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Endocrine system General Infomation • Connected to the nervous system via the Hypothalamus. • Often in this system, the sensor and control center are the same. Component 1: Glands • Endocrine glands release hormones directly into the blood. (They may release other secretions, too) • Master Gland: Pituitary Gland – Produces “tropic hormones”, which regulate hormone production – Anterior section & Posterior section • Anterior: produces 11 hormones! • Posterior: stores ADH & oxytocin Other Glands… Hormones I’m stressed. • Chemical messengers • Carry instructions to target organs. • Very potent! Released in small quantities. I’m hungy. I’m sleepy. Two Types of Hormones: Steroid • Made from cholesterol (hydrophobic) • In the blood they combine with protein carriers until they reach the target cell. • Fat soluble, so they pass through the target cell membrane easily. • Once inside, they form a hormone-receptor complex in the cytoplasm, which enters the nucleus and activates transcription of specific gene(s). (see handout) Two Types of Hormones: NonSteroid • Made from amino acids (hydrophillic) • Cannot pass directly through the cell membrane • Target cells have receptors on their surface for this type of hormone. When activated, they trigger a chain of chemical reactions within the cytoplasm, where ATP is dephosphorylated to create cyclic AMP, which activates the required pathway. (see handout) How The Endocrine System Works • Two possibilities… – Antagonistic hormones constantly work against each other to maintain a constant environment. – Hormones that act through negative feedback will activate one response and inhibit their own release at the same time. Flowcharts: Antagonistic Hormone Effector(s) Action Hormone Gland, Component Effector Action Patient! • Symptoms: – Fatigue – Tingling in hands and feet – Have passed out a few times – Frequent urination – Very thirsty Diabetes • Canadians Banting & Best discovered that insulin was responsible for diabetes Won Nobel Prize. • 3 types: – Type I: Born with an immune system that attacks pancreatic cells. – Type II: Cells stop responding to insulin. Usually due to poor diet and lack of exercise. – Gestational: Diabetes during pregnancy. Usually clear up after birth of baby. The Pancreas: Blood Sugar • After you’ve eaten, your blood sugar increases. – Beta cells in the pancreas release insulin, which stimulates receptors on the liver cells, muscle and other organs to store glucose in the form of glycogen. This lowers blood sugar. • In between meals, your blood sugar decreases – Alpha cells in the pancreas release glucagon, which stimulates receptors on liver cells, muscle and other organs to break down glycogen and release it. This raises blood sugar. Questions • What type of hormone are insulin and glucagon? • What type of homeostatic control is portrayed? Flowcharts: Negative Feedback Event Stimulates Inhibits Gland Releases Hormone Stimulates Gland Releases Hormone Stimulates Action Effector Effector Action