| A | B |
|---|
| neuron | A cell that conducts electrochemical signals; the basic unit of the nervous system; also called a nerve cell |
| glial cells | Nervous-system cells that aid the neurons by providing them with nutrients, insulating them, and removing cellular debris when they die |
| dendrites | A neuron's branches that recieve information from othe neurons and transmit it towards the cell body |
| cell body | The part of the neuron that keeps it alive and determines whether it will fire |
| axon | A neuron's extending fiber that conducts impulses away from the cell body and transmits them to other neurons |
| myelin sheath | A fatty insulation that may surround the axon of a neuron |
| nerves | Bundles of neural fibers (axons and sometimes dendrites) in the PNS |
| synapse | The site where a nerve impulse is transmitted from one nerve cell to another; it includes the axon terminal, the synaptic cleft, and receptor sites in the membrane of the receiving cell |
| neruotransmitter | A chemical substance that is released by a transmitting neuron at the synapse and that alters the activity of a receiving neuron |
| hormones | Chemical substances, secreted by organs called glands, that affect the functioning of other organs |
| endocrine glands | Internal organs that produce hormones and relase them into the bloodstream |
| melatolin | A hormone, secreted by the pineal gland, that is invloved in the regulation of daily biological rhythms |
| adrenal hormones | Hormones that are produced by the adrenal glands and that are involved in emotion and stress; they include cortisol, epinephrine, and norepinephrine |
| sex hormones | Hormones that regulate the development and functioning of the reproductive organs and tha stimulate the development of male and female sexual charecteristics; they include androgens, estrogens, and progesterone |
| endorphins | Chemical substances in the nervous system that are similar in structure and action to opiates; they are invloved in the pain reduction, pleasue, and memory, and they are known techincally as endogenous opioid peptides |
