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54 Cards in this Set
- Front
- Back
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Blood Flow
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rate of blood flow through vessel is directly proportional to pressure gradient and inversely proportional to vascular resistance
F = delta P/R -at rest, goes to liver, digestive tract, kidneys and muscle -during exercise, goes to muscle, skin, heart |
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Pressure Gradient
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pressure difference between beginning and end of vessel
-force exerted by blood against vessel wall depends on volume of blood contained within vessel and compliance of vessel walls |
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Resistance
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hindrance to flow caused by frictional contact of moving blood with vessel wall
R = 8nL/pi(r)^4 determined by viscosity of blood (n), vessel length (L), vessel radius (r) |
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Arteries
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-rapid-transit passageway for blood from heart to organs
-act as pressure reservoir to provide driving force for blood when heart is relaxing (elastic recoil) -thick, highly elastic walls with large radii -connective tissue contains collagen fibres and elastin fibres |
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Elastic Recoil
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-pressure from contraction of left ventricle
1. Ventricle contracts 2. Semilunar valve opens 3. Aorta and arteries expand and store pressure in elastic walls 1. Isovolumic ventricular relaxation 2. Semilunar valve shuts, preventing flow back into ventricle 3. Elastic recoil of arteries sends blood forward into rest of circulatory system |
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Systolic Pressure
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peak pressure exerted by ejected blood against vessel walls during cardiac systole
120 mmHg |
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Diastolic Pressure
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minimum pressure in arteries when blood is draining off into vessels downstream
80 mmHg |
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Sphygmomanometer
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-cuff around arm increases in pressure and beating is heard through stethoscope
-when no sound is heard, cuff pressure has exceeded blood pressure through cardiac cycle and no blood flows through vessel -cuff pressure is released, first sound heard is at peak systolic pressure -when no sound is heard, cuff pressure is below blood pressure throughout cardiac cycle and last sound is heard at minimum diastolic pressure |
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Korotkoff sounds
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sounds heard when determining BP, distinct from heart sounds associated with valve closure
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Pulse Pressure
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pressure difference between systolic and diastolic pressure
-magnitude determined by stroke volume and distensibility of arteries pulse can be felt in artery lying close to surface of skin -pressure wave is pulse when blood is pushed into aorta |
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Mean Arterial Pressure
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average pressure driving blood forward into tissues throughout cardiac cycle
MAP = diastolic pressure + 1/3 pulse pressure -affected by blood volume, cardiac output, resistance to flow, distribution of blood flow (cardiac output) = MAP / R |
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Cardiac Output
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CO = heart rate x stroke volume
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Arterioles
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-major resistance vessels
-highly muscular walls, small radii -radius can be adjusted to distribute cardiac output among systemic organs depending on body's momentary needs; also to help regulate arterial BP |
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Metarterioles
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-if precapillary sphincters are relaxed, they flow into capillary beds
-if sphincters are constricted, they flow into venous circulation |
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Vascular Tone
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smooth muscle displays partial constriction
-myogenic activity of smooth muscle and sympathetic fibres releaseing norepinephrine are responsible for vascular tone |
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Local chemical influences on arterial radius
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Local metabolic change
-O2, CO2, acid, K+, osmolarity, adenosine release (vasodilator), prostaglandin release Histamine release (vasodilation) |
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Local physical influences on arteriolar radius
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Local application of heat or cold
Myogenic response to stretch Shear stress Reactive hyperemia Autoregulation |
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Endothelial cells
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-local vasoactive mediators
-line blood vessels -secrete vasoactive substances in response to local chemical and physical changes that cause vasodilation and vasoconstriction -secrete substances that stimulate new vessel growth -exchange materials across capillaries -formation of platelet plugs and clotting -determination of capillary permeability by varying pore size |
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Nitric Oxide
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-can be triggered by hypoxia
-relaxation of arteriolar smooth muscle -dilates arterioles of penis and clitoris (erection) -against bacteria and cancer cells -interferes with platelets and blood clotting |
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Myogenic response to stretch
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-smooth muscle cells spontaneously contract, BP increases and vessel stretches, bring length back to normal
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Hyperemia
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-when blood flow decreases due to obstruction, metabolic vasodilators accumulate in ECF and arterioles dilate
-when obstruction is removed, decreased resistance increases blood flow, vasodilators wash away and arterioles constrict to return blood flow to normal Active hyperemia: increase in blood flow accompanies increase in metabolic activity Reactive hyperemia: increase in tissue blood flow following period of low perfusion |
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Extrinsic sympathetic control of arteriolar radius
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-influence of total peripheral resistance
-norepinephrine -local controls override sympathetic vasoconstriction -no parasympathetic to arterioles |
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Norepinephrine
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-tonic release of norepinephrine controls arteriole diameter
-increased norepinephrine release onto alpha receptors constricts vessel, decreased dilates |
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Medullary cardiovascular control centre
(Extrinsic control) |
-influence of epinephrine (vasodilation when bound to B2 receptors) and norepinephrine
-influence of vasopressin and angiotension II (vasoconstrictors) that maintain body's fluid balance |
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Capillaries
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-sites of exchange between blood and surrounding tissues
-maximizes surface area and minimizes diffusion distance -thin-walled, small radius, extensively branch -blood flow is slow for adequate exchange time (velocity of flow inversely proportional to total cross-sectional area of all vessels) -surrounded by precapillary sphincters that control blood flow into capillary |
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Pericytes
