GC: n

S: NCBI – https://www.ncbi.nlm.nih.gov/books/NBK551718/ (last access: 31 March 2025); NHS – https://www.acquiredbraininjury-education.scot.nhs.uk/introduction-to-the-brain/structure-of-the-brain/ (last access: 31 March 2025).

N: 1. “soft, grayish mass filling the cranial cavity of a vertebrate,” in the broadest sense, “organ of consciousness and the mind,” Old English brægen “brain,” from Proto-Germanic *bragnan (source also of Middle Low German bregen, Old Frisian and Dutch brein), a word of uncertain origin, perhaps from PIE root *mregh-m(n)o- “skull, brain” (source also of Greek brekhmos “front part of the skull, top of the head”).

But Liberman writes that brain “has no established cognates outside West Germanic” and is not connected to the Greek word. More probably, he writes, its etymon is PIE *bhragno “something broken.”The custom of using the plural to refer to the substance (literal or figurative), as opposed to the organ, dates from 16c. The figurative sense of “intellectual power” is from late 14c.; the meaning “a clever person” is recorded by 1914.To have something on the brain “be extremely eager for or interested in” is from 1862. Brain-fart “sudden loss of memory or train of thought; sudden inability to think logically” is by 1991 (brain-squirt is from 1650s as “feeble or abortive attempt at reasoning”). An Old English word for “head” was brægnloca, which might be translated as “brain locker.” In Middle English, brainsick (Old English brægenseoc) meant “mad, addled.”

2. brain, also known as encephalon, the mass of nerve tissue in the anterior end of an organism. The brain integrates sensory information and directs motor responses; in higher vertebrates it is also the centre of learning. The human brain weighs approximately 1.4 kg (3 pounds) and is made up of billions of cells called neurons. Junctions between neurons, known as synapses, enable electrical and chemical messages to be transmitted from one neuron to the next in the brain, a process that underlies basic sensory functions and that is critical to learning, memory and thought formation, and other cognitive activities. The brain and the spinal cord together make up the system of nerve tissue in vertebrates called the central nervous system, which controls both voluntary movements, such as those involved in walking and in speech, and involuntary movements, such as breathing and reflex actions. It also is the centre of emotion and cognition. (For more information about the human brain, see nervous system, human.)

• In lower vertebrates the brain is tubular and resembles an early developmental stage of the brain in higher vertebrates. It consists of three distinct regions: the hindbrain, the midbrain, and the forebrain. Although the brain of higher vertebrates undergoes considerable modification during embryonic development, these three regions are still discernible.
• The hindbrain is composed of the medulla oblongata and the pons. The medulla transmits signals between the spinal cord and the higher parts of the brain; it also controls such autonomic functions as heartbeat and respiration. The pons is partly made up of tracts connecting the spinal cord with higher brain levels, and it also contains cell groups that transfer information from the cerebrum to the cerebellum.
• The midbrain, the upper portion of which evolved from the optic lobes, is the main centre of sensory integration in fish and amphibians. It also is involved with integration in reptiles and birds. In mammals the midbrain is greatly reduced, serving primarily as a connecting link between the hindbrain and the forebrain. Connected to the medulla, pons, and midbrain by large bundles of fibres is the cerebellum. Relatively large in humans, this “little brain” controls balance and coordination by producing smooth, coordinated movements of muscle groups.
• The forebrain includes the cerebral hemispheres and, under these, the brainstem, which contains the thalamus and hypothalamus. The thalamus is the main relay centre between the medulla and the cerebrum; the hypothalamus is an important control centre for sex drive, pleasure, pain, hunger, thirst, blood pressure, body temperature, and other visceral functions. The hypothalamus produces hormones that control the secretions of the anterior pituitary gland, and it also produces oxytocin and antidiuretic hormone, which are stored in and released by the posterior pituitary gland.

3. Nervous System: encephalon, brain.

4. What are all these terms ending in -encephalon? Well, they come from the Greek encephalon, the word for “brain”, from and en- “in” and cephalon “head”; so “that which is in the head — the brain”. You have no doubt encountered this term as part of electroencephalogram (EEG), “a picture (gram) of electrical activity in the brain” and encephalitis “inflammation of the brain”. The order of the 5 layers can be memorized by remembering that the telencephalon is on the top and that the other four divisions are arrayed below it in alphabetical order. More information about any one of the major divisions above can be found by clicking on the link above or on the appropriate spot in the diagram above.

S: 1. Etymonline – https://www.etymonline.com/search?q=brain (last access: 31 March 2025). 2. EncBrit – https://www.britannica.com/science/brain (last access: 31 March 2025). 3. TERMIUM PLUS – https://www.btb.termiumplus.gc.ca/tpv2alpha/alpha-eng.html?lang=eng&i=1&srchtxt=brain&index=alt&codom2nd_wet=1#resultrecs (last access: 31 March 2025). 4. (last access: 31 March 2025). 4. RiceU – https://www.ruf.rice.edu/~lngbrain/cglidden/ (last access: 31 March 2025).

SYN: encephalon

S: EncBrit – https://www.britannica.com/science/brain (last access: 31 March 2025); TERMIUM PLUS – https://www.btb.termiumplus.gc.ca/tpv2alpha/alpha-eng.html?lang=eng&i=1&srchtxt=brain&index=alt&codom2nd_wet=1#resultrecs (last access: 31 March 2025).

CR: bovine spongiform encephalopathy, cerebrum, encephalitis, Japanese encephalitis, Rasmussen’s encephalitis, transmissible spongiform encephalopathy, West Nile encephalitis.