User:Devitod/Circumventricular organs

Wikipedia Project Proposal-Circumventricular Organs

Susana Benitez, Luke Ollila, and Darla DeVito,

Introduction to Proposal

This is our proposal for the Wikipedia Page project. Our topic is Circumventricular organs and below is a preliminary outline of the page. Because Circumventricular Organs are a classification for parts of the brain, we decided to break the article up into sections based on the six organs. We also plan to further break up each section into anatomy and function. In addition to the anatomy and function of the six CVOs, we plan to include a section in which we provide current research and clinical implications of CVOs.

Within our group, every member has read or plans to read the articles we have found up until now. Each member has been assigned two organs to write. The "introduction" section and the "current research" will be written as a group when we meet to give each other feedback and edits.

For more information regarding the project guidelines please visit Professor Burdo's page.

Introduction

Circumventricular Organs are a classification of sections of the brain. They are unique in their extensive vasculature and lack of a normal blood brain barrier. They allow for the release of hormones and also play a role in sensing hormone concentrations in the brain. The lack of a blood brain barrier allows the CVOs to become an alternative route to central nervous system tissue. CVOs include the subfornical organ, the organum vasculosum of the lamina terminalis, the area postrema, the posterior pituitary and the subcommissural organ. Sometimes the pineal gland, the median eminence, the intermediate lobe of the pituitary and the choroid plexus are also included in this classification.

We plan to expand on this section and go into further detail about the organs that are under speculation. In addition, we intend to explain why there are discrepancies regarding the classification of certain organs such as the pineal gland, the median eminence, the intermediate lobe of the pituitary and the choroid plexus as CVOs.

Subcommissural Organ

Anatomy

The subcommissural organ (SCO) is a small secretory organ located at the entrance of the Sylvian Aqueduct, at the roof of the 3rd Ventricle.

Here we plan to supply pictures to show the location and the anatomy of the subcommisural organ.

Function

The SCO is responsible for glycoprotein secretion along with body water and salt homeostasis. In addition, research suggests that the SCO plays a role in the detoxification of the Cerbrospinal Fluid (CSF,) aldosterone secretion and thirst.

In this section we plan to expand on how it contributes to thirst, detoxification etc.

Pineal Gland

Anatomy

The pineal gland is an intracranial appendicular organ located in the 3rd ventricle of the brain.

We plan to supplement this information with pictures to show the location and description of the Pineal Gland.

Function

The pineal gland secretes the hormone melatonin, which is in charge of maintaining the body's circadian rhythm.

We will elaborate on the importance of melatonin in the body.

Area Postrema

Anatomy

The Area Postrema shows greatest resemblance to the subfornical organ and is located on the surface of the medulla.

Here we plan to provide pictures in order to explain more thoroughly the location and structure of the Area Postrema.

Function

The Area Postrema is in the region where the chemoreceptors triggers for vomiting are located.

Posterior Pituitary

The posterior Pituitary is also known as the neurohypophysis.

Anatomy

We have found research that includes the posterior pituitary as one of the circumventricular organs, as well as research that doesn’t include it. We will investigate this matter further in order to decide if it should be included in this page or not.

Function

The posterior pituitary is a neuroendocrine organ that stores and secretes two hormones produced by the hypothalamus: oxytocin and ADH.

Subfornical Organ (SFO)

Located in the forebrain, considerable scientific evidence has demonstrated the Subfornical Organ’s ability recognize peptides (ANG, ANP, VP, and ET) impermeable to the blood brain barrier.

Anatomy

The subfornical organ is a highly vascularized portion of the third ventricle of the brain. Three sections of the SFO can morphologically be identified, the largest of which is the central region. On the sides of the central region are the rostral and caudal areas. While the central region is comprised of neuronal cell bodies and glial cells, the flanking regions are primarily comprised of nerve fibers. Studies have shown the efferent projections of the SFO reach into the hypothalamus. Further anatomical structure will be discussed and elaborated upon in this section.

Function

The efferent projections of the SFO which terminate in the supraoptic (SON) and paraventricular nuclei (PVN) may have involvement in oxtocin and vassopressin secretion. The SFO may also have a role in modification of autonomic output travelling to the medulla and spinal cord. Afferent projections of the SFO allow signal input from CNS structures. The function will be elaborated upon with specific examples.

