Homeostasis your stable home.. Homeostasis: [sameness, state w/o change] The INTERNAL environment of the body is kept STABLE despite changes around us. Homeostasis must be maintained for normal body functioning and to sustain life Our bodies are constantly subjected to stress Changes in temperature Changes in pressure Potential diseases Ex: Shivering Sweating FEEDBACK MECHANISMS Feedback mechanisms either change a system to a new state or return it to its original state. Negative Feedback : restore the body to normal levels of function Includes most homeostatic control mechanisms Shuts off the original stimulus, or reduces its intensity Works like a household thermostat NEGATIVE FEEDBACK EXAMPLE: ADJUSTING SOLUTE and WATER CONCENTRATIONS The normal concentration of sodium in the blood plasma is mM. If the sodium level falls too low, it's called hyponatremia; if it gets too high, it's called hypernatremia. A sodium level in the blood that is too low is dangerous and can cause seizures and coma. Very high sodium levels can lead to seizures and death. Sodium controls the volume of fluid in the body and helps maintain the acid-base level. Sodium is important in proper nerve conduction, the passage of various nutrients into cells, and the maintenance of blood pressure. Positive Feedback: result in continuous change away from normal levels of functioning Increases the original stimulus to push the variable farther In the body this only occurs in blood clotting and birth of a baby POSITIVE FEEDBACK EXAMPLE: CHILDBIRTH After labor begins the baby's head puts pressure on the cervix, causing the cervix to stretch. This stimulates stretch receptors the trigger the mother's hypothalamus to release oxytocin, which increases the uterine contractions and pushes the baby against the cervix. This causes the cervix to stretch farther and the cycle continues. A positive feedback loop, by definition, is basically a cycle of increasing response. An external factor or event is required for the cycle to stop. In this example, the delivery of the baby is the external event. Once the baby is delivered, the uterine contractions stop, which halts the stretching of the cervix, and oxytocin is no longer released. If the external factor is not introduced, the cycle continues. The duration of the cycle is what we refer to as labor. Bozeman Science Videos feedback-loopsfeedback-loops looploop