Human Biology Chapter: Heart and Circulation

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Questions and Answers

What is the first chamber of the heart that oxygen-poor blood enters?

Left atrium

Right ventricle

Left ventricle

Right atrium (correct)

Which valve does blood cross to move from the right atrium to the right ventricle?

Mitral valve

Aortic valve

Tricuspid valve (correct)

Pulmonary valve

Where does gas exchange occur in the pathway of blood flow through the heart?

Pulmonary veins

Right ventricle

Pulmonary artery

Pulmonary capillaries (correct)

What is the next destination for oxygen-rich blood after it leaves the pulmonary veins?

Left atrium Signup and view all the answers

What is the correct order of blood flow through the heart starting from oxygen-poor blood?

Right atrium → Right ventricle → Pulmonary artery → Pulmonary capillaries Signup and view all the answers

What is one of the main stimuli for renin release in the body?

Decreased blood pressure in the afferent arteriole Signup and view all the answers

Which of the following effects is NOT associated with the activation of the Renin-Angiotensin-Aldosterone System (RAAS)?

Decreased myocardial contractility Signup and view all the answers

How does the Renin-Angiotensin-Aldosterone System (RAAS) primarily influence mean arterial pressure (MAP)?

By increasing cardiac output (CO) and systemic vascular resistance (SVR) Signup and view all the answers

Which mechanism does RAAS use to increase blood volume and pressure?

Increased sodium and water reabsorption Signup and view all the answers

What long-term effect can the overactivation of the Renin-Angiotensin-Aldosterone System (RAAS) have on the heart?

Increased workload on the heart Signup and view all the answers

What is the formula for mean arterial pressure (MAP)?

MAP = CO x SVR Signup and view all the answers

Which factor is NOT a determinant of stroke volume (SV)?

Vascular Resistance Signup and view all the answers

How does the sympathetic nervous system respond to a decrease in cardiac output (CO)?

Increases systemic vasoconstriction Signup and view all the answers

What does a decrease in baroreceptor firing rate signal to the vasomotor center?

Increase in sympathetic activity Signup and view all the answers

What effect does the activation of the renin-angiotensin-aldosterone system (RAAS) have?

Increased preload Signup and view all the answers

Which statement is true regarding the baroreceptor reflex in the context of heart disease?

It helps maintain MAP in response to low CO Signup and view all the answers

What is meant by 'afterload' in cardiovascular physiology?

Resistance the heart must overcome to eject blood Signup and view all the answers

What is the primary goal of the cardiovascular system concerning mean arterial pressure?

To maintain normal MAP under all circumstances Signup and view all the answers

Which condition occurs as a result of heart disease impacting CO?

Decreased MAP Signup and view all the answers

What does a successful short-term response to decreased MAP involve?

Increased heart rate and contractility Signup and view all the answers

What occurs when blood crosses the mitral valve?

It enters the left ventricle. Signup and view all the answers

In which part of the circulatory system is blood under high pressure?

Aorta Signup and view all the answers

What best describes preload in the cardiovascular system?

The stretch on myocytes before contraction. Signup and view all the answers

What does contractility refer to in myocardial performance?

The intrinsic ability of the heart to generate force to eject blood. Signup and view all the answers

What condition is described as the heart's inability to pump adequate blood?

Heart Failure Signup and view all the answers

Which statement is true regarding systemic circulation pressure profiles compared to pulmonary circulation?

Systemic circulation exhibits pulsatile pressures. Signup and view all the answers

What is the role of capillaries in the vascular system?

To exchange substances between blood and tissues. Signup and view all the answers

What physical examination finding is commonly associated with RIGHT-sided congestive heart failure?

Jugular venous distension Signup and view all the answers

What does heart failure result from?

Severe heart disease. Signup and view all the answers

Which sign is least likely to be observed in dogs and cats with RIGHT-sided congestive heart failure?

Dependent peripheral edema Signup and view all the answers

What is the characteristic of a venule in the vascular system?

Collects blood from capillaries. Signup and view all the answers

What is a common respiratory sign observed in LEFT-sided congestive heart failure?

Orthopnea Signup and view all the answers

Which of the following is a clinical manifestation exclusive to cats with LEFT-sided congestive heart failure?

Decreased lung sounds due to pleural effusion Signup and view all the answers

What term describes the process where myocardial filling occurs with subsequent reflex increases in contractility?

Frank-Starling mechanism Signup and view all the answers

What is a common presentation of animals in acute congestive heart failure?

