Cell membranes receive specialized chemicals from neural activity in the brain, and then protein receptors within a cell determine which chemical process to undertake based on the chemical received, according to Scitable. The human body contains hundreds of receptors within individual cells.
Cells receive signals from various stimuli, including neurotransmitters, hormones, mechanical changes from outside the body, and physical changes from within. Neurotransmitters travel between neurons in nerve cells to achieve muscle movement, notes Scitable. Hormones stimulate growth and long-term processes. Changes in touch, smell and hearing signal cells to transmit sensory information. Physical changes such as blood pressure cause cellular signals to be sent throughout the body.
Cell receptors interpret the signals and cause chemical changes within individual cells. Receptors are proteins that bind to signaling molecules and chemicals outside the cell membrane, and then send the signal through molecules inside the cell to start various cellular processes. Cells have three main types of receptors that use proteins, ions or enzymes to communicate, according to Scitable. Receptors do not allow signaling chemicals into the cell because the signaling molecules are too large.
Once a cell receives the extracellular signal, changes occur within parts of the cell. One common messenger within a cell is cyclic AMP, a substance synthesized by the cell membrane enzyme adenylyl cyclase. This enzyme produces hundreds, and even thousands, of molecules of cyclic AMP. This process causes phosphate molecules to create short- and long-term cellular responses to stimuli, explains Scitable.