The Australian Women’s Olympic Cycling Team have received your analysis of the results into the effects of temperature on their cyclists’ heart rate when competing at different temperatures (Figure 1) with great interest.
Figure 1. Changes in mean heart rate of 10 subjects cycling in different air temperatures for 60 minutes.
Hypothesis: When cycling at environmental temperatures over 15°C heart rate will be higher than when cycling at lower temperatures.
The results showed that while mean heart rate when cycling at 31°C was clearly higher than when cycling at lower temperatures, mean heart rate when cycling at 21°C was very similar to mean heart rate when cycling at 4°C and 11°C.
Perhaps this means the Olympic Cycling Team needs to revise their knowledge of thermoregulation and the effects of exercise on heart rates. So they have asked you to help them better understand the scientific knowledge and previous studies that have looked at this phenomena.
The Olympic Cycling Team are particularly interested in understanding how the body regulates its temperature and why strenuous physical exercise at 31°C results in a higher heart rate compared to the same exercise being undertaken at temperatures of 4°C, 11°C and 21°C (Figure 2).
Figure 2. The relationship between exercise, air temperature, thermoregulation and heart rate.
It is well known that intense exercise, such as during sporting competitions, causes heart rate to increase. Part of the increase in heart rate observed during exercise is due to the role played by the cardiovascular system in a negative feedback mechanism used to maintain core body temperature at 36.5 – 37.5°C. In response to a rising core body temperature, the hypothalamus sends a signal via the sympathetic nervous system that tells blood vessels in the skin to dilate. This allows more blood to reach the surface of the body so heat can be lost to the external environment. But the dilation of blood vessels in the skin reduces the amount of blood returning to heart. Since less blood is returning to the heart, the heart pumps out less blood with each heartbeat causing blood pressure to drop. As blood pressure drops, the amount of blood reaching the skin decreases, compromising the effectiveness of this heat loss mechanism. To compensate for the drop in blood pressure, a second negative feedback mechanism comes into play: The medulla oblongata (part of the brain stem) senses the drop in blood pressure and sends a signal to the heart via the sympathetic nervous system. This directly stimulates the heart to increase the speed at which it beats. By increasing heart rate, the body is able to maintain a constant blood pressure and ensures a sufficient flow of blood to the skin so heat can be lost from the body during exercise.
Answer the questions for each part of this assignment as a single, properly structured paragraph that includes a topic sentence and in-text citations. A word count has been provided to indicate approximately how long your response for each part should be. Note, you don’t have to answer the questions in the same order they are given for each part.
To answer the questions for each part of this assignment you must summarise information from the sources provided in the Background Knowledge Sheet available with this assignment on Learnline. No direct quotes should be used in your answers. This is an opportunity for you to practice and develop your paraphrasing skills.
You are expected to proof read your assignment before submitting it. Proof reading means carefully going through your assignment to find and correct mistakes in your grammar, spelling and written expression.
Write a single, properly structured paragraph with a topic sentence and in-text citations that includes answers to the four questions below by summarising information from the two references provided in the Background Knowledge Sheet for Part 1. Direct quotes should not be used. (approximately 150 words)
Write a single, properly structured paragraph with a topic sentence and in-text citations that includes answers to the two questions below by summarising information from the two references provided in the Background Knowledge Sheet for Part 2 (including using and referencing Figure 1 in the Background Knowledge Sheet). Direct quotes should not be used. (approximately 150 words)
Write a single, properly structured paragraph with a topic sentence and in-text citations that includes an answer to the question below by summarising information from the two references provided in the Background Knowledge Sheet for Part 3. Direct quotes should not be used. (approximately 100 words)
Hypothesis: the cycling at environmental temperatures over 15°C heart rate will be higher than when cycling at lower temperatures.
The normal human body temperature is considered to be approximately 37.0 C for the core body and skin temperatures can sometimes be as low as 33.5 C (Houdas & Ring, 2013). When cycling at lower temperatures, the body would have to attain additional temperature to attain the normal body temperature. The human body has a constant heat generation form the organs due to metabolism. Moreover, the body has an internal thermostat mechanism that ensures that the heat remains between 37.0 and 37.2C through the control of the hypothalamus gland (Dobbs, 2009). The rise in the ambient temperature (above 28.8 C) would lead to the glad to regulate heat through sweating that would leave a cooling effect on the skin surface (Houdas & Ring, 2013). When exercising the organs tends to have increased rate of metabolism hence the more heat generation. At rets the optimal working body conditions are attained.
The skin plays a huge role as part of the integumentary system to help protect the skin from damages as well as loss of heat. First, the skin can control the dilation or the constriction of the numerous blood vessel that will either lead to heat loss or heat gain respectively (Houdas & Ring, 2013). This is done for exercise through a process known as flushing (Master, 2003). Secondly, the skin has pores that would be responsible for the loss of water through swat glands and thus bringing a surface cooling effect to the skin (Master, 2003).
The nervous impulse would be felt through stimuli at the effectors, that are located on the skin. The resulting stimulation transmission through the sensory neuron onto the Central nervous system. The resulting action is relayed back through the motor neuron to the intended effector like muscles (Masao , 1984).
As part of the thermoregulation process the skin works together with other body organs like the heart that would distribution the heat through the blood system. At elevated temperatures of about 31 C for the ambient, the skin surface is warmer than usual. Moreover, vigorous exercises would lead to increased heat generation from the body organs. Also, the dilation of the blood vessels would lead to an increased dimeter for the blood vessels. The hypothalamus would trigger the heat to increase the blood distribution in an attempt to dissipate the heat from the organs of generation. The result is an increased heart rate (Houdas & Ring, 2013; Dobbs, 2009).