Maintaining an Internal Balance

Homeostasis body systems are constantly adjusting to changes in the external environment to maintain a constant internal environment or homeostasis

Optimal Human Body temperature: 37ºC blood glucose level: 0.1% blood pH: 7.35 hormone levels, blood pressure & flow, etc. (Image from: http://www.liesyoungwomenbelieve.com/index.php?id=354)

Image from: http://msalvarez1. edublogs Many body systems interact to maintain homeostasis: -nervous system: receives sensory information from environment, and transmits signals throughout the body to regulate homeostasis -excretory system: rids body of waste and maintains clean internal environment -endocrine system: regulates levels of essential hormones -circulatory system: carries hormones & other chemicals, and distributes heat throughout the body -immune system: protects body from and fights infections -digestive system: liver controls amino acid levels, detoxifies harmful substances, manufactures blood proteins -integumentary system: important for maintaining constant body temperature

Homeostatic Mechanisms sensor integrator effector (Image from: http://www.revisescience.co.uk/2010/schools/ilford/abhomeostasis.asp)

Negative Feedback sensors signal integrator (coordinating centre) to counteract any detected changes

(Image from: http://www.freewebs.com/sandra02n/)

Thermoregulation the regulation of body temperature by negative feedback mechanisms very important for homeotherms Image from: http://www.revisescience.co.uk/2010/schools/ilford/abhomeostasis.asp

Image from: http://schoolworkhelper.net/2010/07/thermoregulation/

Ectotherms use external environment to regulate body temperature include invertebrates, fish, amphibians, reptiles behavioural & some physiological mechanisms allow ectotherms to remain somewhat homeothermic

Endotherms use internal mechanisms to regulate body temperature e.g., birds, mammals high energy demands torpor, hibernation, and estivation are behavioural mechanisms that help endotherms to survive in harsh climates

Image from: http://www. nature Requires a lot of energy to maintain constant internal body T

Positive Feedback signals integrator (coordinating centre) to increase any detected changes less common than negative feedback Image from: http://ingrimayne.com/econ/AllocatingRationing/PriceAndFeedback.html

Image from: http://pespmc1.vub.ac.be/feedback.html

Positive Feedback (Image from: http://biologyfiles.fieldofscience.com/2011_01_01_archive.html)