Introduction
The cardiovascular system consists of arteries, capillaries veins blood vessels and the heart. The heart delivers nutrients and oxygen to the tissues and caries waste products for elimination from the tissues (Hester & Lusha, 2012). The regulation of the cardiovascular system occurs through a complex interaction of both neural and non-neural mechanisms that aim at guaranteeing a constant internal environment (homeostasis) in organisms (Malliani 2000). The regulation of the cardiovascular system occurs through hemodynamics, through auto regulation, hormonal regulation and neural control (Khurana, 2008).
The most important of the regulatory mechanisms are closed loop reflexes like baro- reflexes, chemo reflexes and regulation by the cerebral systems. Other important regulators of the cardiovascular system are efferent neural mechanisms like the parasympathetic and sympathetic processes of the autonomic nervous systems (Ellwein, 2008). The autonomous oscillators located in the brain stem like the ones that produce vasomotor and respiratory rhythms, and the peripheral distributed oscillators are important regulators of the cardiovascular system (Klabunde, 2005).
All these neural and non neural mechanisms produce cardiovascular oscillations in different temporal scales that are very visible from the recordings of the cardiovascular variables like heart beats , systolic and diastolic arterial pressure , neural discharges , respiration and blood flow and resistance measurements (Pillowsky et al, 2004).
These cardiovascular variables are routinely checked in medical examinations to decipher an overall picture of the functioning of the cardiovascular system. They are also useful in extracting clinical data for the determination of the pathological state of a person. A deviation from the normal measurements of the cardiovascular variables is associated with defects and ailments (Young, 2010).
Endocrine factors stimulate long-term increases in blood volume and blood pressure resulting in restoration of homeostasis. Auto regulation mechanisms result in a decline in resistance to the flow of blood and increase in blood flow in the blood vessels if homeostasis (normal blood volume and pressure is disturbed) (Pillowsky et al, 2004). Neural mechanisms stimulate the receptors that are sensitive to changes in blood pressure and result in a short-term rise in the pressure of blood (Khurana, 2008). This stimulation is effected through sympathetic stimulation of vasoconstriction of the heart and peripheral vasoconstriction to restore homeostasis (Burne, 2003).
The aim of this experiment
This experiment was performed to determine
- The effect of posture sitting standing and lying down) on the rate of heart beats rate
- Explore the effects of lowering body temperature on the heartbeats rate.
- Exploring the effect of raising the body temperature on the heart beats rate
Hypothesis
The main hypotheses for this experiment are
1) An increase in temperature form the normal body temperature always results in an increase in the heart beats rate
2) A decrease in temperature from the normal body temperature always results in the decrease in the heartbeats rate.
3) The heartbeats rate is also higher in the morning hours than it is in the evening hours
4) The heartbeats rate is highest in a standing posture and lowest in a lying down position.
Instruments needed
Thermometer for measuring the water temperature
Plastic basin for putting the water
Water heater for warming water
Water prepared for use in altering body temperature
Timers for recording the time intervals in the experiment
Herat rate monitor for recording the heart rate in beats per minute
Methods
Three healthy male and two healthy female volunteers aged between 22 and 25 years were identified and selected for this study. The volunteers were assigned random numbers A to D for the purpose of this experiment. The Five volunteer’s were investigated for their diurnal changes in heart beats rate due to Diurnal changes, changes in temperature and posture as described below.
1) Diurnal changes in heart rate
The pulse rate of each volunteer was taken in the morning at six AM and at SIX pm in a period of seven days while each volunteer was seated in a relaxed sitting position.
2) Postural changes in the heart rate
Each volunteer was asked to relax in a supine position for five minutes and his or her pulse rate taken over a 30-second period. Each volunteer was then asked to stand up quickly without making any movements and then their heart rate was taken over a 30-second period instantly. Two other measurements were taken after 2 minutes and four minutes respectively.
3) Thermoregulatory changes in heart rate
a) The effects of an increase in temperature on the heart beats rate.
A plastic container was filled with water at 35 degrees centigrade to half a basin full.
The pulse rate of the volunteers was then taken before the volunteers inserted their legs into the water.
