COGS1000 Notes - Basic Principles of Brain Organisation and Neuroanatomy

Peripheral Nervous System (PNS) and Central Nervous System (CNS)

  • PNS: Nerves and neurons outside of brain and spinal cord.
  • CNS: Nerves and neurons within the brain and spinal cord.

Neuron Structure and Function

  • Neurons: Fundamental information messengers of the nervous system.
    • Functions:
    • Receive sensory input from the environment.
    • Transmit information via electrical and chemical signals.
  • Structure:
    • Multipolar Neuron: Has multiple dendrites and one axon.
    • Dendrites: Receive signals from other neurons.
    • Cell Body (Soma):
    • Houses nucleus, mitochondria, and organelles.
    • Nucleus: Controls cell activity; contains genetic material.
    • Mitochondria: Produces energy for the cell.
    • Golgi Apparatus: Processes cellular materials for export.
    • Axon: Transmits signals away from the cell body.
    • Myelin: Insulates axon for faster signal transmission.
    • Nodes of Ranvier: Gaps in myelin for ion exchange.
    • Oligodendrocytes (CNS) and Schwann Cells (PNS): Produce myelin.

Supporting Cells

  • Glial Cells: Non-neural cells aiding neuron function.
    • Maintain ionic environment.
    • Modulate nerve signal rates through myelination.
    • Aid in neural recovery and maintain blood-brain barrier.
    • Types:
    • Astrocytes: Regulate chemical environment, involved in synapse formation.
    • Oligodendrocytes: Produce myelin in CNS.
    • Microglia: Remove debris and modulate inflammation in injury.

Neural Circuits

  • Neural Circuits: Organized groups of neurons processing specific information.
    • Afferent neurons: Carry information toward the CNS.
    • Efferent neurons: Carry information away from the CNS.
    • Interneurons: Participate in local circuit functions.

Electrical Signals and Ion Movement

  • Equilibrium: Balance of forces affecting ion distribution.
    • Diffusion: Ion movement from high to low concentration.
    • Electrical Force: Attracted to opposite charges, repelled by like charges.
  • Ions:
    • K+: More inside than outside, tends to move out, but electrically attracted back in.
    • Na+: More outside; diffusion drives it into the cell.
    • Cl-: More outside; diffusion attempts to pull it in, repulsed by anions.
    • Anions (A-): Mostly inside, cannot exit due to size.

Channel Types

  • Ion Channels: Facilitate passive transport of ions.
    • Many are closed at rest; K+ channels open, allowing a small influx of Na+.
  • Active Transporters: Use energy to move ions against concentration gradients.
    • Maintain electrochemical gradients essential for neuronal function.
    • Na+/K+ Pump: Critical for maintaining resting membrane potential; pumps 3 Na+ out and 2 K+ in.

Action Potentials

  • Resting Membrane Potential: Typically around -70 mV.
  • Action Potentials: Rapid electrical signals altering resting potential; occur in an all-or-nothing manner.
    • Triggered by reaching a threshold potential.
    • Voltage-gated ion channels responsible for the rapid changes in membrane potential.

Neurotransmission

  • Synaptic Potentials: Changes in membrane potential due to neurotransmitter release, impacting communication between neurons.
  • Receptor Potentials: Response of receptor neurons during sensory transduction.
  • Mechanisms of Signal Strength: Intensity of stimulus encoded in frequency of action potentials, not amplitude.