How Well Do You Know Your Brain?

It's kind of strange to put the mighty brain on a par with the much simpler lung, but they are both organs. "Gland" is not too far off, as parts of the brain have endocrine functions, meaning they are responsible for sending chemical messengers to other parts of the body.

Sorry to throw the metric system at you, but it's the "lingua franca" of the medical world. If you must know, 1.5 kilos is about 3.3 pounds.

This argument has sometimes been used to suggest that humans will someday develop telepathy or psychokinesis, once the unused parts of the brain are developed. The reason we know this isn't true is that trauma or stroke in any part of the brain causes disability of some kind. If 90 percent of the brain went unused, many brain injuries would be harmless.

The skull protects the brain from trauma -- that is, external forces. The blood-brain barrier's job is more subtle: it keeps blood itself and larger molecules from getting into the brain, while letting in water and other elements important to brain function.

When we think of the brain, we often think of the cerebrum, the largest and topmost part. But there's also the cerebellum ("little brain") and brain stem. The spinal cord, though very important, is not part of the brain.

The cerebellum is like a miniature brain underneath the cerebrum (which is about 85 percent of the brain's mass. The cerebellum is involved in motor skills and sensory processing -- those functions begin in the cerebral cortex, but the cerebellum is an important "switching station," to use a metaphor.

The cerebral cortex is the outer layer of the brain, or "gray matter." It's what we're referring to when we refer generally to the brain. Underneath, the cerebral cortex is supported by "white matter," non-nerve cells that have support functions.

These are large regions that are responsible for a multitude of functions, and have names, e.g. "parietal." Don't confuse the brain's lobes with its hemispheres, which are simply "left" and "right."

The notion that "left-brained" people are logical while "right-brained" people are intuitive has been slow to die. But these personality characteristics are based on many factors, like parental influence, early-childhood experiences and the values of the culture around the individual.

It really depends on who you ask. Neurology comes close, but includes the nervous system beyond the brain as well. Psychology is certainly a study of the brain and how it works, but not much use if you have a brain tumor. The only really wrong answer here is "craniology," which is the study of the human head, but not a department you'd find in a hospital directory.

Neurons, or nerve cells, are responsible for cognitive power, and humans have more than any other animal. For example, cats have about 250 million neurons. This means that if your cat is outsmarting you, you have only yourself to blame!

Unlike other cells, neurons do not divide and reproduce. The neurons you have now are the ones you'll have for life, so maybe wear a bike helmet. Just sayin'.

When you see those cool animations of a patient's brain on reruns of "House M.D.," those flashing sparks are synapses firing. Brain activity really is electrical in nature.

The islets of Langerhans are found in the pancreas. They produce pancratic hormones, including insulin, for which we're grateful when we overindulge in ice cream.

The brain keeps an awful lot of data in a small space. So the brain has folds to make the most of the limited room, not unlike the way you might bend an electrical cord over on itself to make it fit in a smaller space.

The singular for a fold is "gyrus," and the singular for a groove between the folds is a "sulcus." The plurals end in i, because Latin.

Magnetism is key to this imaging technology. It can study blood flow and synaptic activity in the brain, which tells doctors which areas are functioning normally and which have a deficit.

Though many glands are "off-site," some are located in the brain. These include the pituitary and pineal glands. The pituitary works closely with a brain region called the thalamus to regulate basic body functions.

"Amygdala" comes from the Latin word for "almond," and is named for its shape. You actually have two, like kidneys, but it's common for people to refer casually to the amygdala as singular.

Of course, this is only one of the functions that that occipital lobe is responsible for; it's a big place. Fun fact: The optical nerve delivers sensory information to the occipital lobe, but the images are actually upside-down! The brain reverses the image based on information from the other senses.

Melatonin is responsible for our sleep cycles. It's also thought that at point of death, the pineal gland releases a large amount of DMT, a hallucinogen, and this might be responsible for near-death experiences.

"Hypothalamus" means "under the thalamus," and it's involved in a number of basic body functions. However, the hypothalamus also influences emotional attachment, like of a parent for a child.

Beware: you'll hear a lot of junk science about neurogenesis. The truth is, it's only been observed in adults in two sections of the brain, one of which is the dentate gyrus, which makes new memories and processes information about new environments. One thing that has been observed to cause neurogenesis in mice? Exercise! (This study wasn't replicated in humans because the radioactive imaging agent isn't approved for use in humans).

Executive function has to do with self-discipline, visualizing the future and understanding consequences. The connection between the prefrontal cortex and the rest of the brain is slow to develop, which is why children and teenagers usually struggle with self-discipline and foreseeing the outcomes of their behavior.

This area is named for Pierre Paul Broca, a doctor and anatomist. He recognized that injuries to an area in the inferior frontal gyrus caused patients to have difficulty with speech production.

Wernicke's area is the area responsible for understanding speech, while Broca's is responsible for creating speech. (We know this one was tough, so we tried to steer you in the right direction by making the other three the names of chocolatiers!).

About 30 percent of brain tumors are gliomas, tumors in the glial cells of the brain. What's a glial cell? They are non-nerve cells that create myelin and white matter.

There are 52 Brodmann areas on the human cerebral cortex. We specify "human" because Korbinian Brodmann also mapped the brains of monkeys.

The retina is part of the eye, of course. The other three are parts of the brain stem, the smallest and lowest part of the brain.

"Limbic system" is one of the less-strictly defined terms in brain science. Generally, it means the parts of the brain responsible for memory, learning and fear. It is sometimes called the "mammalian" brain.

A particular type of dolphin, the long-finned pilot whale, has this distinction. Are they smarter than humans? Observationally, it seems not -- a dolphin hasn't put a Tesla in space, recently. (Maybe that's actually a sign of their superior judgment).

Inflammation is both a necessary biological process in response to illness and injury, and a dangerous phenomenon that should be corrected. Encephalitis, or inflammation of the brain, can be life-threatening.

You've experienced this every time you've had to change a familiar password. There might be five, six or seven times that you accidentally enter the old password instead. When you start entering the new password ... that's long-term potentiation!

Technically, we're pretty sure it's the *synapses* that fire. But we get the point.

The most basic division of the brain is its division into two hemispheres. The rift between them is called the longitudinal fissure, while the corpus callosum, a dense structre of nerves, unites them and allows them to communicate.