Central Nervous System (CNS): composed of the brain and the “spinal cord.” (Patestas, 5) Includes the “cerebrum,” the “cerebellum,” the “brain stem,” the spinal cord, the “diencephalon,” and the “basal ganglia.” (S.Goldberg, 3)

Its purpose is to receive “sensory information” from the skin and to transform it into coordinated “motor commands” that are relayed to the “muscles” for action. (Kandel, 44-45) The command-and-control center of the “nervous system.” Until recently, it was thought to lack "plasticity." (Doidge, 53) Encased entirely inside a thick shield of “bone.” Isolated even from the “blood” and fluids bathing all other “tissues” in the body. This barrier between brain and blood is called the “blood-brain barrier.” (Fields, 42) “Ramon y Cajal” won the Nobel Prize in 1906 for proposing that the central nervous system was made up of individual “neurons” that communicated at what he termed ‘polarized junctions.’ (Ratey, 46)


Meninges: the three connective tissue membranes that line the skull and “vertebral canal” and enclose the brain and spinal cord. (OxfordMed) Three more or less concentric membranes. (Patestas, 84) The three thin layers of tissue that cover and protect the brain and spinal cord. (NCIt) Protect and “vascularize” the (central) nervous system. (Fisch, 2)

Arachnoid Mater: the middle of the three membranes covering the brain and spinal cord. Has a fine, almost cobweb-like texture. (OxfordMed) A delicate membrane enveloping the brain and spinal cord. It lies between the “pia mater” and the “dura mater.” It is separated from the pia mater by the ‘subarachnoid’ “cavity” which is filled with “cerebrospinal fluid.” (MeSH) A fine, spiderweb-like, nonvascular membrane that is interposed between (the meningeal layer of) the dura mater and the pia mater. “Blood vessels” perforate the arachnoid to reach the pia mater. However, each vessel is completely surrounded by arachnoid ‘fibroblasts’ and therefore, the vessels never actually enter the subarachnoid space. (Patestas, 89-90) Also referred to as ‘arachnoid’ and ‘cranial arachnoid.’ 

Subarachnoid Space: the space between the arachnoid and pia meninges of the brain and spinal cord, containing circulating cerebrospinal fluid and large blood vessels. (OxfordMed) The space is occupied by cerebrospinal fluid and is traversed by numerous arachnoid “trabeculae.” (Patestas, 90)

Cisterna: one of the enlarged spaces beneath the arachnoid that act as reservoirs for cerebrospinal fluid. (OxfordMed) As cerebrospinal fluid percolates throughout the subarachnoid spaces, it also enters the cisterns, filling them. (Patestas, 90) Plural - ‘cisternae.’ Also referred to as ‘arachnoid cistern,’ and ‘subarachnoid cistern.’ 

Ambient Cistern: an expansion of the subarachnoid space extending forward between the “corpus callosum” and the “thalamus.” It encloses the internal cerebral veins. (NCIt) Filled with cerebrospinal fluid. Flanks the midbrain (and the “hippocampal formation”). Adjacent to and separated from the “lateral ventricle” by the the “choroid plexus.” (Fisch, 374-375)

Cisterna Magna: lies beneath the cerebellum and behind the “medulla oblongata.” (OxfordMed) The largest of the three principle cisterns in the subarachnoid space which is located between the cerebellum and the medulla oblongata. (NCIt)

Dura Mater: the thickest and outermost of the three meninges surrounding the brain and spinal cord. Consists of two layers. (OxfordMed) Outermost, dense, irregular connective tissue. (Patestas, 84) A "fibrous" membrane of connective tissue that covers the brain and the spinal cord. (MeSH) Most fibrous of the three meninges that surround and protect the brain and spinal cord. (NCIt) Also referred to as ‘pachymenix,’ and ‘dura.’ 

Falx Cerebelli: interposed between the right and left “cerebellar hemispheres.” (Patestas, 89) A small triangular “process” of dura matter beginning at the internal “occipital” crest just beneath the "tentorium cerebelli" and projecting forward. (NCIt)

Falx Cerebri: located in the “longitudinal fissure.” A ‘sickle-shaped’ fold of the meningeal layer of the dura mater. Dips inwards from the skull in the midline between the cerebral hemispheres. (Patestas, 87)

Meningeal Dura Mater: inner layer (of the dura mater) that is intimate contact with the arachnoid. Has no vascular supply. (Patestas, 85) It is mostly fused with the outer layer, the ‘endocranium,’ that (sticks) to the inner (surface) of the cranial bones. These two layers form the dura mater. The latter covers and protects the brain and the spinal cord. (NCIt)

Periosteal Dura Mater: outer layer (of the dura mater). Richly supplied by blood vessels. (Patestas, 85) 

Tentorium Cerebelli: separates the occipital lobe from the cerebellum. (Patestas, 88)

Venous Sinuses of Dura Mater: large “endothelium” lined venous channels situated between the two layers of dura mater. (MeSH) These sinuses collect blood from the brain and also receive cerebrospinal fluid from the subarachnoid spaces. They empty their contents in to the ‘jugular vein.’ (Patestas, 93) Also referred to as ‘cranial sinuses.’

