BME211 Week 3

- Structure and Composition of Arteries:

- Structure: Three layers—intima (inner), media (smooth muscle and elastin), and adventitia (outer connective tissue).

- Composition: Collagen, elastin, and smooth muscle cells provide strength, elasticity, and contractility.

- Mechanical Perspective of Vessels: Vessels are dynamic structures that withstand varying pressures and stresses, allowing for blood flow regulation.

- Stress vs. Strain Behavior in Arteries: Arteries exhibit elastic behavior under low stress but may deform permanently under high stress, showing a nonlinear relationship between stress and strain.

- Tension-Radius Behavior for an Artery: Wall tension increases with the radius of the artery; larger arteries need more tension to withstand the same pressure (Laplace's Law).

- Pressure and Flow Waveforms in Arteries: Arterial pressure and flow fluctuate with the cardiac cycle, showing systolic peaks and diastolic troughs.

- Pulse Wave Velocity: The speed at which pressure waves move through the arteries; indicates arterial stiffness.

- Turbulent vs. Laminar Flow:

- Laminar: Smooth, orderly flow, typical in healthy vessels.

- Turbulent: Disordered, can occur in narrowed or diseased arteries.

- Rotating and Axial Flow: Blood flow has both straight (axial) and swirling (rotational) components, affecting flow dynamics.

- Symmetric vs. Asymmetric Velocity Profiles: Symmetric flow has a uniform velocity distribution, while asymmetric flow can occur due to vessel curvature or obstructions.

- Forces on Arteries: Arteries experience forces like shear stress (from blood flow), circumferential stress (from blood pressure), and longitudinal stress (from vessel stretching).

- Murray’s Law: Describes optimal vessel branching to minimize energy loss and maintain efficient blood flow.

- The Law of Laplace: Wall tension in vessels is proportional to the product of pressure and radius; explains why larger vessels need thicker walls.

- Control Mechanisms Relating to Arterial Structure: Includes 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, influencing cell behavior and vessel function.

- Steps for Mechanotransduction:

- Mechanosensing: Cells detect mechanical stimuli.

- Mechanotransmission: Signal spreads within cells.

- Mechanosignaling: Biochemical pathways are activated.

- Mechanoresponse: Cells adapt, remodel, or change function.

- Cellular Movement: Cells move via cytoskeletal reorganization and signaling pathways, responding to chemical and mechanical cues.

- Conduction System of the Heart: Network of specialized cells (SA node, AV node, bundle of His, Purkinje fibers) that coordinate heartbeats.

- Electrical Excitation: Electrical impulses trigger the heart to contract, starting with the SA node.

- Cardiac Cycle: Sequential contraction (systole) and relaxation (diastole) of the heart chambers.

- Cardiac Cells and Tissue: Composed of cardiac muscle cells (myocytes) that generate force and conduct electrical signals.

- Molecular Component of Excitation-Contraction Coupling: Involves calcium influx, triggering actin-myosin interactions that cause contraction.

- Molecular Components Involved in Tension Generation: Actin, myosin, tropomyosin, and troponin regulate muscle contraction.

- Tension Generation in a Cardiac Myocyte: Calcium binds to troponin, allowing myosin to interact with actin, 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 that trigger contraction, with distinct phases of depolarization and repolarization.

- Atrial Fibrillation: Irregular, rapid heart rhythm due to disorganized electrical activity in the atria.

- Ventricular Tachycardia: Fast, abnormal heart rate originating from the ventricles, which can be life-threatening.

- Ventricular Hypertrophy: Thickening of the ventricular walls, often due to high blood pressure or heart disease.

- Myocardial Infarction: Commonly known as a heart attack; occurs when blood flow to the heart muscle is blocked, causing tissue damage.

- Understanding the Pressure-Volume Loop: Graphical representation of the cardiac cycle showing the relationship between pressure and volume in the ventricles, used to assess heart function.