The pulse rate of each volunteer was then taken ten minutes after inserting the legs in the water, and two other successive measurements taken after twenty or thirty minutes in water. The water was kept at 37 degrees centigrade through the addition of hot water.
b) The effect of lowering of temperature on the heart beats rate
A plastic container was taken and filed with cold water at ten degrees centigrade. The pulse rate of each volunteer was then taken before each volunteer inserted his or her legs in water. After each volunteer had his or her legs in water for ten minutes, their pulse rate was measured. Two successive measurements were then taken after 20 and 30 minutes. The water was maintained at 10 degrees centigrade through the addition of ice into it.
Results
Diurnal Changes in the Heart Beats Rate
The heartbeats rate of all the volunteers was higher at six am in the morning compared to the heartbeats rate measured at six in the evening in all seven days.
POSUTURALCHANGES IN HEART BEATS RATE
The heartbeats rate of all the volunteers was higher in the standing posture compared to the heartbeats rate in the supine position.
Results of Changes in Heart Beats Rate Due To an increase in temperature
The heart beats rate increased in all the volunteers due to temperature increase caused by inserting legs in hot water!
Changes in heartbeats rate due to cold water
The heart beats rate decreased in all the volunteers due to a drop in temperature caused by inserting legs in cold water.
Discussion
Heart rate refers to the number of heartbeats per unit time denoted as (BPM) beats per minute. The normal heart rate during rest varies between sixty and 100 beats per minute. However, the heartbeats rate can increase or decrease depending on the physiological conditions of the body and other independent factors (Khurana, 2008).
Diurnal changes in heartbeats rate
In humans, there is a significant diurnal difference in the heartbeats rate, blood pressure and the regulation of the autonomic nervous system. The heart rate and the blood pressure are low during the night and higher during the day. This occurs because during daytime, sympathetic control of the cardiovascular system is dominant (Solano, 2011). During nighttime, vagal or parasympathetic mode of regulation of the cardiovascular system is dominant. These diurnal changes in heartbeats and pulse rate are associated with the level of posture, the activity level, exposure to light and the sleep- wake patterns. Low levels of heartbeats rate and low levels of blood pressure are associated with sleep onset (Young, 2010).
Circadian rhythms also have a high influence on the diurnal changes in heartbeats rate. The highest levels of heartbeats rate occurs after Ten am and extends to about six pm there us a decline in the heartbeats rate by a rate of 10 to 20 percent in the late evening to the period of going to sleep. The level of physical activity, gender age, and the ethnicity influences the diurnal changes in heartbeats rate (Burne, 2003). The findings of this experiment on diurnal changes in temperature confirm that heartbeats rate is lower in the evening and night and high during the day.
The heart rate and temperature
The hypothesis of the experiment was that, at low temperature, the heart rate would be lower than at high temperature and if the temperature were increased, the heart rate would increase. The results obtained in the experiment confirm the hypothesis. Normally, the blood vessels in the body especially the peripheral blood vessels like those of the skin can either dilate or contract depending on the temperature of the body. When there is a drop in temperature, blood vessels usually vasoconstrict to conserve heat. The vasoconstriction of blood vessels results in an increase in blood pressure where the body compensates by lowering the cardiac output by lowering the rate of heartbeats (Hester & Lusha, 2012).
When the body temperature rises above the normal body temperatures, the peripheral blood vessels vasodilate lowering the blood pressure in the blood vessels. The body compensates for a decrease in blood pressure by raising the cardiac output through an increase in the heart rate (Pilowsky, et al, 2004). An increase in the body temperature therefore results in an increase in the heart rate while a decrease in body temperature results in a decrease in heart rate. Body temperature is therefore an independent determinant of the heart rate and causes an increase n the rate of heartbeats by ten beats per a one-degree rise in temperature (Solano, 2011).
