Chap 6 lec 1 Flashcards
What are the three essential criteria for a neurotransmitter?
- Synthesized and stored in the presynaptic neuron.
- Released in response to action potentials & Ca²⁺ influx.
- Binds to specific receptors on the postsynaptic neuron to elicit a response.
Can a neuron release more than one type of neurotransmitter? What is this called?
Yes, neurons can release multiple neurotransmitters. This is called co-transmission or co-release.
What are the two major categories of neurotransmitters?
- Small Molecule Neurotransmitters (e.g., Acetylcholine, Glutamate, GABA, Dopamine, ATP).
- Neuropeptides (e.g., Endorphins, Enkephalins, Substance P).
What are the precursors for acetylcholine (ACh) synthesis?
Choline + Acetyl-CoA.
What enzyme synthesizes acetylcholine?
Choline Acetyltransferase (ChAT).
How is acetylcholine removed from the synaptic cleft?
Acetylcholinesterase (AChE) breaks ACh into choline + acetate.
Choline is recycled via a sodium-dependent choline transporter.
What are the two major types of acetylcholine receptors?
- Nicotinic (nAChR, Ionotropic) – Fast, excitatory.
- Muscarinic (mAChR, Metabotropic) – Slower, excitatory or inhibitory.
What drugs affect nicotinic receptors?
Agonist: Nicotine.
Antagonist: Curare (blocks receptor, causing paralysis).
What drugs affect muscarinic receptors?
Agonist: Muscarine.
Antagonist: Atropine (blocks parasympathetic effects).
What is the primary function of glutamate?
Main excitatory neurotransmitter in the CNS.
What is the precursor for glutamate?
Glutamine.
What enzyme converts glutamine into glutamate?
Glutaminase.
How is glutamate removed from the synapse?
what converts it back into ________?
Taken up by Excitatory Amino Acid Transporters (EAATs).
Converted back into glutamine by glutamine synthetase in glial cells.
What are the three major ionotropic glutamate receptors?
AMPA receptors
Kainate receptors
NMDA receptors
What makes NMDA receptors unique?
Blocked by Mg²⁺ at resting membrane potential.
Requires glutamate + glycine + depolarization to open.
Ca permability is good -synaptic plasticity
What is the primary function of GABA?
Main inhibitory neurotransmitter in the CNS.
What is the precursor for GABA synthesis?
Glutamate.
What enzyme converts glutamate to GABA?
Glutamic Acid Decarboxylase (GAD).
How is GABA removed from the synaptic cleft?
GABA Transporters (GATs) remove GABA into glial cells and neurons.
-needs NA+
What are the two types of GABA receptors?
- GABA-A (Ionotropic) – Ligand-gated Cl⁻ channel.
- GABA-B (Metabotropic) – Activates K⁺ channels, inhibits Ca²⁺ channels.
What is the primary function of glycine?
Inhibitory neurotransmitter in the spinal cord and brainstem.
What is the precursor for glycine?
Serine.
What enzyme converts serine to glycine?
Serine hydroxymethyltransferase.
What receptor does glycine act on?
Ionotropic glycine receptors (Cl⁻ channels, inhibitory).
What toxin inhibits glycine receptors?
Strychnine – causes convulsions by blocking inhibitory signaling.
What is the major excitatory neurotransmitter in the CNS?
Glutamate.
What are the two major inhibitory neurotransmitters?
GABA (brain) and Glycine (spinal cord & brainstem).
Which neurotransmitter requires a co-agonist and voltage change to activate its receptor?
Glutamate acting on NMDA receptors.
Which neurotransmitter is removed from the synapse via enzymatic breakdown instead of transporters?
Acetylcholine (ACh), broken down by Acetylcholinesterase (AChE).
What is the difference between ionotropic and metabotropic receptors?
Ionotropic – Ligand-gated ion channels, fast synaptic transmission.
Metabotropic – G-protein-coupled receptors, slower, modulatory effects.
Q: What do AMPA receptors do?
Fast excitatory signaling (quick response).
Permeable to Na⁺ and K⁺ (some allow Ca²⁺).
Main receptor for rapid synaptic transmission.
What do Kainate receptors do?
Slower than AMPA, still excitatory.
Permeable to Na⁺ and K⁺ (some allow Ca²⁺).
Modulates synaptic activity.
What do NMDA receptors do?
Excitatory, but slower to activate than AMPA.
Key for learning & memory (LTP).
Needs glutamate + glycine & Mg²⁺ block removal to open.
Permeable to Na⁺, K⁺, and Ca²⁺ (Ca²⁺ triggers plasticity).
