What is the primary function of the cardiovascular system?

The cardiovascular system delivers oxygen and nutrients to tissues, removes carbon dioxide and waste products, maintains blood pressure, regulates temperature, and supports homeostasis.

What is cardiac output?

Cardiac output is the volume of blood pumped by the heart per minute and is calculated as stroke volume multiplied by heart rate.

What factors determine stroke volume?

Stroke volume is determined by preload, afterload, myocardial contractility, and ventricular compliance.

What is the Frank–Starling law of the heart?

The Frank–Starling law states that an increase in venous return leads to increased ventricular filling and stronger myocardial contraction, increasing stroke volume.

What controls heart rate physiologically?

Heart rate is controlled by the sinoatrial node and modulated by autonomic nervous system activity, hormones, and reflexes.

What is the function of the cardiac conduction system?

The cardiac conduction system generates and transmits electrical impulses to coordinate atrial and ventricular contractions.

What causes systolic and diastolic blood pressure?

Systolic pressure is produced by ventricular contraction, while diastolic pressure reflects arterial recoil and peripheral resistance.

What is mean arterial pressure (MAP)?

Mean arterial pressure is the average pressure in arteries during one cardiac cycle and ensures adequate organ perfusion.

What is the role of arterioles in circulation?

Arterioles are resistance vessels that regulate peripheral vascular resistance and control blood pressure.

How does the baroreceptor reflex regulate blood pressure?

Baroreceptors detect changes in arterial pressure and adjust heart rate and vascular tone via autonomic pathways.

What is the physiological basis of venous return?

Venous return depends on skeletal muscle pump, respiratory pump, venous valves, and sympathetic venoconstriction.

What is capillary exchange?

Capillary exchange involves diffusion, filtration, and reabsorption of fluids and solutes regulated by Starling forces.

What is coronary circulation?

Coronary circulation supplies oxygenated blood to the myocardium, primarily occurring during diastole.

How does exercise affect cardiovascular physiology?

Exercise increases heart rate, stroke volume, cardiac output, and redistributes blood flow to active muscles.

What is the physiological basis of shock?

Shock results from inadequate tissue perfusion due to reduced cardiac output, low blood volume, or decreased vascular resistance.

What causes pulse pressure widening?

Pulse pressure widens due to increased stroke volume or reduced arterial compliance, such as in aortic regurgitation.

What is the function of the pulmonary circulation?

Pulmonary circulation carries deoxygenated blood to the lungs for gas exchange and returns oxygenated blood to the heart.

What causes left ventricular hypertrophy?

Left ventricular hypertrophy occurs due to chronic pressure overload, such as hypertension or aortic stenosis.

How does aging affect cardiovascular physiology?

Aging reduces arterial elasticity, increases blood pressure, decreases cardiac reserve, and slows reflex responses.

Why is the refractory period important in cardiac muscle?

The refractory period prevents tetanic contraction and ensures rhythmic and coordinated cardiac contractions.

1. Overview of CVS Physiology

The cardiovascular system ensures continuous circulation of blood to deliver oxygen, nutrients, hormones, and remove metabolic waste. It maintains blood pressure, tissue perfusion, acid–base balance, and body temperature.

Main Components

Heart → Pump
Blood vessels → Transport channels
Blood → Transport medium

2. Functions of the Cardiovascular System

Oxygen and nutrient delivery
Removal of carbon dioxide and waste
Immune defense
Temperature regulation
Hormone transport
Maintenance of blood pressure
Regulation of fluid balance
Homeostasis and metabolic support

3. Heart Physiology

3.1 Structure and Function

The heart has four chambers:

Right atrium
Right ventricle
Left atrium
Left ventricle

Blood Flow Pathway

Body → Right atrium → Right ventricle → Lungs → Left atrium → Left ventricle → Body

3.2 Cardiac Muscle Physiology

Unique Features

Striated and involuntary
Intercalated discs (gap junctions)
Automatic rhythmicity

Key Properties

Automaticity → Self-excitation
Conductivity → Impulse transmission
Excitability → Response to stimulus
Contractility → Force of contraction
Refractory period → Prevents tetany

