bio lab-Homeostasis, the ability to maintain a stable internal environment, is a major characteristic of

09 Jun bio lab-Homeostasis, the ability to maintain a stable internal environment, is a major characteristic of

Question
OVERVIEW OF LAB

Homeostasis, the ability to maintain a stable internal environment, is a major characteristic of living organisms. In this exercise, we will examine some homeostatic mechanisms. The exercise examines adjustments in the cardiovascular system of human subjects.

HUMAN CARDIOVASCULAR PHYSIOLOGY

In order to maintain homeostasis cells must exchange nutrients and wastes with the external environment. In single celled organisms acquisition of nutrients and removal of wastes occurs directly across the cell membrane. However, the cells of complex organisms are isolated from the external environment and normal cell homeostasis must be maintained by coordinated function of specialized organ systems. In mammals, the cardiovascular system functions to allow exchange between cells and the external environment by transporting blood throughout the different tissues of the body. For example, blood is delivered to the lungs where oxygen is provided from the external environment and delivered to cells. Conversely, CO2generated by cells is released into the blood and transported to the lungs for elimination into the external environment. Other wastes are transported by the cardiovascular system to the kidneys and liver to enable excretion from the body. Nutrients from the diet are picked up from the digestive system by the cardiovascular system and distributed to cells for storage and use. The cardiovascular system also functions in the delivery of chemical signals within the body which enables coordination of function between different organ systems.

Blood flows throughout the body as a result of a pressure difference generated by the pumping of the muscular heart. The mammalian heart consists of 2 atria or receiving chambers and two ventricles or pumping chambers. At rest, the heart normally beats 70-75 times per minute. The cardiac cycleincludes the electrical, mechanical and valvular events that occur during one heartbeat. Diastoleis the period of the cardiac cycle during which the ventricles are relaxing, and systole is the period during which the ventricles are contracting.

During systole blood is pumped from the heart into arteries which branch extensively and terminate in arterioles which actively change in diameter to regulate blood flow to different regions of the body. Blood flows from arterioles into thin-walled capillaries which are adapted for exchange of nutrients and waste. Blood is returned from capillaries to the heart by compliant veins. Delivery of blood by the cardiovascular system may be varied physiologically by varying function of either the heart or blood vessels.

The objectives of this lab are: 1) to become familiar with some of the measurements that are used to assess human cardiovascular function including auscultation of heart sounds, palpation of the peripheral pulse and indirect measurement of blood pressures; 2) to examine the relationship between body mass index and fitness using cardiovascular responses to exercise; 3) to determine the homeostatic responses of blood pressure to exercise.

PALPATION OF SUPERFICIAL PULSE POINTS

As the heart ejects blood into the arteries during systole the arteries expand, and because arteries contain elastic tissue they recoil during diastole. This alternating expansion and recoil creates an arterial pulsewhich normally equals the heart rate. In addition to providing a measure of the heart rate, the quality of the pulse (regularity and strength) also provides important functional information.

Activity 1:

The pulse may be easily detected from any superficial artery when the artery is compressed against firm tissue. Palpate the following superficial pulse points: Common carotid artery: lateral to the Adams apple in the neck Brachial artery: in the antecubital fossa (inside the elbow).

Radial artery: inside the wrist near the thumb.

Pulse rate is recorded in beats per min. Take your pulse manually for 20 seconds and multiply it by 3 to calculate beats per minute. Repeat the measurement to see how reproducible your calculation is. Compare these numbers to the recordings from the digital sphygmomanometer.

INDIRECT MEASUREMENT OF BLOOD PRESSURE

Evaluation of arterial blood pressure is a very useful clinical measurement which provides information regarding both function of the heart and condition of the blood vessels. The following pressures are commonly measured or calculated:

Systolic blood pressure: The maximal pressure in an artery produced during the ejection of blood by the heart. Normal average resting pressure for young adults: ~120mmHg.

Diastolic Blood Pressure: The minimal pressure in an artery occurring when the heart is relaxed. Normal average resting pressure for young adults: ~70mmHg.

Blood pressure may be measured directly via a pressure transducer attached to a cannula placed in a blood vessel. However, arterial blood pressure is more commonly measured indirectly by applying a pressure externally to an artery using a sphygmomanometer and listening to arterial sounds using a stethoscope or having a digital sensor that can detect these sounds. The basis of this method is that normal blood flow through an artery is laminar and does not create a sound. However partial occlusion of a blood vessel creates intermittent flow and turbulence which can be heard (auscultated) using a stethoscope. The sounds produced when a cuff is used to apply pressure externally to an artery were first described by Korotkoff in 1905 and are referred to as the sounds of Korotkoff. Human blood pressures are most commonly measured in the brachial artery of the upper arm.

