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Homeostasis Chapter 9

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Presentation on theme: "Homeostasis Chapter 9"— Presentation transcript:

1 Homeostasis Chapter 9

2 Homeostasis  Physiological state of the body  Internal physical and chemical conditions are maintained within a tolerable range  Includes  Temperature, hormone levels, pH, pressure, concentrations of glucose and other solutes in the blood

3 Internal Environment  Extracellular fluid  Interstitial fluid – fills the spaces between cells and tissues (e.g. plasma)  Consists of water, sugars, salts, FA, AA, coenzymes, hormones, neurotransmitters, waster products  Regulates flow of chemicals and allows cells to function properly  Lymphatic system transports fluid throughout the body 

4 Internal Environments  Changes in Extracellular Fluid has negative effects on cellular function  Body uses organ systems to regulate internal conditions  Nervous system  Endocrine system  Muscular system  Integumentary system  Excretory system  Reproductive system

5 Nervous System  Brain, spinal cord, peripheral nerves, sensory organs  Receives sensory data from the environment  Informs body of external conditions  Transmits signals throughout the body

6 Endocrine System  Pituitary, thyroid, pancreas, adrenal (glands)  Regulates levels of hormones and other chemicals

7 Excretory System  Kidneys, bladder, urethra, ureters  Rids the body of waste  Maintains clean internal environment

8 Integumentary System  Skin, sweat glands, hair, nails  Maintains a constant body temperature

9 Immune System  White blood cells  Protects/fights infection

10 Digestive System  Liver  Breaks down amino acids  Detoxifies harmful chemicals (alcohol)  Manufactures important proteins

11 Homeostatic Mechanisms  Respond to internal and external conditions  Feedback systems – Positive/Negative  Help bring the body back into balance  Breathing rate, heart rate, internal temperature, blood glucose levels

12 Negative Feedback  Reduces the output or activity of an organ or system back to its normal range  Include 3 elements  Sensor  tissues or organs - detects change  Integrator - hypothalamus  control centre – compares conditions from environment with to optimal conditions in the body  Set points – ranges of values which need to be maintained  Effector  returns measured condition back to set point – response  Antagnositc effectors – produce opposite effect of change detected






18 Hypothalamus  Body’s thermostat  Maintains body temperature  Optimal body temperature – 35 ⁰ - 37.8⁰  Body temp falls → vasoconstriction in skin/shivering→ reduced blood flow→ less thermal energy lost to environment → body temp increases  Body temp rises → blood vessels dilate/induce vasodilation/sweating → increase blood flow→ increase thermal energy loss to environment→ body temp decreases  Signals from hypothalamus make us aware of our own temperature

19 Positive Feedback Mechanisms  Increases change in environmental condition  Does not result in homeostasis  Cause system to become unstable  “fight or flight” response  reproduction  fever  Positive feedback mechanisms operate within negative feedback mechanisms  Allows body to be brought back into balance


21 Thermoregulation  Internal temperature regulation  Negative feedback mechanism  Thermoreceptors – compare external temp with internal set point  Trigger responses (2)  Rate of exothermic reactions in body (metabolism)  Rate of thermal energy exchange through surface of body


23 Mechanisms of Thermal Energy Exchange  Occurs at the surface where body comes into contact with the external environment  Exchange of thermal energy occurs through 1 of 4 mechanisms  Conduction  Convection  Radiation  Evaporation  All of these mechanisms act simultaneously

24 Conduction  Flow of thermal energy between molecules that are in direct contact

25 Convection  Transfer of thermal energy within a fluid (liquid or gas)

26 Radiation  Thermal energy is transferred electromagnetically

27 Evaporation  Absorbs thermal energy from skin via water/sweat

28 Homeotherms  Animals that maintain a stable internal temperature regardless of external conditions  Includes  Poikilotherms  Endotherms  Ectotherms

29 Poikilotherms  Fish, amphibians, reptiles, and most invertebrates  Body temperature varies with and often matches the temperature of the external environment

30 Endotherms  Warm blooded animals (mammals, birds)  Homeotherms that use internal physiological mechanisms (metabolism) to generate thermal energy and maintain body temp  Remain fully active over a wide range of temperatures  Need a constant supply of energy


32 Ectotherms  Cold blooded animals (reptiles, amphibians, fish)  Homeotherms that use external sources of energy to absorb thermal energy and regulate body temperature  Temperature fluctuates with environmental temperature  Inactive when temp are too low  Undergo thermal acclimatization  Gradual adjustment to seasonal temp

33 Torphor, Hibernation, Estivation  Adaptations to survive extreme climates by conserving energy  Torphor  Sleeplike state  Metabolic rate and body temperature drop in response to daily temp (nocturnal animals, hummingbird)  Hibernation  State of inactivity over an extended period of time  Estivation  Seasonal torphor – environment is hot and water is scarce

34 Water Balance  Extracellular fluid needs to maintain a constant volume (~15L) of water and balance of solute within the body  Mechanism  Osmosis

35 Osmosis  Water molecules move from a high concentration to a region of lower concentration across a selectively permeable membrane  Osmotic pressure  Results from a difference in water concentration gradient between the two sides of the selectively permeable membrane  Hyperosmotic  Hypoosmotic  Isoosmotic

36 Hyperosmotic  Solution with higher concentration of solute molecules  Water tends to move to this side

37 Hypoosmotic  Solution with lower concentration of solute molecules  Water tends to move from this solution

38 Isoosmotic  Solution with the same solute and water concentrations

39 Osmoregulation  Process of actively regulating the osmotic pressure of bodily fluids  Extracellular fluid = intracellular fluid (isoosmotic)  [solute] remains the same  [water] remains the same

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