Structure and Function of Neurons

Jul 8, 2024

Structure and Function of Neurons

Introduction

  • Video Speaker: Ninja Nerds
  • Topic: Structure and Function of Neurons
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Structural Components of a Neuron

  1. Dendrites
    • Extensions from the neuron, called receptive zones.
  2. Cell Body (Soma)
    • Circular structure housing the nucleus and various organelles.
  3. Axon
    • Long, elongated portion of the neuron.
    • Special part: Axon Hillock (high concentration of voltage-gated sodium channels).
  4. Axon Terminal (Synaptic Terminal/Bulb)
    • Bulbous structure at the end of the axon.

Functions of Neuronal Components

Dendrites

  • Receptive Zone: Receives signals from other neurons.
  • Ligand-Gated Ion Channels: Formation of EPSPs (Excitatory Post-Synaptic Potentials) and IPSPs (Inhibitory Post-Synaptic Potentials).
  • Graded Potentials: Small changes in membrane voltage that help generate action potentials.
  • G-Protein Coupled Receptors: Activate second messengers and protein kinases for various cellular responses.

Cell Body (Soma)

  1. Graded Potentials: Shared function with dendrites.
  2. Protein Synthesis: Major Function
    • Rough Endoplasmic Reticulum (Nissl Bodies): Translation of mRNA to proteins.
    • Golgi Apparatus: Protein modification and packaging.

Axon

  • Action Potentials: Electrical currents that travel from the cell body to the axon terminal.
  • Phases of Action Potentials: Depolarization followed by repolarization.
  • Motor Proteins: Kinesin (anterograde transport) and dynein (retrograde transport).
  • Axonal Transport: Movement of vesicles, organelles, and other cellular components.

Microtubules and Motor Proteins

  • Kinesin: Transports vesicles containing neurotransmitters, mitochondria, etc., from cell body to axon terminal.
  • Dynein: Transports degraded or used materials back up to the cell body.
  • Clinical Relevance: Pathogens like polio and herpes viruses utilize these pathways.

Axon Terminal

  • Secretory Region: Release and reuptake of neurotransmitters.
  • Voltage-Gated Calcium Channels: Allow calcium influx, triggering neurotransmitter release.
  • SNARE Proteins: Facilitate vesicle fusion with the axonal membrane for neurotransmitter release.
  • Neurotransmitter Termination: Done by degradation or reuptake.
    • Reuptake Mechanism: Important for recycling neurotransmitters and impacted by SSRIs.

Neuronal Classifications

Structural Classification

  1. Multipolar Neurons
    • Multiple dendritic extensions, found in areas requiring multiple inputs (e.g., motor cortex, cerebellum).
  2. Bipolar Neurons
    • One dendritic extension and one axon, found in special sensory organs (e.g., retina, olfactory epithelium).
  3. Pseudo-Unipolar Neurons:
    • Peripheral and central processes with the cell body in between.
    • Found in dorsal root ganglia and cranial nerves.

Functional Classification

  1. Sensory Neurons (Afferent)
    • General Visceral Afferent (GVA): From visceral organs.
    • General Somatic Afferent (GSA): From skin, muscles, joints.
    • Special Sensory Afferent (SSA): From vision and hearing organs.
    • Special Visceral Afferent (SVA): From taste and smell sensors.
  2. Motor Neurons (Efferent)
    • General Visceral Efferent (GVE): To visceral organs.
    • General Somatic Efferent (GSE): To skeletal muscles.
    • Special Visceral Efferent (SVE): To head and neck muscles derived from pharyngeal arches.
  3. Interneurons
    • Connect sensory and motor pathways; predominantly found in the brain and spinal cord.

Conclusion

  • Summary: Covered the structure and function of different neuron parts.
  • Further Research: Graded potentials, action potentials, protein synthesis in neurons.
  • Importance: Understanding neurons' structure/function is crucial for grasping neurological concepts.