Substances that have been isolated from the blood and have been shown to induce sleep have also been linked to the ________ system.
A) urinary
B) respiratory
C) reproductive
D) integumentary
E) immune

Question

Quizplus · Accepted Answer

The substances that induce sleep and have been found in the blood are likely neurotransmitters or hormones such as melatonin or adenosine, both of which have been linked to the immune system. Melatonin is produced by the pineal gland in response to darkness and is involved in regulating the sleep-wake cycle, while adenosine is a byproduct of cellular metabolism that accumulates in the brain over time and is thought to drive sleep pressure. Both of these substances also have immunomodulatory effects, so they are likely to have some connection to the immune system. The other systems listed (urinary, respiratory, reproductive, integumentary) are not directly related to sleep physiology or the substances that induce sleep.

Substances That Have Been Isolated from the Blood and Have