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

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

7. 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

9. NEGATIVE FEEDBACK SYSTEM

10. 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

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

12. Negative feedback in regulation of mammalian body temperature

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

15. 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

16. 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)

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

18. 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

19. INSECT
DEVELOPMENT

20. Mineral balance in herbivorous mammals

21. 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

22. 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

23. Mammalian kidney
Blood vessel
Urine

24. (glycoprotein)
Steroid hormone
(Enzyme)

25. High K+ in blood
K+ excretion

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

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

28. Plant response to water deficit
Stomates close due to reduced turgor

29. 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

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