ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
(ii) Brain: The ventricles of the brain are cavities inside the brain that are filled with the CEREBROSPINAL FLUID (CSF). They are lined with the ependyma consisting of a single layer of EPENDYMAL CELLS. The ventricular system is comprised of a pair of the lateral ventricles located in the CEREBRAL HEMISPHERES, the third ventricle located at the midline in the DIENCEPHALON, and the fourth ventricle located between the lower BRAINSTEM and CEREBELLUM. The lateral ventricle is the largest and is composed of the anterior horn, the body, the inferior horn and the posterior horn. The lateral ventricles communicate with the third ventricle through narrow passages called the interventricular FORAMINA OF MONRO. These foramina are used as reference points in radiographic studies. The slit-like third ventricle narrows into the CEREBRAL AQUEDUCT (AQUEDUCT OF SYLVIUS) in the MIDBRAIN, and then opens up as the fourth ventricle, a flat and diamond-shaped ventricle between the lower brainstem and cerebellum. At its widest part, a lateral recess communicates with the CISTERNA MAGNA or CEREBELLOMEDULLARY CISTERN, a large SUBARACHNOID SPACE (space between the ARACHNOID MEMBRANE and PIA MATER [see MENINGES]) posterior to the cerebellum. There is also a small median opening called the FORAMEN OF MAGENDIE. Caudally, the fourth ventricle is continuous with the CENTRAL CANAL of the SPINAL CORD. The CIRCUMVENTRICULAR ORGANS are present in the third and fourth ventricles. They usually lack the BLOOD-BRAIN BARRIER and have a role in mediating direct actions of blood-borne substances on neurons.
Introduction: Background Material
Nassir H. Sabah in Neuromuscular Fundamentals, 2020
The CSF also circulates in four cavities, or ventricles, in the brain: two large lateral ventricles on either side in the cerebrum, a small third ventricle along the midline in the diencephalon, and a fourth ventricle of intermediate size along the midline at the back of the pons and the upper half of the medulla. The central canal of the spinal cord is continuous with the fourth ventricle. The CSF is produced from the blood mainly by the choroid plexuses in parts of the ventricles. Each of these plexuses consists of a layer of epithelial cells that is continuous with the ependymal cell layer that lines the ventricles. The epithelial cells surround blood capillaries and form tight junctions that act as a blood-CSF barrier, allowing only some substances to pass. In addition to its cushioning effect, the CSF provides buoyancy to the brain, circulates nutrients and chemicals, and removes waste products from the brain. Regulating the volume of the CSF plays an important role in regulating cerebral blood flow.
Distribution and Characteristics of Brain Dopamine
Nira Ben-Jonathan in Dopamine, 2020
The LC is well conserved across the mammalian species and is the largest group of noradrenergic neurons in the brain. It is a bilateral structure that sits near the wall of the fourth ventricle and the mesencephalic trigeminal nucleus in the pons. The proximity of the LC to the fourth ventricle provides a good access for the noradrenergic neurons to the cerebrospinal fluid (CSF) and also for a potential exposure to regulatory hormones and toxic chemicals. The LC has been most extensively studied in the rat, where it contains about 1,600 medium-sized neurons. It is also known as the pigmented nucleus of the pons because of melanin granules, which give it a blue color under the microscope. The neuromelanin, which is formed by the polymerization of NE, is analogous to the DA-derived black neuromelanin within the substantia nigra.
Cannabis for cancer – illusion or the tip of an iceberg: a review of the evidence for the use of Cannabis and synthetic cannabinoids in oncology
Published in Expert Opinion on Investigational Drugs, 2019
Emesis results from stimulation of complex reflex pathways controlled by the brain. Neurotransmitters such as dopamine, histamine, acetylcholine, serotonin, and substance P are common targets for anti-emetic medicines, each affecting a distinct aspect of the emetic pathways [18]. Endocannabinoid receptors richly populate these very neuronal tracts, thereby signifying an additional target for treating CINV. The dorsal vagal complex is a region in the brain associated with gastrointestinal function and pathophysiology, and at the root of emesis regulation. This region includes the area postrema, the nucleus of the solitary tract (nTS) and the dorsal motor nucleus of the vagus, and contains vagal outputs in the gastrointestinal tract – all of which contain CB-1 receptors that have demonstrated anti-emetic effects when activated by Δ9-THC [18]. In contrast, serotonin agonists that induce nausea have shown opposite effects on the nTS compared to Δ9-THC [19]. Located just outside the blood-brain barrier in the fourth ventricle of the brain, the area postrema provides direct communication between blood-borne signals such as chemotherapy and the autonomic neurons that elicit emesis [18].
Clinical features of patients with high and normal CSFP in venous pulsating tinnitus
Published in Acta Oto-Laryngologica, 2020
The flow of cerebrospinal fluid has a certain directionality. The collateral plexus of the two lateral ventricles is the most abundant and produces most of the cerebrospinal fluid. This cerebrospinal fluid flows into the third ventricle through the interventricular pores and then flows into the fourth ventricle through the midbrain aqueduct. The cerebrospinal fluid produced by the choroid plexus of each ventricle converges in the fourth ventricle and flows into the subarachnoid space of the brain and spinal cord through the median and lateral foramina of the fourth ventricle. Finally, the cerebrospinal fluid infiltrates into the superior sagittal sinus through the arachnoid granules beside the sagittal sinus before returning to the venous system [16–18]. Under normal circumstances, there are arachnoid granules in the cross-sectional area of the transverse sinus and sigmoid sinus on the dominant drainage side. When inflammation occurs, it may cause adhesion and narrowing of the vascular lumen, and hemodynamic changes occur when blood flows through the stenosis. Watane et al also found a correlation between arachnoid granules and BIH [19]. Most MRA and MRV results in this study showed superior drainage of the sigmoid sinus on the tinnitus side. We speculate that high CSFP may impact the hemodynamics of intracranial veins, and abnormal intracranial veins may also affect CSFP; that is to say, intracranial veins and CSFP interact through the important medium – arachnoid granules, and thereby participate in the occurrence and development of vascular tinnitus.
Chiari I malformation in children with transverse myelitis
Published in Developmental Neurorehabilitation, 2018
Sathya Vadivelu, Sudhakar Vadivelu, Maureen Mealy, Smurti Patel, Libby Kosnik-Infinger, Daniel Becker
A more common, related condition to CMI is syringomyelia; a disorder characterized by the formation of a fluid-filled tubular cavity within the spinal cord. Syringomyelia may present in various cavitary patterns anywhere along the spinal cord and has been described in association with a wide range of conditions including posttraumatic states and many inflammatory conditions including multiple sclerosis, Devic’s disease, TM, and sarcoidosis.29–34 When associated with CMI, it typically appears in the cervical spinal cord. Although many theories have been proposed, the pathogenesis of syringomyelia associated with CMI largely remains unclear and controversial. In the setting of CMI, many of the modern hypotheses focus on the obstruction or disruption of CSF flow at the craniocervical junction. The major theories for pathogenesis of syringomyelia differ in their descriptions on how CSF enters into the spinal cord. These main descriptions include CSF entrance from the fourth ventricle, CSF entrance from the subarachnoid space, or an extracellular fluid origin through a variety of mechanisms.30,35