1, 5-HT 2, 5-HT3, 5 HT-4, 5HT5, 5-HT6,5- HT7

29
Q

What is Glu?

A

main excitatory NT of brain & spinal cord

30
Q

Glu receptors?

A

receptors: metabotropic receptors, LGIC- (kainate,
AMPA, NMDA ) NMDAR hippocampus- involved in
memory & learning

31
Q

Effects of Glu?

A

Increased levels are associated with certain neurological diseases

32
Q

What is neuromodulator ? with examples.

A

• Neuromodulators are not restricted to the synaptic cleft : modulate regions or circuits of the brain
• They affect a group of neurons, causing a modulation of that group
• Neuromodulators alter neuronal activity by amplifying or dampening synaptic activity
• eg. dopamine, serotonin, acetylcholine, histamine, glutamate

33
Q

Heteroreceptor vs autoreceptor

A

Heteroreceptors respond to neurotransmitters, neuromodulators, or neurohormones released from adjacent neurons or cells (presynaptic ); they are opposite to autoreceptors, which are sensitive only to neurotransmitters or hormones released by the cell in whose wall they are embedded (postsynaptic).

Physiology - Foundation Module (6 decks)

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