evolution of nervous systems bio334 – neurobiology 1 ... · nervous systems 14. post-synaptic...

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