addiction: The National Institute of Drug Abuse defines this as a complex chronic disorder that is characterized by a difficult-to-control compulsion to use some drug, despite knowing that it will likely have harmful impacts. A first exposure to these drugs is usually voluntary. But repeated use of certain ones, NIDA explains, can create “changes to brain circuits involved in rewards, stress, and self-control.” Those changes can make it very hard to resist the urge to continue using drugs. The term has also been expanded to some behaviors that become dangerous and/or excessive, such as gambling, shopping and video game use.
ADHD: Short for attention deficit hyperactivity disorder. This condition is characterized by an ongoing pattern of being impulsive (acting without thinking, for instance), inattentive (have trouble staying on task) or hyperactive (fidgeting excessively or seeming overly restless and talkative). Someone can have any or all of these symptoms — and often at a level that tends to get in the way of their functioning effectively.
attention: The phenomenon of focusing mental resources on a specific object or event.
blood pressure: The force exerted against vessel walls by blood moving through the body. Usually this pressure refers to blood moving specifically through the body’s arteries. That pressure allows blood to circulate to our heads and keeps the fluid moving so that it can deliver oxygen to all tissues. Blood pressure can vary based on physical activity and the body’s position. High blood pressure can put someone at risk for heart attacks or stroke. Low blood pressure may leave people dizzy, or faint, as the pressure becomes too low to supply enough blood to the brain.
cell: (in biology) The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
chemical: A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
chemical messenger: (in physiology) Molecules that send signals from one place to another within the body. Messages pass from one neuron to another via chemical messengers. Hormones are another family of chemical messengers that relay signals from one body part to another.
develop: To emerge or to make come into being, either naturally or through human intervention, such as by manufacturing. (in biology) To grow as an organism from conception through adulthood, often undergoing changes in chemistry, size, mental maturity or sometimes even shape.
disorder: (in medicine) A condition where the body does not work appropriately, leading to what might be viewed as an illness. This term can sometimes be used interchangeably with disease.
dopamine: A neurotransmitter, this chemical helps transmit signals in the brain.
focus: (in behavior) To look or concentrate intently on some particular point or thing.
hormone: (in zoology and medicine) A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body.
muscle: A type of tissue used to produce movement by contracting its cells, known as muscle fibers. Muscle is rich in protein, which is why predatory species seek prey containing lots of this tissue.
nerve: A long, delicate fiber that transmits signals across the body of an animal. An animal’s backbone contains many nerves, some of which control the movement of its legs or fins, and some of which convey sensations such as hot, cold or pain.
neuron: The main cell type of the nervous system — the brain, spinal column and nerves. These specialized cells transmit information by producing, receiving and conducting electrical signals. Neurons also can transmit signals to other cells with chemical messengers.
neurotransmitter: A chemical released at the end of a neuron to carry a message to a neighboring cell. This chemical travels across the space between two cells, and then binds to molecules on a neighboring cell to transmit a message. Neurotransmitters are released from neurons, and can bind to neurons or to other types of cell, including those that make up muscles or glands.
regulate: (n. regulation) To control with actions.
salt: A compound made by combining an acid with a base (in a reaction that also creates water). The ocean contains many different salts — collectively called “sea salt.” Common table salt is a made of sodium and chlorine.
symptom: A physical or mental indicator generally regarded to be characteristic of a disease. Sometimes a single symptom — especially a general one, such as fever or pain — can be a sign of any of many different types of injury or disease.
synapse: The junction between neurons that transmits chemical and electrical signals.
transmit: (n. transmission) To send or pass along.