Cardio 5

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Questions and Answers

What is the relationship between end-diastolic volume and stroke volume according to the Frank-Starling law?

The end-diastolic volume has no effect on stroke volume.

The greater the end-diastolic volume, the greater the stroke volume. (correct)

The greater the end-diastolic volume, the smaller the stroke volume.

The end-diastolic volume and stroke volume are unrelated.

What is the purpose of the Frank-Starling mechanism?

To increase end-systolic volume.

To increase venous return.

To increase the volume of blood pumped out during systole. (correct)

To increase contractility.

What is the effect of increased contractility on end-systolic volume?

Increased contractility can either increase or decrease end-systolic volume.

Increased contractility has no effect on end-systolic volume.

Increased contractility leads to an increase in end-systolic volume.

Increased contractility leads to a decrease in end-systolic volume. (correct)

What is the formula for stroke volume?

Stroke volume = end-diastolic volume - end-systolic volume. Signup and view all the answers

What is the effect of increased contractility on stroke volume?

Increased contractility leads to an increase in stroke volume, without the need to increase end-diastolic volume. Signup and view all the answers

What is the relationship between preload (end-diastolic volume/fiber length) and diastolic filling?

The greater the preload, the greater the diastolic filling. Signup and view all the answers

What is the definition of stroke volume?

The difference between the end-diastolic volume and the end-systolic volume Signup and view all the answers

What does ejection fraction measure?

The effectiveness of the ventricles in ejecting blood Signup and view all the answers

What is the formula for calculating cardiac output?

Cardiac Output (mL/min) = Stroke Volume (mL) * Heart Rate (beats/min) Signup and view all the answers

Which of the following factors can increase cardiac output?

Increasing stroke volume and/or heart rate Signup and view all the answers

Which of the following is not an intrinsic factor affecting cardiac output?

Afterload Signup and view all the answers

What is the Frank-Starling mechanism?

The relationship between end-diastolic volume and stroke volume Signup and view all the answers

What is the primary endogenous agonist that activates M2 receptors in the heart?

Acetylcholine Signup and view all the answers

Which receptor activation leads to an increase in automaticity (heart rate) in cardiovascular physiology?

Beta 1 receptors Signup and view all the answers

Which neurotransmitter is released from postganglionic neurons and slows down the discharge rate of the SA node?

Acetylcholine Signup and view all the answers

What effect does inhibition of the cAMP pathway have on cardiac HR and output?

Decreases HR and output Signup and view all the answers

Which system predominates in the heart but acts in a reciprocal manner with the other system?

Autonomic nervous system Signup and view all the answers

What is the direct correlation between contractility and intracellular calcium concentration?

The larger the intracellular calcium concentration, the greater the contractility. Signup and view all the answers

Which of the following extrinsic factors increases contractility?

Sympathetic stimulation Signup and view all the answers

How do epinephrine and norepinephrine affect contractility?

They increase contractile force and velocity by stimulating beta-1 adrenergic receptors. Signup and view all the answers

What is the afterload for the left ventricle?

The aortic pressure Signup and view all the answers

What happens when aortic blood pressure increases?

Stroke volume decreases, and end-systolic volume/pressure increases. Signup and view all the answers

What is the primary mechanism by which epinephrine and norepinephrine increase contractility?

Increasing calcium influx and activation of Ryanodine receptors Signup and view all the answers

What is the primary effect of the Anrep effect?

It allows the myocardium to compensate for increased end-systolic volume and decreased stroke volume when aortic blood pressure increases. Signup and view all the answers

What is the mechanism behind the Anrep effect?

It increases the release of catecholamines, which in turn increases ventricular contractility. Signup and view all the answers

What is the relationship between afterload and stroke volume?

Afterload and stroke volume are inversely proportional. Signup and view all the answers

What is the primary determinant of cardiac output?

Heart rate and stroke volume Signup and view all the answers

What is the effect of sympathetic activity on cardiac output?

It increases heart rate, preload, and stroke volume, leading to increased cardiac output. Signup and view all the answers

Which branch of the autonomic nervous system predominates in the heart?

Parasympathetic Signup and view all the answers

Study Notes

Frank-Starling Mechanism

The greater the end-diastolic volume, the larger the stroke volume
The more the heart is stretched, the longer the initial cardiac fiber length before contraction
Increased length leads to a greater force of contraction and a greater stroke volume

Contractility (Inotropism)

Refers to the pumping ability of a ventricle
Intrinsic ability of myocardial cells to develop force at a given muscle cell length
An increase in contractility leads to a more complete emptying of the ventricle during systole
Decrease in end-systolic volume and increase in stroke volume

Afterload

The Anrep effect: allows myocardium to compensate for an increased end-systolic volume and decreased stroke volume that occurs when aortic blood pressure increases
Increase in afterload stimulates the release of catecholamines, which causes an increase in ventricular contractility (inotropy)

Heart Rate and Cardiac Output

Heart rate is affected by the autonomic nervous system
Parasympathetic activity predominates in the heart
Cardiac output is the total volume of blood pumped by the heart per minute
Cardiac output = stroke volume x heart rate

Stroke Volume and Ejection Fraction

Stroke volume is the volume of blood ejected out of the left ventricle during each systolic cardiac contraction
Ejection fraction is the fraction of the end-diastolic volume that is ejected in one stroke volume
Normally around 60% (0.6)
Increase in ejection fraction reflects an increase in contractility

Autonomic Nervous System and Heart Function

Sympathetic activity increases heart rate and contractility
Parasympathetic activity slows down heart rate and decreases contractility
M2 receptors in the heart are inhibited by acetylcholine, which slows down the heart rate and decreases contractility
Beta 1 receptor activation increases contractility and heart rate

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physio 1