Notes: Homeostasis

Homeostasis Homeo=unchanging stasis-=standing Keeping internal conditions the same despite changes in the outside environment. Conditions within the body must remain within a narrow range Blood pH= 7.41 Blood Sugar Level= 70-140 mg/dL Blood osmolality = 275 to 295 mosm/kg Body Temperature=98.7 (F) Blood Pressure= 120/80 - 140/90 BUT……..You live in constantly changing environment

How is this done?....FEEDBACK MECHANISMS Parts of Feedback Mechanisms Sensors: also called receptors, gather information about conditions inside and outside body Control center- receives information from the sensors and responds (E.g. brain) Communicate: controlled by nervous and endocrine system and carry messages to target. Targets: any organ, tissue, or cell that changes its level of activity in response to message

Negative Feedback Mechanisms Control system that counteracts any change in body that moves condition above or below set point The last step (response) decreases the first step (receptor). Examples: Glucose and Insulin, Body temperature and sweat

Positive Feedback Mechanisms Uses information from sensors to increase rate of change A secondary substance increases production or rate of the initial substance or receptor. Not as common as negative feedback Important when rapid change is needed Example: Oxytocin and contractions during childbirth, Platelets during blood clotting