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The most commonly used classification for this gland takes into account its location relative to the diencephalon and the third ventricle of the brain, as well as its size and shape. [40] Under these conditions, the human pineal gland is classified as type A. [ 40 ] A type A pineal gland rests proximally to the posterior section of the ...
The pineal gland is located in the epithalamus, near the center of the brain, between the two hemispheres, tucked in a groove where the two halves of the thalamus join. [4] [5] It is one of the neuroendocrine secretory circumventricular organs in which capillaries are mostly permeable to solutes in the blood. [6]
The larger arteries throughout the brain supply blood to smaller capillaries. These smallest of blood vessels in the brain, are lined with cells joined by tight junctions and so fluids do not seep in or leak out to the same degree as they do in other capillaries; this creates the blood–brain barrier. [44]
Image of the human brain showing sulci, gyri, and fundi shown in a Coronal section. Specific terms are used to represent the gross anatomy of the brain: A gyrus is an outward folding of the brain, for example the precentral gyrus. A sulcus is an inward fold, or valley in the brain's surface - for example the central sulcus. Additional terms ...
The brain is small and simple in some species, such as nematode worms; in other species, such as vertebrates, it is a large and very complex organ. [4] Some types of worms, such as leeches, also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain". [17]
Cerebral blood flow (CBF) is the blood supply to the brain in a given period of time. [8] In an adult, CBF is typically 750 millilitres per minute or 15.8 ± 5.7% of the cardiac output. [9] This equates to an average perfusion of 50 to 54 millilitres of blood per 100 grams of brain tissue per minute. [10] [11] [12]
In a situation of lowered blood volume, secretion of renin by the kidneys results in the production of angiotensin II, which stimulates receptors in the VOLT and subfornical organ to complete a positive feedback loop. [9] [12] [13] These neurons also project to the median preoptic nucleus which is involved in controlling thirst. [11] [9] [12]
Wound scars in the brain largely contain astrocytes. The extracellular matrix also provides support on the molecular level for the brain's cells, vehiculating substances to and from the blood vessels. At the organ level, the nervous system is composed of brain regions, such as the hippocampus in mammals or the mushroom bodies of the fruit fly. [11]