1Nerve messages
Your nervous system carries messages as electrical impulses along nerve cells called neurones. A message from your eyes goes to your brain, and your brain sends messages to your muscles.
impulseneurone
Lesson 16.2 notes
Drugs and the nervous system
How nerve messages travel, stimulants and depressants, testing your reaction time, and addiction.
2Synapses
Between two neurones is a tiny gap, a synapse. When an impulse arrives, a chemical crosses the gap and starts an impulse in the next neurone. Many drugs act at synapses.
synapse
3Stimulants
Stimulants speed up messages in the nervous system. Caffeine, in coffee, tea and cola, and nicotine, in tobacco and vapes, are stimulants: the heart beats faster and people feel more alert.
stimulant
4Depressants
Depressants slow down messages in the nervous system. Alcohol and solvents are depressants: reactions get slower, and balance, speech and judgement get worse.
depressant
5Reaction time
Your reaction time is how long you take to respond. In a ruler-drop test, a partner lets go of a ruler and you catch it. The further it falls, the slower you reacted.
reaction time
6From distance to time
A falling ruler speeds up, so a graph turns the distance into a time: 5 cm is 0.10 s and 20 cm is 0.20 s. Repeat the test and work out the mean.
mean
7Addiction
Many drugs are addictive: the body gets used to the drug, so a person feels they need it. Stopping can cause withdrawal symptoms, such as headaches and feeling irritable.
addictivewithdrawal symptoms
Explore: Reaction time lab
Test your own reaction time with a ruler drop: catch the ruler as fast as you can, three times, and work out the mean.
Common mistake: A depressant slows the nervous system
A depressant doesn't simply make people sad: it slows down the messages in the nervous system, so reactions get slower. And a stimulant isn't harmless: too much caffeine can cause a racing heart and poor sleep.
Remember
- Messages travel along neurones as electrical impulses. At a synapse, a chemical carries the message across the gap to the next neurone.
- Stimulants, such as caffeine and nicotine, speed up messages. Depressants, such as alcohol and solvents, slow them down.
- Many drugs are addictive: the body gets used to the drug, and stopping it causes withdrawal symptoms.
Going further at GCSE