Ventricles, brain

The area postrema is a circumventricular brain region positioned on the dorsal surface of the medulla on the floor of the fourth ventricle. The blood-brain barrier and the cerebrospinal fluid-brain barrier are absent in this region and consequently many substances that do not pass across capillaries in other regions of the brain can do so in the area postrema. The chemoreceptor trigger zone (CTZ), located in the lateral area postrema is sensitive to blood-borne emetogens. Nerves from the CTZ connect with the vomiting centre. 

The locus ceruleus is a structure located on the floor of the fourth ventricle in the rostral pons. It contains more than 50% of all noradrenergic neurons in the brain, and projects to almost all areas of the central nervous system. 

The paraventricular nucleus in the hypothalamus is located adjacent to the third ventricle and has been identified as a satiety center. Neurons in the paraventricular nucleus produce neuropeptides which inhibit feeding when injected into the brain (thyrotropinreleasing hormone (TRH), corticotropin-releasing hormone (CRH), oxytocin). 

The pituitary gland lies deep within the cranial vault, connected to the brain by the infundibular stalk (a downward extension of the floor of the third ventricle) and protected by an indentation of the sphenoid bone called the sella turcica (see Fig. 50-1). The pituitary gland, a small, gray rounded structure, has two parts ... 

In mammals, ciliated cells line the respiratory air passages, the fallopian tubes, and the ventricles of the brain. The cilia beat in a coordinated manner in waves that propel fluids, suspended cells, and small particles along a surface. The motility of the sperm cell is provided by a single flagellum. 

Gavage administration of 1.5 mg/kg/day of methyl parathion to rats on days 6-15 of gestation resulted in increased resorptions, decreased fetal body weight, and hemorrhagic spots in the brain ventricles and skin... 

COMMENT We feel that it is due to the formation of 5,6-DHT in the eortex. These cells are indeed innervated by serotonin cells and, as a matter of fact, we have an experiment that is being published in Brain Research where we show that if we injeet 5,6-DHT into the ventricles, we ean produce exactly the same type of degeneration in the pyramidal cells, due to the formation of the 5,6 from the 5-hydroxytryptamine. We are exploring the possibility of it being another catecholamine in addition to dopamine, so I think both of those may be helpful in answering your question. 

Chemoreceptor trigger zone Located in the area postrema of the fourth ventricle of the brain, it is exposed to cerebrospinal fluid and blood and is easily stimulated by circulating toxins to induce nausea and vomiting. 

Atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) are members of a family of so-called natriuretic peptides, synthesized predominantly in the cardiac atrium, ventricle, and vascular endothelial cells, respectively (G13, Y2). ANP is a 28-amino-acid polypeptide hormone released into the circulation in response to atrial stretch (L3). ANP acts (Fig. 8) on the kidney to increase sodium excretion and glomerular filtration rate (GFR), to antagonize renal vasoconstriction, and to inhibit renin secretion (Ml). In the cardiovascular system, ANP antagonizes vasoconstriction and shifts fluid from the intravascular to the interstitial compartment (G14). In the adrenal cortex, ANP is a powerful inhibitor of aldosterone synthesis (E6, N3). At the hypothalamic level, ANP inhibits vasopressin secretion (S3). It has been shown that some of the effects of ANP are mediated via a newly discovered hormone, called adreno-medullin, controlling fluid and electrolyte homeostasis (S8). The diuretic and blood pressure-lowering effect of ANP may be partially due to adrenomedullin (V5). 

Figure 6.2 Frontal section of the brain. The cerebrum is composed of two types of tissue internal white matter and external gray matter which forms the cerebral cortex. Embedded within the cerebral hemispheres are other masses of gray matter, basal ganglia, and thalamus. The ventricles are filled with cerebrospinal fluid (CSF).

Embedded within the brain are four ventricles or chambers that form a continuous fluid-filled system. In the roof of each of these ventricles is a network of capillaries referred to as the choroid plexus. It is from the choroid plexuses of the two lateral ventricles (one in each cerebral hemisphere) that cerebrospinal fluid (CSF) is primarily derived. Due to the presence of the blood-brain barrier, the selective transport processes of the choroid plexus determine the composition of the CSF. Therefore, the composition of the CSF is markedly different from the composition of the plasma. However, the CSF is in equilibrium with the interstitial fluid of the brain and contributes to the maintenance of a consistent chemical environment for neurons, which serves to optimize their function. 

The CSF flows through the ventricles, downward through the central canal of the spinal cord, and then upward toward the brain through the subarachnoid space that completely surrounds the brain and spinal cord. As the CSF flows over the superior surface of the brain, it leaves the subarachnoid space and is absorbed into the venous system. Although CSF is actively secreted at a rate of 500 ml/day, the volume of this fluid in the system is approximately 140 ml. Therefore, the entire volume of CSF is turned over three to four times per day. 

As early as in 1909, it was recognized that some chemical factor in the brain was responsible for recovery sleep. Cerebrospinal fluid (Legendre Pieron, 1911) or brain extract (Ishimori, 1909) from sleep-deprived dogs resulted in excess sleep when infused into the cerebral ventricles of recipient animals. The fact that the material was ineffective if heated or ultrafiltered pointed to a protein or peptide as sleep factor (Legendre Pieron, 1911). Later studies have... 

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