Sinus tachycardia Signup and view all the answers

Which neurohormonal pathway is associated with fluid retention and vasoconstriction in CHF?

Renin-angiotensin-aldosterone system (RAAS) Signup and view all the answers

Which symptom is indicative of pulmonary edema in LEFT-sided congestive heart failure?

Frothy fluid expectoration Signup and view all the answers

What is the primary objective of neuro-hormonal changes in heart failure?

To maintain normal mean arterial pressure (MAP) Signup and view all the answers

Which response occurs in Phase II of congestive heart failure?

Neuro-hormonal activation Signup and view all the answers

Which factor is primarily involved in the maladaptive response to heart disease?

Sympathetic nervous system (SNS) activation Signup and view all the answers

What is a direct consequence of increased venous/capillary hydrostatic pressure in heart failure?

Development of tissue edema Signup and view all the answers

What role does the Renin-Angiotensin-Aldosterone System (RAAS) play in heart failure?

Increases blood pressure and fluid retention Signup and view all the answers

What is the expected effect of vasopressin (ADH) during heart failure?

Increases water retention Signup and view all the answers

During which phase of congestive heart failure does overt congestion develop?

Phase III: congestion Signup and view all the answers

Which of the following best describes the vicious cycle of heart failure?

Increased workload and decreased cardiac output Signup and view all the answers

What does Na+ + H2O retention indicate in the context of heart failure?

Compensatory mechanism for maintaining MAP Signup and view all the answers

Which of the following cytokines is notable for its role in heart failure?

Pro-inflammatory cytokines Signup and view all the answers

What immediate effect does sympathetic nervous system (SNS) activation have during heart failure?

Increased cardiac workload Signup and view all the answers

What is a physiological consequence of long-term heart failure?

Development of chronic edema Signup and view all the answers

In heart failure management, which of the following is considered a primary target to alleviate symptoms?

Decrease hydrostatic pressure Signup and view all the answers

How does increased hydrostatic pressure contribute to heart failure symptoms?

Leads to fluid leakage into tissues Signup and view all the answers

Study Notes

Pathophysiology of Heart Failure

This presentation covers the pathophysiology of heart failure.
The course is VETM 5291 Cardiovascular, Respiratory, and Hemolymph Systems II
The presenter is Mandy Coleman, DVM, DACVIM (Cardiology)
The presentation will cover 3 lectures.

Roadmap for the Next 3 Lectures

The first lecture will review cardiovascular physiology, contrast heart success and failure, and provide diagnostic criteria for heart failure (HF).
The second lecture will introduce drugs utilized in HF treatment and describe the patient with HF, review radiographic findings, and discuss the maladaptive responses to heart disease leading to heart failure.
The third lecture will focus on the objectives stated later in the presentation.

Learning Objectives

Discuss maladaptive responses to heart disease leading to congestive heart failure (CHF)
List and describe the two classic neurohormonal pathways involved in the genesis of CHF.
Diagram the Frank-Starling relationship to describe the effect on global cardiac function associated with heart disease.
Explain why acute CHF animals often present with sinus tachycardia.
Define "forward" and "backward" heart failure, describing the clinical manifestations of each.
Compare and contrast physical examination findings for right-sided and left-sided CHF.

Overview of the Cardiovascular System

The system shows the oxygenated and deoxygenated blood flow through the heart and lungs in a systemic circulation cycle.

Path of Blood Flow Through the Heart

The path of blood flow through the heart (with numbered steps) is described.

The Systemic Vascular "Tree"

Veins carry blood back to the heart, serving as reservoirs for blood.
Venules collect blood from capillaries.
Capillaries exchange substances between blood and tissues.
Arteries distribute blood under high pressure.
Small arteries and arterioles regulate blood flow into capillaries.

Intravascular Pressure Profiles

Systemic circulation pressures are illustrated with systolic and diastolic values for the heart.
Pulmonary circulation pressures are also illustrated.

Preload is the stretch/tension on relaxed myocytes before contraction.
Afterload is the tension on myocardium during systole, the resistance overcoming to move blood from the ventricle.

Contractility (inotropic state) is the intrinsic ability of the heart to generate force for blood ejection, independent of preload and afterload.

Heart Failure Defined

Heart "Success": enough blood is ejected to maintain normal mean arterial pressure, meet metabolic demands, and adequately drain pulmonary and systemic veins.
Heart Failure: inability of the heart to pump enough blood to meet metabolic demands or to meet them without resulting in increased heart filling pressures and poor venous drainage.
Heart failure is a result of severe heart disease.

