2017 Group Project 1 - Revision history

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2017-10-26T22:15:18Z

Protected "2017 Group Project 1" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite))

← Older revision	Revision as of 09:15, 27 October 2017
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Z5093005: /* Cerebral Cortex */

2017-10-26T11:34:02Z

Cerebral Cortex

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	[[File:Intro section cortex.jpg\|thumb\|right\|350px\|'''Figure1. Cerebral cortex is the outermost layer of the cerebrum''' <ref>Thomas, A. (2015). [image] Available at: http://slideplayer.com/slide/6617450/ [Accessed 23 Oct. 2017].</ref> ]]		[[File:Intro section cortex.jpg\|thumb\|right\|350px\|'''Figure1. Cerebral cortex is the outermost layer of the cerebrum''' <ref>Thomas, A. (2015). [image] Available at: http://slideplayer.com/slide/6617450/ [Accessed 23 Oct. 2017].</ref> ]]
	<br/>		<br/>
	The cerebral cortex is part of the brain which surrounds the cerebral hemispheres. It has a very large surface area (largest part of human brain). The cerebral cortex differs from the cerebrum because, the cerebral cortex is the outermost layer of the cerebral hemispheres (Figure 1). It is a layer of gray matter around 2-4 mm in thickness, and consists of approximately 10 billion nerve cell bodies and dendrites. It appears gray because of the cell bodies (Figure 2).<br/>		The cerebral cortex is part of the brain which surrounds the cerebral hemispheres. It has a very large surface area (largest part of human brain). The cerebral cortex differs from the cerebrum because, the cerebral cortex is the outermost layer of the cerebral hemispheres (Figure 1). It is a layer of gray matter around 2-4 mm in thickness, and consists of approximately 10 billion nerve cell bodies and dendrites. It appears gray because of the cell bodies (Figure 2).<br/><br/>
	[[File:Brain sectin showing cortex.jpg\|thumb\|left\|300px\|'''Figure 2. Section of the human brain''' <ref>Mikayla D (2017). 23. [image] Available at: https://psych-brain-trust.wikispaces.com/Thalamus [Accessed 23 Oct. 2017].</ref> ]]		[[File:Brain sectin showing cortex.jpg\|thumb\|left\|300px\|'''Figure 2. Section of the human brain''' <ref>Mikayla D (2017). 23. [image] Available at: https://psych-brain-trust.wikispaces.com/Thalamus [Accessed 23 Oct. 2017].</ref> ]]

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	The cortex is organised into six horizontal layers. I. Molecular layer, II. External granular layer , III. Xxternal 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. <br/>		The cortex is organised into six horizontal layers. I. Molecular layer, II. External granular layer , III. Xxternal 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. <br/>

	This project will explore the various embryologic aspects of the cerebral cortex, including early development of the brain, development of the cerebral cortex, anatomy and functions of the cortex, and abnormalities associated with cortical development. <br/><ref>Moore, K., Persaud, T. and Torchia, M. (2011). The Developing Human. London: Elsevier Health Sciences, pp.The Nervous System; 379-414.</ref><ref>Van Essen, D. (2005). A Population-Average, Landmark- and Surface-based (PALS) atlas of human cerebral cortex. NeuroImage, 28(3), pp.635-662.</ref><ref>Dartmouth.edu. (2006). Chapter 11: The Cerebral Cortex. [online] Available at: http://www.dartmouth.edu/~rswenson/NeuroSci/chapter_11.html.</ref><ref>Differencebetween.com. (2017). Difference Between Cerebrum and Cerebral Cortex. [online] Available at: http://www.differencebetween.com/difference-between-cerebrum-and-vs-cerebral-cortex/ [Accessed 26 Oct. 2017].</ref><ref name="first">Squier, W. and Jansen, A. (2010). Abnormal development of the human cerebral cortex. Journal of Anatomy, [online] 217(4), pp.312-323. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2992410/ [Accessed 23 Sep. 2017]. </ref>		This project will explore the various embryologic aspects of the cerebral cortex, including early development of the brain, development of the cerebral cortex, anatomy and functions of the cortex, and abnormalities associated with cortical development.<br/><ref>Moore, K., Persaud, T. and Torchia, M. (2011). The Developing Human. London: Elsevier Health Sciences, pp.The Nervous System; 379-414.</ref><ref>Van Essen, D. (2005). A Population-Average, Landmark- and Surface-based (PALS) atlas of human cerebral cortex. NeuroImage, 28(3), pp.635-662.</ref><ref>Dartmouth.edu. (2006). Chapter 11: The Cerebral Cortex. [online] Available at: http://www.dartmouth.edu/~rswenson/NeuroSci/chapter_11.html.</ref><ref>Differencebetween.com. (2017). Difference Between Cerebrum and Cerebral Cortex. [online] Available at: http://www.differencebetween.com/difference-between-cerebrum-and-vs-cerebral-cortex/ [Accessed 26 Oct. 2017].</ref><ref name="first">Squier, W. and Jansen, A. (2010). Abnormal development of the human cerebral cortex. Journal of Anatomy, [online] 217(4), pp.312-323. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2992410/ [Accessed 23 Sep. 2017]. </ref><br/>
	<br/>