Activity 2:

For the data tables, use the baseline blood pressure and pulse readings obtained from the digital sphygmomanometer.

Wait for the digital blood pressure monitor to power up, push the blue button, and wait until the display starts blinking “0.” Have the subject seated with his or her arm resting on the lab bench and make sure they don’t move or talk while the reading is being taken. Wrap the digital blood pressure cuff around the upper arm with the sensor directly above the inside of the elbow and secure the cuff. Make sure the valve on the arm cuff is open (counterclockwise) and squeeze the cuff to make sure all the air from the previous inflation is out. Turn the valve on the cuff clockwise to close it. Inflate the cuff to approximately 160-180 mm Hg.

Note: do not leave the cuff inflated for more than 1 minute.This pressure is above the normal systolic pressure completely collapsing the artery so that no sounds are made. Open the valve by turning it counter- clockwise to slowly lower the pressure in the cuff. Wait until the digital blood pressure meter display stops blinking and displays the blood pressure and pulse readings.

Activity 3: CARDIOVASCULAR ADAPTATION TO EXERCISE

During exercise the demand for blood flow to the heart and exercising muscles increase to several times the resting demand. People who are more physically fit and conditioned to exercise may recover homeostatic balance after exercise than those who do not exercise regularly.

Experimental Exercise:

You should work in pairs to complete the following experiment. Note: any student with a heart problem or other issues that make vigorous exercise unwise such as a respiratory infection or pregnancy should not participate as a subject.

1.Record baseline pulse rate and blood pressure using the digital sphygmomanometer with the subject seated.

2.Body Mass Indexis often used as an indicator of obesity. Have the subject calculate their Body Mass Index (BMI) using the following formula:

BMI = [Weight (in lbs) x 703] / [(Height in inches)2]

For example, a person who weighs 200 pounds and is 6 feet 0 inches tall has a BMI of 27.1.

[200 lbs x 703] / [72 inches x 72 inches] = 27.1

3. The exercise for ascertaining physical fitness is a protocol known as the Harvard Step Test.

a. Perform the step-test: The subject should stand in upright posture at a bench of prescribed height of 16 inches (40 cm). The subject will step up and down on the bench at a rate of 30 steps per minute (all the way up and down equals one step, which should be completed every 2 seconds) for 5 minutes. The pace should be set by a timer who will call “up-2-3-4, up-2-3-4 so that each “up-2-3-4” requires 2 seconds. A second observer must time and monitor the subject to ensure that he or she steps fully on the bench maintaining an upright posture and that he or she reasonably maintains the pace.

b. Once the subject completes the full 5 minutes of exercise, he or she should sit down. The pulse rate and blood pressure should be measured as soon as possible using the digital sphygmomanometer. Wait a full minute after the reading has been taken and then take another reading. Repeat 2 more times for a total of 4 readings, each separated by at least a full minute’s wait.

If the digital sphygmomanometer gives an error reading: 1. Make sure the cuff is on correctly (follow the instruction on the cuff to make sure the

sensor is directly above the brachial artery just above the inside of the elbow). 2. Open the air release valve and make sure all the air has been evacuated from the cuff

before closing the valve. 3. Re-take the measurement as soon as possible, this time inflating the cuff to a slightly

higher pressure. Avoid inflating much above 200 mm Hg Calculation of the Index of Physical Fitness:

fitness index= DURATION OF EXERCISE(INSECONDS)*100 / 2*(SUM OF THREE PULSE COUNTS DURING RECOVERY)

Data table for individual: pulse rates (beats/min.), BMI & fitness index values

MEASURMENT

BASELINE

IMMEDIATE

1MIN

2MIN

3MIN

PULSE RATE

60

67

63

62

55

DURATION OF EXERCISE (SEC)

300

FITNESS INDEX

166

BMI

32.28

Data table for individual: Blood Pressure Measurements

MEASUREMENT

BASELINE

IMMEDIATE

1 MIN

2 MIN

3 MIN

SYSTOLIC BP

129

163

154

102

95

DIASTOLIC BP

60

148

130

83

65

CALCULATION:

1.Calculate the linear regression equationfor the best fit trend line through the data and a graph of this linefor the following pairs of variables from the overall class data: BMI vs FI, BMI vs. resting Systolic Blood Pressure, BMI vs. resting Diastolic BP, FI vs. resting Systolic BP, and FI vs. resting Diastolic BP using the following website:http://www.alcula.com/calculators/statistics/linear- regression/. Include these equations and graphs in the results section of your lab report.

