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73 Cards in this Set
- Front
- Back
the FORCE resisting the flow of blood through a vessel (usually from friction)
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Resistance to Flow (Peripheral Resistance) -
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a measure of the "thickness" or "stickiness" of a fluid flowing through a pipe
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viscosity -
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viscosity -
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water < V blood < V toothpaste
water flows easier than blood |
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the longer the vessel, the greater the drop in pressure due to friction
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tube length -
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smaller diameter = greater friction
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tube diameter -
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Relation Between Blood Flow, Pressure, Resistance
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Blood Flow (F) =
difference in blood pressure ( P) peripheral resistance (R) |
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Relation Between Blood Flow, Pressure, Resistance
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increased P -> increased flow
decreased P -> decreased flow increased R (vasoconstriction) -> DECREASED flow decreased R (vasodilation) -> INCREASED flow |
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Blood Pressure Near the Heart
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Systemic Blood Pressure
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HEART produces blood pressure by
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pumping the blood
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Blood pressure ? with distance from Heart
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decreases
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pressure in aorta (& major arteries) in middle of ventricular contraction (120 mm Hg in healthy adult)
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systolic arterial blood pressure -
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pressure in aorta (& major arteries) during ventricular diastole, when semilunar valves are closed (80 mm Hg in healthy adult)
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diastolic arterial blood pressure -
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the "average" blood pressure produced by the heart (93 mm Hg in healthy adult)
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mean arterial pressure (MAP) -
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mean arterial pressure =
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diastolic pressure + 1/3 pulse pressure
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pulse pressure =
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systolic pressure - diastolic pressure
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blood pressure decreases throughout system
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L ventricle -->120 mm Hg
arteries -->120 - 60 mm Hg arterioles -->60 - 40 mm Hg capillaries -->40 - 20 mm Hg venous -->20 - 10 mm Hg R atrium -->10 - 0 mm Hg |
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venous blood pressure is so low, other factors contribute to venous blood flow
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venous return -
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venous return
breathing action of thorax "squeezes" blood back toward the heart |
respiratory pump -
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venous return
contraction/relaxation of skeletal muscles "milk" blood up veins to heart |
muscular pump -
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endothelium derived factors
strong vasoconstrictor |
endothelin -
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Cardiac Output =
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stroke volume X heart rate
CO = SV (ml/beat) x HR (beats/min) CO = 70 ml/beat x 60 beats/min = 4200 ml/min |
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Cardiac Output
increased cardiac output -> |
increased blood pressure
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Cardiac Output
increased stroke volume -> |
increased blood pressure
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Cardiac Output
increased heart rate -> |
increased blood pressure
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Peripheral Resistance
arteriole constriction ---> |
increased blood pressure
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Peripheral Resistance
resistance inversely proportional to the "fourth power" of the radius change |
for every radius change, resistance is increased by a factor of 4
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Regulation of Blood Pressure
Nervous System Control |
1. control of arteriole diameter
2. directs blood flow to proper organs and tissues that need it 3. REFLEX PATHWAY: |
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REFLEX PATHWAY:
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baroreceptors/chemoreceptors/brain -->
afferent nerve fibers --> medulla (vasomotor center) --> vasomotor (efferent) nerve fibers --> smooth muscle of arterioles |
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Regulation of Blood Pressure
Vasomotor Fibers to Smooth Muscle of Arterioles |
sympathetic fibers that release norepinephrine (NE); cause vasoconstriction of arterioles
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Regulation of Blood Pressure
Vasomotor Center of the Medulla |
1. sympathetic neuron cell bodies in the medulla
2. receive input from baroreceptors, chemoreceptors, and brain 3. vasomotor tone - general constricted state of arterioles set by vasomotor center |
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Regulation of Blood Pressure
Baroreceptors |
1. blood pressure receptors large arteries (carotid sinuses, aortic arch, neck/thorax arteries)
2. send blood pressure information to vasomotor center of medulla |
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Regulation of Blood Pressure
Baroreceptors blood pressure receptors large arteries: |
carotid sinuses, aortic arch, neck/thorax arteries
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Regulation of Blood Pressure
Baroreceptors send blood pressure information to vasomotor center of medulla (increased pressure) |
increased pressure -->
inhibits vasomotor center --> vasodilation |
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Regulation of Blood Pressure
Baroreceptors send blood pressure information to vasomotor center of medulla (decreased pressure) |
decreased pressure -->
stimulates vasomotor center -> vasoconstriction |
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Regulation of Blood Pressure
Chemoreceptors |
1. located in aortic arch and carotid arteries
carotid and aortic bodies 2. monitor OXYGEN and pH levels of the blood low OXYGEN or low pH -------> increase blood pressure, return blood to lungs quickly |
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Higher Brain Centers Control on BP
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hypothalamus & cortex also effect vasomotor area
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Chemical Controls of Blood Pressure
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1. hormones of adrenal medulla -
2. atrial natriuretic factor (ANF) - 3. antidiuretic hormone (ADH) - 4. endothelium derived factors 5. alcohol - |
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"fight-or-flight" response to fear; release of norepinephrine and epinephrine from adrenal medulla; causes vasoconstriction and increased BP
