Axon guidance

Axon guidance

1. Weiss hypothesis- random outgrowth and elimination of non-functional

2. Sperry hypothesis- specific outgrowth due to chemoaffinity

   • usually posterior retina to anterior tectum, vice versa
     • experiments where posterior (temporal) retina removed, anterior (nasal) grew directly to posterior tectum
       • REGENERATION NOT DEVELOPMENT!

3. DEVELOPMENT!

   • Highly stereotyped, find way to target due to guidance cues
   • Pioneering axons, pathway for developing axons to follow
     • If removed then axon growth stunted despite presence of other axons
     • Therefore releases specific cues!!!
       • LABELLED_PATHWAY HYPOTHESIS
         • selective fasciculation of axons with other axons