	==Early Development of the Brain==		==Early Development of the Brain==

Z5093005: /* Glossary */

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Glossary

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	\|'''Radial glial cells '''\|\| A class of distinct nonneuronal cells that are bipolar shaped and span the entire width of the cortex during development.		\|'''Radial glial cells '''\|\| A class of distinct nonneuronal cells that are bipolar shaped and span the entire width of the cortex during development.
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''Seizures'''\|\| ~~are fits~~, which involve a sudden surge of electrical impulses in the brain, causing jerking of limbs and stiffness.		\|'''Seizures'''\|\| Fits, which involve a sudden surge of electrical impulses in the brain, causing jerking of limbs and stiffness.
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''Spasticity'''\|\| Having spasms in muscles or possibly some organs.		\|'''Spasticity'''\|\| Having spasms in muscles or possibly some organs.

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Glossary

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	\|'''Definition'''		\|'''Definition'''
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	\|'''Agenesis'''\|\| The total absence of a tissue or organ		\|'''Agenesis'''\|\| The total absence of a tissue or organ.
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''Cajal-Retzius (CR) cells'''\|\| Cortical neurons that develop early on, at the same time as the preplate, and express an important glycoprotein known as reelin, which helps with the proper migration of neurons into their respective layers.		\|'''Cajal-Retzius (CR) cells'''\|\| Cortical neurons that develop early on, at the same time as the preplate, and express an important glycoprotein known as reelin, which helps with the proper migration of neurons into their respective layers.
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	\|'''Etiology'''\|\| The cause or origin or explaination of a disease.		\|'''Etiology'''\|\| The cause or origin or explaination of a disease.
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''Fissures'''\|\| ~~Large~~ sulci.		\|'''Fissures'''\|\| Grooves or clefts; are actually just large sulci.
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''GABAergic Neurons'''\|\| Generate gamma aminobutyric acid (GABA) as their output, one of the two inhibitory neurotransmitters in the central nervous system (CNS).		\|'''GABAergic Neurons'''\|\| Generate gamma aminobutyric acid (GABA) as their output, one of the two inhibitory neurotransmitters in the central nervous system (CNS).
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	\|'''Heterogeneous'''\|\| Diverse, varied and many components of something.		\|'''Heterogeneous'''\|\| Diverse, varied and many components of something.
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	\|'''Hypoplasia'''\|\| Underdevelopment or incomplete development of a tissue or organ		\|'''Hypoplasia'''\|\| Underdevelopment or incomplete development of a tissue or organ.
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''Hypotonia'''\|\| The state of loss of muscle tone, or tension or stretch strength of muscles		\|'''Hypotonia'''\|\| The state of loss of muscle tone, or tension (or stretch strength) of muscles.
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''Intermediate zone'''\|\| Forms below the subplate between E50-55 and contains only migrating cells and no intermediate precursor cells.		\|'''Intermediate zone'''\|\| Forms below the subplate between E50-55 and contains only migrating cells and no intermediate precursor cells.
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	\|'''Neural Tube\|\| Structure of the embryo that evolves into the spinal cord and brain.		\|'''Neural Tube\|\| Structure of the embryo that evolves into the spinal cord and brain.
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	\|'''Olfactory'''\|\| Relating to nasal organs, sense of smell.		\|'''Olfactory'''\|\| Relating to nasal organs and/or the sense of smell.
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''Pachygyria'''\|\| Gyri can be seen but are very few compared to normal brain		\|'''Pachygyria'''\|\| Gyri can be seen but are very few compared to normal brain.
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	\|'''Preplate'''\|\| First "pioneer neurons" from dividing cells in the ventricular zone for this layer above the ventricular zone		\|'''Preplate'''\|\| First "pioneer neurons" from dividing cells in the ventricular zone for this layer above the ventricular zone.
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	\|'''Radial glial cells '''\|\| A class of distinct nonneuronal cells that are bipolar shaped and span the entire width of the cortex during development.		\|'''Radial glial cells '''\|\| A class of distinct nonneuronal cells that are bipolar shaped and span the entire width of the cortex during development.
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	\|'''Subplate'''\|\| A subsection of the preplate that forms around E50-55.		\|'''Subplate'''\|\| A subsection of the preplate that forms around E50-55.
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	\|'''Subventricular zone (SVZ)'''\|\| Cells in the VZ continue to divide symmetrically and give rise to another zone above the VZ known as the SVZ. This zone later splits into an inner (ISVZ) and outer ventricular zone (OSVZ)		\|'''Subventricular zone (SVZ)'''\|\| Cells in the VZ continue to divide symmetrically and give rise to another zone above the VZ known as the SVZ. This zone later splits into an inner (ISVZ) and outer ventricular zone (OSVZ).
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''Sulcus'''\|\| Sulci (plural) are grooves in the cerebral cortex.		\|'''Sulcus'''\|\| Sulci (plural) are grooves in the cerebral cortex.
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''Total agyria'''\|\|Gyri and sulci absent resulting in 'smooth brain'		\|'''Total agyria'''\|\|Gyri and sulci absent resulting in 'smooth brain'.
	\|-bgcolor="FAF5FF"		\|-bgcolor="FAF5FF"
	\|'''Ventricular zone (VZ)'''\|\| First formed single-celled layer in the cortex, arising from progenitors in the dorsal telencephalon that divide symmetrically. It lies adjacent to the ventricular surface.		\|'''Ventricular zone (VZ)'''\|\| First formed single-celled layer in the cortex, arising from progenitors in the dorsal telencephalon that divide symmetrically. It lies adjacent to the ventricular surface.

