Understanding the Cardiovascular System: Rest and Exercise

Introduction

• The lecture focuses on the cardiovascular system (CV system), exploring the function and composition of blood, heart anatomy, blood circulation, and the regulation of heartbeat.
• Objective: Dive deep into each component for a detailed understanding, crucial for achieving high marks.

Composition and Function of Blood

• Blood Plasma:
  • Makes up 55% of blood.
  • Transports nutrients around the body.
• Red Blood Cells (Erythrocytes):
  • Comprise roughly 45% of blood.
  • Transport oxygen and carbon dioxide.
• White Blood Cells (Leukocytes):
  • Less than 1%.
  • Fight diseases and remove pathogens.
• Platelets (Thrombocytes):
  • Less than 1%.
  • Aid in clot formation to prevent bleeding.

The Heart and Blood Circulation

Heart Anatomy

• Four Chambers: Right atrium, left atrium, right ventricle, left ventricle.
• Four Blood Vessels:
  • Pulmonary artery: Deoxygenated blood to lungs.
  • Aorta: Oxygenated blood to body.
  • Pulmonary vein: Oxygenated blood from lungs.
  • Vena cava: Deoxygenated blood to heart.
• Valves:
  • Prevent backflow: Pulmonary, aortic, tricuspid, bicuspid (mitral).
  • Tips: "Pulmonary" relates to lungs. "Arteries" take blood away. "Veins" bring blood in.

Circulatory Networks

• Pulmonary Circulation:
  • Starts at right ventricle.
  • Pulmonary artery carries deoxygenated blood to lungs.
  • Blood oxygenated in lungs, returns via pulmonary vein to left atrium.
• Systemic Circulation:
  • Begins at left ventricle.
  • Aorta carries oxygenated blood to body systems.
  • Deoxygenated blood returns via vena cava to right atrium.
• These networks provide oxygen and manage carbon dioxide exchange.

Regulation of Heartbeat

Intrinsic Regulation

• SA Node: Pacemaker, triggers atrial contraction.
• AV Node: Slows impulse, allows atria to contract fully before ventricles.
• Bundle of His and Purkinje Fibers: Spread impulse to ventricles.
• Heart's myogenic nature: Generates its own impulse.

Extrinsic Regulation

• Autonomic Nervous System:
  • Sympathetic: Increases heart rate (fight-or-flight).
  • Parasympathetic: Decreases heart rate (rest-and-digest).
• Impact of adrenaline and acetylcholine on heart rate.

Heart Rate, Stroke Volume, and Cardiac Output

• Definitions:
  • Heart Rate (HR): Beats per minute.
  • Stroke Volume (SV): Blood ejected per beat.
  • Cardiac Output (Q): HR x SV.
• Effects of Exercise:
  • Immediate: Increase in HR, SV, and Q.
  • Long-term: Adaptations like increased SV, reduced HR due to cardiac hypertrophy.

Influence of Different Populations

• Males vs. Females: Males generally have larger stroke volumes and cardiac outputs.
• Trained vs. Untrained: Trained individuals have stronger cardiovascular systems, higher SV.
• Young vs. Old: Younger people generally have stronger hearts, higher cardiac outputs.

Cardiovascular Drift

• Definition: Thermal regulatory response to prolonged exercise, leading to dehydration.
• Mechanism:
  • Dehydration reduces blood plasma, affects venous return.
  • Stroke volume decreases, HR increases to maintain cardiac output.
• Key Concept: Heart must compensate to maintain constant cardiac output during prolonged exercise.

Conclusion

• Understanding these cardiovascular principles is crucial for detailed knowledge in IB sport science.
• Further exploration of resources is available for teaching and learning.