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hormones of adrenal medulla -
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secreted by the atria of the heart, promotes general decline in blood pressure kidney releasing more Na+ and water, reducing fluid volume
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atrial natriuretic factor (ANF) -
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endothelium derived factors
endothelium derived relaxing factor |
vasodilation -
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Chemical Controls of Blood Pressure
causes vasodilation |
alcohol -
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released by the hypothalamus, causes increase in blood pressure by getting the kidneys to conserve water in the body; e.g. during hypotensive situations
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antidiuretic hormone (ADH) -
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Renal (Kidney) Regulation of Blood Pressure
fluid loss through urine |
direct regulation -
a. low pressure/volume --> conserve water b. high pressure/volume --> release more water |
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Renal (Kidney) Regulation of Blood Pressure
renin-angiotensin mechanism |
low blood pressure -->
release of renin --> formation of angiotensin II--> vasoconstriction release of aldosterone --> Na+/water reabsorption (by kidney) |
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blood pressure, pulse, respiratory rate, and body temperature
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vital signs -
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the actual VOLUME of blood moving through a particular site (vessel or organ) over a certain TIME period (liter/hour, ml/min)
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Blood Flow -
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the FORCE exerted on the wall of a blood vessel by the blood contained within (millimeters of Mercury; mm Hg)
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Blood Pressure -
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blood pressure =
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the systemic arterial pressure of large vessels of the body (mm Hg)
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auscultory method of blood pressure measurement
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1. sphygmomanometer wrapped around upper arm
2. inflate above systolic pressure of brachial a. 3. pressure released, first sounds - systolic pr. 4. disappearance of sounds - diastolic pr. |
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below normal blood pressure, < 100/60
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Hypotension
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Hypotension
factors - |
age, physical conditioning, illness
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generally in elderly, drop in blood pressure during postural changes
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orthostatic hypotension -
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ongoing low blood pressure
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chronic hypotension -
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chronic hypotension -
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1. low blood protein levels (nutrition)
2. Addisons disease (adrenal cortex malfunction) 3. hypothyroidism 4. also sign of various types of cancer |
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above normal blood pressure at rest, > 140/90
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Hypertension
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Hypertension
factors - |
weight, exercise, emotions, stress
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ongoing high blood pressure
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chronic hypertension -
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chronic hypertension -
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1. prevalent in obese and elderly
2. leads to heart disease, renal failure, stroke 3. also leads to more arteriosclerosis 4. primary hypertension - unidentified source |
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primary hypertension - unidentified source
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1. high Na+, cholesterol, fat levels
2. clear genetic component (in families) 3. diuretics - promote water removal 4. NE blockers - slow vasoconstriction |
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secondary hypertension - identifiable disorder
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i. kidney disorders
ii. endocrine (hormone) disorders iii. arteriosclerosis |
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Blood Flow in the Body
General Features |
1. delivery of oxygen and removal of carbon dioxide
2. gas exchange in the lungs 3. absorption and delivery of nutrients from GI tract 4. processing/waste removal in the kidneys |
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normal blood flow at rest
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abdominal organs 24%
skeletal muscle 20% kidneys 20% BRAIN 13% heart 4% other 15% |
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Velocity of Blood Flow
velocity directly related to: |
TOTAL cross-sectional area of the vessel(s)
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Velocity of Blood Flow
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aorta 40-50 cm/s (FASTEST)
arteries 20-40 cm/s arterioles 1-20 cm/s capillaries 0.1-1 cm/s (SLOWEST) |
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Local Regulation of Blood Flow
regulation of blood flow by altering arteriole diameter |
autoregulation -
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autoregulation - regulation of blood flow by altering arteriole diameter
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1. oxygen and carbon dioxide levels
2. prostaglandins, histamines, kinins 3. needy areas --> more blood flow |
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change in flow through arteriole in response to stretch of smooth muscle
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myogenic response -
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increase in blood flow to area where an occlusion has occurred
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reactive hyperemia -
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results from prolonged lack of oxygen/nutrients to an area (eg. heart)
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increased vasculature -
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Blood Flow to Skeletal Muscles
increased blood flow to muscles during heavy activity |
active (exercise) hyperemia -
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active (exercise) hyperemia - increased blood flow to muscles during heavy activity
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1. decreased oxygen and increased lactic acid
2. visceral organ blood flow is decreased |
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Blood Flow to The Brain
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1. MUST maintain constant blood flow (750 ml/min)
2. sensitive to low pH and high carbon dioxide 3. blood pressure tightly regulated in the brain a. fainting -> below 60 mm Hg b. edema (brain swelling) -> above 180 mm Hg |
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Blood Flow to The Skin
intimately involved in temperature regulation |
increased body temperature ->
hypothalamic inhibition of vasomotor area -> vasodilation of vessels in skin -> increased blood flow -> sweating -> (bradykinin -> more vasodilation) |