________ are chemical substances that act as natural analgesics.

A) Acetylcholines
B) Neurotransmitters
C) Endorphins
D) Receptors

Endorphins are chemical substances that are naturally released by the body in response to pain or stress. They act as natural analgesics, decreasing the perception of pain and promoting a sense of well-being. Acetylcholines act as neurotransmitters and are involved in muscle contraction and cognitive function, but they are not natural analgesics. Neurotransmitters are chemical messengers that transmit signals between neurons, but they are not necessarily analgesic in nature. Receptors are proteins that bind to specific molecules, including neurotransmitters and endorphins, but they do not act as natural analgesics themselves.