NUERO 2/14

  • Communication in the Nervous System

    • Neurons communicate through chemical messengers, primarily neurotransmitters and hormones.
    • Neurotransmitters: Chemicals produced by neurons that have local effects and are stored in synaptic vesicles.
    • Hormones: Chemicals produced by the endocrine system that have global effects, distributed via the bloodstream.

  • Types of Substances Affecting the Nervous System

    • Endogenous Substances: Chemicals produced internally (e.g., neurotransmitters, hormones).
    • Exogenous Substances: Chemicals from external sources (e.g., drugs) that affect neuronal signaling.

  • Criteria of Neurotransmitters

    • Synthesized and stored in neurons, notably in synaptic vesicles.
    • Released into the synaptic cleft upon neuron activation (action potential).
    • Must bind to specific receptors to cause an effect (IPSP or EPSP).

  • Neuronal Communication Process

    1. Action potential reaches the axon terminal.
    2. Calcium channels open, allowing calcium influx, leading to neurotransmitter release.
    3. Neurotransmitters bind to postsynaptic receptors, causing changes (IPSP or EPSP).
    4. Post-action effects:
      • Neurotransmitters can be reabsorbed by transporters or broken down by enzymes.

  • Receptor Types

    • Ionotropic Receptors:
      • Fast-acting; open ion channels directly upon neurotransmitter binding.
      • Can cause immediate EPSP (e.g., sodium influx) or IPSP (e.g., chloride influx).
    • Metabotropic Receptors:
      • Slower; activate G-proteins and second messengers resulting in longer-lasting effects (e.g., altering receptor density, cell growth).

  • Major Neurotransmitters

    • Amino Acid Neurotransmitters:
      • Glutamate: Primary excitatory neurotransmitter crucial for learning and memory.
      • GABA (Gamma-Aminobutyric Acid): Main inhibitory neurotransmitter; balances excitability and is involved in anxiety regulation.
    • Amines:
      • Acetylcholine (ACH): Involved in attention, learning, and muscle contraction in the peripheral nervous system.
      • Dopamine: Associated with motivation, reward pathways, and certain psychological disorders (e.g., Parkinson's, schizophrenia).
      • Norepinephrine and Epinephrine: Related to stress response and regulation of mood.
    • Neuropeptides:
      • Examples include endorphins, oxytocin, and vasopressin, involved in pain regulation and bonding.
    • Gas Neurotransmitters:
      • Nitric oxide and Carbon monoxide: Function differently than other neurotransmitters as they freely permeate cell membranes.

  • Dopamine and Psychological Disorders

    • Parkinson's Disease: Associated with low dopamine, leading to rigidity and difficulty in movement.
    • Schizophrenia: Linked to abnormal dopamine levels, causing symptoms of delusion and motor issues.

  • Impact of Drugs on Neurotransmitters

    • Drugs can enhance, block reuptake, or inhibit the enzymes involved in neurotransmitter degradation, affecting the nervous system.

  • Acetylcholine in Detail

    • Critical in both central (learning, memory) and peripheral nervous systems (muscle movement).
    • Excess acetylcholine can lead to muscle contractions/spasms; insufficient acetylcholine possibly leads to paralysis or weakness.
    • Example: Botulism toxin inhibits acetylcholine release, causing paralysis; black widow venom enhances acetylcholine signaling, leading to muscle spasms.

  • Clinical Applications and Future Directions

    • Understanding neurotransmitter roles can better develop treatments for neurological and psychological disorders.
    • Potential to target specific receptors to alleviate symptoms effectively.