Answer
Receptors are specialized cells or nerve endings that are sensitive to stimuli from a variety of modalities such as light temperature, touch, pressure, stretch, and changes in concentrations of components such as carbon dioxide, oxygen, and ions of potassium sodium, hydrogen etc. receptors usually transmit messages to afferent neurons which transmit then finally to a brain or spinal cord center.
Control Center. A control center in human feedback loops usually a nerve center in the brain or spinal cord. These centers receive afferent stimuli from receptors regarding changes in controlled conditions.
Work Step by Step
Receptor are a specialized cells or nerve endings which are sensitive to input stimuli of various kinds-- light, pressure, stretch, temperature, pH, and concentrations of various molecules and ions. Receptors send messages of changed values of controlled conditions to control centers or comparators ((usually the brain or spinal cord in humans) for comparison with a set point or set range of values. When necessary for restoration of homeostasis or equilibrium, the control centers send out efferent messages to effectors to act to reverse changes ( negative feedback) or to enhance them (positive feedback).
Effector. Effectors in homeostatic phenomena are usually muscles or glands. When they receive efferent messages muscles contract and glands secrete chemical substances such as hormones.
