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NB3 Flashcards

1
Q

What is synaptic transmission

A

Process by which signalling molecules (neurotransmitters) are released by neurone (presynaptic neurone), bind to and activate receptors of another neurone (postsynaptic neurone)

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2
Q

What are Cl ions used for

A

Higher concentration of Cl extracellularly

-used as inhibitory currents

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3
Q

Concentration of ions

A

Higher extracellularly: Na+ and Cl-

Higher intracellularly: K+

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4
Q

What is the resting potential of a typical neurone

A

-70mV

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5
Q

Resting membrane potential

A
  • Chemical gradient acts as a driving force for diffusion of K+ out of cell
  • Residual negative charge acts as a electrical driving force drawing back K+ back into cell
  • Electrical force balance chemical force
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6
Q

What is the Nernst Equation

A

E= 61 x log ( Concentration of ion outside / Concentration of ion inside )

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7
Q

Describe the process of neurotransmitter release

A
  1. Action potential reaches and depolarises the axon terminal
  2. Depolarisation activates voltage-gated pre-synaptic Ca2+ channels (N-type, P-type)
  3. Localised Ca2+ entry triggers the release of nearby vesicles containing the NTs through the activation of Ca2+-sensitive fusion proteins
  4. NTs diffuse into the synaptic cleft and activate NT receptors on the post-synaptic membrane
  5. NT may also activate pre-synaptic NT receptors (+ or - feedback)
  6. Recycling/upcycling of NTs (Glutamine synthetase GLUL)
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8
Q

Function of astrocytes

A
  • Astrocyte processes are in close contact with synapses
  • recycle NTs (glutamine synthetase)
  • secrete neuro and gliotransmitters (glutamate, D-serine, TNF-α)
  • buffer extracellular K+
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9
Q

Type of neurotransmitter receptors

A
  1. Receptor with intrinsic ion channel
    - Ionotropic receptors
    - Fast synaptic transmission
    - Most NTs act on chemically (ligand) gated channels (ionotropic receptors) which increase permeability of ions (e.g. nicotinic receptor for Na+)
  2. GCPR (metabotropic receptor)
    - Slow synaptic transmission
    - Activated receptor triggers the activation of G protein that either directly modifies function of ion channels or triggers the production of chemical second messenger (cAMP) inside cell that modifies ion channels
    - Mediates short term as well as additional long term effects (e.g. gene expression)
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10
Q

Example of excitatory neurotransmitter

A

Glutamate

Acetylcholine

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11
Q

Example of inhibitory neurotransmitter

A

GABA

Glycine

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12
Q

What is Co-transmission

A

Vesicles containing classical, small molecule NT are co-released from a depolarised axon terminal with vesicles containing larger, peptide neurotransmitter

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13
Q

Example of peptide NT

A

Neuropeptide Y
Substance P
Vasoactive intestinal polypeptide (VIP)

*Fast response mediated via classical NT
Slow response mediated via peptide NT

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14
Q

Postsynaptic potentials

A
  1. Excitatory synapse
    - NT binding opens Na+ channels - small depolarisation
    - excitatory post synaptic potential (EPSP)
  2. Inhibitory synapse
    - NT binding increases permeability to either K+ or Cl- causing ‘holding’ of resting membrane potential or small hyperpolarisation
    * K+ moves out of cell
    - inhibitory post synaptic potential (IPSP)
    - membrane potential moves further from action potential threshold
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15
Q

What is summation

A
  • Single EPSP is unable to bring postsynaptic neurone to AP potential
  • Postsynaptic response is result of multiple synaptic events from many neurones
  • Postsynaptic neurone brought to AP threshold via temporal or spatial summation
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16
Q

What is temporal summation

A
  • EPSPs last for about 15msec.
  • High frequency activation of a single presynaptic terminal can cause summation if the interval between impulses is less than 15msec
17
Q

What is spatial summation

A
  1. Most synapses terminate on dendrites (long and thin, extend up to 1mm from soma)
    - loss of current due to membrane leakage
    - EPSP declines with distance
  2. Some synapses terminate on soma
    - very low resistance (large diameter)
    - local EPSP and IPSP can spread through soma
  3. Synapses near the soma have more effect than synapses on dendrites on the potential of the soma
  4. Activation of multiple presynaptic terminals on dendrites can cause summation

NB (4 decks)

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