Human Physiology - Body Fluids and Circulation

Notes from toppers may include the following key points:

1. Blood:

• Plasma: Liquid component of blood that carries nutrients, waste products, hormones, etc.
• Red Blood Cells (RBCs): Contains hemoglobin, which binds to oxygen and transports it to tissues.
• White Blood Cells (WBCs): Involved in the body’s defense mechanism and fighting infections.
• Platelets: Help in blood clotting by forming a clot at the site of injury. (Refer NCERT Biology Class 11 Chapter 15; NCERT Biology Class 12 Chapter 6).

2. Heart:

• Structure: Four chambers - two atria (auricles) and two ventricles, with valves to ensure proper blood flow.
• Cardiac Cycle: Coordinated contraction and relaxation of the heart. It involves systole (contraction) and diastole (relaxation).
• ECG (Electrocardiogram): Graphic representation of heart’s electrical activity, valuable in diagnosing heart problems. (Refer NCERT Biology Class 11 Chapter 18).

3. Blood vessels:

• Arteries: Carry oxygenated blood away from the heart to tissues.
• Capillaries: Microscopic vessels where the exchange of nutrients, oxygen, and waste products occur.
• Veins: Carry deoxygenated blood back to the heart.
• Structure: Walls formed with three layers and contain elastic fibers. (Refer NCERT Biology Class 11 Chapter 15; NCERT Biology Class 12 Chapter 2).

4. Lymph and Lymphatic System:

• Lymph: Fluid present in lymphatic vessels that drains excess fluid from tissues and transports it back into the bloodstream.
• Structure: Lymphatic vessels are similar to blood vessels, but valves ensure the lymph flows in only one direction. (Refer NCERT Biology Class 11 Chapter 15).

5. Fluid Balance and Osmoregulation:

• Water Balance: Body fluids include the fluid part of blood, lymph, and other body fluids. Water intake from drinking and food, and fluid loss through sweating, urine, and breathing needs to be in balance.
• Osmoregulation: Maintaining equilibrium of osmotic pressure between body fluids and their surrounding environment is crucial for cells to function properly. The kidneys play a crucial role in osmoregulation. (Refer NCERT Biology Class 11 Chapter 15).

6. Transport of Substances:

• Cell Membrane Transport: Mechanisms such as diffusion (passive), osmosis (passive), facilitated diffusion (passive), active transport (active), endocytosis (active), and exocytosis (active) help in the transportation of substances across membranes.
• Role of Membrane Proteins: Proteins such as carrier proteins, ion channels, pumps, and vesicles (active transport) play crucial roles in transporting substances across cell membranes. (Refer NCER Biology Class 11 Chapter 6).