Temperature is also a factor involved in the control of chemical reactions. Since heartbeats is under the control of electrical impulses. The myocardial heart muscle fibers that start the chain reactions starting with some complex protein molecules in each cell and then calcium protein interactions are the ones that initiate the contractile event in a reaction that utilizes adenosine tri phosphate as the energy process to drive the contractile process (Ellwein, 2008). In most chemical reactions, the reaction rate us sally doubles for every ten degrees in temperature, and halves every time the temperature drops by 10 degree’s centigrade. A rise in the body temperature therefore results in a speeding of the chemical processes in the body (Batzel, 2007).
A reduction in body temperature is associated with a decrease in chemical processes in the body. An increase in temperature upward 37 degrees centigrade therefore increases heart rate in a correlative manner. This occurs due to an increase in the atomic and molecular movements that occurs due to heating in the systems of the body resulting in an n increase in heartbeats rate. A decrease in temperature is associated with a decrease in the Brownian motion resulting in a decrease in the heartbeats rate (Pilowsky et al, 2004).
There is therefore a high correlation between the temperature of the body and the heartbeats rate. An increase in body temperature from the normal temperature results in an increase in the heart rate. A decrease in the body’s temperature results in a decrease in the heartbeats rate (Klabunde, 2005).
Posture and heartbeats rate
The heart rate is the total number heart beats in one minute. Posture is the position in which a person holds a body upright against gravity while sitting down or standing upright. Posture has an effect on the hear rate. The standing position is the one that produces the highest rate while the lying down posture produces the lowest rate of heartbeats. The reason for different rates of heartbeats related to posture is that in lying down position, the heart easily pumps blood throughout the body due to little resistance from gravitation forces (Malliani, 2000).
In the standing position, the heart must overcome gravity resistance in pumping blood throughout the body resulting in an increase in the heartbeats rate. In a sitting down position or in a twisted posture, the body needs to pump blood faster making the heart to pump blood faster into the body to achieve adequate distribution of blood in the body (Malliani, 2000).
In this experiment, Heart rate monitors were used to measure the heartbeats rate rather the manual method. Heart rate monitors are good for monitoring the heart rate because they allow the continuous measurements of heart rate especially in exercise where manual measurements would be hard. The manual method of taking heartbeats measurements is more prone to errors compared to other methods of measuring the heartbeat rate (Pilowsky, et al 2004).
Conclusion
It is apparent that the heartbeat rate is influenced independently by temperature and posture. The Experiment was successful and the results obtained satisfy the hypothesis of the study that heart beats rate increases with an increase in temperature. The results also support the hypothesis that heartbeat rate decreases with a decline in temperature. The results obtained in this experiment also proved the hypothesis t that posture affects the heartbeats rate. The standing position has the highest heartbeats rate, compared to the sitting posture. The laying down posture has the lowest rates of heartbeats compared to the standing or sitting postures.
This experiment can be improved using a diverse and larger sample of volunteers with bigger demographics to improve the reliability of the results obtained. The experiment can also be improved by an electrocardiogram to measure the heartbeats rate. The electrocardiogram is a better method of measuring the heartbeat rate compared to the manual method because it is a more accurate measure of heart beats rate. An electrocardiogram is even more important during exercise when heartbeats changes need to be taken over short time periods where the heart rate is rapidly changing.
References
Batzel, J. (2007). Cardiovascular and respiratory systems: modeling, analysis and control.
New York; Siam.
Burne, J., & Leonard, R., (2003). Essentials of medical physiology. London: Academic press
Ellwein, l., (2008). Cardiovascular and respiratory regulation, modeling and parameter
Estimation. Michigan: Proquest.
Hester, R., & Lusha, X., (2012). Cardiovascular responses to exercise London: Morgan
and Claypool publishers.
Khurana l, (2008) Essentials of medical physiology. Mumbai: Elsevier.
Klabunde, R., (2005) cardiovascular physiological concepts. Massachusetts .Lippincott&
Williams & Wilkins.
Malliani A., (2000). Principles of cardiovascular neural regulation in health and disease.
London: Springer.
Pilowsky P, et al (2004). Neural mechanisms of cardiovascular regulation: New York:
Springer.
Solaro, J., (2011). Regulation of cardiac contractility. London: Morgan & Claypool life
Sciences.
Young, D., (2010). The regulation of cardiac control. London: Morgan & Claypool
Publisher.