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Disorders due to abnormal cortical maturation and organization/folding

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	Schizencephaly can be bilateral or unilateral; and commonly involves the parasylvian regions, and severity of the disease correlates with the extent of the clefts.<br/>		Schizencephaly can be bilateral or unilateral; and commonly involves the parasylvian regions, and severity of the disease correlates with the extent of the clefts.<br/>
	<ref name="first"/><ref name="imaging"/><ref name="second"/><br/>		<ref name="first"/><ref name="imaging"/><ref name="second"/><br/>
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Z5093005: /* Disorders due to abnormal cortical maturation and organization/folding */

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Disorders due to abnormal cortical maturation and organization/folding

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	If the neurons of the cerebral cortex successfully complete the proliferation and migration stages, but during the last organisation stage, distribute abnormally then multiple small undulating gyri can result. This condition is called '''Polymicrogyria (PMG)''', in which, the gyri become extremely small (hence the term micro) and their number is greater than normal. The cerebral cortex in this condition is flat and thickened, similar to that of pachygyria or agyria, and contains numerous small gyri. <br/>		If the neurons of the cerebral cortex successfully complete the proliferation and migration stages, but during the last organisation stage, distribute abnormally then multiple small undulating gyri can result. This condition is called '''Polymicrogyria (PMG)''', in which, the gyri become extremely small (hence the term micro) and their number is greater than normal. The cerebral cortex in this condition is flat and thickened, similar to that of pachygyria or agyria, and contains numerous small gyri. <br/>

	Polymicrogyria is usually focal. It is most commonly 'perisylvian' (around the Sylvian fissure) and can be 'bilateral' or 'unilateral'. The most common sites, in descending order, are the frontal lobe, parietal lobe, temporal lobe and then occipital lobe. <br/>		Polymicrogyria is usually focal. It is most commonly 'perisylvian' (around the Sylvian fissure) and can be bilateral or unilateral. The most common sites, in descending order, are the frontal lobe, parietal lobe, temporal lobe and then occipital lobe. <br/>

