Hemodynamics, Neural and Hormonal Control of Blood Flow

These flashcards cover key concepts related to hemodynamics, neural and hormonal control of blood flow, and cardiovascular physiology.

How is Cardiac Output calculated?

Cardiac Output (CO) is calculated using the formula CO = Stroke Volume (SV) x Heart Rate (HR).

What is Stroke Volume?

Stroke Volume (SV) is the amount of blood ejected by the left ventricle in one contraction, typically measured in mL/beat.

What is the ejection fraction?

Ejection fraction is the percentage of the end-diastolic volume that is ejected during systole.

What allows cardiac muscle cells to act as syncytium?

Cardiac muscle cells are connected by intercalated discs which facilitate rapid propagation of action potentials (AP).

What events occur from an action potential to muscle contraction?

An AP triggers calcium release from the sarcoplasmic reticulum, leading to muscle contraction.

Define preload.

Preload is the degree of stretch of the cardiac muscle fibers before contraction, often expressed in terms of end-diastolic volume.

What is afterload?

Afterload is the pressure against which the heart must work to push blood out; it refers to the load the heart must overcome to eject blood.

What is the significance of the Pressure-Volume loop?

The Pressure-Volume loop illustrates the changes in pressure and volume in the heart during the cardiac cycle, showing points like aortic valve closure.

What is the left ventricle volume immediately before contraction called?

It is known as end-diastolic volume.

How does an increase in contractility affect Stroke Volume?

An increase in contractility leads to an increase in Stroke Volume.

What produces the S1 heart sound?

The S1 sound is produced by the closure of the mitral and tricuspid valves at the start of ventricular systole.

Where can the left ventricle pressure trace and ventricular volume be found on Wiggers diagram?

They can be found by examining the corresponding pressure and volume curves during the cardiac cycle.

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

MAP is calculated as MAP = CO x SVR, or more simply as MAP ≅ Pdias + 1/3(Psys−Pdias).

What three factors determine resistance to blood flow?

Resistance is determined by vessel diameter (or radius), vessel length, and viscosity.

What is Ohm’s Law as it applies to blood flow?

In blood flow, Ohm's Law is represented as Q = DP/R, where Q is blood flow, DP is the pressure difference, and R is resistance.

What is Poiseuille’s law in regards to blood flow?

Poiseuille's law states that blood flow (Q) through a vessel is directly proportional to the fourth power of the radius and pressure difference, and inversely proportional to the length and viscosity.

What characterizes laminar blood flow?

Laminar blood flow is characterized by streamlined movement of blood, with the highest velocity at the center of the vessel.

What is the Reynolds number used for?

The Reynolds number predicts whether flow will be laminar or turbulent based on velocity, diameter, density, and viscosity.

Define systemic vascular resistance (SVR).

SVR is the resistance to blood flow offered by all systemic blood vessels, excluding pulmonary circulation.

What are the two types of resistance in blood vessels?

Resistance in blood vessels can be parallel or series, depending on how vessels are arranged.

What hormones are involved in humoral control of blood flow?

Hormones like renin, angiotensin, aldosterone, vasopressin, and atrial natriuretic peptide regulate blood flow.

What is the role of nitric oxide in blood flow regulation?

Nitric oxide is a vasodilator released from endothelial cells, promoting relaxation of blood vessels.

What factors can lead to vasoconstriction?

Vasoconstriction can occur due to factors like angiotensin II, vasopressin, and endothelin.

What organs have the best autoregulation of blood flow?

Organs like the brain, heart, and skeletal muscle have well-developed autoregulation to maintain consistent blood flow.

How does blood flow change with resistance?

When resistance increases, blood flow decreases if all other factors remain constant.

What does the term 'vascular tone' refer to?

Vascular tone refers to the state of contraction of the smooth muscle in blood vessels, affecting blood flow.