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.