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Ch 45: Hormones and the Endocrine System

Ch 45: Hormones and the Endocrine System. HOMEOSTASIS = maintaining steady state in body functions. IN ORDER TO MAINTAIN HOMEOSTASIS, there are 3 functional components…. Receptor/sensor : detects a stimulus Ex: increase in blood osmolarity

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Ch 45: Hormones and the Endocrine System

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  1. Ch 45: Hormones and the Endocrine System

  2. HOMEOSTASIS= maintaining steady state in body functions

  3. IN ORDER TO MAINTAIN HOMEOSTASIS, there are 3 functional components… • Receptor/sensor: detects a stimulus • Ex: increase in blood osmolarity • Control center: compares to set point & sends out a stimulus • Ex: osmoreceptor cells in the hypothalamus; sends signal to pituitary gland • Effector: responds to control center • Ex: pituitary gland releases ADH into bloodstream *negative feedback maintains homeostasis!

  4. HORMONE • HORMONE = a chemical signal secreted into body fluids (usually blood); communicates regulatory messages within the body. • TARGET CELLS = cells equipped to respond to specific hormones

  5. Example of Homeostasis: Blood Calcium Levels

  6. INTERNAL COMMUNICATION & REGULATION • 2 systems: Nervous & Endocrine • Nervous System: conveys high speed electrical signals along neurons • Endocrine System: all of an animal’s hormone-secreting cells • Local Regulators

  7. ENDOCRINE SYSTEM - ENDOCRINE GLANDS = hormone-secreting organs (“ductless glands” – they secrete hormones directly into blood/fluid to target cells throughout the body) **overlap with the nervous system includes: - NEUROSECRETORY CELLS: specialized nerve cells that secrete hormones into the blood

  8. LOCAL REGULATORS LOCAL REGULATORS: non-hormones that affect nearby (“local”) cells • Ex #1: Growth Factors -some peptides and proteins can function as local regulators to stimulate cells to grow, divide & develop normally growth factor that stimulates fibroblast cells (skin cells)to divide

  9. LOCAL REGULATORS • Ex #2: Prostaglandins (PGs) -modified fatty acids in semen, stimulate contraction of the smooth muscles of the wall of the uterus; helps sperm reach the egg from placenta, stimulates uterus muscles to contract in labor in immune system, help to induce fever, inflammation, intensify pain

  10. How do Chemical Signals Work? • each chemical signal has a specific shape (recognized by target cell receptor); • hormone binds to specific receptor on or in the target cell (cells are unresponsive if they lack the appropriate receptor);

  11. How do Chemical Signals Work? -binding of a chemical signal to a receptor protein triggers chemical events within the target cell: • Binds to receptor on plasma membrane, OR • Binds to receptor INSIDE the cell

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