Weird Body Quirks Brain freeze “Ice cream headaches” happen when something cold touches nerves in the roof of the mouth, triggering blood vessels in the front of your head to constrict -- producing pain. Try this quick pain relief trick: Press your tongue to the roof of your mouth to warm it up.

Learning goals . . . To explain the process of maintaining homeostasis through feedback loops and their components. You will show your understanding by . . . Presenting an explanation (diagramatic, written or kinesthetic) of thermoregulation

Homeostasis (pg. 334-341) Maintenance of a relatively stable internal, fluid environment (internal milieu) despite a changing external environment http://www.lionden.com/homeostasis.htm Temperature 37oC (98.6oF) Blood pH 7.35 Blood sugar level 0.1%

Homeostatic Control Systems 3 main components A monitor -> senses state of system A coordinating centre -> receives incoming info about system and decides what the next steps should be A regulator or effector -> carries out the appropriate next step to keep system at homeostasis Monitor sales and stock of stores and report to factory manager. Based on stocks, factory manager instructs more or less of something to be made. Works increase or decrease production of certain items.

Feedback loops Positive feedback - a mechanism by which an output is enhanced Contractions in childbirth: contractions stimulate oxytocin which stimulates more muscle contractions Negative feedback mechanism consists of reducing the output or activity of any organ or system back to it's normal range of functioning. Blood vessels can sense resistance of blood flow against the walls when blood pressure increases. The blood vessels act as the receptors and they relay this message to the brain. The brain then sends a message to the heart and blood vessels, both are the effectors. The heart rate would decrease as the blood vessels increase in diameter. This change would result in the blood pressure to fall back to its normal range. The opposite would happen when blood pressure decreases.

Negative feedback - a mechanism by which an output is diminished Any change from normal range of function is resisted in negative feedback. The change initiates responses that bring the function of the organ back to its normal range. Negative feedback loops require a Receptor, A Control Center, and Effectors. Blood vessels have receptors which can measure the resistance of blood flow against vessel walls The brain (control center) receives info about change in body’s internal conditions, sends out signals via nerves Effectors - the muscles, organs, and other structures that receive signals from the control center and respond to correct the deviation.

Negative Feedback Loop

Example of Negative feedback: Blood Pressure Regulation Negative feedback mechanism consists of reducing the output or activity of any organ or system back to it's normal range of functioning. Blood vessels can sense resistance of blood flow against the walls when blood pressure increases. The blood vessels act as the receptors and they relay this message to the brain. The brain then sends a message to the heart and blood vessels, both are the effectors. The heart rate would decrease as the blood vessels increase in diameter. This change would result in the blood pressure to fall back to its normal range. The opposite would happen when blood pressure decreases.

Thermoregulation Text pg. 338 - 341 Assignment: Explain the control of body temperature in terms of a feedback mechanism (positive or negative) Be prepared to present your answer

Tomorrow: Introducing the Kidney For a head start, read pp Tomorrow: Introducing the Kidney For a head start, read pp. 342-348 in text

Charley Horse These startling spasms and tightening in leg muscles can last a few seconds, even several minutes. While the cramps have no exact cause, dehydration, muscle overuse, and a lack of certain nutrients -- like potassium and calcium -- can be culprits. Walk around to relieve the pain, or shake your leg and stretch the muscle.