Transcription
[Applause] Signals from our environment are most often first detected by the brain. When someone is frightened, a stress response is initiated by their reaction to an environmental [Music] signal. But many signals don't stop here.
A signal received by the brain can be passed on to many types of cells throughout the body and have widespread effects. Signals get sent around the body by traveling through the nervous system or bloodstream, going from cell to cell. You could think of the cell's sole purpose in life is keeping signals going or initiating new ones in response to the environment.
Once a signaling molecule from the bloodstream reaches a cell and docks, the signal is passed into the cell. Like a miniature mouse trap game, the cell is filled with complex contraptions called proteins that bump and nudge each other to keep the signal going until it reaches its target. In this case, it's the production of yet another signaling molecule that will get released into the bloodstream, dock on other cell types, and cause them to react in a variety of ways. [Music]
The signal passing machinery inside the cell can look and work very differently depending on the intended effect. Here we see a signaling cascade that results in the release of energy molecules. Once liberated, they are sent on their way via the bloodstream to power cells in another area of the body. When this tiny domino effect is triggered inside cells, some amazing things can happen.
Other signaling cascades triggered during the stress response result in a variety of physical reactions. This signaling molecule can relax or contract different types of muscle cells. When it reaches the skin, the signal docks on muscle cells attached to a body hair. The tiny muscle is stimulated to contract, raising the hair. The signal also docks on cells wrapped around a sweat gland, which contract too, squeezing sweat onto the skin [Music] surface.
In the lungs, the signaling molecule docks on muscle cells wrapped around bronchioles, but these cells relax instead of contract to allow more oxygen into the blood. Because the protein machinery inside each kind of muscle cell is different, this single type of signaling molecule can cause both relaxation and contraction. Many signaling molecules work this way.
When this signal reaches the heart, it docks on beating heart cells. Their response is to beat faster. Blood pressure goes up, up, and the signaling molecule is rushed on to still more cell types around the [Music] body. Constantly and in concert, cells must send and receive a myriad of signals. Cell communication is vital to keeping the body alive.