2017 Group Project 1: Difference between revisions

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-prefrontal areas (prefrontal cortex)
-prefrontal areas (prefrontal cortex)
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==INFO/ Research Links (temporary heading)==
==INFO/ Research Links (temporary heading)==

Revision as of 15:01, 5 October 2017

2017 Student Projects 
Student Projects: 1 Cerebral Cortex | 2 Kidney | 3 Heart | 4 Eye | 5 Lung | 6 Cerebellum
Student Page - here is the sample page I demonstrated with in the first labs.I remind all students that you have your own Group Forum on Moodle for your discussions, it is only accessible by members of your group.
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Cerebral Cortex

Mark Hill (talk) 15:59, 14 September 2017 (AEST) Feedback

  • lots of sub-headings, but no actual text.
  • no defined structure to the sequence of sub-headings.
  • no research images related to what is an extensively researched topic.
  • historic background of key research findings, put our understanding today in perspective.
  • Lon list of abnormalities, with no description.

Introduction

( z5178570 )

What is it?

The cerebral cortex is the largest part of the human brain and is thought to be the main control centre, playing an essential role in cognitive function, memory, sensation and association. The cerebral cortex consists of the thin layer of the grey matter, around 2-4 mm in thickness, that surrounds the cerebrum, and consists of ~ 10 billion nerve cell bodies and dendrites.

The development of the cerebral cortex involves differentiation and migration of neurons, which are organised into six horizontal layers. I. Molecular layer, II. External granular layer , III. external pyramidal, IV. internal granular layer, V. internal pyramidal layer, VI. multiform layer. These individual layers organise the capacity for interconnections between both input and output signals.

Histology of Cerebral Cortex

https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0024757/ Z5177691 (talk) 22:37, 23 August 2017 (AEST)

Stage 22 image 217.jpg


Early Development of the Brain (and Nervous System)

The brain begins to develop during the third week when the neural plate and tube derive from the outer most layer of embryonic cells, the neuroectoderm. The development of the brain is from the neural plate which folds to form the neural groove and then curls forming the neural tube, which is cranial to the fourth pair of somites, and eventually forms the three primary brain vesicles.

Neuroprogenitor cells proliferate, migrate, and differentiate to form specific areas of the brain.

During week four fusion of the neural folds in the cranial region and closure of the rostral neuropore form three primary brain vesicles from which the brain develops:

  • Forebrain/Prosecephalon
  • Midbrain/Mesencephalon
  • Hindbrain/Rhombencephalone


From there three primary vesicles, there is a further division at the anterior extremity of the medullary canal into five secondary vesicles during week five. These are fundamental divisions of the adult brain and communicate freely with each other. They are:

  • Telencephalon: endbrain, forms cerebral hemispheres - derived from Prosecephalon
  • Diencephalon: between brain, forms optic outgrowth - derived from Prosecephalon
  • Mesencephalon: undivided
  • Metencephalon: posterior to the brain - derived from Rhomabencephalon
  • Myelencephalon: medulla - derived from Rhomabencephalon

In the beginning, these five divisions are uniform in size and shape but quickly differentiate at various rates.

Brain Flexures

During the fifth week, the embryonic brain undergoes rapid growth folding the neural tube and consequently resulting in three brain flexures. These are:

  • Cephalic flexure - pushes mesencephalon upwards
  • Cervical flexure - between brain stem and spinal cord at the junction of the spinal cord and hindbrain
  • Pontine flexure - generates fourth ventricle; produced in the opposite direcction as a result of later unequal brain growth, resulting in the thinning of the roof of the hindbrain

The primordial brain initially has the same basic structure as the developing spinal cord, however consideration variations in the outline of transverse sections at different levels of the brain and in the position of the gray and white matter are produced by the brain flexures. The sulcus limitans (the floor of the fourth ventricle) extends cranially to the junction of the midbrain and forebrain, and the alar and basal plates are recognisable only in the midbrain and hindbrain.



Development of Cerebral Cortex

(z5177691)

Main classes of neurons [1]

  • Projection neurons: excitatory neurons (glutamatergic) with axons that project to distant targets and are generated by progenitors in the dorsal pallium of the telencephalon. The have a typical pyramidal structure and send signals to various regions of the brain and neocortex.
  • Interneurons: inhibitory neurons (GABAergic) that have local connections within the cortex and are generated in the subpallium of the telecephalon in the ventral proliferative zone. These neurons have to migrate to the neocortex area.


Key developmental zones in the human cortex:

  • Ventricular zone
  • Subventricular zone
    • Inner Subventricular Zone
    • Outer Subventricular zone
  • Intermediate Zone
  • Preplate: neural progenitor cells split into 2 regions
    • Marginal zone:
    • Subplate:
  • Cortical Plate: where the 6 layers of the cortex form, exists in between the subplate and the marginal zone

Timeline of Corticogenesis

The dorsolateral wall of the telencephalon is initially made up of undifferentiated neuroepithelial cells at the beginning of development. The cells are neural stem cells, capable of dividing into various neuronal subtypes. The timing of birth for these neuronal subtypes determines the location (e.g fate) of the neurons so that specific connections and cortical structure are achieved. "E" relates to embryonic day in relation to corticogenesis.

