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74 Cards in this Set
- Front
- Back
Что означает The Fick principle ?
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The Fick principle can be utilized to calculate the blood flow through an organ.
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Как вычисляется поток,проходящий через орган?
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uptake
Q Flow= A-V Required data are: oxygen consumption of the organ A - V oxygen content (concentration) difference across the organ (not P02) |
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Pulmonary venous (systemic arterial) oxygen content %vol
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Pulmonary venous (systemic arterial) oxygen content = 20 vol%
= 20 volumes 01 per 100 volumes blood = 20 mL 02 per 100 ml. blood = 0.2 mL 02 per mL blood |
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Cardiac index =
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cardiac output
Cardiac index = body surface area |
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Flow is regulated by
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Flow is regulated by constricting and dilating the smooth muscle surrounding the arterioles
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2 вида OF BLOOD FLOW REGULATION
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1- Intrinsic Regulation (Autoregulation)
2- Extrinsic Regulation |
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Intrinsic Regulation (Autoregulation) two main theories
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-Metabolic hypothesis
-Myogenic hypothesis |
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Metabolic hypothesis
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Metabolic hypothesis
• Tissue produces a vasodilatory metabolite that regulates flow, e.g.)adenosine in the coronary circulation. A dilation of the arterioles is produced when the concentration of these metabolites increases in the tissue. The arterioles constrict if the tissue concentration decreases. |
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Myogenic hypothesis
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Myogenic hypothesis
Increased perfusing pressure causes stretch of the arteriolar wall and the surrounding smooth muscle. Because an inherent property of the smooth muscle is to contract when stretched, the arteriole radius decreases, and flow does not increase significantly. |
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autoregulatory range.
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the autoregulatory range is the range of pressure over which flow remains nearly constant
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Major Characteristics of an Autoregulating Tissue
Blood flow in most cases is proportional |
Blood flow in most cases is proportional to tissue metabolism.
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Major Characteristics of an Autoregulating Tissue
Blood flow is independent of |
Blood flow is independent of nervous reflexes (e.g., carotid sinus).
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Major Characteristics of an Autoregulating Tissue
Autoregulating tissues include |
• Cerebral circulation
• Coronary circulation -Skeletal muscle vasculature during exercise Control of renal blood flow is also commonly referred to as autoregulation even though it is partially controlled by neural and hormonal influences. |
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Extrinsic Regulation
These tissues are controlled by |
These tissues are controlled by nervous and humoral factors
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Extrinsic Regulation
sympathetic adrenergic activity,i.e., norepinephrine acting on |
sympathetic adrenergic activity,i.e., norepinephrine
acting on альфа'. receptors, causing constriction. |
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Extrinsic Regulation
epinephrine acting on |
epinephrine acting on B receptors can cause dilation.
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Extrinsic Regulationat
Что будет при high levels, circulating epinephrine |
at high levels, circulating epinephrine has a vasoconstrictor
effect through a-adrenergic receptors; so the response to epinephrine is dose-dependent |
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Extrinsic Regulation
Circulations with mainly extrinsic regulation (those most affected by nervous reflexes |
-Cutaneous circulation
- Resting skeletal muscle |
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Control of Resting muscle
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Flow is controlled mainly by increasing or decreasing sympathetic a-adrenergic activity. But ~2
receptors can contribute to the regulation of blood flow |
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Control of Exercising Muscle
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The increase in flow is mainly via vasodilatory metabolites, but this cannot occur without a
significant contribution via an increase in CO. • В2 activation via circulating epinephrine can contribute to the increase in flow. • Sympathetic adrenergic nerves have no effect on flow in exercising muscle. (a receptors become less responsive to norepinephrine.) |
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Coronary Circulation
Characteristics of left coronary flow (flow to the left ventricular myocardium) |
Left ventricular contraction causes severe mechanical compression of intramyocardial vessels.
Therefore: • Verylittle if any blood flow occurs during systole. • Most of the blood flow is during diastole. |
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Coronary Circulation
Characteristics of right coronary blood flow (flow to the right ventricular myocardium): |
Right ventricular contraction causes modest mechanical compression of intramyocardial vessels.
