Homeostasis Read page 423 and brainstorm answers to questions

The human body works best at a temperature of 37°C with a 0 The human body works best at a temperature of 37°C with a 0.1% blood sugar level and a blood pH level of 7.35 However, the external environment does not always provide the ideal conditions for life; different demands are always placed on our bodies and they must adjust to these variations to maintain a stable internal environment

Homeostasis Refers to the body’s attempt to adjust to a fluctuating external environment Body maintains a constant balance, or steady state, through a series of monitored adjustments; requires constant monitoring and feedback about body conditions

Homeostatic controls have 3 components Sensor (Receptor) located in the organs which signals a control centre once an organ begins to operate outside its normal limits Control Centre (Integrator) relays the information to the appropriate effector, which helps restore the normal balance Effector (Regulator) helps restore normal balance

sensor control centre normal range sensor adjustment effector

Example: CO2 and breathing When CO2 levels increase during exercise, chemical receptors in the body send signal to receptors in the brain stem (control centre). Nerve cells then carry impulses to muscles that increase the depth and rate of breathing (effectors). Increased breathing movements help flush out CO2 from the body

Homeostasis is often referred to as a DYNAMIC EQUILIBRIUM – a condition that remains stable within fluctuating limits Thus, although there are fluctuations in blood glucose levels, body temperature, blood pressure and pH, the homeostatic mechanism ensures that all the body systems function within an acceptable range to sustain life.

Answer the following 1. List the body's responses to being to ohot or too cold. What organ systems are involved? 2. Suggest some situations in which it may be better if the body does not maintain homeostasis?