BIOC14 - Lecture 2 Winter 2025

Lecture Overview

  • Tutorials: Start next week; remember to sign up for a tutorial section.

Lecture Objectives

  • Neuronal Structure & Function

  • Neurotransmitters

  • Synaptic Communications

  • Types of Synaptic Receptors

  • Genetic Influences

  • Neuropharmacology

  • Human Genome Project

  • Genetic Variations

  • SNPs (Single Nucleotide Polymorphisms)

  • GWAS (Genome Wide Association Studies)

Neuronal Structure

  • Neurons: Specialized cells that receive and send information via electrochemical signals.

    • Approx. 100 billion neurons in an average human brain.

    • Length ranges from micrometers to meters.

  • Some neurotransmitters are synthesized and packaged in the soma (cell body) and transported to the axon terminals for release.

Neuronal Function

  • Resting Potential: Difference in electrical charge across the neuronal membrane, typically around -70mV.

  • Ion Channels: Specialized proteins in the membrane control the movement of ions.

    • Movement of ions raises intracellular voltage, reaching a threshold level of approximately -50mV to -55mV to open voltage-sensitive ion channels.

Synaptic Communication Steps

  1. Reception: Receiving the signal.

  2. Transduction: Conversion of chemical signals to electrical signals.

  3. Transmission: Propagation of the signal from the axon terminal to the dendrite.

Neurotransmitters

  • Chemicals that alter the function of adjacent cells, capable of binding, unbinding, and re-binding to their receptors.

  • Reuptake by transporter proteins allows neurotransmitters to be transported back into the presynaptic terminal for reuse.

  • Agonists: Increase neurotransmission by activating postsynaptic receptors or blocking autoreceptors.

  • Antagonists: Decrease neurotransmission by blocking postsynaptic receptors or inhibiting neurotransmitter release.

Major Neurotransmitters**

  • Acetylcholine (ACh): Released at neuromuscular junctions; involved in muscle activation.

  • Norepinephrine (NE): Plays a role in attention and responding actions in the body.

  • Serotonin: Influences mood and emotional state; targets for antidepressant medications.

  • Glutamate: Main excitatory neurotransmitter; critical for memory and learning.

  • GABA: Main inhibitory neurotransmitter; regulates anxiety and has calming effects.

Neuropharmacology

  • Focuses on how drugs affect the nervous system, examining therapeutic uses and risks including addiction.

  • Pharmacogenomics: Study of genetic factors that influence responses to drugs.

The Human Genome Project (HGP)

  • Goals: Identify all human genes, determine DNA base pair sequences, improve analytical methods, and address ethical concerns.

  • Findings: Human genome is approximately 3 billion base pairs with around 20,000-25,000 genes. Majority of the genome does not code for proteins (initially termed "junk DNA").

  • Unique Human Genes: Some genes such as NOTCH2NL linked to human brain evolution.

Genetic Variations**

  • Genetic polymorphisms lead to individual distinctions affecting physical and behavioral traits.

    • SNPs: Single nucleotide differences can predispose to diseases and affect drug responses.

    • Copy Number Variants (CNVs): Variations in the number of copies of certain genes can result in phenotypic differences.

  • GWAS: A tool to examine the association between genetic variants and diseases/traits, often includes sample collections from patients and controls for statistical analysis.