An increase in preload causes a/an ________ in stroke volume in accordance with the ________ law. An increase in afterload causes a/an ________ in stroke volume. An increase in contractility causes a/an ________ in stroke volume.

Verified step by step guidance

1. Understand the concept of preload: Preload refers to the degree of stretch in the cardiac muscle fibers at the end of diastole, just before contraction. According to the Frank-Starling law, an increase in preload leads to an increase in stroke volume because the stretched muscle fibers generate a stronger contraction.
2. Understand the concept of afterload: Afterload is the resistance the heart must overcome to eject blood during systole. An increase in afterload typically decreases stroke volume because the heart has to work harder to push blood against the higher resistance.
3. Understand the concept of contractility: Contractility refers to the intrinsic ability of the cardiac muscle to contract, independent of preload and afterload. An increase in contractility enhances the force of contraction, leading to an increase in stroke volume.
4. Apply the Frank-Starling law to preload: Recall that the Frank-Starling law explains the relationship between preload and stroke volume. Increased preload stretches the cardiac muscle fibers, resulting in a stronger contraction and increased stroke volume.
5. Summarize the relationships: Increased preload leads to increased stroke volume (Frank-Starling law), increased afterload leads to decreased stroke volume, and increased contractility leads to increased stroke volume.

Key Concepts

Preload

Preload refers to the initial stretching of the cardiac muscle fibers prior to contraction, which is influenced by the volume of blood returning to the heart. An increase in preload typically leads to an increase in stroke volume, as described by the Frank-Starling law, which states that the heart pumps more effectively when it is filled with more blood.

Afterload

Afterload is the pressure against which the heart must work to eject blood during systole. An increase in afterload can lead to a decrease in stroke volume because the heart has to exert more force to overcome this resistance, which can limit the amount of blood ejected with each heartbeat.

Contractility

Contractility refers to the intrinsic ability of cardiac muscle fibers to contract and generate force. An increase in contractility enhances the heart's ability to pump blood, resulting in an increase in stroke volume. This is often influenced by factors such as sympathetic nervous system activity and certain medications.