Homeostasis

• the maintenance of a constant or unchanging internal environment

• during rest or unstressed conditions

Steady State

• constant internal environment or metabolism

• during exercise or elevated metabolism

• balance has been achieved between demands of the body and the body’s response

Changes in body core temperature during exercise in thermoneutral environment

Temperature

• core temperature is a very important metabolic parameter

• needs to be maintained within a very narrow range

• much heat is generated during exercise, but is dissipated to maintain constancy

• homeostatic condition will not differ from steady state greatly

Changes in arterial blood pressure across time during rest

Blood Pressure

• blood pressure is another important metabolic parameter

• will vary to a greater extent from rest to exercise

• will be constant during homeostasis or steady state though

A thermostat controlled heating/cooling system

Components that comprise a biological control system

Components

• Stimulus-excites a receptor

• Receptor-receives the stimulus

• Integrating center-relay station (dispatcher)

• Effector-corrects disturbance and removes stimulus

Negative Feedback

• Biological control system

• effector response opposite to stimulus

• very common in biological systems

Example of negative feedback mechanism to lower blood pressure

Regulation of blood glucose concentration

Exercise as a Test of Homeostasis

• During exercise– Heart rate can increase 4-5 fold

– Systolic BP can increase 2-3 fold

– Core temperature remains relatively constant

– Blood glucose remains stable for prolonged periods

• Body possesses wide range of homeostatic mechanisms which counteract physiological stressors