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Homeostasis - l

Homeostasis is? The body's attempt to maintain a constant, stable environment internally.
Dynamic state of equilibrium? Necessary for survival and good health eg. temperature control.
What happens if there is disturbance of homeostasis? Increased risk of disease, contributes to changes associated with ageing, may allow destructive positive feedback to take over eg. heart failure.
What is homeostasis constantly being disrupted by? External and internal stimuli.
External stimuli? Intense heat, cold, lack of oxygen.
Internal stimuli? Psychological stresses, exercise.
Three control mechanisms? Receptor (sensor), control centre, Effector.
Receptor? Monitors environment and responds to stimuli.
Control centre? Determines the set point at which the variable is maintain, receives input from receptor, determines appropriate response.
Effector? Receives output from control centre, provides the means to respond, responds to change the controlled condition and restore homeostasis.
What is negative feedback? The response that reduces or shuts off original stimulus eg. regulation of body temperature (a nervous mechanism), regulation of blood volume by ADH (an endocrine mechanism.
What is positive feedback? The response enhances or exaggerates original stimulus eg pregancy - enhancement of labour contractions by oxytocin.
Negative feedback loop? Reverse the stimulus - causes a reversal in controlled condition.
Positive feedback loop? Enhances the stimulus - must be stopped or interrupted by something outside the system.
Most common feedback system? Negative - enzyme levels, body temperature, blood sugar levels, blood pressure, heart rate.
Created by: Leithj