biolpsy_05

Biological Psychology 1 Lecture 05: The Cellular Physiology of the Neuron

  • Lecturer: Dr. Richárd Reichardt

  • Contact: reichardt.richard@ppk.elte.hu

The Nervous System

  • The nervous system is made up of cells.

  • Electrical Signals:

    • Behavioral and cognitive phenomena arise from the passage of electrical signals through the nervous system.

    • Neurons are responsible for generating, conducting, and transmitting these signals.

Cell Structure

Basic Components:

  • Cell Membrane:

    • Encases the cell, maintaining its integrity.

  • Cytoplasm:

    • Main compartment containing most functional parts.

  • Nucleus:

    • Houses genetic material (DNA).

Organelles and Their Functions:

  • Cytoplasm is filled with organelles that perform vital functions:

    • Endoplasmic Reticulum: Central to protein synthesis.

    • Mitochondrion: Produces energy (ATP).

Cell Membrane Functions

  • Separates the cell from its environment.

  • Maintains a constant internal environment crucial for cellular functions (e.g., controlling cytoplasmic pH).

Mitochondrion and Energy Production

  • Produces ATP through:

    • Cellular Respiration Processes:

      • Glycolysis

      • Citric Acid Cycle

      • Terminal Oxidation

    • Consumes oxygen and glucose, producing carbon dioxide and water.

Resting Potential

  • Ion concentrations differ inside and outside the cell, generating electrical potential.

  • The cell membrane restricts charged particle passage, maintaining this potential.

Stimulation and Membrane Potential Changes

  • The membrane potential can change:

    • Hyperpolarization: Increases potential difference.

    • Depolarization: Decreases potential difference.

Action Potential

  • An action potential occurs if the membrane potential reaches a threshold.

  • Driven by differences in ion concentrations, with significant change propagated throughout the nervous system.

Resting Membrane Potential regulators

  • Key Components:

    • Potassium channels

    • Na-K pumps

    • Intracellular proteins set the resting potential.

Propagation of Action Potential

  • Usually generated at the axon hillock and transmitted through the axon to innervated cells.

Unmyelinated Axons

  • Slow conduction (10 m/s), with local depolarization triggering adjacent sodium channels.

  • Refractory periods temporarily halt action potential re-creation.

Myelinated Axons

  • Rapid conduction (150 m/s) via saltatory conduction, akin to electricity in a wire.

  • Depolarization spreads quickly due to the presence of myelin and nodes of Ranvier, allowing fast nerve signal propagation.

Neural Transmission

Types of Neural Transmission:

  • Excitatory Transmission: Depolarizes the neuron.

  • Inhibitory Transmission: Hyperpolarizes the neuron.

Signal Summation

  • Neurons receive multiple signals from different inputs.

  • Summation types:

    • Spatial Summation: Multiple inputs from different locations.

    • Temporal Summation: Inputs received in rapid succession.

Neural Logic

  • Membrane potential can either be in a resting state or convert to an action potential, analogous to transistor activity.

  • Neurons form circuits that perform logical operations, forming foundations for cognitive science.

Chemical Neurotransmission

  • Otto Loewi's Experiment: Demonstrated chemical neurotransmission via stimulation of a frog's heart, showing neurotransmitters influence heart rate.

Synaptic Transmission

  • An action potential triggers ionic concentration changes at the presynaptic membrane, activating proteins for neurotransmitter exocytosis.

Neurotransmitter Release

  • Neurotransmitters are released from the presynaptic cell through exocytosis, requiring energy and protein mediation.

Receptor Types

  • Ionotropic Receptors: Direct ion channels.

  • Metabotropic Receptors: Activate ion channels via other proteins.

Protein Functions in Cells

  • Most cellular functions are performed by proteins, which constitute the cytoskeleton and create stable environments within compartments.

Axonal Transport

  • Axonal transport relies on the cytoskeleton and transport proteins, crucial for delivering proteins synthesized in the cell body to the axon terminals.

Dendritic Arborization

  • Neurons undergo process changes crucial for neuroplasticity, influenced by the cytoskeleton.

Proteins

  • Composed primarily of amino acids, forming complex structures critical for cellular functions.

  • Misfolded proteins can disrupt normal function.

The Central Dogma of Molecular Biology

  • Genes (blueprints contained in DNA) encode for proteins, with information transferred through mRNA to define amino acid sequences.

Protein Synthesis

  • Involves ribosomes and tRNA creating protein chains based on mRNA triplets.

Gene Expression

  • Different cells express different proteins despite having the same DNA.

  • Expression is regulated and can be assessed through protein or mRNA content.

Conclusion

  • Thank you for your attention!

  • Next class will cover the Phylogeny and Ontogeny of the Brain.