Group Data: BP Lab
SBP (mmHg)
Subject
Seated
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Supine
119.0
110.0
107.5
115.0
117.5
120.0
125.0
94.0
115.0
110.0
119.0
105.0
113.0
122.0
119.0
96.0
95.0
92.5
120.0
125.0
117.0
110.0
119.0
Supine:Legs Elevated Standing
107.5
116.5
114.5
115.0
118.0
115.0
115.0
117.5
100.0
117.5
120.0
113.0
116.5
119.0
110.0
122.0
119.0
109.0
120.0
134.0
139.0
96.0
94.0
101.0
105.0
105.0
101.0
109.0
110.0
118.0
119.0
121.0
120.0
107.5
110.0
107.5
115.0
117.0
107.0
129.0
133.0
116.0
119.0
120.5
113.0
98.0
98.0
90.0
94.5
93.5
91.0
102.5
103.5
102.5
110.0
102.5
117.5
125.0
127.5
147.5
113.0
110.0
123.0
120.0
117.5
121.0
125.0
118.5
128.5
Lab #3: Blood Pressure
Speci c Objectives
1.
To gain knowledge and understanding of the scienti c principle and concept of:
blood pressure.
the physiological factors that in uence blood pressure.
•
the environmental stressors/factors that in uence blood pressure.
the regulation of blo0d pressure.
2.
To learn how to interpret and apply blood pressure results at rest and during exerGise.
3
To learn and develop the following speci c skills:
How to administer a blood pressure test at rest and duing exercise.
Introduction
BloodPressure
The pressure exerted by the blood on the vessel walls. The term blood pressure usually refers to arterial
blood pressure.
SystolicBloodPressure(SBP)
Highest pressure in the arteries during the cardiac cycle.
Pressure during ventricular systolefcontraction (ejection phase).
Average value = 120 mmHg
Diastolic Blood Pressure(DBP)
Lowest pressure in the arteries during the cardiac cycle.
Pressure during ventricular diastolelrelaxation ( ling phase).
Average value = 80 mmHg
PulsePressure(PP)
Used to calculate mean arterial pressure.
Average value = 40 mmHg (SBP -DBP = 120- 80 = 40)
PP
SBP- DBP
Mean Arterial Pressure(MAP)
The force that propels blood throughout the cardiac cycle.
Pressure in the arteries, averaged over time.
Used to determine the rate of blood ow through the systemic system.
MAP is not a simple average of the systolic and diastolic values.
The heart spends more time in diastole than systole, and this must be factored into the equation.
Resting:
Exercise:
MAP = DBP + [1/3 (PP)]
MAP = DBP + (1/2 (PP))
Hypertension
High blood Pressure.
Borderlinehypertension: Systolic pressure =140 mmHg or Diastolic pressure=90 mmHg
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Physiological Factors thatIn uenceBloodPressure
Blood Pressure = Cardiac Output x Peripheral Resistance
1.
Cardiac Output
When the left ventricle (LV) contracts, it ejects blood into the arterial system.
The volume of blood ejected from the LV with each contraction is called stroke volume (SV).
The volume of blood ejected from the LV each minute is called cardiac output (Q or Co).
Cardiac Output (ml/min) = Heart Rate (beats/min) x Stroke Volume (ml/beat)
.
Anything that affects heart rate or stroke volume will also affect cardiac output.
Heart rate increases with sympathetic and decreases with vagus stimulation.
Stroke volume increases as contractility increases.
Stroke volume is directly affected by venous return.
Nicotine increases sympathetic stimulation.
Frank-Starling Law of the Heart
When venous return to the heart increases, end-diastolic volume (EDV) increases. This results in an increased stretch of the myocardial bers in the wall of the ventricle (preload). The greater the stretch on these bers, the greater the force with which they will contract. Greater contraction strength causes a greater stroke volume, and therefore a greater cardiac output.
Systolic blood pressure is directly proportional to cardiac output.
? Cardiac
Output ? ? Systolic Blood
Cardiac Output?
2.
Pressure
Systolic Blood Pressure
Peripheral Resistance
Peripheral resistance (PR) is the force produced by the friction between the blood and the walls of the blood vessel. PR hinders ow; blood pressure must overcome this force to keep the blood owing.
Higher PR increases afterload. (afterload is the resistance to ventricular emptying)
Three main sources of PR:
a. Vessel Diameter – PR is indirectlyproportional to diameter.
Vessel diameter is regulated by vasomotor bers; sympathetic nerves bers which innervate the vessel’s smooth muscle layer. Vasomotor bers release epinephrine, a vasoconstrictor.
Vessel diameter is also affected by vasoconstrictors carried in the blood (epinephrine,
angiotensin II, and vasopressin).
Vasoconstriction decreases vessel diameter and vasodilation increases vessel diameter.
External pressure (pressure surrounding the vessels) can also in uence affect vessel diameter by in uencing the arterial compliance/vessel elasticity.
Atherosclerosis can decrease vessel diameter. Atherosclerosis is higher among obese and smokers.
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b. Blood Viscosity – PR is directlyproportional to viscosity.
Viscosity, or thickness, of a
uid is a physical property related to the ease with which its molecules ow past on anothe.
The greater the concentration of blood cells and plasma proteins in the blood, the greater the viscosity. This is a function of hematocrit (percentage of cells in the blood).
Anemia, hemonhage, and increased body temperature decrease hematocrit and therefore decrease viscosity.
