Endocrine System Overview

Functions of Hormones 1) Control, regulation, and maintenance of a. Growth and development b. Reproduction 2) Maintenance of internal environment ie. Homeostasis

Hormones Cellular signals that signals to a cell to alter its metabolism or function Brain-Gut hormone connection

Two types of Hormones Peptide Hormones – hormones are composed of amino acids. A peptide hormone binds to a cell-surface receptor, it does not enter the cell. Results: Enzymes are activate causing a chemical reaction Steroid Hormones – Steroid hormones enter the cell and bind to receptors in the cytoplasm. Ex. The hormone-receptor complex enters the nucleus where it binds with chromatin and activates specific genes. Genes (DNA) contain information to produce protein. Results: When genes are active, protein is produced.

Peptide Hormones How Peptide Hormones Work

Steroid Hormone

How do hormones bind? Receptor- site on the surface or interior of a cell that binds with substances such as hormones, antigens, drugs, or neurotransmitters. Ligand- An ion or molecule that bind to another chemical/molecule forming a complex with different properties. Substrate- The substance acted upon by an enzyme. Enzyme- acts as a catalyst in living organisms, regulating the rate at which chemical and biochemical reactions occur.

How hormones bind?

Types of Glands Exocrine vs. Endocrine Exocrine - A secretion deposited into a body cavity through a duct Endocrine – A secretion sent directly into the bloodstream Endocrine vs. Exocrine Glands

Ten Endocrine Glands

Types of feedback loops Negative Feedback Loop- controls the rate of a process to avoid accumulation of a product. Positive Feedback Loop - occurs when the rate of a process increases as the concentration of the product increases ie. Will continue to accelerate as long as substrate is available. Menstrual cycle The rate of a process will continuously accelerate under positive feedback as long as substrate is available and the product is not consumed by some other process

Hormone Replacement Therapy Some physician’s are skeptical about efficiency of using oral medications to replace hormones. Mixed results Experimental results are mixed and vary for the individual, however many women had fewer reproductive tract problems and decrease in osteoporosis.

Concept Check Since hormones travel through the bloodstream why don’t all cells react? What is the differences between positive and negative feedback loops? What is the difference in end result between peptide and steroid hormones?