unit 5 blood pressure
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Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Unit 5
The Blood Vessels and Blood Pressure
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Blood Flow
Blood is constantly reconditioned so composition
remains relatively constant
Reconditioning organs receive more blood than
needed for metabolic needs
Digestive organs, kidneys, skin
Adjust extra blood to achieve homeostasis
Blood flow to other organs can be adjusted
according to metabolic needs
Brain can least tolerate disrupted supply
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Distribution of Cardiac
Output at Rest
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Blood Flow
Flow rate through a vessel
volume of blood passing through per unit of time to the pressure gradient and inversely
proportional to vascular resistance
F =P
R
F = flow rate of blood through a vessel
P = pressure gradientR = resistance of blood vessels
Blood viscosity, vessel length, vessel radium
Major determinant of resistance to flow is vessels radius
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Blood Flow
Pressure gradient is pressure difference between beginningand end of a vessel
Blood flows from area of higher pressure to area of lowerpressure
Resistance is measure of opposition of blood flow through avessel
Depends on three things Blood viscosity, vessel length, vessel radium
Major determinant of resistance to flow is vessels radius
Slight change in radius produces significant change inblood flow
R is proportional to 1
r4
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Relationship of
Resistance and Flow
to Vessel Radius
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Vascular Tree
Closed system of vessels
Consists of
Arteries Carry blood away from heart to tissues
Arterioles Smaller branches of arteries
Capillaries Smaller branches of arterioles
Smallest of vessels across which all exchanges are madewith surrounding cells
Venules Formed when capillaries rejoin
Return blood to heart Veins
Formed when venules merge
Return blood to heart
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Basic Organization of
the Cardiovascular
System
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Arteries
Specialized to
Serve as rapid-transit passageways for bloodfrom heart to organs
Due to large radius, arteries offer little resistance to
blood flow
Act as pressure reservoir to provide driving forcefor blood when heart is relaxing
Arterial connective tissue contains
Collagen fibers
Provide tensile strength Elastin fibers
Provide elasticity to arterial walls
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Arteries as a Pressure Reservoir
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Blood Pressure
Force exerted by blood against a vessel wall
Depends on Volume of blood contained within vessel
Compliance of vessel walls
Systolic pressure
Peak pressure exerted by ejected blood againstvessel walls during cardiac systole
Averages 120 mm Hg
Diastolic pressure
Minimum pressure in arteries when blood isdraining off into vessels downstream
Averages 80 mm Hg
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Blood Pressure
Can be measured indirectly using
sphygmomanometer Korotkoff sounds
Sounds heard when determining blood pressure
Sounds are distinct from heart sounds associated
with valve closure
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Blood
Pressure
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Pulse Pressure
Pressure difference between systolic and diastolic
pressure
Example
If blood pressure is 120/80, pulse pressure is 40
mm Hg (120mm Hg80mm Hg)
Pulse that can be felt in artery lying close to surface
of skin is due to pulse pressure
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Mean Arterial Pressure
Average pressure driving blood forward into tissues
throughout cardiac cycle Formula for approximating mean arterial pressure
Mean arterial pressure = diastolic pressure +
pulse pressure
At 120/80, mean arterial pressure = 80 mm Hg +
(40 mm Hg) = 93 mm Hg
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Arterioles
Major resistance vessels
Radius supplying individual organs can be adjusted
independently to
Distribute cardiac output among systemic organs,
depending on bodys momentary needs
Help regulate arterial blood pressure
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Arterioles
Mechanisms involved in adjusting arteriolar
resistance Vasoconstriction
Refers to narrowing of a vessel
Vasodilation
Refers to enlargement in circumference and radius of
vessel
Results from relaxation of smooth muscle layer
Leads to decreased resistance and increased flow
through that vessel
ONLY blood supply to the brain remains constant
Peripheral supply vary according to metabolic NEEDS
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Magnitude and Distribution
Of the Cardiac Output at Rest
and During Moderate Exercise
Arteriole Smooth muscles
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Arteriole Smooth muscles
Precapillary
sphincterMetarteriole
Capillary
VenuleFig. 10-19, p. 357
Ti t b li ti it
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Tissue metabolic activity
O2, CO2and other metabolites
Relaxation of
precapillary sphinctersArteriolar vasodilation
Number of opencapillaries
Capillary blood flow
Capillary surface area
available for exchange
Diffusion distance
from cell to open
capillary
Concentration gradient for
these materials between
blood and tissue cells
Exchange between blood and tissueto support increased metabolicactivity
Delivery of O2,more rapid removal ofCO2and othermetabolites
Fig. 10-20, p. 358
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Lymphatic System
Functions
Return of excess filtered fluid Defense against disease
Lymph nodes have phagocytes which destroy bacteria
filtered from interstitial fluid
Transport of absorbed fat
Return of filtered protein
In the case of protein deficiency Osmotic pressure is low causing fluid retention
