0407 neuro-excitation, inhibition and modulation Flashcards
• Ionotropic receptors act fast; metabotropic receptors allow signal amplification but are slow • Glutamate is the major excitatory transmitter • GABA is the major inhibitory transmitter • Acetylcholine can be excitatory or inhibitory • There are many modulator transmitters and they generally act on second messenger systems
Is a neuromuscular junction and excitatory synapse or a inhibitory synapse?
The NMJ is an excitatory synapse
What are ionotrophic receptors ? Which neurotransmitters are they usually associated with?
Ionotrophic receptors cause rapid opening of ion channels in postsynaptic membrane. They are specific for glutamate, GABA, acetylcholine, glycine, etc
What are metabotrophic receptors ? Which neurotransmitters are they usually associated with?
Meta. receptors are coupled with a secondary messenger protein (G protein). Ligands activate these receptors which activate the second-messenger, initiating downstream responses. They are specific for glutamte, GABA acteylcholine, dopamine, adenosine, noradrenaline
What are excitatory synapses ? Which neurotransmitters are they associated with
Excitatory synapses cause a excitatory post-synaptic potential (EPSP) which increases the membrane potential (brings it closer to AP threshold).They generally use glutamte (Glu) or Aspartate (Asp) as neurotransmitter.
Excitatory synapses generally cause an EPSP by opening non-selective Na+/K+ ion channels.
What are inhibitory synapses ? Which neurotransmitters are they associated with
Inhibitory synapses cause a inhibitory post-synaptic potential (IPSP) which decreases the membrane potential (moves away AP threshold).They generally use GABA or glycine (Gly) as neurotransmitter. Note an IPSP cannot occur below the resting membrane potential (usually -70mV)
Inhibitory synapses generally cause an IPSP by opening selective Cl- ion channels.
What are modulatory synapses ? Which neurotransmitters are they associated with
Modulatory synapses modulate the function of surrounding cells. They use neurotransmitters with complex mechanisms which ‘dampen’ or ‘brighten’ the response of other NTs. They are associate with NTs such as norepinephrine
What are the 3 ways a Neurotransmitter signal might achieve its effect
Ligand-gated channel, Short second-messgener pathway, and Amplification via signal cascade.
A ligand gated channel is where 1 bound receptor directly ones 1 channel (1 ligand: 1 channel). It is the fastest channel action. Short second-messenger pathway is where 1 receptor connected to multiple (10-20) G proteins which in turn can activate multiple channels. It is relatively fast and fairly localised. Amplification via signal cascade is where 1 receptor activates protein kinase A (PKA) via a cascade which opens/modulates a multitide of channels. It is signally throughout the cytoplasm and not just the membrane. it is the least localised method.
What type of transmitter is acetycholine (excitatory, inhibitory or both)
Acetylcholine can be both an excitatory and inhibitory neurotransmitter.
In what bodily system is Glu found as the major excitatory neutrotransmitter
In the central nervous system
What is the role of excitatory amino acid transporters (EAATs) in Glu synapses?
EAATS are used to transport Glu out of the synapse and into either astrocytes (which convert it into glutamine) or back in the the nerve terminal for resuse as NT
What is the role of glutaminase in Glu synapse
Glutaminase converts the amino acid glutamine (enters the nerve terminal from astrocytes) into glutamate (the neutrotransmitter)
Name 3 ionotropic glutamate receptors
AMPA, NMDA and kainate (KA)
Where are inhibitory GABA neurotransmitters most commonly found
Inhibitory GABA NT are mostly found in interneurons
Describe the process of GABA synthesis and entry into the synaptic cleft
GABA is synthesised from glutamate in the nerve terminal via GAD (glutamic acid decarboxylase). It enters the synaptic cleft via the same vesicular mechanism as glutamate and once in the synaptic cleft is deactivated via diffusion or reabsorbed into the glia and reused.
What is the name of GABA specific transporters found in the glia and nerve terminal
GABA transporters GAT1 to GAT4
