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Sensory and Motor Neuroscience > Excitatory and Inhibitory Neurotransmission in the CNS > Flashcards

Excitatory and Inhibitory Neurotransmission in the CNS Flashcards

1
Q

Effect of depolarisation in neurons

A

leads to transmitter release

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2
Q

Effect of entry of + ions (Ca, K, Na) or exit of - ions (Cl)

A

results in a positive charge (depolarisation/excitation)

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3
Q

Effect of exit of + ions or entry of - ions

A

results in negative charge (hyperpolarisation or inhibition)

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4
Q

Action of Na channel agonists

A
  • opens channels
  • causes Na flow into cell
  • results in excitation
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5
Q

Action of Na channel antagonists

A
  • closes channel
  • stops Na ion flow
  • favours inhibition
  • e.g. local anaesthetics
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6
Q

Action of K channel agonist

A
  • opens K channel
  • causes K flow out of cell
  • makes cell more negative
  • inhibitory
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7
Q

Action of K channel antagonist

A
  • closes K channel
  • retains K in cell
  • favours positive rmp
  • excitatory
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8
Q

Describe the events that take place at the synapse

A
  1. AP depolarises axon terminal
  2. depolarisation opens voltage-gated Ca channels and Ca enters cell
  3. Ca entry triggers exocytosis of vesicles
  4. NT diffuses across synaptic cleft and binds with receptors on post synaptic cell
    - NT binding initiates a response in postsynaptic cell
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9
Q

Describe the events that take place at the synapse when NTs are inactivated

A
  1. NTs can be returned to axon terminals for reuse or transported into glial cells
  2. enzymes inactive NTs
  3. NTs can diffuse out of the synaptic cleft
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10
Q

Role of astrocytes

A
  • buffer potassium
  • glutamate released in cleft can be taken up by astrocytes and transported back into neurons
  • ensure synaptic cleft is kept clear of NTs
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11
Q

What are the two modes of post-synaptic action of a NT

A
  • directly (ionotropic receptors) or indirectly (metabotropic receptors)
  • GABA can act on both receptors
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12
Q

Action of ionotropic receptors

A
  • integral component of molecule
  • nAChR channel activation
  • membrane depolarisation
  • AP excitation
  • muscle contraction
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13
Q

Action of metabotropic receptors

A
  • muscarinic ACh receptor activation
  • release of alpha-GTP + By from the heterotrimeric G protein
  • activation of inward rectifier K+ channel by By
  • membrane hyperpolarisation
  • decrease in HR
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14
Q

What are the two major families of ligand-gated channels

A
  • GABAA, Glycine and ACh (nicotinic) receptors
  • Glutamate receptors
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15
Q

Action of glutamate on glutamate receptors

A
  • may have inhibitory effects via its response at metabotropic glutamate receptors
  • ionotropic glutamate receptors directly gate ion channels and may be classified via response to non-endogenous agonists that mimic glutamate
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16
Q

Role of non-NMDA receptors

A
  • bind agonists kainate or AMPA controlling a channel permeable to Na and K
  • mediate fast excitatory synaptic transmission in the CNS
17
Q

Role of NMDA receptors

A
  • controls a channel permeable to Na, Ca, and K
  • contributes a slow component to the excitatory synaptic potential
  • thought to promote neurotoxicity due to high pereability to Ca
18
Q

How do metabotropic glutamate receptors exert their effect

A

by activation of second messenger cascade -> they dont have an integral ion channel

19
Q

Role of metabotropic glutamate receptors

A

modulation of neurotransmission e.g. presynaptic inhibition of Ca channels

20
Q

Role of ionotropic and metabotropic glutamate receptors in retinal pathways

A

discriminate between on/off retinal pathways

21
Q

Action of benzodiazepines

A

positive allosteric modulator of GABA A receptor, enhance Cl entry, decrease rmp, and enhance inhibition in presence of GABA

22
Q

Action of barbiturates

A

similar to benzodiazepines and potentiates the effect of GABA at GABA A receptor

23
Q

Action of baclofen

A

agonist of the GABA B receptor, enhances K current and increases inhibition

24
Q

Role of glycine

A
  • inhibitory NT
  • acts on glycine ionotropic receptor which gates a Cl channel
  • released by interneurons in spinal cord to inhibit antagonist muscles motoneurones
25
Q

Actions of ionotropic receptors

A
  • gating of ion channels is rapid (ms)
  • channels function as on-off switches
26
Q

Actions of metabotropic receptors

A
  • can act indirectly on a variety of channels
  • can close
  • usually the slow actions of metabotropic receptors are insufficient to trigger an AP -> rather they have modulatory synaptic actions
  • act on neighbouring voltage-gated channels
  • actions can occur at presynaptic cell or postsynaptic cell
27
Q

What are modulatory synaptic actions of metabotropic receptors

A
  • acting on channels in the presynaptic terminal to modulate transmitter release
  • modulate transmitter-gated channels to regulate the size of the post synaptic potential
  • modulate the resting and voltage-gated ion channels in the neuronal soma to alter e.g. resting Em and AP firing pattern
28
Q

Cholinergic synaptic transmission in autonomic ganglia

A
  • display both direct and indirect transmitter actions
  • fast epsp is due to activation of nicotinic ACh receptors (channels conduct Na and K)
  • slow epsp follows activation of muscarinic ACh receptors (ACh closes a K channel (M-type))
29
Q

Examples of ion channels (ionotropic receptors)

A

AMPA, NMDA, Kainate, GABA, Glycine, nACh, Seratonin, Purines

30
Q

Examples of GPCRs (metabotropic receptors)

A

Glutamate, GABAB, Dopamine, NE Epi, Histamine, Serotonin, Purines, Muscarinic

31
Q

What region of the brain first receives auditory signals

A

cochlear nucleus

Sensory and Motor Neuroscience (19 decks)

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