Cardiovascular System Summary

Cardiovascular System Summary

• Capillaries: Microscopic vessels facilitating material exchange between blood and interstitial fluid.
• Arteries: Vessels carrying blood away from the heart. The coronary arteries branch most proximally from the aorta.
• Heart Valves: Ensure unidirectional blood flow.
• Hepatic Portal Vein: Carries blood from the digestive tract.
• Blood Flow Driving Force: Pressure gradient.
• Factors Affecting Blood Flow (excluding one): Factors increasing blood flow to tissues include increased blood pressure, relaxation of precapillary sphincters, increased blood volume, and decreased peripheral resistance. Decreased vessel diameter decreases blood flow.
• Resistance and Flow: Increased resistance leads to decreased flow. Increased vessel length increases resistance; decreases flow.
• Increasing Vessel Flow: Increasing vessel radius by one unit has the most significant effect on increasing flow.
• Pericardium: The sac surrounding the heart.
• Pericardial Fluid: Reduces friction between the heart and pericardium.
• Intercalated Discs: Cardiac muscle cells are connected by gap junctions.
• Heart Valve Locations: Located between atria and ventricles, and between ventricles and arteries.
• Bicuspid/Tricuspid Valves: Have chordae tendineae.
• Myogenic Heart: Heart muscle initiates its own electrical signals for contraction.
• Cardiac Contractile Cell Action Potential:
  • Rapid depolarization: Sodium (Na+) ions.
  • Plateau phase: Calcium (Ca2+) and Potassium (K+) ions.
  • Flattening of the plateau: Decreasing K+ permeability, increasing Ca2+ permeability.
  • End of plateau: Closing of Ca2+ channels and opening of K+ channels.
• Pacemaker Action Potential: Increasing Na2+ influx and decreasing K+ efflux.
• Action Potential Duration: At least 200 milliseconds.
• Plateau Phase Importance: Prevents tetanus (sustained contraction).
• Myocardial Cell's Action Potential Potential: Unstable ion channels allow spontaneous action potentials.
• Pacemaker Action Potential Spread: Spreads to adjacent cells through gap junctions.
• Fibrous Skeleton Function: Forces electrical activity through the AV node.
• AV Node Function: Delays electrical impulses to allow atria to finish contracting.
• Heart Attack: Myocardial infarction.
• Complete Heart Block Symptoms: SA node signals don't reach ventricles; atria and ventricles contract independently.
• Heart Fibrillation: Myocardial cells fail to work together, preventing effective ventricle pumping.
• Treating Ventricular Fibrillation: Electrical shock.
• Electrocardiogram (ECG): Shows summed electrical potentials in the heart.
• P Wave: Atrial depolarization.
• QRS Complex: Ventricular depolarization.
• Tachycardia: Heart rate of 124 beats per minute.
• Ventricular Contraction Timing: Begins after the Q wave.
• Atrial Contraction Timing: During the latter part of the P wave.
• Cardiac Cycle Start: SA node firing.
• Blood Entering Heart: Atrial pressure must be lower than venous pressure for entry.
• First Heart Sound: AV valves closing.
• Isovolumic Ventricular Systole: Both AV and semilunar valves are closed.
• ECG QRS precedes: Increase in ventricular pressure.
• AV Valves During Ventricular Systole: Closed.
• Ventricular Ejection: Ventricles in systole.
• End-Diastolic Volume (EDV): Blood in ventricle to be pumped out.
• Stroke Volume: Volume ejected from each ventricle during contraction.
• Cardiac Output Calculation: Heart rate x stroke volume.
• Cardiac Output Definition: Blood volume circulated by the heart per minute.
• Epinephrine/Norepinephrine Effect: Increase ion flow through If and Ca2+ channels.
• Starling's Law: Cardiac output is directly related to venous return.
• Heart Rate Increase Factors: Sympathetic stimulation and epinephrine on SA node.
• Beta Receptor Stimulation: cAMP formation
• Beta Blockers Effect: Decrease heart rate.
• Blood Flow Through Heart Structures: Right atrium, right ventricle, pulmonary artery, pulmonary vein, left atrium, left ventricle.
• Blood Pressure and Resistance on Flow: Doubling both would have no net change in flow. Doubling diameter decreases resistance most.
• Potassium Ion Permeability Effect on Heart Rate: Increased permeability reduces heart rate.
• Cardiac Muscle Refractory Period: Prevents tetany.

Autorhythmic Cells Order:

• Sinoatrial nodes
• Internodal pathway
• Atrioventricular node
• Bundle of His
• Left and Right Bundle Branches
• Purkinje fibers

ECG in Complete Heart Block:

• More P waves than QRS complexes.
• AV node-Bundle of His block: More P waves than QRS complexes.

Cardiac Cycle Order:

• Beginning of atrial systole
• Completion of ventricular filling
• Beginning of ventricular systole
• Closure of AV valves
• Isovolumic contraction
• Opening of semilunar valves
• Ventricular ejection
• Ventricular relaxation.

Acetylcholine Effect on Heart Rate:

• Increases K+ permeability, decreases Ca2+ permeability, slowing heart rate.

Sympathetic Stimulation Effect on Heart Rate:

• Increases ion influx, accelerating depolarization, increasing heart rate.

Manganese Ions on Heart Muscle Contraction:

• Blocking calcium channels reduces contraction force.