Question | Answer |
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. |