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Evolution of nervous systems
Bio334 – Neurobiology 1 – Lecture 2
August 5th 2013 1BIO 334 - Lecture 2 - Evolution of
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
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems2
Why study the evolution of nervous systems
• Curiousity• May provide fundamental insights into nervous
system function and development
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems3
http://freethinkerperspective.blogspot.in/2013/05/mind-body-monismdualism.html
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
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems4
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)
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems5
Metazoan (multicellular) phylogenetic tree
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems6
http://genomebiology.com/2006/7/7/R64/figure/F1?highres=y
Metazoan (multicellular) phylogenetic tree
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems7
http://genomebiology.com/2006/7/7/R64/figure/F1?highres=y
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
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems8
http://www.thebioblog.com/
Metazoan (multicellular) phylogenetic tree
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems9
http://genomebiology.com/2006/7/7/R64/figure/F1?highres=y
Diversity of nervous systems among other members of metazoa
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems10
http://www.pcsd.k12.ny.us/bwoods/Regents%20Biology/Chapter%2014%20Nervous%20Regulation/48-NervousSystems/48-15-NervSystemDiversit-L.gif
Nerve nets – diffuse nervous systems without a brain
• Connect sensory neurons to muscles
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems11
http://www2.estrellamountain.edu/faculty/farabee/biobk/biobooknerv.html
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
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems12
http://www.prokop.co.uk/Research/Drosi-Info/nerve-cords.html
Did these all evolve from a common ancestor?
• Examine the mechanisms and see if subsequent nervous systems could be viewed as modifications
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems13
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
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems14
Post-synaptic density proteins expressed in sponges
• Co-regulation maybe important for forming a functional synapse
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems15
Sakarya et al. PLOS One (2007)Conaco et al. PNAS (2012)
Ventral nerve cord in invertebrates vs. dorsal nerve cord in vertebrates
•Did they evolve independently?
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems16
http://www.prokop.co.uk/Research/Drosi-Info/nerve-cords.html
Vertebrate dorsal nerve cord may be a result of inversion of ventral nerve cord
•Geoffroy Saint-Hilaire, Anton Dohrn
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems17
http://cambrianmammal.wordpress.com/tag/arthropods/l
Conserved expression of genes in the anterio-posterior direction in the CNS
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems18
Origin and evolution of the first nervous system from the bookEvolution of Nervous systems: Vol 1 edited by Jon Kaas
Vertebrate dorsal nerve cord may be a result of inversion of ventral nerve cord – more evidence
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems19
http://cambrianmammal.wordpress.com/tag/arthropods/l
Platynereis – Arendt labhttp://www.embl.de/research/units/dev_biology/arendt/
Tripartite brain might have been present in an ancestor to Bilateria
• Similar divisions in Drosophila and mouse and ascidians• Gene expression similar
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems20
Basic Nervous System Types: One or Many? from the bookEvolution of Nervous systems: Vol 1 edited by Jon Kaas
Ventral and dorsal nerve cords could also have arisen independently from nerve nets
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems21
Evolution of first nervous systems
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems22
Origin and evolution of the first nervous system from the bookEvolution of Nervous systems: Vol 1 edited by Jon Kaas
Evolution of first nervous systems
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems23
Origin and evolution of the first nervous system from the bookEvolution of Nervous systems: Vol 1 edited by Jon Kaas
Evolution of first nervous systems
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems24
Origin and evolution of the first nervous system from the bookEvolution of Nervous systems: Vol 1 edited by Jon Kaas
Brain complexity – expansion of cortex
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems25
https://sphotos-b.xx.fbcdn.net/hphotos-prn1/p480x480/309155_515369375148492_2145532623_n.jpg
Brain size vs. brain weight correlation
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems26
https://pantherfile.uwm.edu/rswain/www/class/SUM05/slect1.html
Encephalization quotent
August 5th 2013BIO 334 - Lecture 2 - Evolution of
nervous systems27
https://pantherfile.uwm.edu/rswain/www/class/SUM05/slect1.html