Excess red blood cells and extreme cold temperature increase hematocrit and therefore
increase viscosity.
C. Total Vessel Length – PR is directlyproportional to vessel length.
Obesity: ? body fat -?
t#blood
vessels -? ? total vessel length -? ? PR
Blood pressure is directly proportional to total peripheral resistance.
? Total Peripheral
Resistance ? ? Systolic & Diastolic Blood Pressure
Total Peripheral Resistance ?
3.
Systolic & Diastolic Blood Pressure
Arterial Blood Volume
Systolic blood pressure is directly proportional to arterial blood volume.
?Arterial Blood Volume ? ?systolic Blood Pressure
Blood volume is the volume of blood in the vascular system.
As blood volume decreases, osmolarity increases.
An increase in blood volume increases the amount of uid pressing against the inner walls of the arteries.
? blood
volume ? Tvenous return ? Tend diastolic volume (EDV) ? ?sv and Co
(Frank-Starling Law).
If someone who is “salt sensitive” eats a lot of salt, his/her sodium channels fail and the kidneys cannot ush out al of the excess sodium. Excess sodium in the blood draws water in, increasing blood volume.
Blood volume decreases with dehydration.
4.
Arterial Compliance / Vessel Elasticity
Blood pressure is indirectly proportional to arterial compliance.
?Arterial Compliance ?
Systolic & Diastolic Blood Pressure
Arterial Compliance ? ? Systolic & Diastolic Blood Pressure
Arterial compliance is the elasticity of the artery walls.
The more compliant a vessel is, the more it is capable of expanding and absorbing the shock of systolic BP.
Arteries lose their compliance with smoking, age, and atherosclerosis.
A decrease in arterial compliance results in greater peripheral resistance.
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Requlationof BloodPressure
ShortTemmRequlation
There are baroreceptors (stretch receptors) in the carotid artery and aortic arch that monitor blood pressure. If the baroreceptors sense an increase in BP, they increase their sensory nerve impulses to the cardiac and vasomotor control centers of the brain. As a result, the brain initiates a response in an attempt to bring the blood pressure back down to normal. The opposite occurs in the case of a decrease in BP.
Short term regulation of blood pressure is controlled by the sympathetic and parasympathetic nervous systems vìa changes in heart rate, contractility, and arterial diameter.
SHORT TERM REGULATION OF HIGH & LOW BP
?BP
L BP
Baroreceptors are stretched
Baroreceptors are inhibited
? Impulses to cardiac & vasomotor control centers
Impulses to cardiac & vasomotor control centers
? Para &
JPara &?Sympatheticactivity
Sympathetic activity
Vasodilation &
? HR&
HR
Vasoconstriction
JPR&COo
? co &PR
BP
BP
Long TemRequlation
Long term control of blood pressure is controlled by the kidneys via changes in blood volume.
Juxtaglomerular cells in the kidney monitor blood pressure.
LONG TERMREGULATIONOF LOW BP
BP
Juxtaglomerular cells in kidney release renin enzyme into blood
Renin attaches to angiotensinogen
Angiotensinogen
-?
angiotensinl
? vasoconstriction
Angiotensin|?angiotensinI|
Aldosteronereleased from adrenalgland
Increased sodium reabsorption in kidney
(waterfollows)
? Blood volume
?BP
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? BP
EnvironmentalStressors/Factorsthat In uenceBlood Pressure
Exercise
Steady-Rate Rhythmic Exercise (such as jogging, cycling, swimming)
Stimulates the SNS. One effect of and ?SNS activity: vasodilation of the vessels in the exercise related tissues (working muscles, heart, brain), and vasoconstriction to the less active tissues.
What are some of the other SNS effects? How do these SNS effects affect BP?
After exercise the SNS-induced vasodilation can remain for several hours.
During the SNS stimulation caused by exercise, the baroreceptors have a higher “set-point”
allowing blood pressure to increase.
Contracting and relaxing muscles exert external pressure on the blood vessels. The result is a “muscle pump” that helps maintain blood ow back to the heart.
Due to smaller vasculature (smaller overal diameter), smaller muscles (e.g. arms compared to legs) performing at the same relative exercise intensity offer more resistance to blood ow.
Resistance Exercise (straining exercise)
The contraction of active muscles causes a mechanical compression (external pressure) on the arterial vessels in the area, making blood ow into that area more dif cult.
If the valsalva maneuver (expiration against a closed glottis) occurs, intrathoracic pressure increases, causing an increase in afterload.
How do you think the blood pressure effect differs with isometric and isotonic contractions?
Can you think of other types of exercise that could affect blood pressure?
Body Position
Orthostatic Hypotension (also known as postural hypotension)
With this condition, people experience a drop in blood pressure with changes in posture. This most
commonly occurs due to the effect of gravity on venous return and a delayed baroreceptor
response when moving from a lying to a standing position.
Gravity
Venous Return ? EDV ? ?SV ? ?Co
JBP
Inversion
How do you think hanging upside-down affects blood pressure?
Can you think of other body positions that could affect blood pressure?
Other
Smoking
Psychological stress
Temperature
Dietary salt
Aging
Obesity
Can you think of any more environmental stressors that could affect blood pressure?
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Classi cationofRestingBloodPressurefor Adults
(18 years andolder)
Classi cation
Systolic BP (mmHg)
Normal
< 120 and