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Iker Lopez
Anatomy & Physiology P2
Wednesday, September 19, 2012

Heart Rate Response to Baroreceptor Feedback Lab

Fundamental Question: Does the body respond to its environment? Testable Question: When the body is in the squat position to normal while the time limit stays the same and how far you squat is the same, will the heart rate recover after returning to standing position in 10 seconds? Hypothesis: If the body moves back to normal position from squatting position while the time limit and squat angle are all relevant in all three trials, then the heart rate will balance in 10 seconds because the baroreceptors will start the feedback mechanism and will quickly rebalance the heart rate? Background:

The feedback mechanism is important to human physiology because if the body is not in balance or at homeostasis, it will not function correctly. Feedback mechanisms attempt to keep the human body in balance. For example, if the body temperature is too high, the feedback mechanism quickly reacts and makes the body sweat. The feedback mechanism contains receptors that sense the stimulus which goes to its rightful control system and the effectors react to the response. In "Human Physiology with Vernier", it explains how heart rate responds to the baroreceptors feedback. As the leg muscles become compressed, it causes a sudden increase in stroke volume (amount of blood pumped with each beat), and pressure which are sensed by the baroreceptors. 2 types of feeback mechanisms are positive and negative feedback mechanisms. The difference between the 2 is that positive feedback mechanisms move away from the setpoint or does not try to balance the human body. While negative feedback mechanisms work on trying to maintain homeostasis. The most prevalent mechanism in humans is the positive mechanisms since it is always doing something that will cause the heart rate to increase or decrease. Three determinants of blood pressure are Heart rate, Resistance, and Stroke Volume. The determinant that is measured in this lab is the Heart Rate. A Baroreceptor senses the pressure which causes the heart rate to react. A feedback loop that contains receptors happens when there is a sudden increase in pressure in the heart or carotid arteries that cause an increase in stretch of the baroreceptor sensors and results in a decrease in heart rate. Ortheostatic hypotension is a drop in blood pressure of 20 points or an increase in heart rate increase of 20 points with standing is considered significant. In this lab, a Baroreceptor feedback is modeled by having subjects squat for a certain amount of time while their heart rate is measured after returning from squat to normal.

Materials:
Meter Stick
Human Subjects
Labquest App
Vernier Hand-Grip Heart Rate Monitor

Procedure:
1.Connect the reciever module of the Heart Rate Monitor to LabQuest and choose New from the File menu. 2.On the Meter screen, tap Length. Change the data collection to 400 seconds. Select OK. 3.Set up the Heart Rate Monitor. Using a Hand-Grip Heart Rate Monitor
a) Locate 2 arrows from the reciever and the handle.b) Grip handles in reference areas. Hold handles vertically.c) Someone else hold reciever near handles so the 2 arrows are facing up. Reciever must be within 60 centimeters of handles during data collection. It ALSO must be 2 meters away from other subjects. 4. Stand so your Heart Rate Monitor is within receotion range of the reciever module. 5. Start data collection. There will be a 15 second delay while data is collected before the 1st point is plotted on the upper graph. Thereafter, a point will be plotted every 5 seconds. Obtain 30 seconds of graphed data as a baseline heart rate for the standing position. 6. After at least 30 seconds of stable baeline data has been collected, rapidly lower yourself into a...
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