BME211 Week 3

Structure and Composition of Arteries

Arteries consist of three layers—intima, media, and adventitia—and are composed of collagen, elastin, and smooth muscle cells.

Mechanical Perspective of Vessels

Vessels are dynamic structures that endure various pressures and stresses to regulate blood flow.

Stress vs. Strain Behavior in Arteries

Arteries display elastic behavior under low stress but may deform permanently under high stress, showing a nonlinear stress-strain relationship.

Tension-Radius Behavior for an Artery

Wall tension in arteries increases with the radius; larger arteries require more tension to withstand the same pressure (Laplace's Law).

Pressure and Flow Waveforms in Arteries

Arterial pressure and flow vary with the cardiac cycle, exhibiting systolic peaks and diastolic troughs.

Pulse Wave Velocity

The speed at which pressure waves propagate through arteries, reflecting arterial stiffness.

Turbulent vs. Laminar Flow

Arterial flow can be smooth and orderly (laminar) or disordered (turbulent), with turbulent flow occurring in narrowed or diseased arteries.

Rotating and Axial Flow

Blood flow in vessels comprises both straight (axial) and swirling (rotational) components, influencing flow dynamics.

Symmetric vs. Asymmetric Velocity Profiles

Symmetric flow in vessels has a uniform velocity distribution, while asymmetric flow can result from vessel curvature or obstructions.

Forces on Arteries

Arteries endure shear, circumferential, and longitudinal stresses from blood flow, pressure, and vessel stretching, respectively.

Murray's Law

Principle describing the optimal vessel branching pattern to minimize energy loss and maintain efficient blood flow.

The Law of Laplace

States that vessel wall tension is proportional to the product of pressure and radius, elucidating why larger vessels necessitate thicker walls.

Control Mechanisms Relating to Arterial Structure

Involves neural, hormonal, and local factors that regulate vessel tone, diameter, and remodeling.

Principles of Mechanotransduction

Cells sense mechanical forces and convert them into biochemical signals, impacting cell behavior and vessel function.

Cellular Movement

Cells reorganize their cytoskeleton and signaling pathways in response to chemical and mechanical cues, facilitating movement.

Conduction System of the Heart

Specialized cell network (SA node, AV node, bundle of His, Purkinje fibers) coordinating heart contractions.

Electrical Excitation

Electrical impulses initiate heart contractions, starting from the SA node.

Cardiac Cycle

Heart chambers undergo sequential contraction (systole) and relaxation (diastole) during each cardiac cycle.

Cardiac Cells and Tissue

Comprised of myocytes that generate force and conduct electrical signals in the heart.

Molecular Component of Excitation-Contraction Coupling

Involves calcium influx triggering actin-myosin interactions leading to muscle contraction.

Molecular Components Involved in Tension Generation

Actin, myosin, tropomyosin, and troponin regulate muscle contraction in the heart.

Tension Generation in a Cardiac Myocyte

Calcium binding to troponin enables myosin-actin interaction, generating contraction force.

Electrocardiogram (ECG) Explained

P Wave: Atrial depolarization.

QRS Complex: Ventricular depolarization.

T Wave: Ventricular repolarization.

The Cardiac Action Potential

Electrical changes in cardiac cells triggering contraction, characterized by distinct depolarization and repolarization phases.

Atrial Fibrillation

Irregular, rapid heart rhythm caused by disorganized electrical activity in the atria.

Ventricular Tachycardia

Fast, abnormal heart rate originating from the ventricles, potentially life-threatening.

Ventricular Hypertrophy

Thickening of ventricular walls often due to high blood pressure or heart disease.

Myocardial Infarction

Commonly known as a heart attack, results from blocked blood flow to the heart muscle, leading to tissue damage.

Understanding the Pressure-Volume Loop

Graphical representation of the cardiac cycle illustrating the pressure-volume relationship in the ventricles, used for heart function assessment.