	Affected patients can have varying degrees of symptoms, including epilepsy and developmental delay. For example, bilateral poylmicrogyria causes developmental delay, hypertonicity, ataxia, and refractory seizures.<br/>		Affected patients can have varying degrees of symptoms, including epilepsy and developmental delay. For example, bilateral poylmicrogyria causes developmental delay, hypertonicity, ataxia, and refractory seizures.<br/>
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	<big><big>'''9) Schizencephaly'''</big></big>		<big><big>'''9) Schizencephaly'''</big></big>

	'''Schizencephaly''' is an organisational developmental disorder classified within the same group as ~~Polymicrogyria~~. It is characterised by a cleft(s) or lesion(s) on the brain surface,extending from the cerebral cortex to the ventricle and is typically filled with CSF (cerebrospinal fluid) and lined by cortex gray matter. These lesions or clefts are thought to be 'destructive'.<br/>		'''Schizencephaly''' is an organisational developmental disorder classified within the same group as polymicrogyria. It is characterised by a cleft(s) or lesion(s) on the brain surface,extending from the cerebral cortex to the ventricle and is typically filled with CSF (cerebrospinal fluid) and lined by cortex gray matter (Figure 18). These lesions or clefts are thought to be 'destructive'.<br/>

	The clefts can be small with closed walls in '''Type I or Closed lip type''' schizencephaly; or the clefts can be large with free communication between the ventricle and subarachnoid spaces in '''Type II or Open lip type''' schizencephaly. Type I presents with partial seizures or spastic hemiparesis, while Type II presents with epilepsy or seizures, spasticity, severe developmental delay and microcephaly.		The clefts can be small with closed walls in '''Type I or Closed lip type''' schizencephaly; or the clefts can be large with free communication between the ventricle and subarachnoid spaces in '''Type II or Open lip type''' schizencephaly. Type I presents with partial seizures or spastic hemiparesis, while Type II presents with epilepsy or seizures, spasticity, severe developmental delay and microcephaly.

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Disorders due to abnormal neuronal migration

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	<big><big>'''7) Kallmann Syndrome'''</big></big>		<big><big>'''7) Kallmann Syndrome'''</big></big>

	The Kallman Syndrome is syndrome ~~which~~ results from the migration of neurons that secrete ~~leuteinizing hormone~~-~~releasing hormone~~ (LHRH) from the olfactory placode to the hypothalamus~~, causing congenital hypogonadism (since LHRH~~ is necessary for normal gonadal function).		The Kallman Syndrome is a syndrome characterised by congenital Hypogonadism (diminished or failed activity of male or female gonads). Kallman Syndrome results from the failed migration of neurons that secrete Leuteinizing Hormone-Releasing Hormone(LHRH) also known as Gonadotropin Releasing Hormone(GnRH), from the olfactory placode to the hypothalamus. The hypothalamus normally secretes GnRH as this is necessary for normal gonadal function. Because of failed migration of aforementioned neurons to the hypothalamus, GnRH production is disrupted causing hypogonadism.

	Clinical presentation of Kallman Syndrome includes ~~Archinencephaly~~, which is hypoplasia (underdevelopment or incomplete development) of the olfactory cortex and olfactory bulb, and deficient or absent sense of smell.<br/>		Clinical presentation of Kallman Syndrome includes archinencephaly, which is hypoplasia (underdevelopment or incomplete development) of the olfactory cortex and olfactory bulb, and deficient or absent sense of smell.<br/>
	<ref name="imaging"/><ref name="third"/><br/>		<ref name="imaging"/><ref name="third"/><ref>Reference, G. (2017). Kallmann syndrome. [online] Genetics Home Reference. Available at: https://ghr.nlm.nih.gov/condition/kallmann-syndrome [Accessed 26 Oct. 2017].</ref><br/>

	===Disorders due to abnormal cortical maturation and organization/folding===		===Disorders due to abnormal cortical maturation and organization/folding===

Z5093005: /* Disorders due to abnormal neuronal migration */

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Disorders due to abnormal neuronal migration

