Organisms Use Feedback Mechanisms

1. College Board: 2.C – Organisms Use Feedback Mechanisms to Regulate Growth and Reproduction, and to Maintain Homeostasis

2. Organisms Use Feedback Mechanisms • Negative feedback mechanisms maintain dynamic homeostasis for a particular condition (variable) by regulating physiological processes, returning the changing condition back to its target set point. • Operons in gene regulation • Temperature regulation in animals • Plant responses to water limitations

3. Organisms Use Feedback Mechanisms • Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set-point. Amplification occurs when the stimulus is further activated which, in turn, initiates an additional response that produces system change • Lactation in mammals • Onset of labor • Ripening of fruit

4. Organisms Use Feedback Mechanisms • Alteration in the mechanisms of feedback often results in deleterious consequences • Diabetes mellitus in response to decreased insulin • Dehydration in response to decreased antidiuretic hormone (ADH) • Grave’s disease (hyperthyroidism) • Blood clotting

5. Homeostasis • Cells/organisms use energy to maintain homeostasis • Two mechanisms: • Negative feedback • Positive feedback

6. Feedback • __________________= hypothalamus, detects a stimulus beyond the threshold (cold/hot) • ___________________= brain • ___________________=muscle, sweat gland

7. TRH Examples of Negative Feedback Loops Anterior pituitary T3 T4

8. Negative Feedback - _______________________ • Basic unit of genetic expression in _________________ • Sequence of genes that produces a series of _________________ that produce a final product • Advantages: • All enzymes are produced at the _______ _______ • Can be controlled at one site _________________

10. Operons • 4 parts: • _______________________ gene – produces a controller protein • ____________________site – attachment for RNA polymerase • ______________________site – blocks/unblocks RNA polymerase • Structural genes – produces enzymes for a reaction Structural genes - enzymes Regulatory gene Promoter Gene 1 Gene 2 Gene 3 Operator DNA

11. lacOperon • Normally ___ (bacteria normally use ______________) • Must be _________________ (‘turned on’) • Repressor protein produced by the regulatory gene blocks operator • Lactose ___________________________________of the repressor • Regulatory protein is removed from operator site • Operon becomes active (‘induced’)

12. TrpOperon • Repressible – normally ____ must be turned ____ • If _______________________is present it attaches to regulatory protein • Regulatory protein + ___________________attaches to operator site blocking transcription

13. Negative Feedback - Temperature Regulation • Receptors • Integrator • Effectors • Fever

14. Negative Feedback - Plant Responses to Dehydration • ___, ________

15. Positive Feedback • A stimulus causes ____________________ response to an activity that is already happening • Ex. ________________, _______________________ • Can be dangerous (fever)

16. Positive Feedback - Ripening of Fruit • _____________________Gas stimulates production of enzymes • ‘One bad apple spoils the bunch’

17. Alterations of Feedback – • Diabetes mellitus in response to decreased insulin • Too much glucose excreted (mellitus – ‘sweet’) • Role of insulin __________________________ • Dehydration in response to decreased antidiuretic hormone (ADH) (vasopressin) • Neuro-secretory • ____________ water absorption in collecting tubule of kidneys

18. Regulation by ADH • ADH • Stored and secreted by the posterior pituitary • Concentrates nitrogenous wastes as urine • Urea with less _______________ • Diabetes insipidus

19. Aquaporins

20. Alterations of Feedback • Grave’s disease: • Autoimmune – antibodies attach to TSHR on cells of the thyroid gland causing the thyroid to overproduce thyroid hormones (T3 and T4) • Most common cause of ____________________ • Hereditary – mostly females • Goiter

21. Alterations of Feedback • Blood clotting • Hemophilia – genes for clotting factors VIII and IX

22. Integration and Coordination • Nervous system - brain, spinal cord, nerves, and sense organs • Integrates incoming information from receptors and sends impulses to muscles and glands (electrical) • Hypothalamus – neurohormonal • Endocrine system - glands that secrete hormones • Control metabolic functions (chemical) • Review: steroid and nonsteroid hormones