How does a headache tablet know where it hurts?

Does water boiled in a microwave oven taste different from kettle-heated water? How long does it take the body to absorb a drink of water? Does too much water cause a kidney problem? What are essential fatty acids? Why do farts linger longer in the shower? What's better for your body, hot water, cold water, or warm water? How does the body know to swallow a drink and breathe air? How does an aspirin know where it hurts? And how does the anus tell a fart from a shart? Like this podcast? Please help us by supporting the Naked Scientists