Cardiovascular Physiology Overview
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Questions and Answers

Increased venous return decreases stroke volume.

False (B)

Increased sympathetic stimulation of the heart decreases stroke volume.

False (B)

Arteries carry blood toward the heart.

False (B)

The tunica media of blood vessels is composed mostly of endothelial cells.

<p>False (B)</p> Signup and view all the answers

Capillaries are the primary site for exchange of substances between blood and tissues.

<p>True (A)</p> Signup and view all the answers

Arterioles have precapillary sphincters that control blood flow into venues.

<p>False (B)</p> Signup and view all the answers

Vasoconstriction of arterioles decreases blood pressure.

<p>False (B)</p> Signup and view all the answers

Fenestrated capillaries have pores or small openings in their walls.

<p>True (A)</p> Signup and view all the answers

Sinusoid capillaries have smaller fenestrations than continuous capillaries.

<p>False (B)</p> Signup and view all the answers

Veins are considered 'resistance vessels'.

<p>False (B)</p> Signup and view all the answers

Baroreceptors are pressure-sensitive receptors.

<p>True (A)</p> Signup and view all the answers

Veins have a thicker tunica media with a lot of smooth muscle when compared to arteries.

<p>False (B)</p> Signup and view all the answers

The carotid sinus reflex and aortic reflex are the least important baroreceptor reflexes.

<p>False (B)</p> Signup and view all the answers

The mean arterial pressure can be calculated by the equation: MAP = Diastolic BP + 1/4 (systolic BP - diastolic BP)

<p>False (B)</p> Signup and view all the answers

When blood pressure decreases, baroreceptors send impulses at a faster rate to the cardiovascular center (CVC).

<p>False (B)</p> Signup and view all the answers

A systolic blood pressure of 130 mmHg is considered normal.

<p>False (B)</p> Signup and view all the answers

Chemoreceptors detect hypoxia, hypercapnia, and alkalosis.

<p>False (B)</p> Signup and view all the answers

The main function of valves in veins is to prevent the backflow of blood, aiding in venous return.

<p>True (A)</p> Signup and view all the answers

Proprioceptors monitor the concentration of chemicals in the blood.

<p>False (B)</p> Signup and view all the answers

The sympathetic nervous system has an inhibitory effect on the cardiovascular system.

<p>False (B)</p> Signup and view all the answers

Blood viscosity is one of the factors that does not affect vascular resistance.

<p>False (B)</p> Signup and view all the answers

Angiotensin II is a potent vasodilator produced by the adrenal glands.

<p>False (B)</p> Signup and view all the answers

A diagnosis of hypertension is given for a blood pressure reading of 130/85.

<p>False (B)</p> Signup and view all the answers

Potassium ions ($K^{+}$) cause vasoconstriction.

<p>False (B)</p> Signup and view all the answers

An approximate mean arterial pressure of $60$ mmHg is needed to perfuse the coronary arteries, brain, and kidneys.

<p>True (A)</p> Signup and view all the answers

The total blood flow through the body is equal to the cardiac output ($CO$).

<p>True (A)</p> Signup and view all the answers

Magnesium ions (Mg2+) typically promote vasoconstriction by enhancing the actions of Calcium ions.

<p>False (B)</p> Signup and view all the answers

An increase in hydrogen ions (H+) leads to vasoconstriction, while a reduction results in vasodilation.

<p>False (B)</p> Signup and view all the answers

Acetate and citrate are anions that induce vasoconstriction within the body.

<p>False (B)</p> Signup and view all the answers

Carbon dioxide (CO2) primarily results in vasoconstriction, particularly within the brain.

<p>False (B)</p> Signup and view all the answers

The renin-angiotensin-aldosterone system (RAAS) functions to lower blood pressure through vasodilation and reduced water reabsorption.

<p>False (B)</p> Signup and view all the answers

Epinephrine and norepinephrine, released from the adrenal cortex, decrease cardiac output by reducing the heart's rate and force of contractions.

<p>False (B)</p> Signup and view all the answers

Antidiuretic hormone (ADH), also known as vasopressin, is released in response to overhydration, causing vasodilation to reduce blood pressure.

<p>False (B)</p> Signup and view all the answers

Atrial natriuretic peptide (ANP) is released by cells in the atria and increases blood pressure by promoting salt and water retention.

<p>False (B)</p> Signup and view all the answers

Systemic blood vessel walls constrict in response to low O2 levels.

<p>False (B)</p> Signup and view all the answers

Pulmonary blood vessels dilate when oxygen levels are low.

<p>False (B)</p> Signup and view all the answers

Aging can lead to a decrease in hematocrit levels in the blood.

<p>True (A)</p> Signup and view all the answers

Cardiac output increases with aging due to enhanced heart efficiency.

<p>False (B)</p> Signup and view all the answers

Calcium deposits in blood vessels can lead to complications such as stroke or infarction.

<p>True (A)</p> Signup and view all the answers

Shock is characterized by high cardiac output and rising peripheral blood pressure.

<p>False (B)</p> Signup and view all the answers

Stroke can result from a lack of blood flow to the brain.

<p>True (A)</p> Signup and view all the answers

Thrombi are formed solely at healthy blood vessels without any underlying conditions.

<p>False (B)</p> Signup and view all the answers

Flashcards

What are arteries?

Arteries are blood vessels that carry blood away from the heart.

What are arterioles?

Arterioles are small arteries that branch off from larger arteries and regulate blood flow into capillaries.

What are capillaries?

