Neurotransmitters
| System | Preganglionic Neuron Neurotransmitter | Postganglionic Neuron Neurotransmitter / Adrenal Medulla Release | Target Organ(s) / Systemic Effect |
|---|---|---|---|
| Motor (Somatic) | ACh (Single motor neuron) | N/A (No postganglionic neuron) | Skeletal Muscle |
| Sympathetic | ACh | 1. Typical Targets: NE (α/β adrenergic receptors) 2. Eccrine (Thermo): ACh (M receptors) 3. Apocrine/Stress Eccrine: NE (α1 adrenergic receptors). Also sensitive to circulating Epi/NE. 4. Adrenal Medulla: Hormones (primarily Epi, some NE) into bloodstream |
1. Smooth/Cardiac muscle, Glands; Contraction/Relaxation, ↑HR/Force, Secretion 2. ↑Thermo Sweating 3. ↑Stress Sweating 4. Systemic "Fight/Flight" effects |
| Parasympathetic | ACh | ACh (M receptors). | Smooth/Cardiac muscle (↓HR), Glands ("Rest & Digest" functions) |
| Neurotransmitter & Receptor Pair | Functions in the CNS |
|---|---|
| Ionotropic: Ligand-gated ion channels | Transmembrane proteins that allow ions to cross the membrane |
| Glutamate [E] → NMDA receptor: Ca2+ & Na+ influx | Long-term potentiation of learning & memory |
| GABA [I] → GABAA receptor: Cl− & HCO3− influx | Sedation, anxiolytic & anticonvulsive |
| Glycine [I] → Glycine receptor: Cl− influx | Inhibit spinal interneurons (prevents spasticity) |
| Metabotropic: G protein-coupled receptors | Act through second messengers (eg, cAMP, PKA) |
| Dopamine → D1-5 receptors | Modulate attention, movement & reward |
| Serotonin → 5-HT receptors | Modulate mood, nausea & trigeminovascular nociception (migraine) |
| Norepinephrine → α & β adrenoceptors | Promotes vigilance, attention & emotional memory |
| Histamine → H3 receptors | Promotes wakefulness |
- Acetylcholine
- Usually excitatory
- Increased levels
- Decreased levels
- Alzheimer disease, Acetylcholine and Alzheimer's both start with A
- Huntington disease
- Dopamine
- Drive to GET a reward. NOT the feeling of reward. Both excitatory and inhibitory
- D1 receptor: Subsequent activation of protein kinase A causes smooth muscle relaxation
- D2 receptor: located mainly in the substantia nigra, striatum, area postrema, and pituitary gland.
- See dopaminergic pathway
- Increased levels
- Decreased levels
- Depression
- Parkinson disease
- Neuroleptic malignant syndrome (D2 receptor blocked)
- Drive to GET a reward. NOT the feeling of reward. Both excitatory and inhibitory
Functions of dopamine
D rugs
psych O sis
P rolactin inhibition
A ttention
M otivation
I nvoluntary movements
N ausea
E nergy
- Norepinephrine
- Alertness
- Increased levels
- Anxiety
- Decreased levels
- Depression
- Serotonin (aka 5-HT)
- Satiety, Tranquilty, Peace
- Increased levels
- Decreased levels
- Anxiety
- Depression
- Parkinson disease
- Satiety, Tranquilty, Peace
- GABA
- GABA A receptor mediates a fast response to GABA because it is an ion-gated chloride channel. Activation of this receptor leads to rapid muscle relaxation and sedation. Its activity is enhanced by benzodiazepines, which can be used to treat spasticity.
- GABA B receptor mediates a slower response to GABA because it is mediated by a G protein–coupled receptor that opens potassium channels. It is agonized by baclofen, which can also be used to treat spasticity.
- Inhibitory in the brain
- Increased levels
- Decreased levels
- Anxiety
- Huntington disease
- Histamine
- Wakefulness. Think about benadryl (antihistamine) makes us drowsy and sleepy)
- Glutamate
- Excitatory in the brain, opposite to GABA
- GlutaMATE
- GlutaMATE
- Long-term potentiation of learning & memory
- Glutamate-induced excitotoxicity
- Excitatory in the brain, opposite to GABA
- Glycine
- Inhibitory in the spine