Essential Idea:
Hormones are not secreted at a uniform rate
and exert their effect at low concentrations
Understandings:
- Endocrine glands secrete hormones directly into the bloodstream
- Steroid hormones bind to receptor proteins in the cytoplasm of the target cell to form a receptor-hormone complex
- The receptor-hormone complex promotes the transcription of specific genes
- Peptide hormones bind to receptors in the plasma membrane of the target cell
- Binding of hormones to membrane receptors activates a cascade mediated by a second messenger inside the cell
- The hypothalamus controls hormone secretion by the anterior and posterior lobes of the pituitary gland
- Hormones secreted by the pituitary control growth, developmental changes, reproduction and homeostasis
Applications:
- Some athletes take growth hormones to build muscles
- Control of milk secretion by oxytocin and prolactin