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Organization of the nervous system
Raghav Rajan
Bio 334 – Neurobiology I
August 19th 2013
19th August 2013
Bio 334 - Neurobiology I - Organization of the nervous system
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Mammalian brain is very similar in its organization
across species
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Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
Orienting within the brain – absolute axes and relative
axes
SUPERIOR
(above)
●
●
ANTERIOR
(in front)
Anterior/Posterior,
Superior/Inferior –
absolute axis system
Rostral/Caudal,
Dorsal/Lateral – relative
to the long axis of the
brain or spinal cord
POSTERIOR
(behind)
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INFERIOR
(below)
http://www.rci.rutgers.edu/~uzwiak/AnatPhys/APFallLect19.html
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Medial – lateral axes
LATERAL
(away
from the
midline)
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MEDIAL
(near the
midline)
LATERAL
(away
from the
midline)
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Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
Ipsilateral and contralateral – things on the same side
or the opposite side
IPSILATERAL
(same side)
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CONTRALATERAL
(opposite side)
Bio 334 - Neurobiology I - Organization of the nervous system
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Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
Absolute and relative axes are the same in rats
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Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
Planes of brain sections
Kandel, Schwartz and Jessell, Principles of Neural Science
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Bio 334 - Neurobiology I - Organization of the nervous system
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Planes of brain sections
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http://homepage.smc.edu/russell_richard/Psych2/Graphics/human_brain_directions.htm
Divisions of the nervous system
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Bio 334 - Neurobiology I - Organization of the nervous system
http://serendip.brynmawr.edu/exchange/brains/structures
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Central Nervous System (CNS) consists of brain and
spinal cord
Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
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Bio 334 - Neurobiology I - Organization of the nervous system
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Brain is covered by 3 membranes called the meninges
●
Dura mater
●
Arachnoid mater
●
Pia mater
●
●
●
http://www.mayoclinic.com/health/medical/IM03177
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●
Along with CSF – they serve
as protection
CSF flows between
Arachnoid and Pia mater
Fish – one membrane
Birds, reptiles, amphibians two
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Ventricular system of the brain makes CerebroSpinal
Fluid (CSF)
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Bio 334 - Neurobiology I - Organization of the nervous system
Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
12
Parts of the brain – continuing from development of
the tripartite brain
Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
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Bio 334 - Neurobiology I - Organization of the nervous system
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Forebrain divides further into telencephalon, optic
vesicles and diencephalon
●
Optic vesicles give
rise to retina and
optic nerves – part
of CNS
Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
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Telencephalon grows into cerebral hemispheres,
olfactory bulbs
●
Cerebral lobes grow
●
Olfactory bulbs sprout out
●
Cells of the wall divide and differentiate
White matter systems develop
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●
Bio 334 - Neurobiology I - Organization of the nervous system
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Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
Gray matter and white matter
●
Gray matter – Collection of neuronal cell bodies
●
White matter – Collection of axons
●
Brain – gray matter outside, white matter inside
●
Spinal cord - opposite
http://www.studyblue.com/notes/note/n/peripheral-nerve/deck/1119699
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Organization of telencephalic and diencephalic
structures
Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
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Bio 334 - Neurobiology I - Organization of the nervous system
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Cortex connects with other parts through 3 major
white matter systems
●
Cortical white matter – axons to and from cortex
●
Corpus callosum – connects the two hemispheres
●
Internal capsule – connects cortex to thalamus, brain
stem
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Lateralization of brain function – studied extensively
in split brain patients by Roger Sperry
●
●
●
●
●
Corpus callosum severed to treat
epilepsy
Mostly normal people
Clever experiments revealed brain
lateralization of function
Sperry won the Nobel in 1981 for his
work on split-brain patients
"The great pleasure and feeling in my
right brain is more than my left brain
can find the words to tell you." Roger
Sperry
http://en.wikipedia.org/wiki/Roger_Wolcott_Sperry
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Experiment on split-brain patient
●
●
Right hemisphere shown a
picture of snow
Left hemishere shown a
chicken foot
http://thebrain.mcgill.ca/flash/capsules/experience_bleu06.html
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Forebrain is the seat of voluntary action, perceptions,
conscious awareness, cognition, etc.
●
●
Telencephalon
–
Cortex – neocortex, hippocampus, olfactory cortex
–
Basal telencephalon – basal ganglia, amygdala, etc.
Diencephalon
–
Thalamus
–
Hypothalamus
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Cerebral cortex – a layered structure important for
sensations, voluntary movements, cognition, etc.
