26th August 2013 Bio 334 - Neurobiology I - Organization of the nervous system 3 1

Organization of the nervous system 3

Raghav RajanBio 334 – Neurobiology I

August 26th 2013

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Spinal cord

● Dorsal roots carry sensory information

● Ventral roots carry motor information

● Controls voluntary and reflexive movements

● Receives sensory input from skin, joints, muscles

● Paralysis inferior to location of damage

Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7

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PNS

● Somatic PNS – related to voluntary control

● Visceral PNS – involuntary – innervates internal organs, glands, blood vessels, etc.

http://en.wikipedia.org/wiki/Peripheral_nervous_system

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General functions of nervous system

● To find food● To avoid being eaten● To reproduce

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Evolution of complex nervous systems

● Evolution selects for adaptations that promote the ability to pass on genetic material

● Works on what is already there● Needs some amount of redundancy to tinker and

make changes

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General principles of organization of nervous system

● Organization of sensory and motor areas dependent on environment, relative importance of different sense organs, motor capabilities

● Based on anatomy, we can delineate functional systems

● Functional systems are organized into maps● Hierarchy of functional systems?● Functional systems on one side of the brain

(cerebral cortex) get information and control the contralateral side of the body

Kandel, Schwartz and Jessell, Principles of Neural Science

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Sensory and motor cortical representations not proportional to external size

http://www.autismindex.com/Therapies/Therapy_Key_Word_Site_Map/sensory/motor_sensory_homunculus.html

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Important sensory organs are better represented in the cortex and sub-cortical structures

http://www.pnas.org/content/109/Supplement_1/10647.long

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Functional systems – like the visual system – two streams of processing

● Dorsal pathway - “vision for action” - where

● Ventral pathway - “vision for perception” - what

● Now, considerable evidence for interaction between both pathways

http://www.waece.org/cd_morelia2006/ponencias/stoodley.htm

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Maps – sensory, motor, etc.

http://uc.exteenblog.com/highwind/images/Know/brain_homunculus1.jpghttp://www.wiringthebrain.com/2010_12_01_archive.htmlhttp://neurowww.cwru.edu/faculty/strowbridge/OlfactoryBulb/bulb1.htmhttp://www3.unil.ch/wpmu/neuroaudio/resaerch/auditory-cortex/

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Hierarchichal processing within functional systems – is there really a hierarchy?

Felleman DJ, Van Essen DC. Distributed hierarchical processing in the primate cerebral cortex. Cerebral Cortex (1991)http://www.cse.buffalo.edu/~rapaport/575/F07/006010.jpg

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Plasticity – changes in strength of connections not reflected in simple anatomy

● In congenitally blind people, primary visual cortex is active during sentence comprehension task

http://www.pnas.org/content/108/11/4429.long

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Assignment on disorders

● 1 page write-up – in layman language● Description of disorder● Present understanding of the cause?● What does this tell us about the brain?● Caveats● Send by email before the 2nd of September