Student Handout

One of the weapons developed during World War II was nerve gas. The idea was to develop a weapon that would not harm the land, only the people on it, since the victors would have no use for damaged or contaminated land. Fortunately, nerve gas was not actually used during World War II, but it has been used in more recent times. In the mid-1980s, Iraq used nerve gas in its war with Iran, killing thousands of people. More recently, a cult group in Japan, used nerve gas in a terrorist attack in a Tokyo subway, killing 12 people and wounding 5500 and US soldiers were exposed to nerve gas in Iraq during the clean-up after the Gulf War. Today, countries still store nerve gas and other chemical weapons, and they spend a great deal of money and time developing potential antidotes to nerve gas poisoning.

How toxic is nerve gas? For those unfortunate people that are exposed to high levels of nerve gas, they die a rapid (within minutes), horrible death. With lower levels of exposure, people may suffer over hours or up to a day before finally succumbing. And in the case of mild exposure, such as in the Tokyo subway or after the Gulf War, those who survive can suffer long-lasting neurological problems.

1. What is “nerve gas”?

2. Describe the chemical and physical characteristics of nerve gas.

3. Make a list of the things that nerve gas does to the body.

In order to become poisoned by nerve gas, it must enter the body and reach certain targets. Nerve gas can be breathed in through the lungs and it can be absorbed through the skin, the eyes and any other body surface. This occurs very rapidly. Once the nerve gas gets into the lungs or into the skin cells, it diffuses into the bloodstream capillaries. As the gas moves throughout the bloodstream, it reaches every cell in the body.

4. Explain how the nerve gas gets from the lungs into the bloodstream.

5. Describe how the nerve gas gets absorbed through the skin and through the eyes into the bloodstream.

6. Why is it so easy for the nerve gas to be absorbed through the skin?

7. Does the nerve gas stay in a gaseous form once in the blood? Explain your answer.

Nerve gas affects many parts of the body, yet it has only 1 action. Basically, it causes excessive information to flow between neurons and their target tissues all over the body, essentially causing the tissues to function in “overdrive”. To understand how this one chemical can have so many effects on the body, we must understand how the nervous system is constructed and how the nerve gas actually works.

The brain contains neurons that travel short distances within the brain and neurons that travel long distances, outside the brain. Neurons travel all over the body to provide information to target cells to perform some kind of work (depending on the target). Information travels along the axons of neurons in the form of electrical impulses. When electrical impulses reach the nerve terminal, special chemicals called neurotransmitters are released. One of the major neurotransmitters in the brain and in the peripheral neurons is acetylcholine.

8. Draw a neuron and label its parts.

9. What is the difference between the central nervous system and the peripheral nervous system? Draw a map showing the 2 nervous systems.

10. The peripheral nervous system can be divided into the autonomic and the somatic nervous systems. On your map, show where these nervous systems originate and which structures are targets of their axons.

11. The autonomic nervous system can be divided into 2 more nervous systems. They are called the sympathetic (SNS) and the parasympathetic nervous systems (PSNS). These 2 systems usually innervate the same structures, but the neurotransmitters within them differ. On your map, draw an example of the SNS and the PSNS. Place an arrow to show where the acetylcholine is released within these 2 systems. Where else is acetylcholine released (hint: there are 2 other major areas)?

Once released from the nerve terminal, acetylcholine binds to special proteins, called receptors, on neighboring nerves or on muscles (the neuromuscular junction). When acetylcholine binds to its receptors it causes an electrical current to spread across the cell membrane. Depending on the type of cell, the current has different functions. Acetylcholine plays a very important role in controlling everyday functions within the body. When acetylcholine binds to receptors on neurons, the electrical current causes a new electrical impulse to be generated. When acetylcholine binds to receptors on non-neuronal cells in organs such as the heart, stomach, bladder, glands and eyes, and in tissues such as skeletal muscle, they respond with specific functions.

12. Below is a list of organs or tissues that receive acetylcholine signals from various nerve pathways. To the right of each target are two functions. Indicate which function is produced by acetylcholine:

Intestines: contraction (diarrhea) – relaxation (constipation)
Heart: decreased heart rate – increased heart rate
Lungs (bronchii): dilation – constriction
Sweat glands: no secretion (dry) – secretion (sweat)
Salivary glands: secretion (saliva) – no secretion (dry)
Tear ducts: secretion (tears) – no secretion (dry)
Eyes: pupil constriction (miosis) – pupil dilation
Muscles: relaxation – contraction
Brain (vomit center): inhibit – stimulate (vomit)

Acetylcholine’s actions must be terminated to prevent its effects from being too strong or too prolonged. The body synthesizes a special enzyme to do this. It is called acetylcholinesterase. It destroys acetylcholine by the process of hydrolysis. This is the process that is disrupted by nerve gas. Nerve gas prevents the ability of acetylcholinesterase to destroy acetycholine. When nerve gas is in the body, acetylcholine levels accumulate at the receptors, causing too much activation.

13. What kind of chemical reaction is hydrolysis? How does the acetylcholinesterase hydrolyze the acetylcholine?

14. When acetylcholinesterase hydrolyzes acetylcholine, what products are formed? How is the acetylcholine replaced?

15. Where is the acetylcholinesterase found?

16. How does nerve gas inactivate the acetylcholinesterase?

17. Now that you know what acetylcholine does, you can predict how nerve gas affects the body. Make a new list of the effects of nerve gas and compare it to the original list you made in question #3.

18. Which action of nerve gas actually causes death?

In our country, every day there are people exposed to other poisons that work in the same way that nerve gas works. The victims don’t die from the exposure, but they do suffer neurological problems from long-term exposure to these compounds.