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

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Presentation on theme: "College Board: 2.C – Organisms Use Feedback Mechanisms to Regulate Growth and Reproduction, and to Maintain Homeostasis."— Presentation transcript:

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) – Graves 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 Examples of Negative Feedback Loops TRH Anterior pituitary T3T3 T4T4

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 _________________

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

11 lac Operon 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 Trp Operon 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 Graves disease: – Autoimmune – antibodies attach to TSHR on cells of the thyroid gland causing the thyroid to overproduce thyroid hormones (T 3 and T 4 ) – 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


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