Therefore: • Significant flow can occur during systole. The greatest flow under normal conditions is still during diastole. |
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Coronary Circulation
Oxygenation |
In the coronary circulation, the tissues extract almost all the oxygen they can from the blood,
even under "basal" conditions. Therefore: -The venous P02 is extremely low. -Because the extraction of oxygen is almost maximal under resting conditions, increased oxygen delivery to the tissue can beaccomplished only by an increased blood £low. -In the coronary circulation, flow must match metabolism. -Coronary blood flow is most closely related to cardiac tissue oxygen consumption |
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Coronary blood flow (mLImin) is determined by
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- the pumping action, or stroke work times
- heart rate,of the heart. |
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Increased pumping action means ( coronary flow)
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Increased pumping action means increased metabolism, which means increased production of
vasodilatory metabolites, which means increased coronary flow. |
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Increased pump function occurs with
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-Exercise: increased volume work (more volume pumped at the same pressure)
-Increased arterial pressure (hypertension): increased pressure work (a similar volume pumped against a greater pressure) -increased systolic ventricular pressure development will require a greater increase of coronary blood flow than a similar increase in stroke volume only. |
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Cerebral Circulation
от чего зависит поток в |
Flow is proportional to arterial PC02.
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Under normal conditions the main factor regulating cerebral blood flow is
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arterial PC02
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Hypoventilation increases arterial peo
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thus it increases cerebral blood flow.
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• Hyperventilation decreases arterial PCOl ,
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thus it decreases cerebral blood flow.
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Что будет с цебральным поток при снижении in arterial P02?
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a (large) decrease in arterial P02 will increase cerebral blood flow. Under
these conditions, it is the low arterial P02 that is determining flow. |
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Baroreceptor влияют ли на церебральный поток?
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Baroreceptor reflexes do not affect flow.
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Сutaneous Circulation controlled via
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controlled via sympathetic adrenergic nerves
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Сutaneous Circulation
Largc venous plexus innervated by |
sympathetics
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Сutaneous Circulation
A-V shunts innervated by |
A-V shunts innervated by sympathetics
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Sympathetic stimulation to the skin will cause
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-Constriction of arterioles and a decrease in blood flow
-Constriction of the venous plexus and a decrease in blood volume in the skin -Increase in velocity of blood (decreased cross-sectional area) |
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Sympathetic activity to the skin Для чего нужна?
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Sympathetic activity to the skin varies mainly with the body's need for heat exchange
with the environment. Increased skin temperature directly causes vasodilation, which increases heat loss. |
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Temperature regulation
Sensor represents the temperature-sensitive neurons in the... |
anterior hypothalamus
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Temperature regulation
Circadian rhythm: |
low point, morning; high point, evening
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When a fever is developing, body temperature is rising.. what .mechanisms include?
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heat-conserving and heat-generating mechanisms include
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heat-conserving and heat-generating mechanisms include
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-Shivering
- Cutaneous vasoconstriction |
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body ternperature is decreasing. what mechanisms include:
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Heat-dissipating
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Heat-dissipating mechanisms include:
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-Sweating (sympathetic cholinergics)
•-Cutaneous vasodilation |
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Renal and Splanchnic Circulation
какая регуляция работает при normal conditions? |
autoregulation.
A small change in blood pressure will invoke an autoregulatory response to maintain renal blood flow. |
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Situations in which there is a large increase in sympathetic activity (e.g., hypotension)
usually cause |
vasoconstriction and a decrease in blood flow.
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Renal and Splanchnic Circulation
ПОчему venous P02 is high ? |
Renal circulation is greatly overperfused in terms of nutrient requirements, thus the
venous P02 is high. |
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Pulmonary Circuit
Low-pressure circuit, arterial= venous= |
arterial =15 mm Hg,
venous =5 mm Hg |
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Pulmonary Circuit
Characteristics |
-Low-resistance circuit
-Very compliant circuit; both arteries and veins are compliant vessels -Hypoxic vasoconstriction (low alveolar P02 causes local vasoconstriction) -Passive circuit; total flow not regulated -Blood volume proportional to blood flow |
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Pulmonary Circuit
Because of the passive nature of the pulmonary circuit, pulmonary pressures are proportional to |
the output of the right ventricle.
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Pulmonary Circuit
Because of the very compliant nature of the pulmonary circuit, large changes in the output of the right ventricle are associated with |
only small changes in pulmonary
pressures. |
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Pulmonary response to exercise
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• A large increase in cardiac output means increased volume pumped into the circuit.
This will produce a rise in pulmonary pressures. -Because of the passive, compliant nature of the circuit, the response to a rise in pressure is vessel dilation. • This response leads to apical blood vessel recruitment. The overall response is a large decrease in resistance. • Consequently, during exercise, there is only a slight increase in pulmonary pressures. If the pulmonary circuit was not a passive, very compliant circuit, increasing the output of the right ventricle would cause pulmonary hypertension. |
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Pulmonary response to hemorrhage
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-A large decrease in CO means decreased volume pumped into the circuit. This will
produce a decrease in pulmonary pressures. -Because of the passive, compliant nature of the circuit, the response to a decrease in pressure is vessel constriction. This results in a large increase in resistance. • Consequently, during hemorrhage, there is often only a slight decrease in pulmonary pressures. • Vessel constriction also means less blood is stored in this circuit. |
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Fetal Circulation
какой % фетального СО goes to the placenta. |
55%
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Fetal Circulation
The umbilical vein and ductus venosus have highest O/OHb02 saturation |
80%
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Fetal Circulation
inferior vena caval blood Hb02) |
26%
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Fetal Circulation
saturation of blood entering the right atrium is |
67%.
