Homeostasis: maintaining an internal balance

1. Homeostasis:maintaining an internal balance SBI 4U, December 12th, 2012

2. Maintaining an Internal Balance • Ray Zahab vs. Fennec Fox • Fennec fox  ears allow for efficient hearing and act as radiator

3. Maintaining and Internal Balance • Homeostasis: the physiological state of the body in which the internal physical and chemical conditions are maintained within an acceptable or tolerable range that is suitable for essential biological processes • Dynamic state

4. Maintaining an Internal Balance • Body has several conditions that must be monitored. Such as: -internal temperature -hormone levels -pH -flow and concentration of glucose and other solutes *some tolerable ranges are narrow, while others are more broad*

5. The Internal Environment • Purpose of homeostasis: to maintain internal physical and chemical conditions that are appropriate for the cells to function properly • Internal environment: the extracellular fluid, which consists of the fluid that surrounds the cells and tissues in the body and the plasma portion of the blood • Focus on fluid outside of the cells

6. Organ Systems Involved in Homeostasis • Nervous System • Endocrine System • Muscular System • Integumentary System • Excretory System • Reproductive System

7. Organ Systems Involved in Homeostasis • All of the organ systems are coordinated to carry out the tasks necessary for the survival of the organism. No matter how simple or complex the animal, these functions include: • Taking in nutrients and other required chemicals, processing and excreting • Synthesizing proteins, fats and carbs • Sensing and responding to changes in external environment • Protecting body • Reproducing, protecting and feeding offspring

8. Organ Systems Involved in Homeostasis • Homeostatic Mechanisms: a system that monitors internal and external conditions and changes bodily functions to maintain homeostasis • Ex: shivering in response to cold weather

9. Negative Feedback Mechanisms • Primary mechanism of homeostasis • Negative feedback: the response of a system that acts to maintain equilibrium by compensating for any changes made to the system • 3 components: sensor, integrator and effector

10. Negative Feedback Mechanisms • Sensor: consists of tissues or organs that detect any change in external or internal factors • Info transmitted to integrator acts as a processing or control centre. Compares environmental conditions with the optimal function conditions called set points • Integrator activates the effector  the element of a feedback system that acts to return the system to its optimal state

11. Negative Feedback Mechanisms • Antagonistic effects  response opposite to change • Ex: thermostat • Sensor measures temperature • Integrator compares the measures temperature to set point • Integrator activates electrical effector (furnace or air conditioner) • Temperature returned to normal state

12. Negative Feedback in Animals • Ex: humans • Neurons in preoptic region of hypothalamus receive info from thermoreceptors • Hypothalamus compares info to set point • Hypothalamus activates effectors that induce vasoconstriction in skin. Less thermal energy lost. Body temperature increases

13. Positive Feedback Mechanisms • Positive Feedback: the response of a system that acts to increase the effect of any changes made to the system • Do not result in homeostasis • Operate when a continuous increase in some internal variable is required (ex: fight or flight) • Ex: childbirth contractions  release of oxytocin