DAY DEVELOPMENT
E30 Progenitors in the dorsal telencephalon divide symmetrically and give rise to the initial ventricular zone (VZ), a single layer of cells that attach their "feet" to the cerebral wall and divide. These neurons lay adjacent to the ventricular surface. [2]
E31-32 Dividing cells from the VZ begin to differentiate into "pioneer" neurons to form the preplate. These neurons migrate radially and tangentially from the VZ to the pial surface in an upward fashion. These cells are often referred to as radial glial cells (RGCs) because they contain radial fibers that span the entire embryonic wall from the VZ to the pial surface. These fibers create a "scaffolding" for subsequent migrating neurons to attach to and travel along in order to expand the neocortex. These cells are multipotent cells that divide asymmetrically to produce intermediate precursor cells that can become projection neurons, astrocytes, and oligodendrocytes [3] . The preplate is referred to as heterogeneous because it contains many developing cell types.
E40-45 Cells in the VZ continue to divide symmetrically and give rise to another zone known as the subventricular zone (SVZ). This proliferative layer lies above the ventricular zone and is not attached to the ventricular surface. Radial glial cells also populate this area as well as the preplate and many of the cells in the SVZ contribute to the later cortical neurons. The SVZ also separates into the outer subventricular zone (OSVZ) and the inner subventricular zone (ISVZ). The OSVZ continues to expand as it produces more migrating immature neurons and intermediate precursor cells. [4]
E50-55 The preplate begins to split into two subsections: the marginal zone and the subplate. An intermediate zone forms below the subplate and contains only migrating cells (migrating to the target destination) and no intermediate precursor cells. The cortical plate also begins to form in between the two regions. Newly born neurons that migrate to the cortical plate are developed "inside out". This term "inside-out" means that earlier born cells populate the deep layers first and later born neurons populate the superficial layers of the neocortex by migrating past the deep layers. Therefore, layers 6 is populated before layer 5; layer 5 is populated before layer 4 and so on. Each layer condenses and the neurons are closely packed. As the layers form, the cortex expands.
Stage22 HPA2L.jpg

Migration and division of all six layers of the cortex is completed during the third trimester. Each layer has distinct synaptic connections and cell types that contribute to the specific functions of the cortex.

Corticogenesis of mouse and humans.jpeg

Cell Signaling

(z5178570)

Anatomy of the Cerebral Cortex

( Jess)

-layer grey matter outer surface of cerebrum

-2-4mm thickness

-most anterior (rostral) brain region

-outer zone of neuronal tissue (grey matter) containing neuronal cell bodies

-densely packed in humans with over 10 billion nerve cells (about 10% of all the neurons in the brain)

-where much of the neural activities of the cerebrum takes place

-divided left and right hemispheres by longitudinal fissure

-two hemispheres joined by corpus callosum at midline

-divided into functional areas that serve various sensory, motor and cognitive functions

-subdivisions of layers organizing input and output connectivity of resident neurons

-is folded in larger mammals to increase surface area, important allows addition and evolution of a greater diversity functional areas

-gyrus (gyri)= folds/ ridges

-sulcus (sulci)= groove

Layers

https://en.wikipedia.org/wiki/File:Gray754.png

Layer 1

-outer layer (pial surface)

-molecular layer, few scattered neurons

-mainly extensions of pyramidal neuron apical dentrite tufts

-some spiny stellate cells

-inputs to apical tufts crucial for feedback interactions in cortex in associative learning and attention

Layer 2

-external granular layer

-small pyramidal neurons

-many stellate neurons

Layer 3

-external pyramidal layer

-small and medium sized pyramidal neurons

-non-pyramidal neurons with vertically orientated intracortical axons

-layers 1, 2, 3 main target of interhemisphere corticocortical afferent fibres

-layer 3 main source of cortiocortical efferent fibres

Layer 4

-internal granular layer

-different types stellate and pyramidal neyrons

-main target thalamocortical afferents from thalamus type C neurons and intra-hemipsheric corticocortical afferents

Layer 5

-internal pyramidal layer

-large pyramidal neurons

-give rise to axons leaving cortex and run down to subcortical structures e.g. basal ganglia

-In primary motor cortex of the frontal lobe, this layer contains Betz cells and their axons travel through the internal capsule, the brain stem and the spinal cord forming the corticospinal tract

-which is the main pathway for voluntary motor control

Layer 6

-polymorphic/ multiform layer

-few large pyramidal neurons

-many small spindle like pyramidal and multiform neurons

-sends efferent fibers to thalamus forms exact reciprocal interconnection between thalamus and cortex

-connections are both inhibitory and excitatory

Other info to add

three large surfaces: superolateral surface, medial surface, inferior surface

-surfaces characterised by sulci and gyri

three borders: superomedial border, inferomedial border, inferolateral border

lobes defined by large sulci (fissures)

named according to their relation to bones of skull

1) frontal lobe

2) parietal lobe

3) temporal lobe

4) occipital lobe


Blood Supply

Functions of the Cerebral Cortex

( Jess)

https://www.youtube.com/watch?v=n6zQbTT0yoY

https://www.youtube.com/watch?v=X-m0JDCw6TE

Functional Areas

-Motor area (primary motor cortex)

-premotor area (motor association cortex)

-sensory area (pimary somatosensory cortex)

-auditory (acoustic) area

-olfactory area

-visual areas

-occipital eye field

-prefrontal areas (prefrontal cortex)

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INFO/ Research Links (temporary heading)

For concept: https://www.youtube.com/watch?v=dNngOlsLuGI

You might find this helpful (although you need to request copyright permission):

"Difference Between Cerebrum and Cerebral Cortex." DifferenceBetween.Com. August 7, 2012. < http://www.differencebetween.com/difference-between-cerebrum-and-vs-cerebral-cortex/ >

PubMed Searches: Cerebral Cortex Development | Cerebrum Development

BMC Dev Biol Search: Cerebral Cortex Development

Recent papers

<pubmed limit=5>Cerebral+Cortex+Development</pubmed>

References

[Harvard Style]

  1. <pubmed> PMC3876965 </pubmed>
  2. <pubmed> 18209730 </pubmed>
  3. <pubmed> PMC4334136 </pubmed>
  4. <pubmed> PMC4334136 </pubmed>