HOMEOSTASIS The bodys ability to maintain stable internal

HOMEOSTASIS The body’s ability to maintain stable internal conditions in spite of the changing internal & external conditions.

HOMEOSTASIS Most of the physiological processes that occur in your body are designed to maintain homeostasis. n Examples: blood glucose concentration, Blood pressure, body temperature, ion concentration, water balance, etc. * These are all variables n

Homeostatic Control Mechanism n n n Receptor: responds to stimuli, sends information to the control center Control center: analyzes information and determines response Effector: Will cause a change, either to shut down or increase the reaction

2 Types of Feedback n 1) Negative feedback Self terminating n Most common n Blood pressure, glucose, Ca++ n

Negative Feedback Example: Thermostat n n n The thermostat (control center) is preset and reads the current temperature (receptor). After thermostat measures the temperature (variable), it compares the current value to a preset standard value. Effectors turn the system on and off to maintain a specific temperature range

Homeostatic Control

Negative Feedback

Example: Blood Glucose Level

Increased BP Sensed by pressure receptors in aortic arch and carotid sinus Input sent via afferent pathway to medulla oblongata BP DECREASES Heart rate & force of contraction decrease Blood vessel diameter increases Output sent along efferent pathway to heart and blood vessels Current BP compared with set point and error signal generated

2 Types of Feedback n 2) Positive feedback Outside factor required to shut off n Less common due to danger to organism n Birthing process, blood clotting n

Example: Childbirth

Positive Feedback