The brain senses that it isn't receiving enough oxygen and sends a signal to the person to wake up.
From the latimes.com
Fall and winter rains are the signal for these plants to wake up from their summer dormancy and get growing.
From the ocregister.com
Although that is not an immediate wake-up signal, once the hormone recedes from the system, we may tend to wake up spontaneously.
From the denverpost.com
The chip reacts to a signal transmission from a reader to wake up digital logic and sends back a 128-bit identification telegram.
From the sfgate.com
It didn't respond to two wake-up calls from Earth but sent a signal late Thursday when the orbiting Odyssey spacecraft passed overhead.
From the dispatch.com
Given the high expectations for months, if not years, that today would signal a rebound in St. Louis, the reality of another decade of decline should be a wake-up call, he said.
From the stltoday.com
This computer has no internal power supply, but when a specially designed reader sends out a radio signal, a tiny antenna draws power from the wave and uses it to wake the computer up.
From the economist.com
For China, the fiscal crisis and Great Recession offered a wake-up call, a signal to rebalance and move away from unsustainable external demand toward untapped internal consumption.