Endocrine System: all an animals hormone secreting cells

1. Endocrine System: all an animals hormone secreting cells

2. Chemical Signals • Categories of Signals • Chemical signals that are secreted into the circulatory system and communicate regulatory messages to the body: • between individuals • between body parts • between cells

4. The Action of Hormones • The Action of Hormones (between body parts) • A hormone does not seek out a target organ; the organ is awaiting the arrival of the hormone. • Different cells/organs have specialized receptors that recognize specific hormones • Steroid hormones • Peptide hormones

5. Target Cell Concept

6. Action of Hormones • Chemical signals produced by one cell that regulate the metabolism of other cells • Steroid Hormones -Can cross cell membranes • Peptide Hormones • Most bind to receptor in plasma membrane • First Messenger • Causes internal release of cAMP • Second Messenger

7. Review of Cell Signaling • Reception: target cell detection • Transduction: single-step or series of changes • Response: triggering of a specific cellular response

8. Steroid Hormone Hormone-receptor complex binds to DNA resulting in activation of genes that produce enzymes Steroid hormones are lipids and cross cell membranes freely

10. Breaking down glycogen in a liver cell Peptide hormones never enter a cell so theybind to a receptor protein in plasma membrane.

11. Examples of Hormone Activity

12. Different activity for same hormone • Many times hormones can elicit a myriad of responses. The same hormone can activate different receptors on different cell types to elicit several responses • In each case, there is some sort of signal transduction pathway, but with a different effect • Example: Release of epinephrine in the “fight or flight” response

14. The Action of Hormones • The Action of Hormones (between cells) • Paracrine signaling is the term given to hormone signaling, locally, between cells • Release of a hormone can activate neighboring cells in seconds (much quicker response than body to organ – long distance signaling) • Examples: • Cytokines (remember immune system) • Growth factors (stimulate cell growth and differentiation – after a cut or broken bone) • Nitric Oxide (improves blood flow by vasodilation when low O2 levels are sensed) • Prostaglandins (general group of modified fatty acids that modify neighboring cells depending on cell type)

15. Homeostasis • Endocrine system is especially involved with homeostasis. • Effect of hormones is controlled in 3 ways: • Negative Feedback • Stops release of hormone • PostivieFeedback • Enhances hormone release • Antagonistic hormones • Hormones have opposing (or opposite) effect

16. Homeostasis • Negative feedback (ex.) • Pancreas produces insulin when blood glucose rises; this causes liver to store glucose. • When glucose is stored, level goes down and pancreas stops insulin production. • Positive feedback (ex.) • Oxytocin stimulates uterine muscle contractions during birth • As more contractions occur, more oxytocin is released • Antagonistic hormones (ex.) • Effect of insulin is offset by glucagon • Thyroid lowers blood calcium level; parathyroidsraise blood calcium level.

17. Negative Feedback • All body cells utilize glucose; therefore, its level must be closely regulated. • Beta cells secrete Insulin • Secreted when blood glucose level is high after eating • Alpha cells secrete Glucagon • secreted between meals in response to low blood glucose level.

18. pancreas & insulin.ram

19. Positive Feedback • Oxytocinis also made in hypothalamus & stored in posterior pituitary. • Oxytocin • stimulates uterine muscle contraction • stimulates release of milk from mammary glands • This positive feedback increases intensity; positive feedback does not maintain homeostasis.

20. Antagonistic hormones • Thyroid hormones increase metabolic rate; there is no one target organ, all organs respond • Thyroid gland also produces calcitonin • Calcitoninlowers calcium level in blood and increases deposit in bone by reducing osteoclasts. • Low calcium levels stimulaterelease of parathyroid hormone (PTH) from the parathyroid gland • The two hormones (calcitonin and parathyroid hormone) counteract the effects of the other

22. What type of regulation? • Antidiuretic hormone (ADH) promotes reabsorption of water from collecting ducts in kidneys. • Nerve cells in the hypothalamus determine when blood is too concentrated; ADH isreleased and kidneys respond by reabsorbing water. • As blood becomes dilute, ADH is no longer released • What type of feedback is this?

23. NEGATIVE FEEDBACK

24. Example: Hormone Disease • Diabetes mellitusis a common disease where body cells do not take up or metabolize sugar. • Liver is not storing glucose as glycogen & cells are not utilizing glucose for energy. • Type I (insulin-dependent) diabetes - pancreas does not produce insulin (autoimmune disease: immune system destroys insulin producing beta-cells in the pancreas a.k.a. islet cells) • type II (noninsulin-dependent) diabetes - usually occurs in obese & inactive individuals of any age. Cells do not respond to insulin