: Biology - Laboratory Report

 Introduction
The aim of the experiments was to observe the impact various effects have on
heart rate. Diurnal changes, postural changes and thermoregulatory changes
were viewed and the effects they had on heart rate were recorded.
Various factors can affect the heart rate. However, in each case changes in the
heart rate caused by different factors have an adaptive value. A number of
studies have already been performed to represent the changes in heart rate
with respect to action of particular factors. Some of the experiments carried out
in the past appeared to be incorrect when tested again. For example, in the
experiments performed on frogs it was investigated that heart rate depends on
the temperature. However, more recent data indicate that there is no such
correlation (Taylora E.T. et al. 2012) Increase in temperature makes heart
beating faster while decrease in temperature makes it beating slower. In
addition, it is a well-known fact that heart can be slowed down when significant
pressure is applied to eyes. This feature is well-known as Dagnini Aschner or
oculocardiac reflex (Levine J.M. et al. 2012)
Thus, there are a lot of factors that can affect the heart rate and in the current
experiment we tried to evaluate the impact of some factors and compare them
with already known facts and theories.
Generally heart rate is lower when sleeping compared to being awake (Meier N.
2013.). Heart rate will be lower before getting up in the morning than it will be
before falling asleep. Metabolic rate of the body slows when sleeping because
the heart doesn’t need to work as hard. Before going to sleep the bodies
metabolic rate is still high so the heart rate although not high, should still be
working harder than when first awakening after a night’s sleep. Thus, we
suspected to observe the higher heart rate in the evening and the lower one in
the morning. The hypothesis we testes sounded as follows: heart rate in the
evening is statistically significantly higher than the heart rate observed in the
morning.
Heart rate will spike with a sudden movement such as standing up quickly. The
body uses many skeletal muscles when standing up; the heart needs to supply
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Sample: Biology - Laboratory Report
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Final Laboratory Report
these muscles with more blood and oxygen. Once standing the muscles no
longer need as much oxygen so the heart can slow down again. Thus, our
hypothesis for this experiment stated that heart rate increases when person
stands up and decreases when the person sits down.
When limbs are exposed to warm water, heart rate will increase. When limbs
are exposed to cold water, heart rate will slow.Generally, heart rate slows when
the body is cold and speeds up when hot. This creates Homeostasis and the
heart changes its rate to keep the bodies internal temperature constant.
Therefore, we suspected that cold water causes increase in the number of heart
beats per minute while warm water decreases them.
These data are well-known and easily-deductible. However, still we tested them
in order to persuade in their correctness and obtain our own reliable results.
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Final Laboratory Report
Materials and Methods
Equipment List
x Test Subject - Male, 31 years old, fit and healthy.
x Large Plastic Bucket
x Stopwatch or Clock
x Thermometer - Monitor water temperature
x Warm Water - 37°C
x Cold Water - 10°C
x Ice - assist in maintaining water temperature
Diurnal Variation
The subject was made to relax in a lying down position, for 5 minutes. Pulse
was then taken over 30 seconds, then multiplied by 2 to determine heart rate in
BPM. Measurements were taken over a 7-day period from the 27th August
2012 till the 2nd September 2012, before rising in the morning at 6am and them
again before falling asleep at 11pm.
Postural Changes
Relaxing in a supine position for 5 minutes, the subject’s heart rate was
measured in BPM. The subject then stood upright quickly and heart rate was
measured again. Remaining in a standing position, heart rate was measured
again after 2 minute and then again after 4 minutes.
Thermoregulatory Changes
Relaxing in a sitting position for 5 minutes, the subject’s heart rate was
measured in BPM. The subject then placed hands and forearms in a bucket of
warm water (water temperature at 37°C). Heart rate was then measured after
10 minutes, 20 minutes and 30 minutes. The same experiment was then
repeated using cold water (water temperature at 10°C).
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Results
Diurnal Changes
The results showed an average of 44.43bpm (beats per minute) at 6am and an
average of 49.86bpm at 11pm. The results show a clear change in heart rate
between morning and evening, showing an average of 10.85% (Table 1). It can
be clearly seen that heart rate is much higher in the evening c