Overview
This lecture covers the anatomy of the cardiovascular system and explores how skeletal and cardiac muscles adapt to different types of training, as well as the structure, components, and functional circuits of the heart.
Muscle Adaptation and Training
- Skeletal muscle adapts to endurance training by increasing capillary density and mitochondrial content.
- Resistance training leads to neural adaptations and increased contractile protein in skeletal muscle.
- Disuse of skeletal muscle causes atrophy, as seen in prolonged space flights.
- Cardiac muscle's primary function is to pump blood and it adapts to training similarly to skeletal muscle.
Cardiac Adaptations to Training
- Endurance training induces eccentric hypertrophy: main adaptation is increased ventricular chamber size and blood volume.
- Weightlifting causes concentric hypertrophy: main adaptation is increased wall thickness, little change (or decrease) in chamber size.
- Eccentric hypertrophy results from series addition of cells; concentric from parallel addition.
- Acute blood pressure spikes during weightlifting prompt heart muscle growth; chronic high blood pressure causes pathological thickening and stiffness.
Anatomy of the Cardiovascular System
- The cardiovascular system includes the heart, blood vessels, and blood.
- The heart is fist-sized, beats ~100,000 times daily, and is located just above the diaphragm, slightly left.
- The heart is encased in the pericardium, a double-walled sac providing protection, anchoring, and frictionless movement.
Heart Structure and Blood Flow
- Heart layers: epicardium (outer), myocardium (muscle), endocardium/endothelium (inner).
- Four heart chambers: right/left atria and right/left ventricles.
- Valves ensure unidirectional blood flow: tricuspid, pulmonary semilunar, mitral (bicuspid), and aortic semilunar valves.
- Chordae tendineae and papillary muscles prevent valve inversion.
Circulation Pathways
- Pulmonary circulation: right ventricle → lungs → left atrium (for gas exchange).
- Systemic circulation: left ventricle → body organs → right atrium.
- Parallel flow ensures all organs receive oxygen-rich blood; series flow (e.g., GI tract to liver) allows filtration (first pass metabolism).
- Coronary circulation supplies heart muscle, with left coronary artery supplying most myocardium.
Coronary Circulation and Medical Interventions
- Blood enters coronary circulation mainly when the heart is relaxed.
- Blocked coronary arteries can cause heart attacks; treatments include angioplasty (balloon and stent) and coronary artery bypass graft (CABG).
- CABG involves grafting a new artery to bypass the blockage, often using an artery from the arm.
Key Terms & Definitions
- Eccentric Hypertrophy — enlargement of heart chambers due to endurance training.
- Concentric Hypertrophy — thickening of heart walls due to resistance training or hypertension.
- Pericardium — double-walled sac surrounding the heart for protection and support.
- Chordae Tendineae — cords anchoring heart valves to prevent backflow.
- First Pass Metabolism — filtration of blood from the GI tract through the liver.
- Coronary Circulation — blood supply system for heart muscle itself.
- CABG (Coronary Artery Bypass Graft) — surgical procedure to restore blood flow by bypassing a blocked coronary artery.
Action Items / Next Steps
- Review structural differences between cardiac adaptations from endurance vs. resistance training.
- Study heart anatomy diagrams, especially chambers, valves, and main vessels.
- Prepare questions on coronary circulation or heart disease interventions for next class.