It has been claimed that thyroxine is a hormone produced when the body is expose

Question

It has been claimed that thyroxine is a hormone produced when the body is exposed to cold temperatures. Thyroxine is purported to stimulate an increase in the basal metabolic rate of body cells and also to stimulate an increase in heart rate. Both of these responses result in an increase in body temperature.

a) Design an experiment to test the role of thyroxine in helping the body adjust to cold temperatures. Describe the overall investigation to be done, the variables to be changed, the variables to be kept constant, the subjects to be used, the control and experimental conditions to be used, the type of data collected, and how the data will be collected. Explain how these data can be used to justify the conclusion that thyroxine is involved in adjusting body temperature in response to cold.

b) Suppose that your experiment from Part A above demonstrated that thyroxine is involved in body-temperature regulation. Now another claim has been made: that thyroxine is under negative feedback control. Design an experiment to test whether thyroxine’s effect on response to cold is under negative feedback control. Describe the overall investigation to be done, the variables to be tested, the variables to be kept constant, control and experimental conditions to be used, the type of data collected, and how the data will be collected. Explain how these data can be used to justify the conclusion that thyroxine is involved in adjusting body temperature in response to cold.

Explanation / Answer

Ans.a) Thyroxine is synthesized by thyroid gland and released into the blood. It plays a significant role in maintaining body metabolic rate and as result maintains the body heat in cold temperatures. When the body makes too much thyroid hormone, body temperature rises and metabolic rate also tends to increase and eventually results in survival in cold conditions.
In designing the experiment to test the role of thyroxine in maintaining body temperature, few variables are very important; internal heart production and heat transfers (between the body and surrounding environment), vasomotor responses (loss of dry heat) and metabolic responses (metabolic heat production). In addition physical fitness, predominantly aerobic ability on thermoregulatory response to cold also influences this entire phenomenon. These are the variables which are considered during the experiment to monitor the activity of thyroxin. Difference in above mentioned variables greatly affects the overall functioning of thyroxin.

b.) Secretion of Thyroxin is managed by negative feedback control. The thyroid hormones namely; thyroxine and triiodothyronine (T4 and T3) are produced and secreted by thyroid glands and have an effect on metabolism all the way through the body.
In this experimental design the variables are thyroid releasing hormone (triggers cells to release thyroid-stimulating hormone). After release of thyroid-stimulating hormone (TSH); it binds to receptors on epithelial cell in the thyroid gland and triggers the production and secretion of thyroid hormones. But, when concentrations of thyroid hormones increase in body, the TRH-secreting neurons in the hypothalamus automatically are slow down and halt secretion of TRH. In this way thyroxine is controlled by negative feedback.

By observing this whole process of thyroxine administration, one can conclude that how thyroxine is involved in adjusting body temperature in response to cold.

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