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decrease capillary permeability
-can influence capillary growth and become endothelial / smooth muscle cells |
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Capillary Pores
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-narrow, water-filled gaps lie at junctions between cells that permit passage of water-soluble substances
-lipid soluble substances readily pass through endothelial cells by dissolving in lipid bilayer barrier |
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Continuous Capillaries
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endothelial cells joined by leaky junctions (ex, blood-brain barrier)
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Fenestrated Capillaries
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large pores that allow high volumes of liquid to pass rapidly through (ex, kidney, intestines)
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Paracellular Pathway
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exchange between plasma and interstitial fluid takes place by movement between endothelial cells
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Bulk Flow
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mass movement of fluid by hydrostatic / osmotic pressure gradients
-regulates distribution of ECF between plasma and interstitial fluid -keeps plasma volume constant to ensure circulatory system functions effectively -influenced by capillary BP, plasma-colloid osmotic pressure, interstitial fluid hydrostatic pressure, interstitial fluid-colloid osmotic pressure |
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Colloid Osmotic Pressure (pi)
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created by proteins in plasma and gradient favours water movement by osmosis from interstitial fluid into plasma
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Hydrostatic Pressure (P capillary)
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pushes fluid out through capillary pores and decreases along length of capillary
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Filtration
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P out = P capillary - P IF
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Absorption
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pi in = pi IF - pi capillary
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Net Pressure
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P out + pi in
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Lymphatic System
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one-way movement of ISF from tissues into circulation
-returns excess filtered fluid that leaks out of capillaries and filtered protein -defends against disease (lymph nodes have phagocytes which destroy bacteria filtered from ISF) -transport of absorbed fat -tonsils, thymus and spleen are lymphoid organs |
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Initial Lymphatics
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small, blind-ended terminal lymph vessels that permeate almost every tissue of body
-fluid pressure on outside of vessel pushes endothelial cell's free edge inward, permitting entrance of ISF that is now lymph -fluid pressure on inside of vessel forces overlapping edges together so that lymph cannot escape |
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Lymph
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interstitial fluid that enters lymphatic vessel
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Lymph Vessels
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formed from convergence of initial lymphatics
-eventually empty into venous system near where blood enters right atrium -one way semilunarvalves spaced at intervals direct flow of lymph toward venous outlet in chest -flow aided by contraction |
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Edema
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caused by inadequate drainage of lymph and filtration exceeding absorption
-disruption between filtration and absorption can be caused by increase in hydrostatic pressure, decrease in plasma protein concentration, or increase in interstitial proteins |
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Lymph Nodes
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nodules of tissue with fibrous outer capsule and immunologically active cells (lymphocytes and macrophages)
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Venous System
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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 |
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Veins
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large radius offers little resistance to blood flow
-blood reservoir thin walled |
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Venous Return
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facilitated by:
-driving pressure from cardiac contraction -sympathetically induced venous vasoconstriction -skeletal muscle pump -effect of venous valves -respiratory activity -effect of cardiac suction |
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Blood Pressure
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determined by cardiac output, total peripheral resistance, and mean arterial pressure
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Baroreceptor Reflex
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Short-term control adjustments which occur within seconds made by alterations in cardiac output and total peripheral resistance
-mediated by ANS influences on heart, veins and arterioles Long-term control adjustments require minutes-days, involve adjusting total blood volume by restoring normal salt and water balance through mechanisms that regulate urine output and thirst -carotid and aortic baroreceptors act on heart and medullary control centre which innervate parasympathetic and sympathetic neurons |
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Osmoreceptors
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left atrial receptors and hypothalamic osmoreceptors affect long-term regulation of BP by controlling plasma volume
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Chemoreceptors
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carotid and aortic arteries are sensitive to low O2 or high acid levels in blood; reflexively increase respiratory activity
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Hypertension
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blood pressure above 140/90 mm Hg
-heart failure, stroke, heart attack, haemorrhage, renal failure or damage -can be treated with Ca2+ channel blockers, diuretics, beta-blocking drugs, ACE inhibitors, angiotensin receptor blockers |
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Primary Hypertension
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category for BP elevated by variety of unknown causes rather than by single disease
-potential causes include defects in salt management by kidneys, excessive salt intake, diets low in K+ and Ca2+, plasma membrane abnormalities, abnormalities in NO, endothelin, locally acting vasoactive chemicals, angiotensinogen gene, excess vasopressin |
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Secondary Hypertension
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~10% of hypertension cases
Renal hypertension - buildup of fat inhibiting blood flow to kidneys Endocrine hypertension - tumour invades adrenal gland & hormones are sent into blood stream that act on heart and raise BP Neurogenic hypertension - nerve derived |
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Hypotension
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blood pressure is below 100/60 mm Hg
-when too little blood fills vessels or heart is too weak to drive blood Orthostatic (postural) hypotension when person moves from horizontal to vertical position |
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Circulatory Shock
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when BP falls so low that adequate blood flow to tissues can no longer be maintained
1. Hypovolemic (low volume) -hemorrhage, vomiting, diarrhea 2. Cardiogenic (heart produced) -weakened heart 3. Vasogenic (vessel produced) -septic shock or anaphylactic shock 4. Neurogenic (nerve produced) -decreased sympathetic nerve activity |
