L3 Development Annotated

Lecture Overview

  • Lecture 3: Development in Bio Psychology

  • Date: January 14th, 2025

Learning Objectives

  • 3.1: Understand the influence of the chemical signal Noggin on cell development.

  • 3.2: Predict cell fate based on exposure to varying concentrations of Sonic Hedgehog (SHH).

  • 3.3: Explain how developing axons find destinations; discuss permissive, attractive, and repulsive cues.

  • 3.4: Examine the ocular dominance columns (ODC) ratio in cats based on early visual exposure.

Neural Development

  • Focus on how the nervous system develops, highlighting key timepoints and themes.

3.1 - Noggin

  • Development Stage: Gastrula

    • Key stage for major organ system precursors.

    • Formation of the gastrointestinal tract.

Layers of Cells in Gastrula

  • Three Major Layers:

    • Ectoderm: precursor for skin cells and nervous system.

    • Mesoderm: often involved in muscle and skeleton formation.

    • Endoderm: forms internal organs and linings.

Ectoderm Development

  • Exploring how ectoderm cells develop into neurons vs. skin cells.

  • Factors influencing this fate include:

    • Chemical signals

    • Electrical signals

    • DNA and environmental interactions.

Chemical Signals Overview

  • Chemical Signals: Molecules that influence cellular processes.

  • Signals interact with cell surface receptors, activating or inhibiting cellular functions.

Noggin as a Key Chemical Signal

  • Noggin: specialized signal determining nervous system development.

    • Produced by gastrula cells along the back pore.

  • Cells in contact with Noggin are directed to develop into the nervous system.

Neurulation

  • Ectoderm exposure to Noggin leads to neural tube formation, evolving into the brain and spinal cord.

  • Implications of Noggin Manipulation:

    • Excess Noggin could lead to additional nervous system formation.

3.2 - Sonic Hedgehog (SHH)

  • Function: Determines body axis and cell fate in the neural tube.

  • Concentration Gradient:

    • High at the base (front of the nervous system).

    • Low at the top (back of the nervous system).

  • Exposure levels dictate regional specialization during development.

3.3 - Axon Guidance

  • Growth Cone: Specialized structure at the tip of an axon aiding in directional growth.

  • Guided by chemical signals, including:

    • Permissive cues: Allow attachment/survival.

    • Attractive cues: Draw the axon towards them.

    • Repulsive cues: Push the axon away.

Dynamic Cues

  • Same signal can act differently depending on the originating cell type, allowing axons to navigate properly.

3.4 - Synaptic Refinement

  • Developing nervous system generates more axons than necessary, competing for connections.

  • Strong connections develop through:

    • Hebbian Plasticity: "Cells that fire together, wire together."

  • Experiential Learning:

    • Ocular dominance columns in the primary visual cortex are shaped by visual exposure during the critical period.

Cat ODC Example

  • ODCs respond variably based on visual exposure:

    • Normal cats retain connections from both eyes.

    • Ocular dominance changes observed in kittens exposed to visual deprivation.

Importance of Experience-Based Plasticity

  • Critical periods exist where exposure to specific experiences shapes neural development.

  • Broader implications for learning and environmental exposures in early development.


The learning objectives for Lecture 3 on Development in Bio Psychology include the following:

3.1: Understand the influence of the chemical signal Noggin on cell development, specifically how it directs ectodermal cells to develop into the nervous system during the gastrulation stage.

3.2: Predict cell fate based on exposure to varying concentrations of Sonic Hedgehog (SHH), noting that high concentrations at the base of the neural tube promote certain cell fates while lower concentrations influence others.

3.3: Explain how developing axons find destinations, discussing the roles of permissive, attractive, and repulsive cues in guiding axons through their growth cones.

3.4: Examine the ocular dominance columns (ODC) ratio in cats based on early visual exposure, emphasizing the impact of visual experiences on synaptic refinement and neural development.