Cardiac Output and Stroke Volume Regulation

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Questions and Answers

What primarily influences stroke volume according to the Frank-Starling law of the heart?

Contractility

Afterload

End systolic volume

Preload (correct)

Which factor is not considered a major determinant of peripheral resistance in the circulatory system?

Vessel diameter

Viscosity of blood

Blood temperature (correct)

Total blood volume

Which hormone is most likely to increase contractility of the heart muscle?

Adrenaline (correct)

Thyroxine

Insulin

Aldosterone

What is the relationship between preload and stroke volume?

Increased preload can increase stroke volume. Signup and view all the answers

Which of the following factors would likely decrease contractility?

Calcium channel blockers Signup and view all the answers

What is the role of venous pressure in the circulation?

It represents the average pressure in the venous compartment. Signup and view all the answers

What effect does a slow heartbeat have on stroke volume?

Increases venous return and can increase stroke volume. Signup and view all the answers

Which condition could lead to a decrease in peripheral resistance?

Vasodilation. Signup and view all the answers

Which of the following would primarily cause a decrease in stroke volume during rapid heartbeats?

Decreased end diastolic volume. Signup and view all the answers

What effect does vasodilation have on systemic vascular resistance (SVR)?

It decreases SVR. Signup and view all the answers

What role does norepinephrine play in heart contractility?

It activates a cyclic AMP second-messenger system. Signup and view all the answers

Which of the following conditions is most likely a response to severe hypocalcemia?

Depressed cardiac function. Signup and view all the answers

What is the major impact of the sympathetic nervous system (SNS) during acute stress?

It increases the heart rate via the cardioacceleratory center. Signup and view all the answers

Which type of shock is characterized by inadequate blood flow due to extreme vasodilation?

Vascular shock. Signup and view all the answers

What characterizes chronic hypertension?

It can lead to heart failure and stroke. Signup and view all the answers

How does bradycardia affect heart function?

It may indicate underlying health problems. Signup and view all the answers

Which statement best describes the relationship between hyperkalemia and heart function?

It can cause cardiac arrest. Signup and view all the answers

What is the primary cause of pericarditis?

Inflammation of the pericardium. Signup and view all the answers

What is the effect of the parasympathetic nervous system (PNS) on heart rate?

It causes vagal tone, slowing the heart rate. Signup and view all the answers

Study Notes

Cardiac Output (CO) and Reserve

Cardiac Output (CO) is the amount of blood pumped by each ventricle in one minute
CO is the product of heart rate (HR) and stroke volume (SV)
HR is the number of heart beats per minute
SV is the amount of blood pumped out by a ventricle with each beat
Cardiac reserve is the difference between resting and maximal CO

Regulation of Stroke Volume

SV = end diastolic volume (EDV) minus end systolic volume (ESV)
EDV = amount of blood collected in a ventricle during diastole
ESV = amount of blood remaining in a ventricle after contraction

Factors Affecting Stroke Volume

Preload – amount ventricles are stretched by contained blood
Contractility – cardiac cell contractile force due to factors other than EDV
Afterload – back pressure exerted by blood in the large arteries leaving the heart

Frank-Starling Law of the Heart

Preload, or degree of stretch, of cardiac muscle cells before they contract is the critical factor controlling stroke volume
Slow heartbeat and exercise increase venous return to the heart, increasing SV
Blood loss and extremely rapid heartbeat decrease SV

Extrinsic Factors Influencing Stroke Volume

Contractility is the increase in contractile strength, independent of stretch and EDV
Increase in contractility comes from:
- Increased sympathetic stimuli
- Certain hormones
- Ca2+ and some drugs
Agents/factors that decrease contractility include:
- Acidosis
- Increased extracellular potassium
- Calcium channel blockers

Venous Pressure

Venous pressure generally refers to the average pressure within the venous compartment of circulation
Blood from all the systemic veins flows into the right atrium of the heart, therefore the pressure in the Right atrium is called Central Venous Pressure

Peripheral Resistance

Peripheral Vascular Resistance (systemic vascular resistance, SVR) is the resistance in the circulatory system that is used to create blood pressure
It also contributes to the flow of blood and is a component of cardiac function
When blood vessels constrict (vasoconstriction) this leads to an increase in SVR
When blood vessels dilate (vasodilation), this leads to a decrease in SVR
If referring to resistance within the pulmonary vasculature, this is called pulmonary vascular resistance (PVR)

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Description

This quiz explores the concepts of cardiac output (CO) and stroke volume, including definitions, formulas, and factors influencing their regulation. Understand how heart rate, preload, contractility, and afterload impact stroke volume and overall heart function. Test your knowledge on the Frank-Starling Law and its significance in cardiac physiology.