EDEMA
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Lymphatic
System
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Edema
Swelling of tissues Occurs when too much interstitial fluid accumulates
Causes of edema
Reduced concentration of plasma proteins Increased permeability of capillary wall
Increased venous pressure
Blockage of lymph vessels
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Veins
Venous system transports blood back to heart
Capillaries drain into venules Venules converge to form small veins that exit
organs
Smaller veins merge to form larger vessels
Veins
Large radius offers little resistance to blood flow
Also serve as blood reservoir
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Veins
Factors which enhance venous return
Driving pressure from cardiac contraction Sympathetically induced venous vasoconstriction
Skeletal muscle activity
Effect of venous valves
Respiratory activity
Effect of cardiac suction
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Fig. 10-32b, p. 368
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Chapter 10 The Blood Vessels and Blood PressureHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Mean Arterial Pressure
Blood pressure that is monitored and regulated inthe body
Primary determinants
Cardiac output
Total peripheral resistance
Mean arterial pressure = cardiac output x total
peripheral resistance
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Chapter 10 The Blood Vessels and Blood Pressure
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Determinants of Mean Arterial Pressure
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Chapter 10 The Blood Vessels and Blood Pressure
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Mean Arterial Pressure
Constantly monitored by baroreceptors (pressure
sensors) within circulatory system
Short-term control adjustments
Occur within seconds
Adjustments made by alterations in cardiac output and
total peripheral resistance
Mediated by means of autonomic nervous system
influences on heart, veins, and arterioles
M A i l P
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Mean Arterial Pressure
Long-term control adjustments
Require minutes to days
Involve adjusting total blood volume by restoring
normal salt and water balance through mechanisms
that regulate urine output and thirst
Chapter 10 The Blood Vessels and Blood Pressure
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Bl d P Ab liti
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Chapter 10 The Blood Vessels and Blood Pressure
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Blood Pressure Abnormalities
Hypertension Blood pressure above 140/90 mm Hg
Two broad classes
Primary hypertension
Secondary hypertension
Hypotension
Blood pressure below 100/60 mm Hg
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Chapter 10 The Blood Vessels and Blood Pressure
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Hypertension
Most common of blood pressure abnormalities
Primary hypertension
Affected by variety of unknown causes rather than by a
single disease entity
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Potential causes
Defects in salt management by the kidneys
Excessive salt intake
Diets low in K+and Ca2+
Plasma membrane abnormalities
such as defective Na+-K+ pumps
Variation in gene that encodes for angiotensinogen
Abnormalities in vasoactive chemicals
NO, endothelin, or other locally acting
Excess vasopressin
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Chapter 10 The Blood Vessels and Blood Pressure
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Hypertension
Secondary hypertension
Accounts for about 10% of hypertension cases
Occurs secondary to another known primary
problem
Examples of secondary hypertension
Renal hypertension
Endocrine hypertension
Neurogenic hypertension
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Chapter 10 The Blood Vessels and Blood Pressure
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Hypertension
Complication of hypertension
Congestive heart failure Stroke
Heart attack
Spontaneous hemorrhage
Renal failure
Retinal damage
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Chapter 10 The Blood Vessels and Blood Pressure
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Hypotension
Low blood pressure
Occurs when There is too little blood to fill the vessels
Heart is too weak to drive the blood
Orthostatic (postural) hypotension
Transient hypotensive condition
resulting from insufficient compensatory responses to
gravitational shifts in blood when
person moves from horizontal to vertical position
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Chapter 10 The Blood Vessels and Blood Pressure
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Hypotension
Circulatory shock
blood pressure falls so low that adequate bloodflow to the tissues can no longer be maintained
Four main types
Hypovolemic (low volume) shock
Cardiogenic (heart produced) shock
Vasogenic (vessel produced) shock
Neurogenic (nerve produced) shock
S t Sh k
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Symptoms Shock
Hypotension
Systolic pressure below 90mmHg Pale, cool & moist skin
Confusion, disorientation
Rise in heart rate, with peak pulse
Cessation of urination
Lack of blood flow to kidneys
Drop in blood pH
acidosis
Chapter 10 The Blood Vessels and Blood Pressure
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Circulatory shock
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Circulatory shock
( mean arterial pressure)
Cardiac output Cardiac output Total peripheral resistance
Loss of blood volume Widespreadvasodilation
Loss of fluidsderived from
plasma
Vasodilator
substancesreleased from
bacteria
Histamine
releasedin severeallergicreaction
Loss ofvascular tone
Severe
hemorrhage
Excessivevomiting,diarrhea,urinary losses,
etc.
Weakened
heart
Septic
shockAnaphylactic
shock
Sympathetic
nerve activity
Hypovolemic
shock
Cardiogenic
shock
Cardiogenic
shock
Neurogenic
shock