Neurotransmitter
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🤖 AI addition (14/06/26):
What is a Neurotransmitter?
A neurotransmitter is a small chemical molecule released by a neuron to transmit a signal across the synaptic cleft to a target cell (another neuron, muscle, or gland). They are the brain’s fast, point-to-point communication system — acting in milliseconds.
Synaptic transmission: action potential → vesicle fusion → neurotransmitter release → receptor binding (Wikimedia Commons, CC BY-SA)
How It Works — The 5-Step Synapse Cycle
- Synthesis — NT is made in the presynaptic neuron (in the cytoplasm or at axon terminals)
- Storage — packed into synaptic vesicles at the axon terminal
- Release — action potential triggers Ca²⁺ influx → vesicles fuse with membrane → NT released into cleft (~20 nm wide)
- Receptor binding — NT binds to ionotropic (fast, ion channel) or metabotropic (slower, G-protein) receptors on postsynaptic membrane
- Termination — NT is either reuptaken by the presynaptic neuron (e.g., serotonin via SERT / 5HTT) or broken down enzymatically (e.g., ACh by acetylcholinesterase)
Classification
By Function
| Type | Effect | Examples |
|---|---|---|
| Excitatory | Increases likelihood of firing | Glutamate, Acetylcholine |
| Inhibitory | Decreases likelihood of firing | GABA, Glycine |
| Modulatory | Adjusts sensitivity/gain | Dopamine, Serotonin, Norepinephrine |
By Chemistry
- Amino acids — Glutamate (main excitatory), GABA (main inhibitory), Glycine
- Monoamines (biogenic amines) — Dopamine, Serotonin, Epinephrine, Norepinephrine (→ Noradrenaline)
- Acetylcholine — unique class; neuromuscular junction + memory
- Gases — Nitric oxide (NO), Carbon monoxide (CO) — diffuse freely, no vesicles needed
- Purines — ATP, Adenosine
Key Examples (from vault)
| Neurotransmitter | Role | Vault Note |
|---|---|---|
| Dopamine | Reward prediction, motivation | Dopamin und Belohnung |
| Epinephrine (Adrenaline) | Fight-or-flight, arousal | Epinephrine |
| Serotonin | Mood, sleep, appetite | 5HTT (transporter) |
| L-DOPA | Dopamine precursor | L-DOPA |
Key Distinction from Neuropeptides & Hormones
- NTs act locally (one synapse), last milliseconds
- Neuropeptides (Neuropeptide) act diffusely, last minutes–hours
- Hormones act systemically via bloodstream, last hours–days
→ Full comparison: Neurotransmitter vs Neuropeptide vs Hormone
Clinical Relevance
- SSRIs (e.g., Prozac) block serotonin reuptake → more serotonin in cleft
- Parkinson’s = loss of dopamine-producing neurons in substantia nigra → treated with L-DOPA
- Cocaine blocks dopamine + serotonin + norepinephrine reuptake
see also
Tags: neurobiology HormoneNeurotransmitter science
Superlink: 051 ☣Neurobiology 050 🧠Neuroscience 052 🫧Hormone und Neurotransmitter
Linked notes: Neuropeptide · Neurotransmitter vs Neuropeptide vs Hormone · Dopamin und Belohnung · Epinephrine · 5HTT · L-DOPA · Noradrenaline · Neuron Cell
Quellen
Neurotransmitter – Wikipedia
Synapse diagram – Wikimedia Commons
Erstellt: 08-08-22 11:31
Erweitert: 14/06/26