Homeostasis Talkie time and Recap

1. HomeostasisTalkie time and Recap This Powerpoint is hosted on www.worldofteaching.com Please visit for 100’s more free powerpoints

2. Competencies: • explain how some organisms maintain steady internal conditions that possess various structures and processes (STEM_BIO11/12-IVi-2) • 2. describe examples of homeostasis (e.g., temperature regulation, osmotic balance and glucose levels) and the major features of feedback loops that produce such homeostasis (STEM_BIO11/12-IVi-3)

3. (15 mins) Film Viewing https://www.youtube.com/watch?v=-aRut2kyksQ Buzz Session 1. What is Homeostasis? 2. How does our body maintain balance? 3. Re-Explain the example in the video about homeostasis? 4. Can you give or think of another example?

4. Physiology • Science of body functions • Teleological vs Mechanistic views • Teleological – the why, explains purpose of a physiological process • Mechanistic – the how, explained in terms of cause and effect of physiological process • Example: shivering • Teleological - shivering elevates a low body temperature • Mechanistic - when body temperature drops below normal, a reflex pathway causes involuntary oscillating skeletal muscle contractions which produce heat

5. Levels of Organization • Chemical • Cellular • Tissue • Organs • System Level • Organismic Level

6. Levels of Structural Organization • Chemical Level - atomic and molecular level • Cellular level - smallest living unit of the body • Tissue level • Group of cells and the materials surrounding them that work together on one task • 4 basic tissue types: epithelium, muscle, connective tissue, and nerve

7. Levels of Structural Organization • Organ level - consists of two or more types of primary tissues that function together to perform a particular function or functions • Example: Stomach • Inside of stomach lined with epithelial tissue • Wall of stomach contains smooth muscle • Nervous tissue in stomach controls muscle contraction and gland secretion • Connective tissue binds all the above tissues together • System - collection of related organs with a common function, sometimes an organ is part of more than one system • Organismic level - one living individual

8. Body Systems • Groups of organs that perform related functions and interact to accomplish a common activity essential to survival of the whole body • Do not act in isolation from one another • Human body has 11 systems

9. Body Systems

10. Body Systems

12. Homeostasis • Defined as maintenance of a relatively stable internal environment • Does not mean that composition, temperature, and other characteristics are absolutely unchanging • Homeostasis is essential for survival and function of all cells • Each cell contributes to maintenance of a relatively stable internal environment

13. Basic Cell Functions • Sensing and responding to changes in surrounding environment • Control exchange of materials between cell and its surrounding environment • Obtain nutrients and oxygen from surrounding environment • Eliminate carbon dioxide and other wastes to surrounding environment • Perform chemical reactions that provide energy for the cell • Synthesize needed cellular components

14. Homeostasis • Body cells are in contained in watery internal environment through which life-sustaining exchanges are made • Extracellular fluid (ECF) - Fluid environment in which the cells live (fluid outside the cells) • Two components: • Plasma • Interstitial fluid • Intracellular fluid (ICF) - Fluid contained within all body cells

15. Homeostasis

16. ICF ISF plasma organs external environment internal environment Balancing the Internal and External Environment Cells, the fundamental units of life, exchange nutrients and wastes with their surroundings: The intracellular fluid is “conditioned by”… the interstitial fluid, which is “conditioned by” … the plasma, which is “conditioned by” … the organ systems it passes through.

17. Homeostasis • Homeostasis involves dynamic mechanisms that detect and respond to deviations in physiological variables from their “set point” values by initiating effector responses that restore the variables to the optimal physiological range. • Two systems that maintain homeostasis are: Nervous system & Endocrine system

18. Maintenance of Homeostasis • Nervous system • Controls and coordinates bodily activities that require rapid responses • Detects and initiates reactions to changes in external environment • Endocrine system • Secreting glands of endocrine regulate activities that require duration rather than speed • Controls concentration of nutrients and, by adjusting kidney function, controls internal environment’s volume and electrolyte composition

19. Homeostasis Factors homeostatically regulated include • Concentration of nutrient molecules • Concentration of water, salt, and other electrolytes • Concentration of waste products • Concentration of O2 = 100mmHg and CO2 = 40 mmHg • pH = 7.35 • Blood volume 4-6 L and pressure 120/80 • Temperature = 37o C

20. Control of Homeostasis • Homeostasis is continually being disrupted by • External stimuli • heat, cold, lack of oxygen, pathogens, toxins • Internal stimuli • Body temperature • Blood pressure • Concentration of water, glucose, salts, oxygen, etc. • Physical and psychological distresses • Disruptions can be mild to severe • If homeostasis is not maintained, death may result

21. Control of Homeostasis

22. Homeostatic Control Systems • In order to maintain homeostasis, control system must be able to • Detect deviations from normal in the internal environment that need to be held within narrow limits • Integrate this information with other relevant information • Make appropriate adjustments in order to restore factor to its desired value