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	*Vertically oriented Sylvian fissures of the brain, giving the brain an 'hourglass' configuration <br/>		*Vertically oriented Sylvian fissures of the brain, giving the brain an 'hourglass' configuration <br/>

	Lissencephaly is of different types; ~~even so~~ common clinical symptoms ~~are '~~epilepsy' and 'severe mental retardation'. Types of Lissencephaly are the following: <br/>		Lissencephaly is of different types; but these types have some common clinical symptoms, namely epilepsy and severe mental retardation. Types of Lissencephaly are the following: <br/>

	*'''Classical (Type I) Lissencephaly'''- results from neuronal undermigration (failed or incomplete neuronal migration) due to varying causes like mutation; additional clinical features include motor deficits. Patients often also have microcephaly [discussed later in Microlissencephaly]. <br/>		*'''Classical (Type I) Lissencephaly'''- results from neuronal undermigration (failed or incomplete neuronal migration) due to varying causes like mutation; additional clinical features include motor deficits. Patients often also have microcephaly [discussed later in Microlissencephaly]. <br/>

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Disorders due to the abnormal proliferation, growth or differentiation of neuroblasts

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	Tuberous sclerosis complex (TSC) is a multi-organ disease resulting from mutations of certain genes, and is usually classified under defects of early cell proliferation and growth although it is also associated with defects of neuronal migration.		Tuberous sclerosis complex (TSC) is a multi-organ disease resulting from mutations of certain genes, and is usually classified under defects of early cell proliferation and growth although it is also associated with defects of neuronal migration.

	Tuberous sclerosis complex (TSC) is characterised by benign abnormal mass of cells (tumors, cysts, and other malformations including hamartomas and neoplasms), which can occur in several tissues of the body, including cerebral cortex. In the cortical gray matter, cortical tubers and bizarre cells are seen because laminar disorganisation occurs (like Focal Cortical Dyplasia). TSC is thus called because ~~at the~~ scientists thought that the lesions ~~seen~~ resembled potato tubers. <br/>		Tuberous sclerosis complex (TSC) is characterised by benign abnormal mass of cells (tumors, cysts, and other malformations including hamartomas and neoplasms), which can occur in several tissues of the body, including cerebral cortex. In the cortical gray matter, cortical 'tubers' and bizarre cells are seen because laminar disorganisation occurs (like Focal Cortical Dyplasia). TSC is thus called because initially scientists thought that the lesions they saw resembled potato tubers. <br/>

	No signs or symptoms are known to be observed for TSC, and diagnosis is determined after a brain scan. <br/>		No signs or symptoms are known to be observed for TSC, and diagnosis is determined after a brain scan. <br/>

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Disorders due to the abnormal proliferation, growth or differentiation of neuroblasts

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	Amongst cortical congenital disorders, Microcephaly Vera is a relatively common disorder. Microcephaly or 'small brain', can be caused by abnormal cell proliferation or cell division along with the involvement of other organs, and can be caused by genetic or non-genetic factors. <br/>		Amongst cortical congenital disorders, Microcephaly Vera is a relatively common disorder. Microcephaly or 'small brain', can be caused by abnormal cell proliferation or cell division along with the involvement of other organs, and can be caused by genetic or non-genetic factors. <br/>

	'''Microcephaly Vera or Primary Microcephaly''' is genetic and does not involve other organs. It from abnormal cortical development, specifically cell division or proliferation. In this malformation the circumference of the head (and so the brain) is much ~~less~~ than normal, while the rest of the body is of normal size. ~~Microcephaly Vera clinically most~~ frequently presents with mental retardation and sometimes epilepsy, although some other features ~~can~~ be observed ~~ocassionally~~ (Figure 16). <br/>		'''Microcephaly Vera or Primary Microcephaly''' is genetic and does not involve other organs. It results from abnormal cortical development, specifically cell division or proliferation. In this malformation the circumference of the head (and so the brain) is much smaller than normal, while the rest of the body is of normal size. Clinically, microcephaly vera frequently presents with mental retardation and sometimes epilepsy, although some other features may also be observed (Figure 16). <br/>
	<ref name="imaging"/><ref name="second"/><ref name="third"/><br/>		<ref name="imaging"/><ref name="second"/><ref name="third"/><br/>
	<br/>		<br/>