Cardiovascular Physiology Overview

Mean Arterial Pressure (MAP)

• Normal range is 70-105
• Less than 60 indicates inadequate organ perfusion
• Formula: MAP = (2 * Diastolic Blood Pressure) + Systolic Blood Pressure / 3

Cardiac Index (CI)

• Tells if cardiac output (QT) is adequate for patient size
• Larger patients need a higher CI
• Normal range is 2.5-4.0 L/min/m²
• Formula: CI = QT / BSA

Cardiac Output (QT)

• Amount of blood pumped from the left ventricle per minute
• Formula: QT = Stroke Volume (SV) * Heart Rate (HR)
• Normal range is 4-8 L/min at rest

Sympathetic Nervous System

• Releases norepinephrine (NE)
• Increases heart rate and electrical impulses
• Affects all areas of the heart
• Converts glycogen to glucose
• Causes pupil dilation
• "Fight or flight" response

Parasympathetic Nervous System

• Releases acetylcholine (ACh)
• Reduces electrical impulses
• Decreases heart rate
• Affects atrioventricular (AV) nodes
• Causes pupil constriction
• "Rest and digest" response

Factors Affecting Heart Rate

• Increased heart rate: sympathetic activity, anxiety, pain, hypoxia, and vasodilator medications
• Decreased heart rate: parasympathetic activity, beta blockers, and vomiting

Systolic & Diastolic Blood Pressure

• Systole: top number, normal 90-120 mmHg, ventricles contract, semilunar valves open, AV valves close
• Diastole: bottom number, normal 60-90mmHg, ventricles relax, semilunar valves close, AV valves open

Venous System

• Acts as a reservoir for 60% of total blood volume
• Venous return equals cardiac output (QT)

Ejection Fraction (EF)

• Normal range is 65-70%
• Reduced EF (below 50%) indicates reduced cardiac function
• Severely reduced EF (below 30%) leads to severely limited exercise tolerance.

Preload, Afterload, Contractility

• Preload: Ventricular stretch before contraction, influenced by filling, compliance, venous return, and end diastolic volume
• Afterload: Resistance to ventricular emptying, influenced by vascular resistance, ventricular wall tension, and viscosity of blood
• Contractility: Strength of ventricular contraction, impacted by preload

Pulse Pressure (PP)

• Difference between systolic and diastolic blood pressure.
• Normal range is 30-40mmHg.
• A low PP (less than 30mmHg) can indicate low stroke volume

Positive Pressure Ventilation (PPV)

• Augments preload and cardiac output.
• Positive pressure ventilation (PPV) hazards impact preload and contractility, and can have negative effects on blood pressure and urinary output (↓ VR, ↓ BP&QT, Urinary output)

Pulmonary Artery Wedge Pressure (PAWP)

• Measures pressure in the left atrium.
• Normal range is 5-10 mmHg.

Cardiac Work

• Measure of the energy used ejecting blood from the ventricles to overcome arterial pressures.
• Correlates with oxygen needed by the heart
• Higher in the left ventricle.

Key Properties of the Heart Muscle

• Excitability: responding to stimuli
• Inherent rhythmicity: initiating spontaneous electrical impulses
• Conductivity: spreading electrical impulses
• Contractility: responding to electrical impulses with contractions

Layers of the Heart

• Epicardium
• Myocardium (middle layer)
• Endocardium (inner layer lining the heart chambers)

Explore the fundamentals of cardiovascular physiology, focusing on Mean Arterial Pressure (MAP), Cardiac Index (CI), and Cardiac Output (QT). Understand the roles of the sympathetic and parasympathetic nervous systems in heart function. This quiz will test your knowledge of these critical concepts in human physiology.