BLOOD BRAIN BARRIER
| A | Schwann cells | |
| B |
Oligodendrocytes |
|
| C |
Astrocytes |
|
| D |
Microglia |
Blood brain barrier is formed by which of the following cells?
| A |
Schwann cells |
|
| B |
Oligodendrocytes |
|
| C |
Astrocytes |
|
| D |
Microglia |
- Fibrous astrocytes, which contain many intermediate filaments, are found primarily in white matter.
- Protoplasmic astrocytes are found in gray matter and have a granular cytoplasm. Both types send processes to blood vessels, where they induce capillaries to form the tight junctions making up the blood–brain barrier.
Which area is out of the blood-brain barrier ?
| A |
Thalamus |
|
| B |
Cerebral cortex |
|
| C |
4th ventricle |
|
| D |
Area postrema |
Ans.D. Area Postrema
– Circumventricular organs are out of BBB and include subfornical organ, organum vasculosum (lamina terminalis), neurohypophysis, area postrema and medial eminence of hypothalamus.
Blood-brain barrier (BBB) is formed by capillary endothelium, basement membrane of endothelium, foot process of astrocytes, neuroglia and ground substance of brain.
| A |
Water |
|
| B |
Lipophilic drugs |
|
| C |
Gas |
|
| D |
Proteins |
D i.e. Proteins
Blood-CSF Barrier & Blood-Brain Barriers are highly permeable to water, CO2 (carbon dioxide), 02 (oxygen)2, and most lipid soluble (lipophilic) substances such as free forms of steroid hormones, alcohol and anesthetics; slightly permeable to electrolytes like Na+ (sodium), K+ (potassium) and Cl- (chloride); and almost totally impermeable to plasma proteins, protein bound forms of steroid hormones, protein antibodies and most non lipid soluble large organic molecules (i.e. impermeable to, in general, all proteins and polypeptides). It slows penetration of some smaller molecules like urea.
Blood Brain Barrier (BBB) & Blood Cerebrospinal fluid Barrier (BCSFB)
– BBB & B-CSF-B exist between the blood & brain interstitial fluid and CSF respectively to uniquely limit the exchange of substances into the brain. That is why the constituents of CSF are not the same as in ECFs (extracellular fluids) elsewhere in body.
– These barriers exist both at the choroid plexus [between choroid epithelium (CSF) and capillary endothelium (blood)] and at tissue capillary membranes. The cause of low permeability is presence of tight junctions b/w the adjacent endothelial cells.
| A | Habenular nucleus | |
| B |
Subfornical organ |
|
| C |
Cerebellum |
|
| D |
Pontine nucleus |
B i.e. Subfornical organ
Effectiveness of blood brain barrier is by:
| A | Tight endothelial function | |
| B |
Microglial cell |
|
| C |
Thick basement membrane |
|
| D |
Tight arrangement of astrocyfes |
A i.e. Tight endothelial function
The blood–brain barrier (BBB) is a highly selective semipermeable border of endothelial cells that prevents solutes in the circulating blood from non-selectively crossing into the extracellular fluid of the central nervous system where neurons reside.
Blood brain barrier is absent in ‑
| A |
Adenohypophysis |
|
| B |
Neurohypophysis |
|
| C |
Hypothalamus |
|
| D |
Thalamus |
Ans. is ‘b’ i.e., Neurohypophysis C. Hypothalamus
Blood-brain barriers exist both at the choroid plexus and at the tissue capillary membranes in essentially all areas of the brain parenchyma except in some areas of the hypothalamus, pineal gland, area postrema, where substances diffuse with greater ease into the tissue spaces.
Four areas that are outside of BBB are (l) the posterior pituitary (neurohypophysis) and the adjacent ventral part of the median eminence of the hypothalamus, (2) the area postrema, (3) the organum vasculosum of the lamina terminalis (OVLT, supraoptic crest), and (4) the subfornical organ (SFO).
Referred to collectively as the circumventricular organs.
