Neurotransmitters

• Neurotransmitters are chemical messengers that play a crucial role in transmitting signals between neurons in the nervous system.

• Released by the presynaptic neuron at a synapse, they diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic neuron.

• This binding can either excite or inhibit the postsynaptic neuron, influencing the likelihood of generating an action potential.

Categories of Neurotransmitters

1) Amino Acids

• The most common neurotransmitters in the central nervous system (CNS).

• Examples:

  1. Glutamate: Primary excitatory neurotransmitter in the CNS; involved in learning and memory.

  2. Gamma-aminobutyric acid (GABA): Primary inhibitory neurotransmitter in the CNS; reduces neuronal excitability.

  3. Glycine: Inhibitory neurotransmitter found mainly in the spinal cord and brainstem.

2) Monoamines:

• Derived from single amino acids.

• Examples:

  1. Dopamine: Regulates movement, reward, motivation, and cognition.

  2. Norepinephrine (noradrenaline): Regulates attention, alertness, and the fight-or-flight response.

  3. Serotonin: Regulates mood, appetite, sleep, and cognitive functions such as learning and memory.

  4. Histamine: Regulates arousal, wakefulness, and inflammatory responses.

3) Neuropeptides:

• Short chains of amino acids acting as neurotransmitters or neuromodulators.

• Examples:

  1. Endorphins: Involved in pain relief and emotion regulation.

  2. Substance P: Involved in pain transmission and inflammation.

  3. Oxytocin: Involved in social bonding, childbirth, and lactation.

4) Acetylcholine:

• Found in both the central and peripheral nervous systems.

• Functions: Involved in muscle movement, memory, and the regulation of autonomic functions such as heart rate and digestion.

5) Purines:

• Involved in energy metabolism and cellular signaling.

• Examples:

  1. Adenosine: Involved in energy metabolism.

  2. ATP (Adenosine Triphosphate): Involved in cellular signaling.

6) Gasotransmitters:

• Small gaseous molecules that can act as neurotransmitters.

• Example:

  1. Nitric Oxide (NO): Plays a role in vasodilation and synaptic plasticity.