Pia Mater: the innermost layer of the three meninges covering the brain and spinal cord. It is the fine “vascular” membrane that lies under the arachnoid and the dura mater. (MeSH) A moderately tough membrane of connective-tissue “fibers” that cling to the brain's surface. (Kolb, 40) (The) membrane is closely attached to the surface of the brain and spinal cord, faithfully following each … “sulcus.” It contains numerous finely branching blood vessels that supply the nerve tissue within. The subarachnoid space separates it from the arachnoid. (OxfordMed) Also referred to as ‘pia.’

Ventricular System: continuous system of internal watercourses. (Bainbridge, 38) Assists the meninges in their task of nourishing and supporting the rest of the nervous system. (Fisch, 2) By the ‘five-bulge stage’ (in the development of the “neural tube”) most of the brain fluid is held in four "ventricles." (Bainbridge, 49) Cells that line the ventricles make the cerebrospinal fluid (CSF) that fills them. The ventricles are connected; so the CSF flows from the two “lateral ventricles” to the “third” and “fourth ventricles” and into the canal that runs the length of the spinal cord. (Kolb, 45) 

Aqueduct of Sylvius: narrow channel that connects the third and fourth ventricles. (MeSH) Travels through the midbrain. (Blumenfeld, 136) Also referred to as 'central aqueduct’ and ‘cerebral aqueduct.’

Cerebrospinal Fluid: the fluid that flows in and around the hollow spaces of the brain and “spinal cord,” and between two of the meninges. (NCIt) Clear, colorless, odorless fluid. (Bainbridge, 38) Rich in sodium, potassium, and chloride ions, but has almost no protein. Forms a protective cushion for the brain and spinal cord. (Patestas, 95) Because the fluid leaks out under the meninges, there is also a thin layer of fluid surrounding the brain. In fact, the brain actually floats in this shock-absorbing fluid (because) the organ has few direct connections with the skull around it. (Bainbridge, 57)

Choroid Plexus: blood vessels forming structures in the third, fourth, and lateral ventricles of the brain. (NCIt) A rich network of blood vessels in each of the brain’s ventricles. Responsible for the production of cerebrospinal fluid. (OxfordMed) A "villous" structure of tangled masses of “blood vessels” contained within the third, lateral, and fourth ventricles of the brain. It regulates part of the production and composition of cerebrospinal fluid. (MeSH)

Ependyma: extremely thin membrane composed of cells that line the ventricles and the choroid plexus. It is responsible for helping to form cerebrospinal fluid. (OxfordMed) A thin membrane that lines the fluid-filled spaces in the brain and the central canal of the spinal cord. It is made up of a type of cell called an ependymal cell. (NCIt) Adjective - ‘ependymal.’

Foramen of Luschka: right and left openings in the fourth ventricle draining the cerebrospinal fluid into the subarachnoid space. (Patestas, 96) Also referred to as ‘lateral aperture.’

Foramen of Magendie: opening in the fourth ventricle draining the cerebrospinal fluid into the "subarachnoid space." (Patestas, 96) Also referred to as ‘medial aperture.’

Foramen of Monroe: connect the lateral ventricles with the third ventricle. (Bainbridge, 49) Cerebrospinal fluid flows from the lateral ventricles through the foramen of monroe in each hemisphere, into the third ventricle. (Blumenfeld, 134) Also referred to as ‘monroe’s holes.’

Ventricle: fluid-filled cavity within the brain. (OxfordMed) Formed in early development as cavities within the “neural tube.” There are two lateral ventricles (one inside each cerebral hemisphere), a third ventricle located within the diencephalon, and a fourth ventricle, which is surrounded by the “pons,”  medulla (oblongata), and cerebellum. (Blumenfeld, 132-133) Also referred to as ‘cerebral ventricle.’

Fourth Ventricle: an irregularly shaped cavity in the (forebrain), between the medulla oblongata, the pons… and the cerebellum. (MeSH) Continuous with the “spinal canal” in the center of the spinal cord. (Supplied by) the aqueduct of Sylvius. (OxfordMed)

Lateral Ventricles: separated from one another by two closely adjoined… membranes. Ependymal cells line each lateral ventricle. Protruding into each ventricle is a choroid plexus. (Patestas, 70) Have extensions called “horns” that are named after the lobes or after the direction in which they extend. (Blumenfeld, 135)

Third Ventricle: a narrow (split) “inferior” to the corpus callosum, within the diencephalon. Its floor is formed by the “hypothalamus.” (MeSH) A narrow slit-like space (which separates) the right and left halves of the diencephalon. (Patestas, 77) (Supplied by) the lateral ventricles. (OxfordMed) The lateral ventricles (connect) with the third ventricle via the foramen of Monroe. (Blumenfeld, 136)