Systems Physiology SBEG103 Lecture 7

Systems Physiology SBEG103 Lecture 7

• Cardiovascular System (CVS) is composed of the heart, arteries, veins, and blood.
• The heart acts as a double pump.
• Blood flows from the heart through arteries to arterioles and then capillaries before returning via venules and veins.

Objectives for Today

• Describe the function of different components of the cardiovascular system.
• Introduce how heart function is regulated.
• Give examples of devices relevant to the cardiovascular system.

The Heart

• The heart has four chambers: two atria and two ventricles.
• It has two systems: pulmonary and systemic.
• The heart contains valves (tricuspid, bicuspid, pulmonary, aortic) that control blood flow.

Cardiac Cycle

• Includes diastole (ventricular relaxation and filling) and systole (ventricular contraction and ejection).
• The heart pumps blood to deliver oxygen and nutrients while removing waste.

Components of the Cardiovascular System

• Heart: Acts as a hydraulic pump with four chambers (two atria and two ventricles) to maintain blood flow.
• Blood Vessels: Arteries carry blood away from the heart, veins return blood to the heart, and capillaries facilitate the exchange of gases and nutrients.
• Blood: The fluid being transported, composed of red blood cells (carrying oxygen), white blood cells (immune response), platelets (clotting), and plasma (liquid component).

Heart Structure

• Outermost: Pericardium and epicardium (membrane anchoring the heart to the diaphragm and sternum) which secretes lubricant.
• Middle: Myocardium (outermost muscle tissue), containing contractile muscle fibers.
• Innermost: Endocardium (lines the cardiac chambers).

Heart Chambers

• Two atria: Superior and inferior vena cavae bring deoxygenated blood into the right atrium and pulmonary veins bring oxygenated blood into the left atrium.
• Two ventricles: The right ventricle pumps blood to the lungs (pulmonary circulation) and the left ventricle pumps blood to the body (systemic circulation).

Circulation: Pulmonary

• Pulmonary circulation involves deoxygenated blood flowing from the right atrium to the right ventricle, through the pulmonary valve to the pulmonary artery, to the lungs for oxygenation, and back to the left atrium via pulmonary veins.
• The pathway starts with the Superior/ Inferior Vena Cava, to the Right Atrium, Tricuspid Valve, Right Ventricle, Pulmonary Semilunar Valve and then to the lungs (via the Left Pulmonary Artery).

Circulation: Systemic

• Systemic circulation involves oxygenated blood flowing from the left atrium to the left ventricle, through the aortic valve to the aorta, to the body tissues for delivery of oxygen and nutrients, and returns to the right atrium via venae cavae.
• The pathway starts with the Left Pulmonary Vein, to the Left Atrium, Bicuspid Valve, Left Ventricle, Aortic semilunar valve and then to all other tissues via the aorta.

Cardiac Control (Valves)

• Relaxation: Blood passively fills the atria and passes through the tricuspid and bicuspid valves. Semilunar valves stay closed.
• Contraction: Tricuspid and bicuspid valves close, blood is ejected from the ventricles, and the semilunar valves open.

Cardiac Cycle

• The cycle involves several phases including atrial and ventricular diastole, isovolumic ventricular contraction, ventricular ejection, and isovolumic ventricular relaxation
• These phases allow for the efficient pumping of blood throughout the body during both resting and active periods.

Conduction System

• The heart's inherent and rhythmical beat is due to autorhythmic fibers in the cardiac muscle.
• These fibers function as pacemakers and form the conduction system.
• Key components such as the SA node, AV node, AV bundle, and Purkinje fibers coordinate the electrical signals needed for proper heart contraction.

Physiologic Characteristics

• Automaticity
• Excitability
• Conductivity
• Rhythmicity
• Contractility
• Tonicity

Cardiac Receptors

• Baroreceptors: Respond to pressure changes, sending impulses to the medulla to respond to blood pressure changes
• Chemoreceptors: Respond to pH, carbon dioxide, and oxygen in blood, sending impulses to the medulla (influence both breathing and the cardiovascular system via the autonomic nervous system) to coordinate adjustments to blood chemistry.

Signal Transmission

• Local: Within the SA and AV nodes.
• Central: Through the sympathetic and parasympathetic nervous systems influencing the heart rate. The autonomic nervous system is responsible for maintaining homeostasis in the heart rate.

How Heart Rate is Regulated by the Medulla

• Sensory input relates to blood oxygen, pH or low carbon dioxide levels. This prompts the medulla (with chemoreceptors) to send impulses down the parasympathetic/sympathetic nervous system. This causes the release of acetylcholine or noradrenaline, regulating the heart rate as necessary.

Regulation of Blood Pressure

• The cardiovascular system maintains homeostasis via several processes to regulate blood pressure, including the baroreceptor reflex for rapid adjustments and vasoactive compounds for intermediate and long-term adjustments.

Heart Sounds

• Produced by blood turbulence caused by the closing of heart valves (as it moves through vessels and structures) S1, S2, S3, S4 (related to atrial systole, ventricular filling, rapid ventricular filling, and also reflecting the various valve actions during the cardiac cycle).

Devices (Used for Cardiovascular Monitoring)

• iStethoscope: Wireless stethoscope attachment allowing ECG, digital auscultation, and instant analysis.
• CardioSleeve: Provides ECG and digital auscultation, enabling instant analysis of cardiac function.
• ECG (Electrocardiogram): Traces electrical conduction signals through the heart..
• Pacemakers: Manage and regulate heartbeats via electrical impulses to the heart.

Pacemaker

• Monitors heart rhythm, sending electrical pulses if necessary.

Artificial Heart

• Prosthetic, implantable device, replacing the natural heart. (AbioCor)

Summary of the slides presented

• The presented slides are covering a detailed overview of the cardiovascular system. This includes the structure of the heart, blood flow through the heart and the body, local and central regulations that influence heart rate and blood pressure, various types of devices (medical) used for assessment, and examples of how the heart responds to stimulus.

This quiz covers the key concepts of the cardiovascular system presented in Systems Physiology SBEG103 Lecture 7. You will explore the structure and function of the heart, including its chambers and valves, the cardiac cycle, and the regulation of heart function. Gain insights into the importance of the cardiovascular system in delivering oxygen and nutrients to the body.