Final answer:
Target cells for hormones have specific hormone receptors that allow them to respond to particular hormones. These receptors are found either on the cell's surface or within the cell for various hormones. The sensitivity of a cell to a hormone can change over time due to the number of receptors through upregulation or downregulation.
Step-by-step explanation:
The cells that make up the target tissue for a hormone have specific hormone receptors to which the hormone can attach. These receptors operate like a lock and key, where the hormone fits into its receptor much like a key fits a lock. This specificity allows hormones to affect only target cells that possess the necessary receptors, which can be found on the cell's surface or within the cell. When hormones bind to these receptors, they can trigger a wide range of cellular responses. There are two main categories of hormone receptors: cell-surface receptors and intracellular receptors. Cell-surface receptors are necessary for water-soluble (hydrophilic) hormones, as these hormones cannot pass through the lipid bilayer of the cell membrane. Conversely, lipid-derived hormones such as steroids can diffuse across the cell membrane and interact with intracellular receptors in the cytoplasm or nucleus, ultimately regulating gene transcription and affecting protein synthesis. The cell's response to a hormone depends on the number of receptors that respond to that hormone. This number can change over time through processes like upregulation and downregulation, affecting the cell's sensitivity to the hormone.