Basics of Function & Neural Development


Neural Communication

  • Receptor channels:

    • Mechanically-gated Receptor: Responds to physical pressure.

    • Ligand-gated Receptor: Opens in response to a neurotransmitter binding.

    • Voltage-gated Ionotropic Receptor: Opens in response to changes in membrane potential.

    • Metabotropic Receptor: Affects cellular processes via second messenger systems.

Electrical Communication

  • Voltage-Gated Channels (Saltatory Conductance): Facilitate communication by allowing ions to flow at nodes of Ranvier, leading to faster signal transmission.

Conversion Processes

  • From Electrical to Chemical Communication: Voltage-gated (Calcium) channels.

  • From Chemical to Electrical Communication: Ligand-gated channels (involved in Excitatory and Inhibitory Postsynaptic Potentials - EPSP/IPSP).

Structure of Neurons

  1. Dendrite: Receives information from other neurons through dendritic spines.

  2. Cell Body: Site of protein synthesis.

  3. Axon Hillock: Integrates signals and determines action potential firing threshold.

  4. Axon: Conveys signals to target areas.

  5. Myelin Sheaths: Insulates the neuron and enhances signal transmission.

  6. Nodes of Ranvier: Gaps in myelin allowing for saltatory conduction.

  7. Axon Terminal: Releases neurotransmitters into the synapse.

  8. Synaptic Cleft: Space where neurotransmitters are released to convey signals to neighboring neurons.

Summation of Postsynaptic Potentials

  • Spatial Summation: Summation of multiple EPSPs from different locations on the neuron.

  • Temporal Summation: Summation of multiple EPSPs from the same location over time.

Sodium-Potassium Pump

  • Mechanism: Responsible for the resting membrane potential and resetting after action potentials.

    1. Na+ binds to the pump.

    2. Pump phosphorylated by ATP.

    3. Na+ is released, K+ binds to pump.

    4. Pump returns to original conformation.

Synaptic Communication Overview

Steps in Synaptic Communication

  1. Presynaptic Neuron:

    • Neurotransmitters are enclosed in synaptic vesicles.

    • Action potential opens Ca2+ voltage-gated channels leading to Ca2+ influx.

    • Ca2+ causes vesicles to fuse with the membrane, releasing neurotransmitters into the synaptic cleft.

  2. Postsynaptic Neuron:

    • Neurotransmitters bind to receptors leading to changes in postsynaptic potential.

    • Excess neurotransmitters are cleared through:

      • Degradation: Breakdown by enzymes (e.g., monoamine oxidase - MAO).

      • Reuptake: Reabsorption of neurotransmitters into presynaptic neurons (e.g., SSRIs inhibit this).

Distinction Between MAOIs and SSRIs

  • MAOIs: Inhibit monoamine oxidase, preventing the breakdown of multiple neurotransmitters, including serotonin.

  • SSRIs: Selectively inhibit the reuptake of serotonin, leading to longer synaptic presence of serotonin.

  • Key Differences:

    • SSRIs are more selective with fewer side effects than MAOIs, which can affect multiple neurotransmitter systems.

Action at Postsynaptic Neuron

  • Neurotransmitters activate receptors in postsynaptic dendrites:

    • Ionotropic Receptors: Fast-acting, allow for immediate ion movement.

    • Metabotropic Receptors: Slow-acting, involve second messenger pathways, leading to prolonged changes.

  • Generation of EPSPs and IPSPs occurs on post-synaptic membranes, summed at the axon hillock for action potential initiation.

Specific Neurotransmitters Summary

  • GABA: Inhibitory neurotransmitter; important for calming effects.

  • Glutamate: Main excitatory neurotransmitter involved in learning and memory.

  • Serotonin: Involved in mood regulation and sleep cycles, synthesized from tryptophan.

  • Dopamine: Involved in motor function and the reward system; synthesized from tyrosine or phenylamine.

  • Acetylcholine: Supports CNS functions and muscle contractions; has two types of receptors:

    • Muscarinic: Metabotropic, slow signaling.

    • Nicotinic: Ionotropic, fast signaling.

  • Adrenaline/Epinephrine & Noradrenaline/Norepinephrine: Support fight or flight response; affect blood flow and oxygen delivery.


  • Neuroplasticity: The ability of neurons to form new connections and for brain regions to assume new functions.

  • Influences behavior and is heavily affected by environmental factors.