HomeostasisHomeostasis

HomeostasisHomeostasis

The process of maintaining the The process of maintaining the body’s internal environment, despite body’s internal environment, despite changes in the external environmentchanges in the external environment

This makes sure that the body’s This makes sure that the body’s organs and cells are operating at organs and cells are operating at ideal conditions, and thus are most ideal conditions, and thus are most efficientefficient

Factors that are regulatedFactors that are regulated

Things regulated include:Things regulated include:– Blood pressureBlood pressure– Blood pHBlood pH– Body temperatureBody temperature– Water levelsWater levels– Blood glucose levelsBlood glucose levels– Heart rateHeart rate– Respiratory rateRespiratory rate

Homeostasis continuedHomeostasis continued

Also called Also called dynamic equilibriumdynamic equilibrium because small changes are constantly because small changes are constantly occurringoccurring

All homeostatic control systems have:All homeostatic control systems have:– A monitor (sensors that detect imbalance)A monitor (sensors that detect imbalance)– Coordinating center (relays information)Coordinating center (relays information)– Receptor (works to restore balance)Receptor (works to restore balance)

These systems of control are called These systems of control are called feedback loopsfeedback loops

Negative Feedback LoopNegative Feedback Loop

Mechanisms that work to restore the Mechanisms that work to restore the system to normal levelssystem to normal levels

Negative feedback ensures that Negative feedback ensures that small changes do not get too largesmall changes do not get too large

Ex. When body temperature rises, Ex. When body temperature rises, you begin to sweat in order to lower you begin to sweat in order to lower temperaturetemperature

The more common type of feedback The more common type of feedback looploop

Positive Feedback LoopPositive Feedback Loop

When the change in a system causes When the change in a system causes the system to amplify the changethe system to amplify the change

Less commonLess common Ex. During childbirth, as the baby Ex. During childbirth, as the baby

moves towards the cervix, more moves towards the cervix, more oxytocin is released, which increases oxytocin is released, which increases contractions.contractions.

ThermoregulationThermoregulation

The maintaining of body temperatureThe maintaining of body temperature Ectotherms (fish, amphibians, reptiles) Ectotherms (fish, amphibians, reptiles)

depend on the air to regulate body depend on the air to regulate body temperaturetemperature

Endotherms (mammals and birds) Endotherms (mammals and birds) maintain a constant body temperature via maintain a constant body temperature via internal systemsinternal systems

Normal body temperature in humans = Normal body temperature in humans = 37°C37°C

Hypothalamus acts as the ‘thermostat’Hypothalamus acts as the ‘thermostat’