Capillaries are microscopic blood vessels that form networks throughout the body and are the site of exchange between blood and tissues.

What are venules?

Venules are small veins that collect blood from capillaries and merge to form larger veins.

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What are veins?

Veins are blood vessels that carry blood toward the heart.

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What is the tunica interna?

The tunica interna is the innermost layer of a blood vessel, composed of endothelium, basement membrane, and internal elastic lamina. It provides a smooth surface for blood flow.

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What is the tunica media?

The tunica media is the middle layer of a blood vessel, composed of smooth muscle and external elastic lamina. It regulates blood vessel diameter and blood pressure.

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What is the tunica externa?

The tunica externa is the outermost layer of a blood vessel, composed of connective tissue. It anchors the blood vessel to surrounding tissues.

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What are metarterioles?

Metarterioles are short vessels that connect arterioles to capillaries. They have precapillary sphincters which regulate blood flow into capillaries.

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What are resistance vessels?

Resistance vessels are blood vessels that resist blood flow. Arterioles are the primary resistance vessels in the circulatory system.

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Diffusion

The movement of substances across a cell membrane down their concentration gradient, from a region of high concentration to a region of low concentration. No cellular energy is required.

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Transcytosis

A type of transport across a cell membrane that involves the movement of substances through the cell, using vesicles.

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Bulk Flow

Bulk flow is the mass movement of fluid due to a pressure gradient, usually driven by pressure differences within the circulatory system.

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Blood Flow

The volume of blood that flows through any tissue in a given period of time (in mL/min).

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Cardiac Output

The amount of blood pumped by the heart per minute. It's the total blood flow in the circulatory system.

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Systolic Blood Pressure

The highest arterial pressure attained during systole (contraction phase of the heart).

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Diastolic Blood Pressure

The lowest arterial pressure during diastole (relaxation phase of the heart).

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Mean Arterial Pressure (MAP)

The average pressure in the arterial system over a given time.

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Neural Control of Blood Pressure

Refers to the body's ability to regulate blood pressure through the nervous system.

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Baroreceptors

Specialized sensory receptors that detect changes in blood pressure by sensing the stretch of blood vessels.

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Baroreceptor Reflexes

The carotid sinus reflex and aortic reflex, both of which are triggered by changes in blood pressure detected by baroreceptors.

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Cardiovascular Center (CVC)

The control center in the brainstem that receives input from baroreceptors and other sensors, and regulates heart rate and blood vessel tone.

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Chemoreceptor Reflexes

A reflex that helps maintain blood pressure by monitoring the chemical composition of blood, specifically oxygen levels, carbon dioxide levels, and pH.

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Humoral Control of Blood Pressure

The regulation of blood pressure by hormones and other chemical substances present in the blood.

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Vasoconstrictors

Substances that cause constriction of blood vessels, leading to increased blood pressure.

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Vasodilators

Substances that cause dilation of blood vessels, leading to decreased blood pressure.

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What is the role of renin in the RAAS?

The release of renin from the juxtaglomerular apparatus triggers a cascade of events, leading to the production of angiotensin II.

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What is the effect of angiotensin II on blood pressure?

Angiotensin II is a potent vasoconstrictor, increasing peripheral resistance and raising blood pressure.

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How does aldosterone contribute to blood pressure regulation?

Aldosterone, stimulated by angiotensin II, promotes sodium reabsorption in the kidneys, leading to increased water retention and blood volume, further contributing to elevated blood pressure.

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How do epinephrine and norepinephrine impact blood pressure?

Epinephrine and norepinephrine, released from the adrenal medulla, stimulate an increase in heart rate and contractility, resulting in a higher cardiac output and elevated blood pressure.

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What is the role of antidiuretic hormone (ADH) in blood pressure regulation?

Antidiuretic hormone (ADH) or vasopressin is released in response to dehydration or low blood volume, causing vasoconstriction and an increase in blood pressure.

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What is the effect of Atrial Natriuretic Peptide (ANP) on blood pressure?

Atrial natriuretic peptide (ANP) is released from the heart's atria in response to high blood volume, causing vasodilation, sodium and water excretion, and ultimately a decrease in blood pressure.

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What is shock?

A condition in which the heart fails to maintain adequate blood circulation throughout the body, resulting in low cardiac output and falling blood pressure.

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What is autoregulation in blood vessels?

The process by which blood vessels automatically adjust their diameter to regulate blood flow to specific tissues based on local conditions. This is essential to maintain proper organ function and oxygen delivery.

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What is decreased hematocrit in aging?

A decrease in the proportion of red blood cells to total blood volume, often associated with aging.

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What is a blood clot (thrombus) in aging?

A blood clot that forms inside a blood vessel, often due to a build-up of plaque or venous valve deterioration.

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What is atherosclerosis?

The buildup of plaque within blood vessels, narrowing the passageway and leading to reduced blood flow, often associated with aging.

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What is a stroke?

A major disturbance in the blood supply to the brain, causing loss of brain function due to ischemia or hemorrhage.

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What is an aneurysm?

A bulge in the weakened wall of an artery, often associated with aging and loss of artery elasticity.

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What is reduced elasticity of fibrous skeleton in aging?

The stiffening and loss of elasticity in the fibrous skeleton of the heart that occurs with aging, reducing the heart's ability to pump effectively.

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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 (Oâ‚‚, COâ‚‚, 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 Oâ‚‚ to increase Oâ‚‚ delivery.
  • Pulmonary vessels constrict with low Oâ‚‚ 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.

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