Evolution of nervous systems Bio334 – Neurobiology 1 – Lecture 2 BIO 334 - Lecture 2 - Evolution of August 5th 2013 1 nervous systems Questions from the last lecture • Patients with Broca’s area lesions do have trouble writing • Golgi – Cajal debate – reticular theory of the brain vs. individual cells BIO 334 - Lecture 2 - Evolution of August 5th 2013 2 nervous systems Why study the evolution of nervous systems http://freethinkerperspective.blogspot.in/2013/05/mind-body-monismdualism.html • Curiousity • May provide fundamental insights into nervous system function and development BIO 334 - Lecture 2 - Evolution of August 5th 2013 3 nervous systems How to study evolution of nervous systems? • Soft tissue not preserved properly so fossil record is not useful • Instead study and compare the nervous systems of living animals from different phyla • Caveat – these animals have also gone through evolution BIO 334 - Lecture 2 - Evolution of August 5th 2013 4 nervous systems What is a nervous system? • A nervous system is an organized constellation of cells (neurons) specialized for the repeated conduction of an excited state from receptor sites or from neurons to effectors or to other neurons” • Bullock and Horridge (1965) • Additionally should be capable of endogenously generating activity • Passano (1963) BIO 334 - Lecture 2 - Evolution of August 5th 2013 5 nervous systems Metazoan (multicellular) phylogenetic tree http://genomebiology.com/2006/7/7/R64/figure/F1?highres=y BIO 334 - Lecture 2 - Evolution of August 5th 2013 6 nervous systems Metazoan (multicellular) phylogenetic tree http://genomebiology.com/2006/7/7/R64/figure/F1?highres=y BIO 334 - Lecture 2 - Evolution of August 5th 2013 7 nervous systems Sponges – no nervous system – just muscle- like organs • Non-motile • Just muscle-like effectors that can control the flow of water • These muscle-like cells also sense environmental cues http://www.thebioblog.com/ BIO 334 - Lecture 2 - Evolution of August 5th 2013 8 nervous systems Metazoan (multicellular) phylogenetic tree http://genomebiology.com/2006/7/7/R64/figure/F1?highres=y BIO 334 - Lecture 2 - Evolution of August 5th 2013 9 nervous systems Diversity of nervous systems among other members of metazoa http://www.pcsd.k12.ny.us/bwoods/Regents%20Biology/Chapter%2014%20Nervous %20Regulation/48-NervousSystems/48-15-NervSystemDiversit-L.gif BIO 334 - Lecture 2 - Evolution of August 5th 2013 10 nervous systems Nerve nets – diffuse nervous systems without a brain • Connect sensory neurons to muscles http://www2.estrellamountain.edu/faculty/farabee/biobk/biobooknerv.html BIO 334 - Lecture 2 - Evolution of August 5th 2013 11 nervous systems Bilateralia – animals with bilateral symmetry have a organised nervous system • Brain and nerve cord • Cephalization – brain and sense organs close to one end of the body http://www.prokop.co.uk/Research/Drosi-Info/nerve-cords.html BIO 334 - Lecture 2 - Evolution of August 5th 2013 12 nervous systems Did these all evolve from a common ancestor? • Examine the mechanisms and see if subsequent nervous systems could be viewed as modifications BIO 334 - Lecture 2 - Evolution of August 5th 2013 13 nervous systems Action potential present in unicellular organisms • Calcium based • Could have been adapted to use sodium and potassium based currents • Electrical signaling is fast and can travel quickly over long distances • High fidelity • Is also specific – can activate target neurons without activating neurons on the way BIO 334 - Lecture 2 - Evolution of August 5th 2013 14 nervous systems Post-synaptic density proteins expressed in sponges • Co-regulation maybe important for forming a functional synapse Sakarya et al. PLOS One (2007) Conaco et al. PNAS (2012) BIO 334 - Lecture 2 - Evolution of August 5th 2013 15 nervous systems Ventral nerve cord in invertebrates vs. dorsal nerve cord in vertebrates • Did they evolve independently? http://www.prokop.co.uk/Research/Drosi-Info/nerve-cords.html BIO 334 - Lecture 2 - Evolution of August 5th 2013 16 nervous systems Vertebrate dorsal nerve cord may be a result of inversion of ventral nerve cord • Geoffroy Saint-Hilaire, Anton Dohrn http://cambrianmammal.wordpress.com/tag/arthropods/l BIO 334 - Lecture 2 - Evolution of August 5th 2013 17 nervous systems Conserved expression of genes in the anterio-posterior direction in the CNS Origin and evolution of the first nervous system from the book Evolution of Nervous systems: Vol 1 edited by Jon Kaas BIO 334 - Lecture 2 - Evolution of August 5th 2013 18 nervous systems Vertebrate dorsal nerve cord may be a result of inversion of ventral nerve cord – more evidence Platynereis – Arendt lab http://www.embl.de/research/un its/dev_biology/arendt/ http://cambrianmammal.wordpress.com/tag/arthropods/l BIO 334 - Lecture 2 - Evolution of August 5th 2013 19 nervous systems Tripartite brain might have been present in an ancestor to Bilateria • Similar divisions in Drosophila and mouse and ascidians • Gene expression similar Basic Nervous System Types: One or Many? from the book Evolution of Nervous systems: Vol 1 edited by Jon Kaas BIO 334 - Lecture 2 - Evolution of August 5th 2013 20 nervous systems Ventral and dorsal nerve cords could also have arisen independently from nerve nets BIO 334 - Lecture 2 - Evolution of August 5th 2013 21 nervous systems Evolution of first nervous systems Origin and evolution of the first nervous system from the book Evolution of Nervous systems: Vol 1 edited by Jon Kaas BIO 334 - Lecture 2 - Evolution of August 5th 2013 22 nervous systems Evolution of first nervous systems Origin and evolution of the first nervous system from the book Evolution of Nervous systems: Vol 1 edited by Jon Kaas BIO 334 - Lecture 2 - Evolution of August 5th 2013 23 nervous systems Evolution of first nervous systems Origin and evolution of the first nervous system from the book Evolution of Nervous systems: Vol 1 edited by Jon Kaas BIO 334 - Lecture 2 - Evolution of August 5th 2013 24 nervous systems Brain complexity – expansion of cortex https://sphotos-b.xx.fbcdn.net/hphotos-prn1/p480x480/309155_515369375148492_2145532623_n.jpg BIO 334 - Lecture 2 - Evolution of August 5th 2013 25 nervous systems Brain size vs. brain weight correlation https://pantherfile.uwm.edu/rswain/www/class/SUM05/slect1.html BIO 334 - Lecture 2 - Evolution of August 5th 2013 26 nervous systems Encephalization quotent https://pantherfile.uwm.edu/rswain/www/class/SUM05/slect1.html BIO 334 - Lecture 2 - Evolution of August 5th 2013 27 nervous systems.