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Questions and Answers
Increased venous return decreases stroke volume.
Increased venous return decreases stroke volume.
False
Increased sympathetic stimulation of the heart decreases stroke volume.
Increased sympathetic stimulation of the heart decreases stroke volume.
False
Arteries carry blood toward the heart.
Arteries carry blood toward the heart.
False
The tunica media of blood vessels is composed mostly of endothelial cells.
The tunica media of blood vessels is composed mostly of endothelial cells.
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Capillaries are the primary site for exchange of substances between blood and tissues.
Capillaries are the primary site for exchange of substances between blood and tissues.
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Arterioles have precapillary sphincters that control blood flow into venues.
Arterioles have precapillary sphincters that control blood flow into venues.
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Vasoconstriction of arterioles decreases blood pressure.
Vasoconstriction of arterioles decreases blood pressure.
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Fenestrated capillaries have pores or small openings in their walls.
Fenestrated capillaries have pores or small openings in their walls.
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Sinusoid capillaries have smaller fenestrations than continuous capillaries.
Sinusoid capillaries have smaller fenestrations than continuous capillaries.
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Veins are considered 'resistance vessels'.
Veins are considered 'resistance vessels'.
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Baroreceptors are pressure-sensitive receptors.
Baroreceptors are pressure-sensitive receptors.
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Veins have a thicker tunica media with a lot of smooth muscle when compared to arteries.
Veins have a thicker tunica media with a lot of smooth muscle when compared to arteries.
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The carotid sinus reflex and aortic reflex are the least important baroreceptor reflexes.
The carotid sinus reflex and aortic reflex are the least important baroreceptor reflexes.
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The mean arterial pressure can be calculated by the equation: MAP = Diastolic BP + 1/4 (systolic BP - diastolic BP)
The mean arterial pressure can be calculated by the equation: MAP = Diastolic BP + 1/4 (systolic BP - diastolic BP)
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When blood pressure decreases, baroreceptors send impulses at a faster rate to the cardiovascular center (CVC).
When blood pressure decreases, baroreceptors send impulses at a faster rate to the cardiovascular center (CVC).
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A systolic blood pressure of 130 mmHg is considered normal.
A systolic blood pressure of 130 mmHg is considered normal.
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Chemoreceptors detect hypoxia, hypercapnia, and alkalosis.
Chemoreceptors detect hypoxia, hypercapnia, and alkalosis.
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The main function of valves in veins is to prevent the backflow of blood, aiding in venous return.
The main function of valves in veins is to prevent the backflow of blood, aiding in venous return.
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Proprioceptors monitor the concentration of chemicals in the blood.
Proprioceptors monitor the concentration of chemicals in the blood.
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The sympathetic nervous system has an inhibitory effect on the cardiovascular system.
The sympathetic nervous system has an inhibitory effect on the cardiovascular system.
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Blood viscosity is one of the factors that does not affect vascular resistance.
Blood viscosity is one of the factors that does not affect vascular resistance.
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Angiotensin II is a potent vasodilator produced by the adrenal glands.
Angiotensin II is a potent vasodilator produced by the adrenal glands.
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A diagnosis of hypertension is given for a blood pressure reading of 130/85.
A diagnosis of hypertension is given for a blood pressure reading of 130/85.
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Potassium ions ($K^{+}$) cause vasoconstriction.
Potassium ions ($K^{+}$) cause vasoconstriction.
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An approximate mean arterial pressure of $60$ mmHg is needed to perfuse the coronary arteries, brain, and kidneys.
An approximate mean arterial pressure of $60$ mmHg is needed to perfuse the coronary arteries, brain, and kidneys.
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The total blood flow through the body is equal to the cardiac output ($CO$).
The total blood flow through the body is equal to the cardiac output ($CO$).
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Magnesium ions (Mg2+) typically promote vasoconstriction by enhancing the actions of Calcium ions.
Magnesium ions (Mg2+) typically promote vasoconstriction by enhancing the actions of Calcium ions.