Potential Underlying Causes of Heart Failure

Causes of heart failure in animals, broken into classifications, are presented.

Congestive Heart Failure (CHF)

Increased venous/capillary hydrostatic pressure leads to edema and/or cavitary effusion (fluid buildup).
Maladaptive response to heart disease, involving neurohormonal changes to maintain normal mean arterial pressure (MAP).

Congestive Heart Failure (CHF) (Cont.)

Neurohormonal responses associated with CHF: SNS activation, RAAS activation, overexpression of endothelin, and vasopressin (ADH), with pro-inflammatory cytokines.

Maintenance of Normal MAP is Priority #1!

MAP = cardiac output (CO) x systemic vascular resistance (SVR)
CO = sum of flows to all tissues in the body (volume of blood pumped into aorta per minute)

Maintenance of Normal MAP is Priority #1! (Cont.)

Cardiac output (CO) is affected by factors like heart rate (HR) and stroke volume (SV); factors influencing SV include preload, afterload, and contractility

Sympathetic Nervous System in early response to heart disease: Baroreceptor Reflex

Heart disease leads to decreased cardiac output = lowered MAP; the body responds by stretching arterial baroreceptors and lessening their firing rate, resulting in signals to the vasomotor center in the brain.
This leads to increased sympathetic nervous system outflow and restoration of MAP.

Renin-Angiotensin-Aldosterone System (RAAS) in intermediate- and long-term response to heart disease

The RAAS plays a role in intermediate and long-term adjustments to heart disease.

Renin-Angiotensin-Aldosterone System (RAAS) in intermediate- and long-term response to heart disease (Cont.)

There are stimuli for renin release, which affect blood pressure and trigger the release of hormones like ADH and cause changes in myocardial contractility, Na+/H2O reabsorption, and vasoconstriction.

Renin-Angiotensin-Aldosterone System (RAAS) in intermediate- and long-term response to heart disease (Final Notes)

The net result of RAAS activity is changes in preload, HR, contractility, and SVR to restore MAP.

Congestive Heart Failure (CHF) - Frank-Starling Relationship

Discusses the Frank-Starling relationship and how it connects to cardiac output and normal/diseased heart function.
In normal hearts, increased preload increases stroke volume and cardiac output

Cardiogenic Pulmonary Interstitial Edema (Left-sided CHF)

Describes the fluid exchange in the lungs in the case of left-sided CHF, including the lymphatic system and abnormal pressures.

Cardiogenic Pulmonary Interstitial Edema (Left-sided CHF) (Cont.)

Provides details for the exchange of fluid, emphasizing a key factor of pressure.

Harm of Increased Afterload in Heart Disease and Failure

The Frank-Starling mechanism adjusts to acute changes in afterload and reduces stroke volume and cardiac output unless the afterload is severely increased or the heart is diseased.

Clinical Manifestations of Heart Failure

Forward/outflow failure versus backward/congestive failure
Signs/symptoms of forward failure (inadequate output): generalized weakness, reduced exercise tolerance, syncope, hypotension, hypothermia, lactic acidosis, azotemia, and oliguria.
Signs/symptoms of backward failure (congestion): abnormal fluid accumulation, interstitial or pulmonary edema, pleural effusions (cats), and peripheral edema.

Congestive ("Backward") Heart Failure (CHF)

Right-sided CHF: visual evidence of heightened right-sided filling pressures (jugular venous distension/pulsation, hepatojugular reflux, abdominal distension from liver enlargement or ascites, decreased/absent lung sounds from pleural effusion, and dependent peripheral edema).

Congestive ("Backward") Heart Failure (CHF) (Cont.)

Left-sided CHF: respiratory signs due to pulmonary edema (dyspnea, tachypnea, orthopnea, cough, fluid expectoration, and fine inspiratory pulmonary crackles in animals with pulmonary edema; cats may have decreased/absent lung sounds due to pleural effusions).

Clinical Manifestations of Heart Failure image (additional notes)

Provides a more detailed diagrammatical overview of the various manifestations, including forward and backward failure, and output versus congestion.

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Description

This quiz covers essential concepts related to the human heart and circulatory system, focusing on blood flow, the Renin-Angiotensin-Aldosterone System (RAAS), and their physiological effects. Test your knowledge about the chambers of the heart, valves, and the impact of RAAS on blood pressure and heart health.