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Detailed Notes on Neurotransmitters

Overview of Neurotransmitters

  • Neurotransmitters are chemicals that transmit signals across synapses between neurons.
  • Focus on two types: Excitatory and Inhibitory neurotransmitters.

Membrane Potential

  • Membrane Potential (VM) can be altered by neurotransmitters leading to:
    • Depolarization: Membrane potential becomes more positive; cell is excited.
    • Hyperpolarization: Membrane potential becomes more negative; cell is inhibited.

Acetylcholine (ACh)

  • First neurotransmitter discovered.
  • Can be both excitatory and inhibitory, depending on the receptor:
    • Excitatory: ACh released onto skeletal muscles causes them to contract (depolarization).
    • Inhibitory: ACh released onto heart muscles slows the heartbeat (hyperpolarization).
  • Functions of ACh:
    • Important for memory formation.
    • Essential for attention and arousal.
    • Involved in regulating sleep.

Abnormal Levels of ACh

  • Low levels associated with Alzheimer's disease:
    • Loss of neurons that release ACh leads to memory loss.
    • Treatments include reuptake inhibitors, which increase the availability of ACh in the synaptic cleft.

Medications Controlling Neurotransmitter Levels

  • Agonists: Mimic neurotransmitter effects, used when levels are too low.
  • Antagonists: Block neurotransmitter effects, used when levels are too high.
  • Reuptake inhibitors: Prevent reabsorption of neurotransmitters, making them more available.

Monoamines

  • Includes Serotonin, Norepinephrine, and Dopamine. All share similar functions affecting mood and behavior.
  • Serotonin:
    • Involvement in temperature regulation, mood stabilization, sleep, and nausea control.
    • Low serotonin levels linked to depression and anxiety; treated with SSRIs (selective serotonin reuptake inhibitors).
  • Dopamine:
    • Plays a role in motivation, pleasure, and movement control.
    • Low levels associated with Parkinson's disease.
    • High levels linked to Tourette’s syndrome and schizophrenia; treated with dopamine antagonists.
  • Norepinephrine:
    • Involved in decision-making, attention, and mood regulation.
    • Low levels affect behavior in similar ways as serotonin and dopamine; treated using norepinephrine reuptake inhibitors.

Amino Acids as Neurotransmitters

  • Glutamate:
    • Always excitatory, plays a crucial role in synaptic plasticity, learning, and memory.
    • High levels can lead to seizures; treated by antagonists to glutamate receptors.
  • GABA (Gamma-Aminobutyric Acid):
    • Only inhibitory. It decreases the likelihood of neuronal firing and is crucial in preventing overstimulation of neurons.

Conclusion

  • Understanding neurotransmitters is essential for associating their functions with various psychological and physiological effects.
  • Emphasize that abnormalities in neurotransmitter levels can lead to significant health issues, highlighting the importance of targeted treatments.