Answer: The correct answer to the question is option B
INCREASED SHIVERING AND HEAT GENERATION IN RESPONSE TO COLD TEMPERATURES.
Explanation: Homeostasis is maintained by the control systems that detect and respond to changes in the internal environment, this is achieved effectively by the detector,control centre and the effector.
This dynamic process allows for the constant readjustment of many physiological variables.
Nearly all are being controlled by negative feedback mechanisms, positive feedback is much less common but important example is;
increased platelet activation and recruitment to form a blood clot and control of uterine contraction during childbirth.
The body temperature is one of the physiological variable that is controlled by negative feedback mechanism.
When the body falls below the preset level (close to 37°C), This is detected by specialised temperature sensitive nerve endings in the hypothalamus of the brain,where the body's control centre is located,the centre then activates mechanisms that raise the body temperature (the effectors). these includes;
- Stimulation of skeletal muscles causing shivering.
- Narrowing of the blood vessels in the skin reducing the blood flow to,and heat loss from the peripheries.
- Behavioural changed example; we put in more clothes to curl up.
When the body temperature rises within the normal range again,the temperature sensitive nerve endings are no longer stimulated,there signal to the hypothalamus will stop, therefore,the shivering stops too and the blood flow to the peripheries return back to normal.
This clearly explains option B which is the the correct answer of a negative feedback mechanism.