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An increase in hydrogen ions (H+) leads to vasoconstriction, while a reduction results in vasodilation.
An increase in hydrogen ions (H+) leads to vasoconstriction, while a reduction results in vasodilation.
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Acetate and citrate are anions that induce vasoconstriction within the body.
Acetate and citrate are anions that induce vasoconstriction within the body.
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Carbon dioxide (CO2) primarily results in vasoconstriction, particularly within the brain.
Carbon dioxide (CO2) primarily results in vasoconstriction, particularly within the brain.
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The renin-angiotensin-aldosterone system (RAAS) functions to lower blood pressure through vasodilation and reduced water reabsorption.
The renin-angiotensin-aldosterone system (RAAS) functions to lower blood pressure through vasodilation and reduced water reabsorption.
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Epinephrine and norepinephrine, released from the adrenal cortex, decrease cardiac output by reducing the heart's rate and force of contractions.
Epinephrine and norepinephrine, released from the adrenal cortex, decrease cardiac output by reducing the heart's rate and force of contractions.
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Antidiuretic hormone (ADH), also known as vasopressin, is released in response to overhydration, causing vasodilation to reduce blood pressure.
Antidiuretic hormone (ADH), also known as vasopressin, is released in response to overhydration, causing vasodilation to reduce blood pressure.
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Atrial natriuretic peptide (ANP) is released by cells in the atria and increases blood pressure by promoting salt and water retention.
Atrial natriuretic peptide (ANP) is released by cells in the atria and increases blood pressure by promoting salt and water retention.
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Systemic blood vessel walls constrict in response to low O2 levels.
Systemic blood vessel walls constrict in response to low O2 levels.
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Pulmonary blood vessels dilate when oxygen levels are low.
Pulmonary blood vessels dilate when oxygen levels are low.
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Aging can lead to a decrease in hematocrit levels in the blood.
Aging can lead to a decrease in hematocrit levels in the blood.
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Cardiac output increases with aging due to enhanced heart efficiency.
Cardiac output increases with aging due to enhanced heart efficiency.
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Calcium deposits in blood vessels can lead to complications such as stroke or infarction.
Calcium deposits in blood vessels can lead to complications such as stroke or infarction.
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Shock is characterized by high cardiac output and rising peripheral blood pressure.
Shock is characterized by high cardiac output and rising peripheral blood pressure.
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Stroke can result from a lack of blood flow to the brain.
Stroke can result from a lack of blood flow to the brain.
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Thrombi are formed solely at healthy blood vessels without any underlying conditions.
Thrombi are formed solely at healthy blood vessels without any underlying conditions.
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Study Notes
Physiology of the Cardiovascular System (Part II)
- The presentation covers the cardiovascular system, focusing on venous return, sympathetic stimulation, blood vessels, and hemodynamics.
Venous Return
- Venous return is the volume of blood returning to the right atrium each minute.
- It's determined by venous pressure and various factors like:
- Muscle contractions.
- Venous compliance.
- Respiratory activity.
- Vena cava compression.
- Gravity.
Blood Vessels and Hemodynamics
- Five main types of blood vessels are: arteries, arterioles, capillaries, venules, and veins.
- Arteries carry blood away from the heart.
- Arterioles control blood flow into capillaries.
- Capillaries are the site of exchange.
- Venules collect blood from capillaries.
- Veins carry blood to the heart.
Basic Structure of Blood Vessels
- Blood vessels have three main layers:
- Tunica interna (innermost layer) – endothelium, basement membrane, internal elastic lamina.
- Tunica media (middle layer) – smooth muscle, external elastic lamina.
- Tunica externa (outermost layer) – connective tissue.
- Arteries have a thicker tunica media than veins to withstand high pressure.
- Veins have valves to prevent backflow.
Arterioles
- Microscopic vessels that monitor blood flow to capillaries.
- Metarterioles have precapillary sphincters.
- Sympathetic innervation and chemical mediators control their diameter, hence affecting blood flow and resistance.