23. Homeostatic Control Systems • Control systems are grouped into two classes • Intrinsic controls • Local controls that are inherent in an organ • Extrinsic controls • Regulatory mechanisms initiated outside an organ • Accomplished by nervous and endocrine systems

24. Homeostatic Control Systems • Feedforward - term used for responses made in anticipation of a change • Feedback - refers to responses made after change has been detected • Types of feedback systems • Negative • Positive

25. Feedback Loops: Types • Negative feedback loop • original stimulus reversed • most feedback systems in the body are negative • used for conditions that need frequent adjustment • Positive feedback loop • original stimulus intensified • seen during normal childbirth

26. Negative Feedback Loop • Negative feed back loop consists of: • Receptor - structures that monitor a controlled condition and detect changes • Control center - determines next action • Effector • receives directions from the control center • produces a response that restores the controlled condition

27. Negative Feedback Loop

28. Negative Feedback Loop

29. Homeostasis – Negative Feedback Loop • Blood glucose concentrations rise after a sugary meal (the stimulus), the hormone insulin is released and it speeds up the transport of glucose out of the blood and into selected tissues (the response), so blood glucose concentrations decrease (thus decreasing the original stimulus).

30. Homeostasis of Blood Pressure • Baroreceptors in walls of blood vessels detect an increase in BP • Brain receives input and signals blood vessels and heart • Blood vessels dilate, HR decreases • BP decreases

31. Positive Feedback during Childbirth • Stretch receptors in walls of uterus send signals to the brain • Brain induces release of hormone (oxytocin) into bloodstream • Uterine smooth muscle contracts more forcefully • More stretch, more hormone, more contraction etc. • Cycle ends with birth of the baby & decrease in stretch

32. Role of Body Systems in Homeostasis

33. Glossary • Maintain – keep up. • Constant – the same. • Internal – inside the body. • Environment – surroundings of the body. • Feedback - a cycle in which the output of a system “feeds back” to modify or reinforce the actions of the system in order to maintain homeostasis.

34. Glossary • Negative feedback - a change causes system 1 to send a message to system 2 to restore homeostasis. When system 1 detects that system 2 has acted, it stops signaling for action and system 2 stops (turned off). • Positive feedback - the original stimulus is promoted rather than stopped. Positive feedback is rarely used to maintain homeostasis. An example of positive feedback is childbirth.

35. What is Homeostasis? • Body cells work best if they have the correct • Temperature • Water levels • Glucose concentration • Your body has mechanisms to keep the cells in a constant environment.

36. What is Homeostasis? The maintenance of a constant environment in the body is called Homeostasis

37. Controlling body temperature • All mammals maintain a constant body temperature. • Human beings have a body temperature of about 37ºC. • E.g. If your body is in a hot environment your body temperature is 37ºC • If your body is in a cold environment your body temperature is still 37ºC

38. Controlling body temperature • Animals with a large surface area compared to their volume will lose heat faster than animals with a small surface area. Volume = _______ Surface area = ______ Volume : Surface area ratio = ___________ Volume = _______ Surface area = ______ Volume : Surface area ratio = ___________

39. Controlling body temperature Volume : Surface area ratio = 1:6 Volume : Surface area ratio = 1:5 For every 1 unit of heat made, heat is lost out of 6 sides For every 1 unit of heat made, heat is lost out of 5 sides

40. Controlling body temperature Volume : Surface area ratio = 1:6 Volume : Surface area ratio = 1:5 The bigger the Volume : Surface Area ratio is, the faster heat will be lost.

41. Penguins huddling to keep warm

42. What mechanisms are there to cool the body down? • Sweating • When your body is hot, sweat glands are stimulated to release sweat. • The liquid sweat turns into a gas (it evaporates) • To do this, it needs heat. • It gets that heat from your skin. • As your skin loses heat, it cools down.

43. Sweating The skin

44. What mechanisms are there to cool the body down? • Vasodilation • Your blood carries most of the heat energy around your body. • There are capillaries underneath your skin that can be filled with blood if you get too hot. • This brings the blood closer to the surface of the skin so more heat can be lost. • This is why you look red when you are hot!

45. This means more heat is lost from the surface of the skin If the temperature rises, the blood vessel dilates (gets bigger).

46. What mechanisms are there to warm the body up? • Vasoconstriction • This is the opposite of vasodilation • The capillaries underneath your skin get constricted (shut off). • This takes the blood away from the surface of the skin so less heat can be lost.

47. This means less heat is lost from the surface of the skin If the temperature falls, the blood vessel constricts (gets shut off).

48. What mechanisms are there to warm the body up? • Piloerection • This is when the hairs on your skin “stand up” . • It is sometimes called “goose bumps” or “chicken skin”! • The hairs trap a layer of air next to the skin which is then warmed by the body heat • The air becomes an insulating layer.

50. Controlling Glucose levels • Your cells also need an exact level of glucose in the blood. • Glucose moves into the cells for cellular respiration • Excess glucose gets turned into glycogen in the liver • This is regulated by 2 hormones (chemicals) from the pancreas called: Insulin Glucagon