●
●
Olfactory cortex,
hippocampus
–
older cortices
–
at most 3 layers
–
divided into subfields
Neocortex
–
newer cortex
–
6 layers
–
arranged into columns
Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
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Cortex has layered organization of cell bodies and
neuronal processes
●
●
●
●
●
Neocortex has 6 layers
Layer 1 does not have cell
bodes
Golgi – cell bodies and
processes
Nissl – cell bodies and
proximal dendrites
Weigert stain – myelinated
fibers
Kandel, Schwartz and Jessell, Principles of Neural Science
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This layering develops through neurogenesis from the
ventricular zone
●
●
Cells from the
ventricular
zone exit the
cell cycle and
migrate
outwards
Pre-plate
forms layer I
Dan H Sanes, Thomas A Reh, William A Harris, Development of the nervous system 2005. Chapter 3
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Newly born neurons “pull” themselves up to their final
place or migrate along radial glia scaffolds
●
Early born
neurons
may “pull”
themselves
up by somal
translocatio
n
Later born
neurons
migrate
along radial
glia
scaffolds
Nadarajah B and Parnavelas JG. Modes of neuronal migration in the developing cortex. Nature Revs Neuros. (2002)
●
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Radial glia
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Two modes of neuronal migration
Somal translocation
Radial glia migration
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Bio 334 - Neurobiology I - Organization of the nervous system
Nadarajah B and Parnavelas JG. Modes of neuronal migration in the developing cortex. Nature Revs Neuros. (2002)
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Interneurons are formed from a different source – the
lateral ganglionic emminence
●
●
LGE – ventral telencephalon
Migrate tangentially into
cortex
Nadarajah B and Parnavelas JG. Modes of neuronal migration in the developing cortex. Nature Revs Neuros. (2002)
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Mammalian cortex (layers II-VI) develops in an insideout fashion – first neurons form inner layers
Monkey
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Bio 334 - Neurobiology I - Organization of the nervous system
Dan H Sanes, Thomas A Reh, William A Harris, Development of the nervous system 2005. Chapter 3
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Special features of human CNS
●
More cortex – sulci and gyri
Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
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More lobes in the cortex
Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
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Layering of neocortex is different in different portions
of cortex
●
●
Brodmann made a
cytoarchitechtural
map of cortex –
n=1!
Constantin von
Economo and
Georg N Koskinos
Kandel, Schwartz and Jessell, Principles of Neural Science
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Brodmann divided cortex into 47 areas based on
cytoarchitechture
●
Functionally, there
can be even more
areas within each
Brodmann area
Mark F Bear, Barry W Connors, Michael A Paradiso. Neuroscience: Exploring the brain (2007) – Chapter 7
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Layering may separate out inputs and outputs from
different regions
●
●
●
Projections to
different regions
arise from different
layers
Layer I – III –
intracortical
connections
Layer IV –
thalamocortical
input connections
Layer V, VI – output
connections
Kandel, Schwartz
and Jessell, Principles to
of Neural Science
subcortical
●
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Different types of connections may also come into
different layers
●
●
Feedforward and feedback connections may originate and
terminate in different layers
Such connections may be used to determine the position
of a particular area in the hierarchy of cortical areas
Kandel, Schwartz and Jessell, Principles of Neural Science
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And different areas connect up in a simple hierarchy
like this!
●
●
Visual system
Connections from 1991
paper (20 years ago)
Felleman DJ, Van Essen DC. Distributed hierarchical processing in the primate cerebral cortex. Cerebral Cortex (1991)
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So what can we take from all of this about the
organization of neocortex?
●
Two important concepts
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The right hemisphere senses the left side and controls
the left side of the body
http://scienceblogs.com/thoughtfulanimal/2010/06/30/ask-a-scienceblogger-sensation/
http://www.stanford.edu/group/hopes/cgi-bin/wordpress/2010/06/the-hopes-brain-tutorial-text-version/
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Columnar organization of cortex – cells in one column
do similar things
Vernon B Mountcastle. The columnar organization of neocortex. Brain (1997)
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Columnar organization of cortex – cells in one column
do similar things
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Bio 334 - Neurobiology I - Organization of the nervous system
Vernon B Mountcastle. The columnar organization of neocortex. Brain (1997)
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Blue brain project – simulate one rat cortical column –
building block for brain with 100,000 columns!
●
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About 10,000 neurons
Bio 334 - Neurobiology I - Organization of the nervous system
http://bluebrain.epfl.ch/page-52063.html
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