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.