Biology56

Experiment 2: Stress Response

A number of different environmental factors can illicit a physiological stress response from the body. Some of the most common triggers are temperature, exercise, pain, posture, and noise. In this experiment, you will test the body’s natural response to temperature and posture through manipulation of blood pressure and/or heart rate.

Note: One volunteer should monitor the subject throughout the experiment. Volunteers should remain attentive in case the subject should ever feel faint or dizzy.

Procedure

Testing Temperature

1. Construct a hypothesis indicating how you anticipate your body’s heart rate and blood pressure to respond to decreased temperature. Record your hypothesis in Post-Lab Question 1.

2. Obtain a deep bowl or bucket (large enough to submerge subject’s hand), and fill approximately 50% with ice cubes. Fill the container with cool water until the ice cubes are covered.

Note: Be sure to leave enough space at the top of the container empty to compensate for the mixture that will be vertically displaced when the subject’s hand is immersed in it.

3. Select a subject. The subject should roll up his/her shirt-sleeve or change into a short-sleeved shirt to expose the bare skin of the forearm in preparation for the blood pressure cuff.

4. Wrap the blood pressure cuff around the subject’s forearm. Blood pressure cuffs are traditionally placed between the elbow and shoulder, but may be placed below the elbow if the upper arm is too large to accommodate the cuff.

Note: Blood pressure readings taken from below the elbow are typically not as accurate as readings taken from above the elbow.

5. Verify that the cuff is evenly positioned around the circumference of the forearm, lining up the patch which says “artery ” with the subject’s brachial artery. Place the diaphragm on the stethoscope on the brachial artery (see Figure 5), and secure the cuff with the Velcro. Be sure that the cuff is not so tight that it causes pain. The gauge should be clipped to a flat, sturdy surface. It should not be clipped to the cuff.

6. Make sure that the ice water and stopwatch are within arm’s reach. The subject should sit comfortably for five minutes. If possible, elevate the arm with the cuff on it to heart-level by resting it on a piece of furniture. Do not hold the arm out in the air without support as this may result in muscle fatigue.

7. After five minutes have passed, palpate the subject’s pulse by placing the pointer and middle fingers on the radial artery (located on the posterior side subject’s wrist). Count the number of heart beats in 15 seconds, and multiply the value by four. Record the value in Table 3 as beats per minute. Then, measure subject’s blood pressure. To do this…

a. Insert the earpieces of the stethoscope into the subject’s ears. Inflate the cuff by closing the valve on the bulb and repeatedly squeezing the bulb until it sounds like the blood flow has stopped through the stethoscope. This will likely occur at approximately 130 – 180 mmHg.

b. Rotate the silver valve on the bulb to slowly release the cuff pressure.

c. Listen with the stethoscope for the return of blood flow into the forearm, called the sounds of Korotkoff.

d. Systolic pressure is the pressure at which the first sound of blood flow is heard after pressure is released. You may also see a tapping of the needle on the pressure gauge that corresponds with the pulse.

e. As the pressure continues to decrease, blood flow returns to normal and the sounds of Korotkoff can no longer be heard. The pressure at which this transition occurs is diastolic pressure.

f. Record the blood pressure measurement in Table 3.

8. Deflate the cuff, but leave it secured on the subject’s arm.

9. Place the subject’s hand (from the same arm with the blood pressure cuff) in the bucket of ice water.

10. Leaving the hand in the water, measure the blood pressure and heart rate in 30 second intervals for up to two minutes. Record your data in Table 3.

Note: Remove subject’s hand from the ice water if it becomes uncomfortably cold. The subject may stop the experiment early or try again later if necessary.

11. Remove subject’s hand from the ice water and pat dry with a paper towel for approximately two minutes. The subject should remain still during this time.

12. Measure subject’s blood pressure and heart rate a final time, and record the data in Table 3.

Testing Body Position

1. Construct a hypothesis indicating how you anticipate the body’s heart rate and blood pressure to respond to postural changes. Record your hypothesis in Post-Lab Question 2.

2. Roll up your sleeve or change into a short-sleeved shirt to expose the bare skin on your forearm in preparation for the blood pressure cuff.

3. Select a subject. The subject should roll up his/her shirt-sleeve or change into a short-sleeved shirt to expose the bare skin of the forearm in preparation for the blood pressure cuff.

4. Wrap the blood pressure cuff around the subject’s forearm. Blood pressure cuffs are traditionally placed between the elbow and shoulder, but may be placed below the elbow if the upper arm is too large to accommodate the cuff. Note: Blood pressure readings taken from below the elbow are typically not as accurate as readings taken from above the elbow.

5. Verify that the cuff is evenly positioned around the circumference of the forearm, lining up the patch which says “artery” with the subject’s brachial artery. Place the diaphragm on the stethoscope on the brachial artery (see Figure 5), and secure the cuff with the Velcro. Be sure that the cuff is not so tight that it causes pain. The gauge should be clipped to a flat, sturdy surface. It should not be clipped to the cuff.

6. Make sure that the stopwatch is within arm’s reach. The subject should sit comfortably for five minutes.

7. After five minutes have passed, measure the subject’s heart rate and blood pressure. Refer to Step 7 from “Testing Temperature” for instructions regarding how to take these measurements. Record the values in Table 4.

8. Deflate the cuff, but leave it secured on the subject’s arm.

9. The subject should now stand up with his/her back resting against a wall for support. Try to relax and remain quiet. Take the subject’s initial blood pressure and heart rate. Record values in Table 4. Note: Standing up too quickly can result in light-headedness. Volunteers should pay special attention at this step to ensure that the subject does not feel faint or dizzy.

10. Continue to take blood pressure and heart rate measurements at one minute intervals for two minutes. Record all measurements in Table 4.

11. Sit back down comfortably for two minutes. Take a final blood pressure and heart rate measurement. Record in Table 4.

Post-Lab Questions

1. Write your hypothesis for the “Testing Temperature” portion of this experiment. Be sure to include how you think the decreased temperature will affect blood pressure and heart rate, and, why.

2. Write your hypothesis for the “Testing Body Position” portion of this experiment. Be sure to include how you think blood pressure and heart rate will vary when you sit versus when you stand.

3. Explain your results in terms of the endocrine system. Indicate how the endocrine system is involved in the physiological response to temperature and body position.

4. Which glands are most likely to be involved with the physiological response caused in this experiment? Which hormones are most likely to be involved?

5. How does this experiment demonstrate the “fight or flight” response?

The Endocrine and Reproductive System Structures

POST LAB QUESTIONS for Endocrine System lab:

1. What surprised you about the internal anatomy of the pig overall?

2. Explain the function of the thyroid gland and the hormones it secretes. Include how the release of hormone is regulated and what cells the hormone act on.

POST LAB QUESTIONS for Reproductive System lab:

Virtual model questions

1. What female reproductive structure is functionally homologous to the glans penis?

2. What female reproductive structure is functionally homologous to the testes?

Pig Dissection questions

1. Describe any observations you made while dissecting the reproductive system of your pig.

2. What is meant by urogenital opening?

3. Why do most male mammals have testes in an external sac?

4. What is the vaginal orifice?