Organum Vasculosum of the Lamina Terminalis (OVLT)

Anatomy

The organum vasculosum of the lamina terminalis is considered a midline structure, protruding into the third vesicle. It is situated dorsal to the optic chiasm and is comprised of glial cells, small neurons, and thin-walled vessels The OVLT demonstrates some prostaglandin receptors which provide a role in febrile responses. The OVLT receives afferent input from the subfornical organ and other structures located in the hypothalamus.

Function

Lacking a blood brain barrier, the OVLT features receptors for ANG that allows ANG to exert an excitatory action upon OVLT neurons in the brain. The organum vasculosum may also be involved in the regulation of LH via a negative feedback mechanism. Because studies have shown the OVLT as responsive to changes in temperature, it is suspected that it is involved in other homeostatic mechanisms and that it may be the site through which pyrogens act on the CNS. The full range of functions of the OVLT is still not known. This will be mentioned later in the full wiki article.

Current Research

As we continue our research we will include a portion regarding the current and ongoing research we find particularly important.

References

1. Lee, Kristie, Jacqueline Tan, Michael B. Morris, Karine Rizzoti, James Hughes, Pike See Cheah, Fernando Felquer, Xuan Liu, Sandra Piltz, Robin Lovell-Badge, and Paul Q. Thomas. "Congenital Hydrocephalus and Abnormal Subcommissural Organ Development in Sox3 Transgenic Mice." Www.ncbi.nlm.nih.gov. N.p., 26 Jan. 2012. Web. 14 Sept. 2012. <http://www.ncbi.nlm.nih.gov.proxy.bc.edu/pmc/articles/PMC3266892/>.

2. Cottrell, G. T., & Ferguson, A. V. (2004). Sensory circumventricular organs: Central roles in integrated autonomic regulation. Regulatory Peptides, 117(1), 11-23. doi: 10.1016/j.regpep.2003.09.004

3. Ferguson, A. V., & Bains, J. S. (1996). Electrophysiology of the circumventricular organs. Frontiers in Neuroendocrinology, 17(4), 440-475. doi: 10.1006/frne.1996.0012

4. Elgot, A., Ahboucha, S., Bouyatas, M. M., Fèvre-Montange, M., & Gamrani, H. (2009). Water deprivation affects serotoninergic system and glycoprotein secretion in the sub-commissural organ of a desert rodent meriones shawi. Neuroscience Letters, 466(1), 6-10. doi: 10.1016/j.neulet.2009.08.058

5. Saha, S., & Subhedar, N. (2011). Calcitonin-like immunoreactivity in the subcommissural organ–Reissner's fiber complex of some freshwater and marine teleosts. Journal of Chemical Neuroanatomy, 41(2), 122-128. doi: 10.1016/j.jchemneu.2010.12.004

6. Schiller, F. "Pineal Gland, Perennial Puzzle." Journal of the History of Neurosciences4.3-4 (1995): 155-65. Web of Knowledge. Web. 14 Sept. 2012. <http://apps.webofknowledge.com.proxy.bc.edu/CitedFullRecord.do?product=UA>.

7. Macchi, M. M., and J. N. Bruce. "Human Pineal Physiology and Functional Significance of Melatonin." Frontiers in Neuroendocrinology 25.3-4 (2004): 177-95. Web of Knowledge. Sept. 2004. Web. 14 Sept. 2012. <http://apps.webofknowledge.com.proxy.bc.edu/CitedFullRecord.do?product=UA>.

8. Borison, H. L. (1989). Area postrema: Chemoreceptor circumventricular organ of the medulla oblongata. Progress in Neurobiology, 32(5), 351-390. doi: 10.1016/0301-0082(89)90028-2

9. "Posterior Pituitary." Wikipedia. Wikimedia Foundation, 30 Aug. 2012. Web. 14 Sept. 2012. <http://en.wikipedia.org/wiki/Posterior_pituitary>.

10. Uschakov, A., McGinty, D., Szymusiak, R. and McKinley, M. J. (2009), Functional correlates of activity in neurons projecting from the lamina terminalis to the ventrolateral periaqueductal gray. European Journal of Neuroscience, 30: 2347–2355. doi: 10.1111/j.1460-9568.2009.07024.x

11. Taraszewska, A., Andrychowski, J., Czernicki, Z. (2005), Microscopic Stucture of the Lamina Terminalis: Implications for Microsurgical Third Ventriculostomy. Central European Neurosurgery, 66, 4: 202-206. doi: 10.1055/s-2005-836603