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Fetal Circulation
Superior vena caval blood |
(40% Hb02)
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Fetal Circulation
% of the right ventricular output flows into the ductus arteriosus and % to the lungs |
90% into the ductus arteriosus
only 10% to the lungs |
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Fetal Circulation
saturation of aortic blood is |
60%.
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Fetal Circulation (описать)
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The umbilical vein and ductus venosus--mixed with inferior vena caval blood--entering the right atrium--blood is directed through the foramen ovale to the left atrium, left ventricle, and
ascending aorta to perfuse the head and the forelimbs.---Superior vena caval blood is directed through the tricuspid valve into the right ventricle and pulmonary artery and shunted by the ductus arteriosus to the descending aorta-- |
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Arterial-venous difference is positive if
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substance extracted by the organ, e.g., 02' substrates like glucose, lactate in
heart muscle |
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Arterial-venous difference is negative if
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if substance produced by the organ, e.g., CO2, glucose in liver, lactate in
skeletal musele and ischemic heart muscle |
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Skeletal Muscle
• Resting muscle venous P02 = |
Skeletal Muscle
• Resting muscle venous P02 - 45 mm Hg |
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Skeletal Muscle
Exercising muscle venous P02 = |
Exercising muscle venous P02 - 20 mm Hg
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BASIC ALTERATIONS DURING EXERCISE
Pulmonary Circuit |
Blood flow (CO): large increase
Pulmonary arterial pressure: slight increase • Pulmonary vascular resistance: large decrease Pulmonary blood volume: increase -Number of perfused capillaries: increase • Capillary surface area: increase, which means increased rate of gas exchange |
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BASIC ALTERATIONS DURING EXERCISE
Systemic Circuit Arterial system |
P02: no significant change, hemoglobin still fully saturated
PC02: no significant change, increase in ventilation proportional to increase in metabolism pH: no change or a decrease due mainly to the production of lactic acid • Mean arterial pressure: slight increase • Body temperature: slight increase -• Vascular resistance (TPR): large decrease, dilation of skeletal muscle beds -Blood flow: large increase |
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BASIC ALTERATIONS DURING EXERCISE
Systemic Circuit Venous system |
Venous system
• P02: decrease • PC02: increase |
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BASIC ALTERATIONS DURING EXERCISE
Regional Circulations Exercising skeletal muscle |
Blood flow increases.
• Vascular resistance decreases. • Capillary pressure increases. • Capillary filtration increases. • Lymph flow increases. • Venous P02 decreases and can reach extremely low levels. • Extraction of oxygen increases. |
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BASIC ALTERATIONS DURING EXERCISE
Regional Circulations Cutaneous blood flow |
Cutaneous blood flow
Initial decrease, then an increase to dissipate heat |
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BASIC ALTERATIONS DURING EXERCISE
Regional Circulations Coronary blood flow |
Coronary blood flow
Increase due to increase in volume work of the heart |
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BASIC ALTERATIONS DURING EXERCISE
Regional Circulations Cerebral blood flow |
Cerebral blood flow
No significant change (arterial CO2 remains unchanged) |
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BASIC ALTERATIONS DURING EXERCISE
Regional Circulations Renal and GI blood flow |
Renal and GI blood flow
Any change would be a decrease. This is more likely in the splanchnic circuit |
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BASIC ALTERATIONS DURING EXERCISE
Regional Circulations Heart |
Heart
Exerciseproduces an increase in the volume work of the heart that is mainly carried out by an increase in heart rate rather than an increase in stroke volume. In light and moderate exercise, there may be no increase in preload. Preload does increase in heavy exercise. |
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BASIC ALTERATIONS DURING EXERCISE
Regional Circulations Physical conditioning |
Physical conditioning
• Regular exercise will raise maximal oxygen consumption (V02max) by: Increasing the ability to deliver oxygen to the active muscles. It does this by increasing the CO. The resting conditioned heart has a lower heart rate but a greater stroke volume (SV) than does the resting unconditioned heart. During exercise, there is an increase in stroke volume, as much as35% above resting levels. However, the maximal heart rate remains similar to that of untrained individuals. Regular exercise also increases the ability of muscles to utilize oxygen. There are: An increased number of arterioles, which decrease minimal resistance during exercise. An increased capillary density, which increases the surface area and decreases diffusion distance. An increased number of oxidative enzymes in the mitochondria. |