4. Electrical Activity of the Heart

4.1 Cardiac Conduction System

Sinoatrial (SA) node → Pacemaker
Atrioventricular (AV) node
Bundle of His
Purkinje fibers

Heart Rate

Normal adult: 60–100 bpm

4.2 Action Potentials

Pacemaker Cells

Phases: Slow depolarization → Threshold → Repolarization

Ventricular Muscle Cells

Phases:

Phase 0: Rapid depolarization (Na⁺ influx)
Phase 1: Initial repolarization
Phase 2: Plateau (Ca²⁺ influx)
Phase 3: Repolarization (K⁺ efflux)
Phase 4: Resting potential

Significance

Plateau prevents sustained contraction
Coordinates effective pumping

5. Cardiac Cycle Physiology

Phases

Systole

Isovolumetric contraction
Ventricular ejection

Diastole

Isovolumetric relaxation
Rapid filling
Atrial contraction

Heart Sounds

S1 → AV valve closure
S2 → Semilunar valve closure

6. Cardiac Output (CO)

Formula

CO = Stroke Volume × Heart Rate

Normal Value

4–6 L/min (rest)

6.1 Stroke Volume Determinants

Preload

Ventricular filling volume

(Frank–Starling law)

Afterload

Resistance against ventricular ejection

Contractility

Strength of myocardial contraction

Increased by sympathetic stimulation

7. Blood Pressure Physiology

Normal BP

120/80 mmHg

Determinants

Cardiac output
Peripheral vascular resistance
Blood volume
Arterial elasticity

7.1 Mean Arterial Pressure (MAP)

MAP = Diastolic BP + 1/3 Pulse Pressure

8. Hemodynamics (Blood Flow Dynamics)

Laminar Flow

Smooth, parallel blood movement

Poiseuille’s Law

Flow ∝ Radius⁴

(Small radius change → major flow change)

Vascular Resistance

Highest in arterioles

Primary regulators of blood pressure

9. Blood Vessel Physiology

Arteries

High pressure
Elastic walls

Arterioles

Resistance vessels
BP control

Capillaries

Exchange vessels

Veins

Blood reservoir
Venous return system

10. Microcirculation and Capillary Exchange

Exchange Mechanisms

Diffusion
Filtration
Reabsorption

Starling Forces

Capillary hydrostatic pressure
Plasma oncotic pressure

11. Venous Return Physiology

Mechanisms

Skeletal muscle pump
Respiratory pump
Venous valves
Sympathetic venoconstriction

12. Coronary Circulation Physiology

Supplies myocardium
Occurs mainly during diastole
Regulated by metabolic demand

13. Pulmonary Circulation Physiology

Low-pressure system
Gas exchange function
Regulates blood oxygenation

14. Regulation of Cardiovascular Function

14.1 Neural Regulation

Sympathetic

↑ Heart rate
↑ Contractility
Vasoconstriction

Parasympathetic (Vagus)

↓ Heart rate

14.2 Reflex Regulation

Baroreceptor Reflex

Responds to BP changes

Chemoreceptor Reflex

Responds to O₂, CO₂, pH

14.3 Hormonal Regulation

Renin–Angiotensin–Aldosterone System (RAAS)
ADH (Vasopressin)
Atrial Natriuretic Peptide (ANP)
Adrenaline/Noradrenaline

15. Exercise and CVS Adaptation

During Exercise

↑ Cardiac output
↑ Heart rate
↑ Stroke volume
Redistribution of blood to muscles

Long-Term Training Effects

Increased cardiac efficiency
Lower resting heart rate

16. Shock and CVS Physiology

Types

Hypovolemic
Cardiogenic
Septic
Neurogenic

Key Feature

Reduced tissue perfusion

17. Aging and Cardiovascular Changes

Reduced arterial elasticity
Increased BP
Decreased cardiac reserve

18. Clinical Relevance Summary

| Parameter | Normal Value |

| ----------------- | ------------ |

| Heart Rate | 60–100 bpm |

| Cardiac Output | 4–6 L/min |

| Stroke Volume | 70 mL |

| Blood Pressure | 120/80 mmHg |

| Ejection Fraction | 55–70% |

Cardiovascular System Physiology Complete Detailed Guide for Medical Students