- Vasoconstriction raises blood pressure.
Capillaries
- Capillaries are the site of exchange between blood and interstitial fluid.
- Three types of capillary structure:
- Continuous capillaries (e.g. brain).
- Fenestrated capillaries (e.g. kidneys).
- Sinusoids (e.g. liver).
Capillary Networks
- Network of vessels regulate blood flow.
- Arteriovenous anastomosis allows blood to bypass capillaries.
- Precapillary sphincters control blood flow in capillaries.
Capillary Exchange
- Diffusion, transcytosis, and bulk flow are the three mechanisms for movement between blood and interstitial fluid.
Veins
- Veins have the same three layers as arteries.
- Tunica intima in veins is thinner than in arteries.
- Tunica media in veins is thinner with little smooth muscle.
- Tunica externa in veins is the thickest.
- Veins are less designed to withstand high pressure.
- Valves prevent backflow in veins.
Hemodynamics
- Hemodynamics is the study of blood flow in the circulatory system.
Factors Affecting Blood Flow
- Blood flow depends on:
- Cardiac output (CO) – total blood flow.
- Pressure differences driving circulation.
- Resistance to blood flow, specifically in blood vessels.
- Increased CO increases blood flow.
- Blood pressure is the force of blood against vessel walls.
Blood Pressure
- Created by ventricular contraction.
- Systolic BP: highest pressure during ventricular contraction.
- Diastolic BP: lowest pressure during ventricular relaxation.
- Blood pressure also depends on total blood volume (BP = CO x TPR) .
Mean Arterial Pressure
- Average pressure in the arterial system over a given time.
- Normal value: 80-100 mmHg.
Abnormal Blood Pressure
- Hypertension: abnormally high blood pressure (above 140/90 mmHg).
- Hypotension: abnormally low blood pressure.
Neural Regulation of Blood Pressure
- Baroreceptor reflexes: pressure-sensitive receptors (carotid sinus, aortic arch) adjust sympathetic/parasympathetic output to maintain blood pressure.
- Chemoreceptor reflexes: sensitive to chemical composition of blood (O₂, CO₂, pH); affect blood vessel dilation/constriction and breathing rate.
Location of Baroreceptors
- Located in highly distensible regions of the circulatory system (carotid sinus, aortic arch).
- They sense blood pressure fluctuations to adjust vascular tone accordingly.
Hormone Regulation of Blood Pressure
- Hormones adjust vascular resistance and blood volume (e.g. Renin-angiotensin-aldosterone system).
- Antidiuretic hormone (ADH) and epinephrine/norepinephrine also regulate blood pressure.
- Atrial natriuretic peptide (ANP) lowers blood pressure.
Autoregulation of Blood Pressure
- Local regulatory mechanisms that maintain blood flow to match metabolic demands (physical/chemical stimuli adjust blood vessel diameter. Peripheral systemic vasculature dilation/constriction maintain blood flow matching metabolic requirements.)
Circulation
- Important differences exist in pulmonary and systemic circulation during autoregulatory responses.
- Systemic vessels dilate with low O₂ to increase O₂ delivery.
- Pulmonary vessels constrict with low O₂ to direct blood flow to better ventilated areas.
Shock
- Severe circulatory failure with low and falling blood pressure, decreased cardiac output from several possible causes: decreased blood volume and cardiac failure, bacterial/anaphylactic toxins.
Stroke
- Loss of brain function due to disruption in blood supply (ischemia/hemorrhage).
- Associated with impaired limb function, vision, or speech.
Aging and the Cardiovascular System
- Blood, heart, and blood vessels are all affected by age.
- Examples of changes: decreased hematocrit, blood clots, blood pooling in legs, reduced maximum cardiac output, progressive atherosclerosis.
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Description
This quiz covers key concepts in cardiovascular physiology, including the function of blood vessels, the role of baroreceptors, and the mechanics of blood pressure regulation. Test your knowledge on venous return, stroke volume, and various types of capillaries in the circulatory system.
