Khan Academy
Khan Academy: Ligands & Receptors
Article looks at different types of receptors and ligands, seeing how they interact to turn information from outside the cell into a change inside the cell.
OpenStax
Open Stax: Anatomy & Physiology: The Pituitary Gland and Hypothalamus
Learn about the hormones released by the pituitary gland, their target cells, and their principal actions, as well as the structure and function of the hypothalamus.