Lecture+11+Vascular+2+2025

Vascular System Overview

The vascular system plays a critical role in cardiovascular function, involving complex interactions between the heart, blood vessels, and blood flow. It serves as a network that not only facilitates the transport of oxygen and nutrients to tissues but also aids in the removal of carbon dioxide and metabolic waste, maintaining homeostasis throughout the body.

Cardiovascular Function Curves

Function Curves

These curves illustrate the dynamic relationship between cardiac output, total peripheral resistance (TPR), and mean arterial pressure. Understanding these curves is crucial for analyzing various physiological states of the cardiovascular system.

Page 1: Cardiovascular Function Curves

The cardiovascular system functions like a closed circuit with a series of pathways through which blood flows, delivering vital substances to organs and tissues while returning deoxygenated blood back to the heart.

Page 2: Circuit Dynamics

• Arteries and Veins: Blood flow through arteries increases when pressure builds up, especially during systole (heart contraction).

• Pressure Changes: Stopping the heart results in an immediate drop in arterial pressure, leading to blood pooling in veins, which is crucial for understanding shock and circulatory collapse.

• Mean Circulatory Filling Pressure: Approximately 8 mmHg is noted as blood accumulates in veins, which helps in understanding the baseline central venous pressure.

Page 3: Total Peripheral Resistance (TPR)

• TPR Changes: It can be influenced by vasoconstriction (narrowing of blood vessels) and vasodilation (widening of blood vessels), which are critical mechanisms controlling blood flow and pressure.

• Independence from Pressure and Cardiac Output: TPR remains relatively independent of pressure (∆P) or cardiac output (CO), meaning that changes in TPR can occur without direct changes in these variables.

• Dependence on Pressure & CO: Pressure (P) varies with CO and TPR, while CO varies inversely with TPR, highlighting the interconnected nature of these variables.

• Effects of Vascular Dynamics: Small changes in arterial pressure or stroke volume can significantly impact CO, emphasizing the importance of maintaining stable arterial function.

Page 4: CardioViz Program

• Utility: Download the executable program related to cardiovascular function available on your Canvas site; this executable (.exe) file can be used on Physio lab computers for better visualization of cardiovascular parameters and pathophysiology.

Page 5: Cardiac Output vs Venous Return

Equilibrium Points

The relationship between cardiac output and venous return is graphically represented against right atrial pressure. Normal cardiac output and venous return can be noted with alignment to specific points on this graph, illustrating the physiological balance essential for sustaining adequate circulation.

Page 6: Cardiac Function Curve

• Influencing Variables: The curve is impacted by heart rate, contractility, preload, and afterload, which dictate the effectiveness of the heart's pumping capacity.

• Effects of Increased Venous Return: Higher right atrial pressure (RAP) results in increased preload, leading to an increase in stroke volume based on the Frank-Starling mechanism, a crucial principle in cardiac physiology.

Page 7: Vascular Function Curve

• Graphical Representations: The independent variable is plotted on the Y-axis and the dependent variable on the X-axis, allowing for direct comparison between cardiac and vascular curves for educational understanding.

Page 8: Vascular Function Influences

Key Factors Impacting Vascular Function:

• Total Peripheral Resistance (TPR)

• Mean Circulatory Filling Pressure

• Blood Volume

• Vein Capacitance, which describes the ability of veins to hold blood and how this influences venous return and overall circulatory dynamics.

Page 9: Cardiovascular Function Overview

A visual representation shows cardiovascular function curves indicating various states of health (e.g., heart failure) and their implications on systemic blood pressure and organ perfusion.

Page 10: Cardiac Output Adjustments

• Discussion: This section addresses the factors affecting cardiac output due to changes in blood volume and how vascular curves shift in response to different physiological and pathological conditions.

Page 11: Blood Loss Impact

An understanding of how conditions like acute blood loss can drastically impact cardiovascular function by affecting parameters such as blood volume, cardiac output, and total peripheral resistance.

Page 12: Sympathetic vs Parasympathetic Activity

This section explores the interaction between sympathetic (fight or flight) and parasympathetic (rest and digest) activation on heart rate and vascular resistance, providing a comprehensive view of autonomic regulation of the heart.

Page 13: Heart Failure Dynamics

Various states of heart function are discussed, particularly in the context of impaired contractility and systemic responses to altered pressures as seen in heart failure syndromes.

Page 14: Baroreceptor Reflex in Orthostatic Hypotension

Overview of Baroreceptor Reflex

This pathway includes stimulus detection, receptor response, and the body's adjustments to changes in mean arterial blood pressure when standing to prevent fainting.

Page 15: Negative Feedback Mechanism

The autonomic nervous system's response to increased blood pressure is outlined here, displaying its regulatory mechanisms as depicted in baroreceptor reflex pathways.

Page 16: Capacitance of Veins

Influences on Vascular Function: This includes venous pressure, blood volume, and the sympathetic nervous system's role in regulating venous return, essential for maintaining circulatory efficiency.

Page 17: Responses to Hemorrhage

An examination of physiological compensations following blood loss, focusing on cardiac output dynamics and responses via baroreceptor activity.

Page 18: Reflex Compensations

The relationship of heart rate, stroke volume, cardiac output, and total peripheral resistance during reflex compensatory responses is critical for sustaining arterial pressure post-injury or hemorrhage.

Page 19: Restoration of Blood Volume

Mechanisms for restoring arterial pressure are explored, including capillary exchange dynamics and fluid absorption via the lymphatic and renal systems.

Page 20: Kidney's Role in Blood Volume Regulation

The kidney regulates blood volume through sodium and water balance, adjusting during fluctuations in arterial pressure to maintain stable hemodynamics.

Page 21: Stroke Volume Dynamics

A comparative analysis of stroke volume in normal versus failing hearts is provided, explaining variations through the Frank-Starling mechanism and the impact of ventricular compliance.

Page 22: Heart Failure Medications

This section provides an overview of heart failure medications and their mechanisms, emphasizing how they relate to cardiovascular functions like volume loss management and adrenergic effects on heart contractility.

Page 23: Mechanisms of Hypertension

Key mechanisms leading to hypertension are discussed, detailing how they directly correlate with processes discussed within cardiovascular content, including vascular tone and volume overload.

Page 24: Exercise-Induced Cardiovascular Changes

The influence of exercise on baroreceptors, sympathetic and parasympathetic outputs, and resulting adjustments in cardiac output and peripheral resistance is essential for understanding how the body adapts to physical stressors.