Download Blood Pressure changes reflected by Posture and Activity Anatomy

Blood Pressure changes reflected by Posture and Activity
Anatomy and Physiology 503 Lab
Rebecca Levenstein
Tara Gionfriddo, Giselle Hardy, Deniahn Wade, (and others)
October 15, 2013
Introduction:
The purpose of this experiment is to measure the changes in blood pressure and pulse rate
of two subjects with varying degrees of fitness, based upon posture changes and physical
activity, and then calculate and compare the mean arteriole pressure during each phase,
and also to measure the changes in pulse pressure and blood pressure when spelling tests
are administered.
Blood pressure is the amount of force exerted on the vessel walls, and is expressed in
mm^3 (Marieb and Hoehn 2012). Blood always flows from a higher pressure gradient to
a lower gradient, and is forcibly generated through blood vessels by the pumping
mechanism of the heart. Pressure results from the presence of peripheral resistance, such
as thickening of the blood and the narrowing of the diameter of the vessel (Marieb and
Hoehn 2012). Normal blood pressure is 120/80 mm^3. The number on the top expresses
systolic pressure, or the pressure exerted during the peak of the ventricular contraction
phase, and the bottom number expresses diastolic pressure, which is the pressure exerted
at the time when the heart is least contracted. Pulse pressure, also referred to as heart rate
for this experiment, is the difference between diastolic pressure and systolic pressure (PP
= DP – SP). Pulse pressure is measured by counting the number of pulsations per minute
that one feels when touching the artery. In this experiment, the pulse rate was measured
at the wrist(!!_) Mean arteriole pressure (MAP), the value used for comparison in this lab
because aortic pressure fluctuates with each heartbeat, is the pressure that sends the blood
out into the tissue (Marieb and Hoehn, 702, 2012). MAP is calculated using the equation:
MAP = diastolic pressure + (pulse pressure/3). Since diastole typically extends for a
slightly longer period of time than systole, MAP cannot be simply the halfway point
between systolic and diastolic pressures (Marieb and Hoehn, 702, 2012). Changes in
blood pressure are detected by baroreceptors, also referred to as pressoreceptors, and
chemoreceptors, which are receptors found in the aorta and carotid arteries.
Baroreceptors detect pressure, as in the case of increased blood pressure, or lack of
pressure, as in a decreased blood pressure, in the vessel and send a signal via the
glossopharyngeal and vagus nerves to the medulla oblongata which then activates the
cardioinhibitory center or the cardioacceleratory center. The signal then travels through
the vagus nerve to the sinoatrial node in the right atrium of the heart, which then transfers
the signal through the heart. Chemoreceptors, located in aorta and carotid arteries as well,
detect changes in pO_2_ and pH. These are stimulated by the sympathetic nervous
system (SNS) activation which causes the release of epinephrine and norepinephrine, and
the parasympathetic nervous system (PNS) activation, which causes the release of
acetylcholine (ACH). This lab demonstrates the effects of the SNS by stimulating stress,
as when spelling, and physical activity. It measures the amount of time that the body
takes to activate the PNS and decrease blood pressure and heart rate. It also demonstrates
the effects of posture on blood pressure and heart rate, and how changing posture
suddenly, such as going from a prone to upright position, affects these.
Results:
Table 1: Effect of Postural Changes
Subject 1
Blood Pressure
Sitting Quietly
(baseline)
Reclining (after 2-3
minutes)
Immediately Upon
Standing
After Standing for 3
minutes
Pulse Rate
MAP
100/70
84 bpm
80
90/60
60 bpm
70
86/60
92 bpm
68.7
90/70
72 bpm
80
The subject’s blood pressure and pulse rate were first measured after having sat quietly
for a few minutes to ensure relaxation, to establish a baseline, to compare further data to.
The baseline systolic pressure was slightly elevated, while the baseline diastolic pressure
was slightly below normal, but still well within healthy range. The baseline pulse is on
the higher range of normal, but as the normal blood pressure range is 75 to 85 beats per
minute, it is still within normal. Upon reclining for 2 to 3 minutes, the subject’s blood
pressure and pulse rate can be expected to decrease, due to relaxation and the consequent
effects of the PNS, which will result in a decrease in resistance, which in turn lowers
blood pressure and heart rate (‘Human physiology in space’ 2013). One error that
occurred in this stage of the experiment was that the subject, while partially relaxed,
didn’t relax completely. The effects of the sudden change to standing was expected to
increase blood pressure and pulse rate, partially because the heart has to increase the
stroke volume in order to pump blood to muscles that have suddenly had to exert
themselves, but also because peripheral resistance has increased. MAP has decreased
because the heart had adjusted its force to the decrease in resistance. It required less force
to reach body tissues in a prone position, and now that the body has returned to an upright
position, it has not finished adjusting itself to reach the areas of the body that require
more blood supply now that the muscles of posture and legs are being used. The subject
also exhibits a small amount of orthostatic hypotension, which is a decrease in blood
pressure immediately upon standing, caused by the pooling of blood in the legs due to
gravity, which will decrease the venous return, until the baroreceptors signal the heart to
adjust (‘Mayoclinic’ 2011). After standing for 3 minutes, the body has adjusted to being
in the upright position again. The pulse rate, while still slightly low, which could be
because although the subject is standing upright, she is still more relaxed than she was
when the baseline was measured, has decreased, and the blood pressure has increased to
allow for the use of postural muscles and to overcome increased resistance, due to
gravity. MAP has increased to supply the increased amount of tissues being used with
adequate blood supply.
Table 2: Exercise
Subject 1: Poorly conditioned subject
Subject 2: Well-conditioned subject
Well
Conditioned
Subject
Poorly
Conditioned
subject
Baseline Immediately
1
Minute
2
Minutes
3
Minutes
4 Minutes
5
Minutes
BP:
117/68
HR: 84
MAP:
80
BP:
100/70
HR: 84
MAP:
80
BP:
118/69
HR: 76
MAP:
92.3
BP:
104/72
HR: 88
MAP:
82.7
BP:
116/69
HR: 80
MAP:
95.3
BP:
90/66
HR: 100
MAP:
74
BP:
117/72
HR: 76
MAP:
87
BP:
84/62
HR: 108
MAP:
69.3
BP:
117/68
HR: 76
MAP:
84.3
BP:
82/60
HR: 72
MAP:67.3
BP:
117/66
HR: 76
MAP:
83
BP:
80/60
HR: 72
MAP:
66.7
BP:
123/75
HR: 76
MAP: 91
BP:
120/78
HR: 160
MAP: 92