2. Use the following website to calcultate the correlation coefficientfrom the data:http://www.alcula.com/calculators/statistics/correlation-coefficient/ _______________ Correlation coefficient is a statistic that measures how well 2 variables fit a regression line. If Fitness Index increases linearly as BMI increases, the correlation coefficient will be close to 1. If Fitness Index decreases perfectly linearly as BMI increases, the correlation coefficient will be -1. If there is no trend to the data at all and the points are randomly distributed, the correlation coefficient will be 0. Record the Correlation Coefficients for all of the comparisons above and include them in the results section of your lab report.

3.Much like a t-test, whether two variables are significantly correlated depends on the sample size as well as how close the data fit the regression line. A dataset of 7 points with a correlation coefficient of 0.9 has a highly significant p-value of 0.006, whereas a dataset of 3 points with a correlation coefficient of 0.9 is not statistically significant (p-value= 0.29). Use the following website to determine whether the correlation coefficients from the above comparisons are statistically significant (use two tailed probability):

http://www.danielsoper.com/statcalc3/calc.aspx?id=44

ASSIGNMENT

Your assignment on this lab will be to write a full lab manuscriptbased on the class BMI and FI data. -The Titleshould be less than 20 words and give the reader a good idea of the subject of the manuscript -The Abstractshould summarize your introduction, Results, and Conclusions in 150 words or less. It is something quick for the reader to peruse in order to ascertain if it is worth their time to read the entire manuscript.

-The Introductionshould give a brief background on the subject matter and present the hypotheses to be tested. You should have a hypothesis for each of the 5 comparisons you are performing to calculate Correlation Coefficient. You should cite the lab protocol if you use it for background information. An example hypothesis: “There will be a negative relationship between body mass indexes (BMI) (independent variable) and fitness indexes (dependent variable) among individuals.”

-The Materials and Methods section should allow someone to replicate the experiment exactly, but you shouldn’t re-write everything in the lab manual. After summarizing how the experiment was performed, cite this lab manualfor further details (Bostick et al. 2013). Also be sure to state how the analyses were performed and cite the web sites used.

-In the Resultssection, you should present all of your data (data tables from page 6, regression line equations and graphs, correlation coefficients, and p-values for the correlation coefficients).

-The Discussionsection is where you should interpret the meaning of the results. This includes discussing the significance (or lack thereof) of the p-value for the correlation coefficent. Clearly state how the results compared to your predictions (hypotheses). • Describe whether or not the data and statistical tests support your predictions.

• For any results that don’t support your predictions, give possible explanations as to why the results didn’t support your hypothesis; note any flaws in the lab procedure that may have influenced the results, but also mention biological reasons as to why the results might differ from what you predict. • Discuss future experiments and experimental design that could more accurately test the relationship between physical fitness and obesity.

-Literature Cited

To cite the lab manual, use the template provided in the assignment for the Fish Lab.

For the websites, cite according to the following example:

Statistics Calculator: Linear Regression. 2013. GraphPad Software. 10/6/2014.

10/6/2014 refers to the date you accessed the website. In general, it’s best to cite research published in peer-reviewed journals and notto cite web pages, but we’re making an exception for this course since there isn’t a lot of current research on this particular type of experiment.

This assignment is to be done individually; you will submit the assignment to turnitin.com, which will check for plagiarism. Do not read anyone else’s report or let them read yours.

Literature Cited

Smith JJ, Kampine JP, Circulatory Physiology, The Essentials(2nd edition). Baltimore: Williams and Wilkins, 1984. Tharp GD, Experiments in Physiology(4th edition) Burgess Publishing Company, 1980.

BMI

FI

Resting Systolic

Resting Diastolic

22.9

46.4

126

82

23.7

41.0

125

83

24.7

53.7

125

55

27.4

42.1

123

53

26.6

76.9

118

73

24.3

52.8

110

71

20.1

83.3

110

60

23.9

44.5

110

71

22.0

46.5

101

72

24.2

53.6

120

72

23.6

67.3

121

79

19.4

55.8

118

75

25.0

35.4

119

72

20.8

71.1

117

75

22.9

53.9

141

95

29.8

62.0

141

82

24.4

60.5

138

73

18.9

61.0

108

70

21.8

50.6

115

70