Makindo Medical Notes

🔎 Overview

Neurotransmitters are chemical messengers that transmit signals across synapses to neurons, muscles, or glands. They underpin communication in the nervous system and are essential for cognition, movement, mood, and autonomic function.

🧩 Types of Neurotransmitters

• 🟢 Acetylcholine (ACh)
  • Muscle activation, memory, learning.
  • Acts on nicotinic & muscarinic receptors.
  • Clinical links: Alzheimer’s disease, myasthenia gravis.
• 🔵 Amino Acid Neurotransmitters
  • Glutamate – main excitatory NT; synaptic plasticity & memory; excess → excitotoxicity (stroke, ALS).
  • GABA – main inhibitory NT; prevents over-excitation; dysfunction → anxiety, epilepsy, insomnia.
  • Glycine – inhibitory (spinal cord, brainstem); co-agonist with glutamate at NMDA receptors.
• 🟠 Monoamines
  • Dopamine – reward, motor control, mood. Deficiency → Parkinson’s; excess → schizophrenia.
  • Norepinephrine – attention, arousal, stress response; linked to anxiety & depression.
  • Serotonin (5-HT) – regulates mood, appetite, sleep; implicated in depression, migraine.
  • Histamine – arousal, appetite, immune response.
• 🧬 Neuropeptides
  • Substance P – pain transmission & inflammation.
  • Endorphins – endogenous opioids; natural analgesia & reward.
  • Neuropeptide Y – appetite, stress, circadian rhythm.
• ⚡ Purines
  • Adenosine – promotes sleep, modulates neuronal excitability.
  • ATP – acts as NT in CNS & PNS.
• 💨 Gasotransmitters
  • Nitric Oxide (NO) – vasodilation, plasticity, immune regulation.
  • Carbon Monoxide (CO) – neuromodulatory signalling role in brain.

⚙️ Mechanisms of Neurotransmitter Action

• Release: Stored in vesicles, released by exocytosis after an action potential.
• Receptor Binding: NTs act on ionotropic (fast) or metabotropic (slow, GPCR) receptors.
• Termination: By reuptake, enzymatic degradation, or diffusion away.

🏥 Clinical Relevance

• Mental Health: Depression, anxiety, schizophrenia linked to NT imbalance. SSRIs, antipsychotics target these pathways.
• Neurodegeneration: Parkinson’s (dopamine), Alzheimer’s (ACh).
• Addiction: Drugs hijack dopamine reward circuits.
• Epilepsy: Excitatory (glutamate) vs inhibitory (GABA) imbalance → seizures. AEDs restore balance.
• Autonomic Disorders: Dysregulation of ACh, NE affects HR, BP, gut motility.

📌 Summary

Neurotransmitters are vital messengers for brain and body function. Disruption leads to major psychiatric and neurological disorders. Clinical management often targets specific neurotransmitter systems.

📚 References

• Kandel ER et al. Principles of Neural Science, 6th ed.
• Bear, Connors & Paradiso. Neuroscience: Exploring the Brain.
• National Institute of Mental Health – Neurotransmitters and the Brain.