Affectors, also known as effectors, are molecules that directly cause cellular responses. They can be classified into different categories based on their functions. Signaling molecules are affectors that transmit information from one cell to another. Hormones are also affectors that regulate physiological processes. Neurotransmitters are affectors that transmit signals across synapses in the nervous system. Enzymes are affectors that catalyze biochemical reactions and regulate cellular metabolism. Receptors are affectors that bind to signaling molecules and initiate cellular responses. Lastly, effector cells are cells that respond to affectors and carry out specific actions. Understanding the different categories of affectors is essential for comprehending cellular physiology and the mechanisms of various diseases.