Nerves

4. a signal transmitted along a nerve fiber. It consists of a wave of electrical depolarization that reverses the potential difference across the nerve cell membranes.
6. a bacterium, virus, or other microorganism that can cause disease.
10. the state or quality of being resistant to a particular infectious disease or pathogen.
13. chemical messengers that your body can't function without.
14. a short branched extension of a nerve cell, along which impulses received from other cells at synapses are transmitted to the cell body.
17. a gap between the pre- and postsynaptic cells that is about 20 nm (0.02 μ) wide
18. a rapid sequence of changes in the voltage across a membrane.

1. A tiny, disc-shaped piece of cell that is found in the blood and spleen
2. sit behind the ears and are the second largest lobe
3. a colorless cell that circulates in the blood and body fluids and is involved in counteracting foreign substances and disease; a white (blood) cell. There are several types, all amoeboid cells with a nucleus, including lymphocytes, granulocytes, monocytes, and macrophages.
5. treatment with a vaccine to produce immunity to a particular infectious disease or pathogen
7. nerve cells that send messages all over your body to allow you to do everything from breathing to talking, eating, walking, and thinking
8. an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord.
9. the site of transmission of electric nerve impulses between two nerve cells (neurons) or between a neuron and a gland or muscle cell (effector).
11. A type of white blood cell that surrounds and kills microorganisms, removes dead cells, and stimulates the action of other immune system cells
12. a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.
15. a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.
16. the electrical potential difference across the plasma membrane when the cell is in a non-excited state.