University:
High School
Course:
High School Biology
Academic year:

2019
Views:

439

Pages:

18
Author:

5CelestialChronicle

HOMEOSTASIS & NEGATIVE FEEDBACK “Keeping Everything Balanced” Homeostasis Homeostasis: ! process by which organisms keep internal conditions relatively constant despite changes in external environments. What we need to keep the same in our body: Temperature (98.6 F) Blood pH (7.4) almost neutral Blood pressure (average 120/80) Heart rate (80 beats per minute) Blood sugar level Hydration/amount of water Amount of salts Amount of blood (2 pints per every 25 lbs) Negative Feedback Loops Homeostasis is maintained by negative feedback loops Negative Feedback Loops: mechanisms that tell the body to stop what it is doing and return to the “set point” when conditions go outside the acceptable range. ! EX) Thermostat in your house ! Always has 2 different mechanisms, 1 for raising conditions and 1 for lowering conditions. If the temperature inside the house drops below the set point the thermostat turns on the furnace until set point is reached If the temperature rises above the set point, the thermostat turns on the air conditioner until the set point is reached. What it really means (in English!) (DON’T COPY) The human body needs to maintain things like body temperature (98.6 F). If you get too hot or cold then your body will not thrive. ! Too hot and your brain will overheat and “cook” ! Too cold and your body’s systems will shut down Each system of the body contributes some aspect to maintaining homeostasis (stable internal balance) NERVOUS SYSTEM It is more than “the brain controls everything”! Nervous System Hypothalamus - controls body temperature with the following feedback loop: ! Too low - causes shivering of muscles and reduced blood flow (blue skin) to create heat ! Too hot - causes sweating and increased blood flow (red skin) to get rid of heat Brain Stem - Controls heart rate with the following feedback loop: ! Too low - increases nerve impulses to make heart beat faster ! Too high - decreases nerve impulses to keep the heart rate at 80 beats per minute DIGESTIVE SYSTEM Doesn’t just break down food so you can eat! Digestive System Liver – Controls blood sugar level with the following feedback loop: ! Too low - converts stored glycogen (glucose) into sugar ! Too high - removes sugar from the blood and stores as glycogen URINARY/EXCRETORY SYSTEM Besides getting rid of wastes and filtering toxins out of the blood, it also….. Urinary/Excretory System Kidneys - Controls amount of water and salt in body with the following feedback loop: ! Too low - retains water/salt and keeps them from going to the bladder ! Too high - pushes more water and salt into the bladder CIRCULATORY & RESPIRATORY SYSTEMS Circulatory/Cardiovascular System Circulatory & Respiratory Systems – work together to maintain oxygen level ! If oxygen too low – HR speeds up to take O2 from the lungs to the tissues ! If too high – HR slows down to decrease O2 intake Respiratory System Lungs - Controls blood pH, amount of carbon dioxide in blood using the following feedback loop: ! If gets too low (acidic, pH below 7.4), gets rid of excess CO2 (which caused the acid) ! If gets too high (basic, pH above 7.4), retains more CO2 Brainwork Left page Answer the essential question(s) Pick one body system and construct a diagram showing the negative feedback loop in that system Notes Summary Right Page Homeostasis is __________. The body maintains homeostasis by using ______ ______ loops. The purpose of these loops is to _______. Examples of the conditions the body tries to keep stable include _______. If the body fails to maintain homeostasis, then __________.