Evolution of nervous systems

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Evolution of nervous systems
Bio334 Neurobiology 1 Lecture 2
August 5th 2013
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BIO 334 - Lecture 2 - Evolution of nervous systems
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Questions from the last lecture

• Patients with Brocas 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
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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

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BIO 334 - Lecture 2 - Evolution of nervous systems
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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

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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)

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Metazoan (multicellular) phylogenetic tree
http//genomebiology.com/2006/7/7/R64/figure/F1?hi
ghresy
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BIO 334 - Lecture 2 - Evolution of nervous systems
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Metazoan (multicellular) phylogenetic tree
http//genomebiology.com/2006/7/7/R64/figure/F1?hi
ghresy
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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/
August 5th 2013
BIO 334 - Lecture 2 - Evolution of nervous systems
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Metazoan (multicellular) phylogenetic tree
http//genomebiology.com/2006/7/7/R64/figure/F1?hi
ghresy
August 5th 2013
BIO 334 - Lecture 2 - Evolution of nervous systems
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Diversity of nervous systems among other members
of metazoa
http//www.pcsd.k12.ny.us/bwoods/Regents20Biology
/Chapter201420Nervous20Regulation/48-NervousSys
tems/48-15-NervSystemDiversit-L.gif
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Nerve nets diffuse nervous systems without a
brain

• Connect sensory neurons to muscles

http//www2.estrellamountain.edu/faculty/farabee/b
iobk/biobooknerv.html
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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

http//www.prokop.co.uk/Research/Drosi-Info/nerve-
cords.html
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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

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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

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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)
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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
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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
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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
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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/resear
ch/units/dev_biology/arendt/
http//cambrianmammal.wordpress.com/tag/arthropods
/l
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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

Basic Nervous System Types One or Many? from the
book Evolution of Nervous systems Vol 1 edited
by Jon Kaas
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Ventral and dorsal nerve cords could also have
arisen independently from nerve nets
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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
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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
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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
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Brain complexity expansion of cortex
https//sphotos-b.xx.fbcdn.net/hphotos-prn1/p480x4
80/309155_515369375148492_2145532623_n.jpg
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Brain size vs. brain weight correlation
https//pantherfile.uwm.edu/rswain/www/class/SUM05
/slect1.html
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Encephalization quotent
https//pantherfile.uwm.edu/rswain/www/class/SUM05
/slect1.html
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