Heart II - Fundamentals in Anatomy & Physiology I

Lecture Overview

Lecture 15: Heart IIDr. Michael Ha, M.D.Course: BIO 111C - Fundamentals in Anatomy & Physiology IUniversity of the District of Columbia

Key Topics Covered

• Cardiac Anatomy and Cycle

  • In-depth examination of the heart's structures including:

    • Atria: Upper chambers of the heart responsible for receiving blood.

    • Ventricles: Lower chambers that pump blood out of the heart.

    • Valves: Structures that prevent backflow and ensure unidirectional blood flow during cardiac cycles.

    • Major Blood Vessels: Includes the aorta, pulmonary arteries, and veins that transport blood to and from the heart.

  • Detailed processes involved in the cardiac cycle:

    • Atrial and Ventricular Roles: Understanding the synchrony of contractions between atria and ventricles.

    • Conduction Pathways: Highlighted pathways include the SA node, AV node, Bundle of His, and Purkinje fibers to coordinate contractions.

• Physiological Parameters

  • Exploration of heart metrics emphasizing the importance of:

    • Heart Rate (HR): Normal range varies based on activity and physiological states.

    • Cardiac Output (CO): Vital for assessing cardiovascular health; evaluated in clinical scenarios.

Cardiac Cycle

• Definition

  • The cardiac cycle consists of a complete contraction (systole) and relaxation (diastole) of the heart’s chambers, crucial for blood circulation.

• Phases

  • Diastole (0.5 sec):

    • Focus on passive filling phases and the significance of atrial kick in ventricular filling.

  • Systole (0.3 sec):

    • Details about isovolumetric contraction and ejection phases, emphasizing pressure dynamics and valve openings.

Heart Rate and Cardiac Output

• Heart Rate (HR): Explored the factors influencing HR, including hormones (e.g., adrenaline), fitness level, and autonomic nervous inputs.

• Cardiac Output (CO): Explained CO formula with numerical examples for better understanding.

  • Formula: CO = HR x Stroke Volume (SV)

  • Average resting HR: 70 bpm, SV: 70-80 ml/beat, CO: 5-5.5 L/min as baseline metrics.

Principles of Pressure and Flow

• Fluid Dynamics: Illustrated with examples of pressure gradient effects on blood flow, emphasizing importance in pathological conditions.

Blood Flow Dynamics

• Atria and Ventricles Interaction:

  • How atrial contraction facilitates effective ventricular filling, emphasizing pressure changes during various phases.

Phases of Cardiac Cycle Explained

• Early Diastole: Blood flow dynamics and the significance of gravity in passive ventricular filling.

• Atrial Systole: Key role in completing atrial filling and its timing concerning ventricular function.

• Ventricular Systole: Explaining the significance of valve closure contributing to heart sounds and how pressure is established during contraction.

• Ventricular Ejection: Highlighting the interaction with systemic and pulmonary circulation pressures.

• Ventricular Diastole: Role of ventricular relaxation on pressure changes and implications for subsequent cardiac cycles.

Pressure Changes During Cardiac Cycle

• Details about S1 and S2 heart sounds linked to specific valve dynamics during systole and diastole, underscoring their clinical relevance.

Autonomic Nervous System Regulation

• Heart Rate Modulation: Detailed mechanisms of how the nervous system adjusts HR during stress or rest phases with neurotransmitter roles.

• Stroke Volume Regulation: Detailed discussion on Frank-Starling law with diagrams illustrating myocardial stretching influence on contractility.

Venous Return and Its Effects

• Importance of venous return in preload dynamics. Discuss factors such as body position, muscle pump activity, and respiratory phase changes on venous pressure gradients.

Factors Affecting Cardiac Output

• Specific examples of acute and chronic conditions that can lead to variations in CO, including exercise, dehydration, and heart disease.

Conclusion

• Reinforcement of understanding heart function, its regulation, and interaction with physiological parameters being critical for students' grasp of cardiovascular health.