circumventricular organs - succinct presentation - sanjoy sanyal
DESCRIPTION
Circumventricular Organs (System) have been well studied, starting with Paul Ehrlich work with Trypan Blue in 1882, and research on their functions is still going on. However, Neuroscience medical students find it difficult to understand them. This short PPTX is meant to succinctly explain the Circumventricular Organs. Short Video clips pertaining to each CV Organ on a human brain specimen, created and uploaded on YouTube by the author, Dr Sanjoy Sanyal, Professor and Course Director of Neuroscience, are embedded between slides, to provide a narrative highlight to what is mentioned in the slides. Tags: Median Eminence, Tuber Cinereum, Arcuate Nucleus, Organum Vasculosum, Lamina Terminalis, Subfornical Organ, Pineal, Epiphysea, Subcommissural Organ, Area Postrema, Supraoptic Nucleus, Suprachiasmatic nucleus, Preoptic nucleus "Copyright Disclaimer Under Section 107 of the Copyright Act 1976, allowance is made for "fair use" for purposes such as criticism, comment, news reporting, teaching, scholarship, and research. Fair use is a use permitted by copyright statute that might otherwise be infringing. Non-profit, educational or personal use tips the balance in favor of fair use."TRANSCRIPT
Circumventricular Organs
Dr Sanjoy Sanyal MBBS, MS (Surgery), MSc (Royal College of Surgeons of Edinburgh),
ADPHAProfessor and Course Director of Neuroscience – FCM-III Neurology
No Blood Brain Barrier (BBB)
Paul Ehrlich (1882) After IV injection of Trypan
Blue, most Brain areas did
not get stained These areas are inside the BBB Some areas of Brain did get stained These structures are outside the
BBB; i.e. they do not have a BBB
Micro-Structure of BBB Tight Junctions (Claudin
/ Occludin) between
Endothelial Cells They form a continuous
Lipid Bi-layer Continuous Basement
Membrane outside Astrocyte Podocytes
form complete circle
Red arrows indicate lack of permeability
Micro-Structure of Non-BBB Highly Vascularized Fenestrations of
Endothelial Cells Permeable
Basement Membrane
Astrocyte Podocytes do not form complete circle
Red arrows indicate permeability
Exception: Sub-Commissural Organ has Non-fenestrated Capillaries
Non-BBB – Role of Tancytes Tancytes line the
Floor of 3rd Ventricle Body of Tancyte is in
contact with CSF Multiple Foot-Process
extend towards
adjacent Capillary Provides conduit
between CSF and
Blood
Tancytes play important role in certain Non-BBB areas
Circumventricular Organs Most Non-BBB
areas are around 3rd Ventricle, and one in 4th Ventricle
They are called Circumventricular Organs
They are bathed by CSF and are also in contact with Capillaries
Median Eminence of Tuber Cinereum
Organum Vasculosum of Lamina Terminalis
Sub-Fornical Organ Pineal Gland Sub-Commissural
Organ Area Postrema Wall of Optic Recess Posterior Lobe of
Pituitary
Functions of CV Organs
Chemosensitive Organs Allow ‘sampling’ of Blood Endocrine Feedback and
Regulation Homeostasis Metabolic Regulation Fluid Electrolyte Balance Detect Toxins in Blood CSF Circulation(?)
1. Median Eminence of Tuber Cinereum ME-TC#1 Tancytes line the Floor of
3rd Ventricle and ME-TC Has Arcuate Nucleus that
detects Endocrine Feedback to Hypothalamus via the Tancytes
Releases RH/IH, P-IH, and maintains Basal Levels of Hormones (FSH-LH)
In Floor of 3rd Ventricle: Raised Central Part of a Convex gray matter in the Ventral-most part of Hypothalamus #1
2. Organum Vasculosum of Lamina Terminalis (OV-LT) #2 Has Osmoreceptors Regulates ADH
release by
Supraoptic Nucleus Provides Vascular
Outlet for LH-RH by
Pre-optic and GH-IH
by Suprachiasmatic
(Both are adjacent
to LT)
A.k.a. Vascular
Organ of
Lamina
Terminalis #2
3. Subfornical Organ (SFO) #3 On inferior surface of
Fornix, at level of
Foramen of Monroe (#3) Angiotensin II Receptors Neurons from SFO
project to SO Nucleus
and OV-LT (Both are
Osmoreceptors) Fluid Electrolyte balance
4. Pineal Gland #4 Pinealocytes
(Epiphyseal Cells) #4 Highly Vascular Fenestrated Capillary Release Melatonin
into 3rd Ventricle Transported by
Tancytes in Floor of 3rd Ventricle
Act on Pituitary Gland
5. Subcommissural Organ #5 Special Epithelial /
Glial Cells Non-fenestrated
Capillaries Functions: (a)
Circulation of CSF
(Hydrocephalus); (b)
Clearance of certain
compounds (?)
Below Posterior Commissure #5
At 3rd Ventricle–Aqueduct of Sylvius Junction
6. Area Postrema Modified Astrocyte-
like Neurons Fenestrated
Capillaries 5-HT3 Receptors
(Excitatory Ionotropic) Induces Vomiting from
Morphine, Blood 5-HT Gets Afferents from
CTZ and GIT Plays Role in Food
Intake / CVS Control
In Floor of 4th Ventricle, Between Vagal Triangle and Inferolateral margin of Rhomboid Fossa, just Rostral to Obex