Cardiovascular System - The cardiovascular system—also called the circulatory system—is the body’s transport network. It includes the heart, blood, and blood vessels, working together to deliver oxygen and nutrients to every cell while removing waste products. This system is crucial for maintaining homeostasis, regulating blood pressure, and supporting metabolic activity in all tissues.
Major Components of the Cardiovascular System
1. Heart: The muscular pump that maintains continuous circulation of blood. It has four chambers—right atrium, right ventricle, left atrium, and left ventricle—separated by valves to ensure one-way flow.Key Terminologies and Hormones
ADH (Antidiuretic Hormone):
Secreted by the posterior pituitary gland, ADH promotes water reabsorption in the kidneys. This increases water retention and helps maintain blood volume and pressure.Aldosterone:
Produced by the adrenal cortex, aldosterone stimulates the kidneys to retain sodium and water, which raises blood volume and consequently blood pressure.Angiotensin:
A powerful vasoconstrictor hormone that narrows blood vessels and triggers the release of aldosterone and ADH, thereby elevating blood pressure.Renin-Angiotensin-Aldosterone System (RAAS):
A compensatory mechanism that activates when blood pressure falls. The kidneys secrete renin, which converts angiotensinogen to angiotensin I and then to angiotensin II—leading to vasoconstriction and increased water retention.Result: ↑ Blood pressure and ↑ blood volume
Cardiac Function Terms
Cardiac Output (CO):
The total volume of blood pumped by the heart per minute. It depends on heart rate (HR) and stroke volume (SV).Tachycardia:
A fast heart rate, typically above 100 beats per minute. It can occur during exercise, stress, fever, or cardiac disorders.Bradycardia:
A slow heart rate, usually below 60 beats per minute. It may be normal in athletes or caused by heart block or medication.Blood Pressure Regulation
Hypertension:
Refers to high blood pressure (↑ BP), where arterial pressure remains elevated persistently. Chronic hypertension strains the heart and damages blood vessels.Hypotension:
Refers to low blood pressure (↓ BP), which can lead to dizziness, fainting, or shock due to inadequate perfusion.Vasoconstriction:
Narrowing of blood vessels, increasing resistance and raising blood pressure.Vasodilation:
Widening of blood vessels, decreasing resistance and lowering blood pressure.Flow of Blood Through the Heart
- Deoxygenated blood from the body enters the right atrium via the superior and inferior vena cava.
- It passes through the tricuspid valve to the right ventricle.
- The pulmonary valve opens to send blood to the lungs via the pulmonary artery.
- After oxygenation in the lungs, oxygen-rich blood returns to the left atrium via pulmonary veins.
- It then flows through the mitral valve into the left ventricle.
- Finally, it exits through the aortic valve into the aorta, supplying oxygenated blood to the entire body.
Major Blood Vessels
- Aorta: The largest artery, carrying oxygenated blood from the left ventricle to systemic circulation.
- Vena Cava: The largest vein, returning deoxygenated blood to the heart.
- Pulmonary Arteries: Carry deoxygenated blood to the lungs.
- Pulmonary Veins: Carry oxygenated blood from the lungs to the heart.
- Capillaries: Microscopic vessels where nutrient and gas exchange occurs.
Homeostatic Control of Blood Pressure
The body maintains stable blood pressure through several feedback mechanisms:
- Baroreceptors in the carotid sinus and aortic arch detect changes in BP.
- Medulla oblongata processes this input and adjusts heart rate and vessel diameter.
- RAAS system activates when BP drops, increasing vasoconstriction and fluid retention.
- ADH release further promotes water reabsorption in the kidneys.
Together, these systems ensure adequate perfusion even during changes in posture, blood loss, or dehydration.
Common Disorders of the Cardiovascular System
1. Atherosclerosis: Build-up of fatty plaques inside arteries, narrowing them and increasing the risk of heart attack or stroke.Role of Exercise and Lifestyle
Regular exercise strengthens cardiac muscles, enhances blood circulation, and lowers resting heart rate.
Healthy habits—like balanced diet, low salt intake, and avoiding smoking—support optimal cardiovascular health.
Summary Table
| Term | Definition | Effect on Body |
|---|---|---|
| ADH | Antidiuretic hormone | ↑ Water retention |
| Aldosterone | Adrenal hormone | ↑ Sodium & water retention |
| Angiotensin | Vasoconstrictor hormone | ↑ BP & aldosterone secretion |
| RAAS | Renin-Angiotensin-Aldosterone System | ↑ BP and blood volume |
| Tachycardia | Fast heart rate | ↑ Cardiac output |
| Bradycardia | Slow heart rate | ↓ Cardiac output |
| Hypertension | High blood pressure | Strain on heart & vessels |
| Hypotension | Low blood pressure | Poor organ perfusion |
| Vasoconstriction | Narrowing of vessels | ↑ BP |
| Vasodilation | Widening of vessels | ↓ BP |
The cardiovascular system is the lifeline of the human body. By maintaining consistent circulation, it delivers oxygen, hormones, and nutrients while removing waste. Understanding its components and regulatory mechanisms—such as the RAAS system, ADH, and aldosterone—helps students grasp how the body maintains equilibrium even under stress. Maintaining heart health through proper diet, exercise, and stress management is key to lifelong wellness.
FAQs About the Cardiovascular System
Q1. What organs are part of the cardiovascular system?
The cardiovascular system includes the heart, blood, and blood vessels (arteries, veins, and capillaries).
Q2. What is the main function of the cardiovascular system?
Its primary function is to transport oxygen, nutrients, and hormones to cells and remove waste products like carbon dioxide.
Q3. What hormone increases blood pressure by retaining water?
ADH (Antidiuretic Hormone) increases water reabsorption in the kidneys, raising blood volume and pressure.
Q4. How does the RAAS system regulate blood pressure?
The Renin-Angiotensin-Aldosterone System increases vasoconstriction and promotes sodium and water retention to restore low BP.
Q5. What is the difference between vasoconstriction and vasodilation?
Vasoconstriction narrows blood vessels (increasing BP), while vasodilation widens them (decreasing BP).
Q6. What causes tachycardia and bradycardia?
Tachycardia (fast HR) may result from stress, fever, or cardiac disease; bradycardia (slow HR) may occur in athletes or due to heart block.
Q7. Why is blood pressure important?
It ensures continuous flow of blood to vital organs, supplying oxygen and nutrients necessary for their function.
