| A | B |
|---|
| addiction | Physical dependence on a habit-forming substance. |
| axon | The branch of a neuron (a nerve cell) which sends messages to other neurons. |
| dendrite | A branch of a neuron (nerve cell) which receives messages from other cells. |
| drug | A chemical taken into the body which causes changes in the body. |
| drug abuse | The excessive use of drugs. |
| glands | Organs or tissues in the body which make and release chemicals. |
| hormones | Chemicals released by glands. |
| motor nerve cells | Nerve cells which send signals to the muscles. |
| neurotransmitter | A chemical in the brain which carries messages between the neurons. |
| nerve | A bundle of nerve cells. |
| nervous system | The organ system made up of the brain, spinal cord, and the nerves. |
| neuron | Another name for a nerve cell. |
| neuroscientist | A scientist who studies the nervous system. |
| over-the-counter drug | A drug which is able to be sold without a doctor's prescription. |
| prescription drug | A drug which can only be sold by doctor's order. |
| reflex | A quick, automatic action which does not involve the brain. |
| sensory nerve cells | Nerve cells which send information from the muscles to the brain or spinal cord. |
| side effect | An effect of a drug, usually unwanted, which is not intentional. |
| peripheral nervous system | The part of the nervous system which is outside the central nervous system. |
| central nervous system | The nerves of the brain and spinal cord. |
