Evolution of nervous systems
Bio334 – Neurobiology 1 – Lecture 2
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
1
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 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
2
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
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
3
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 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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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 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
5
Metazoan (multicellular) phylogenetic tree
http://genomebiology.com/2006/7/7/R64/figure/F1?highres=y
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
6
Metazoan (multicellular) phylogenetic tree
http://genomebiology.com/2006/7/7/R64/figure/F1?highres=y
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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Sponges – no nervous system – just musclelike 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/
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
8
Metazoan (multicellular) phylogenetic tree
http://genomebiology.com/2006/7/7/R64/figure/F1?highres=y
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
9
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
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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Nerve nets – diffuse nervous systems
without a brain
• Connect sensory neurons to muscles
http://www2.estrellamountain.edu/faculty/farabee/biobk/biobooknerv.html
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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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 2013
http://www.prokop.co.uk/Research/Drosi-Info/nerve-cords.html
BIO 334 - Lecture 2 - Evolution of
nervous systems
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Did these all evolve from a common
ancestor?
• Examine the mechanisms and see if
subsequent nervous systems could be
viewed as modifications
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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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 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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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)
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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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
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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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
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
17
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
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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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
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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Tripartite brain might have been present in
an ancestor to Bilateria
• Similar divisions in Drosophila and mouse and
ascidians
• Gene expression similar
August 5th 2013
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
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nervous systems
Ventral and dorsal nerve cords could also
have arisen independently from nerve nets
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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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
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
22
Evolution of first nervous systems
August 5th 2013
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
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
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
24
Brain complexity – expansion of cortex
August 5th 2013
https://sphotos-b.xx.fbcdn.net/hphotos-prn1/p480x480/309155_515369375148492_2145532623_n.jpg
BIO 334 - Lecture 2 - Evolution of
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nervous systems
Brain size vs. brain weight correlation
https://pantherfile.uwm.edu/rswain/www/class/SUM05/slect1.html
August 5th 2013
BIO 334 - Lecture 2 - Evolution of
nervous systems
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Encephalization quotent
https://pantherfile.uwm.edu/rswain/www/class/SUM05/slect1.html
BIO 334 - Lecture 2 - Evolution of
August 5th 2013
nervous systems
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