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HOMEOSTASIS – REGULATION OF INTERNAL CONDITIONS

HOMEOSTASIS – REGULATION OF INTERNAL CONDITIONS. Patterns of internal regulation in animals Principles of regulatory systems Signaling in internal regulation Animal example: mineral-balance regulation in animals Plant example: plant responses to drought. -50 F, Body = 98.6 F.

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HOMEOSTASIS – REGULATION OF INTERNAL CONDITIONS

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  1. HOMEOSTASIS – REGULATION OF INTERNAL CONDITIONS • Patterns of internal regulation in animals • Principles of regulatory systems • Signaling in internal regulation • Animal example: mineral-balance regulation in animals • Plant example: plant responses to drought

  2. -50 F, Body = 98.6 F + 119 F, Body = 98.6 F

  3. Homeostasis • = ability of animals to regulate their internal environment • Regulator = uses mechanisms of homeostasis to moderate internal change in face of external fluctuation Salt Water Fresh Water Constant solute, water concentration in blood, body fluids

  4. Conformers – allow some conditions within their bodies to vary with certain external changes

  5. Homeostasis • Some constancy • But also includes regulated change essential for normal function, survival • Hormonal changes in reproductive cycles • Responses to challenges

  6. Homeostasis depends on feedback circuits • Three components Receptor – detects a change in some variable of the animal’s internal environment Control Center – process information from receptor, directs signal to the effector Effector – brings about the change to return conditions toward normal

  7. NEGATIVE FEEDBACK SYSTEM

  8. FEEDBACK SYSTEMS Negative – a change in one direction fuels response in a control system and effector in the opposite direction - inherently regulatory Positive – a change in one direction fuels response in a control system and effector in the same direction - non-regulatory

  9. Positive Feedback Systems • Non-regulatory • Unstable • Short-lived, produce radical change • Mammalian birth • Generation of nerve impulse • Swallowing or vomiting

  10. Negative feedback in regulation of mammalian body temperature

  11. Homeostatic Mechanisms • Communication and signaling between a receptor and a control center • AND between a control center and an effector

  12. Homeostatic Mechanisms • Communication and signaling between a receptor and a control center • AND between a control center and an effector • Signaling and communication are dominant themes in biology

  13. Signaling and Communication in Homeostasis • Nervous system – high-speed, electrical signals along specialized cells (neurons) • Endocrine system – slower communication, via hormones = chemical messengers secreted directly into body fluids by endocrine glands (organs)

  14. Cell signaling in nervous and endocrine systems Produce protein, change in membrane permeability, release of material

  15. Nervous and endocrine systems are closely linked • Epinephrine (adrenalin) • Produced in adrenal gland (an endocrine organ) • Hormone: “flight or fight” response • Neurotransmitter – conveys signals between neurons in the nervous system • Neurosecretory cells – specialized nerve cells that secrete hormones in endocrine organs and tissues

  16. INSECT DEVELOPMENT

  17. Mineral balance in herbivorous mammals

  18. Sodium - predominant cation in extracellular fluids, needed for many metabolic purposes Most plants – do not require sodium, do not accumulate it -very high potassium levels when growing High sodium intake from animal flesh

  19. Herbivores face physiological challenges in mineral balance - how to take in enough sodium? - how to reduce sodium loss? - how to get rid of enough potassium Very little sodium in urine and feces (sodium retention) Salt blocks, mineral licks, geophagy (behavioral solution) High excretion of potassium

  20. Mammalian kidney Blood vessel Urine

  21. (glycoprotein) Steroid hormone (Enzyme)

  22. High K+ in blood K+ excretion

  23. High K+ in blood ACTH Hypothalamus K+ excretion STRESS

  24. Plant responses to external changes (drought stress) Water is lost through leaves via transpiration (stomates) Drought: transpiration > water uptake Processes to control

  25. Plant response to water deficit • Stomates close due to reduced turgor

  26. Plant response to water deficit Water deficit increases synthesis of abscissic acid, hormone that keeps stomates closed (changed permeability) Reduced leaf growth = lower rate of increase in leaf surface = lower transpiration Leaves wilt, roll, expose less surface area to air Root growth in deeper, moist soil, inhibited shallow root growth

  27. Bio 103 Home

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