DIMS Lectures CVS Physiology PDF

Here is the complete pdf lecture of cvs physiology by Dr. Tahir Malik

Introduction to Cardiovascular Physiology

The cardiovascular system (CVS) is responsible for transporting oxygen, nutrients, hormones, and waste products throughout the body. It consists of the heart, blood vessels, and blood, all working together to maintain homeostasis. Understanding CVS physiology is crucial for medical students, as it forms the foundation for clinical applications related to hypertension, heart failure, arrhythmias, and shock.

This guide provides a complete revision resource covering all essential topics of CVS physiology, making it ideal for medical exams, practical applications, and clinical understanding.

Anatomy and Function of the Heart

The heart is a muscular organ that functions as a pump, circulating blood through two circuits:

Pulmonary Circulation – Sends deoxygenated blood to the lungs for oxygenation.
Systemic Circulation – Delivers oxygenated blood to tissues.

Chambers of the Heart

The heart consists of four chambers:

Right Atrium – Receives deoxygenated blood from the body via the superior and inferior vena cava.
Right Ventricle – Pumps blood to the lungs through the pulmonary artery.
Left Atrium – Receives oxygenated blood from the lungs via the pulmonary veins.
Left Ventricle – Pumps oxygenated blood to the systemic circulation via the aorta.

Heart Valves and Their Function

Valves ensure unidirectional blood flow:

Atrioventricular (AV) Valves: Prevent backflow into the atria.
- Tricuspid Valve (Right side)
- Mitral Valve (Left side)
Semilunar Valves: Prevent backflow into the ventricles.
- Pulmonary Valve
- Aortic Valve

Cardiac Cycle: The Phases of Heartbeat

The cardiac cycle consists of two main phases:

Systole (Contraction Phase):
- Ventricles contract to pump blood into circulation.
- AV valves close (First heart sound - S1 "lub").
- Semilunar valves open.
Diastole (Relaxation Phase):
- Ventricles relax and fill with blood from the atria.
- Semilunar valves close (Second heart sound - S2 "dub").
- AV valves open.

Understanding the pressure changes in atria, ventricles, and major arteries is key to interpreting echocardiograms and heart sounds.

Electrical Conduction System of the Heart

The heart generates electrical impulses autonomously, regulated by specialized pacemaker cells:

Sinoatrial (SA) Node: Primary pacemaker (60–100 bpm).
Atrioventricular (AV) Node: Delays impulse to allow ventricular filling.
Bundle of His: Conducts impulses to the ventricles.
Purkinje Fibers: Ensure rapid ventricular contraction.

Electrocardiogram (ECG) provides insights into electrical activity and can diagnose arrhythmias, myocardial infarction, and conduction blocks.

Regulation of Blood Pressure and Cardiac Output

Blood Pressure (BP) = Cardiac Output (CO) × Total Peripheral Resistance (TPR)

Cardiac Output (CO)

CO = Stroke Volume (SV) × Heart Rate (HR)
Stroke Volume is determined by:
1. Preload – Volume of blood in ventricles before contraction.
2. Contractility – Strength of ventricular contraction.
3. Afterload – Resistance ventricles must overcome to eject blood.

Blood Pressure Control Mechanisms

Short-Term Regulation:
- Baroreceptors in the aortic arch and carotid sinus detect changes in BP.
- Sympathetic Nervous System (SNS) increases heart rate and contractility.
- Parasympathetic Nervous System (PNS) slows heart rate.
Long-Term Regulation:
- Renin-Angiotensin-Aldosterone System (RAAS) increases BP by vasoconstriction and sodium retention.
- Antidiuretic Hormone (ADH) promotes water retention to increase blood volume.

Clinical Relevance

1. Hypertension (High Blood Pressure)

Caused by increased cardiac output or peripheral resistance.
Managed using beta-blockers, ACE inhibitors, diuretics.

2. Heart Failure

Failure of the heart to pump effectively.
Left-sided HF: Leads to pulmonary congestion.
Right-sided HF: Causes peripheral edema.
Treated with diuretics, ACE inhibitors, beta-blockers.

3. Arrhythmias (Abnormal Heart Rhythms)

Bradycardia (<60 bpm): Slow heart rate.
Tachycardia (>100 bpm): Fast heart rate.
Diagnosed with ECG and treated with medications or pacemakers.

4. Myocardial Infarction (Heart Attack)

Caused by blockage of coronary arteries.
Symptoms: Chest pain, shortness of breath, sweating.
Diagnosed via ECG, Troponin levels.
Treated with aspirin, thrombolytics, angioplasty.

Case Example:

A 35-year-old male presents with episodes of dizziness and syncope during intense exercise. He has no significant past medical history but reports occasional palpitations. His blood pressure is 110/70 mmHg, and heart sounds are normal at rest. ECG shows left ventricular hypertrophy (LVH) with deep Q waves in leads V1-V4. An echocardiogram reveals asymmetrical septal hypertrophy with left ventricular outflow tract (LVOT) obstruction.

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Diagnosis: Hypertrophic Cardiomyopathy (HCM) with Left Ventricular Outflow Tract (LVOT) Obstruction

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