If Melatonin's half life is only 20 min (or up to 2 hours), why does drowsiness persist?

[miragesyzygy]

ok I'm no math genius here but from a chemistry formula I have to know,

Mass(after time t) = Mass(original) X (.5)^(t/(half life))

so if I took 1mg of melatonin 12 hours ago

m(in kg) = (10^-6)(.5)^(720/20)

=

10^-6 (.5)^36 = (10^-6)(1.5 X 10^-11)

or 1.5 X 10 ^-17 kg

or about 1.5 X 10^-11 mg

or basically nothing

if 2 hours
10^-6 (.5)^6
10^-6 (1.6 X 10^-2) or 1.6X 10^-8 kg or 1.6 X 10^-2 mg which is still very little.

Unless the amount of melatonin necessary to have any effect is smaller than the true amount which I expect to be somewhere between those 2 extremes?

[Francis Vaughan]

Melatonin doesn't cause drowsiness directly. Its job is to trigger the onset of sleep. Once the trigger has been pulled its job is done.

[Squink]

Any complete answer will contain phrases like this:
Involvement of the nitric oxide cascade in melatonin-induced inhibition of long-term potentiation at hippocampal CA1 synapses.
The short and sweet of it is that melatonin acts to trigger other processes that operate on timescales longer than melatonin's half-life.

[Mahaloth]

Wait. Melatonin actually does work to help people go to sleep? I thought the evidence was inconclusive.

[Squink]

Originally Posted by Mahaloth

I thought the evidence was inconclusive.

Last I looked for it, that was true. However, melatonin does trigger some long lasting biochemical effects.

[Francis Vaughan]

Internally generated melatonin is known to mediate the synchronisation of the circadian rhythm. How useful taking additional melatonin is in trying to modify the rhythm, or resynchronise it, is a different problem.

[Rachellelogram]

Neurotransmitters can act as catalysts, too.