Body Fluids:

Blood Plasma:

• Composition: Reference: NCERT Biology Book 1, Chapter 17. Blood

• 90-92% water
• 6-8% proteins (albumins, globulins, fibrinogen)
• Electrolytes (sodium, potassium, chloride)
• Other molecules (glucose, amino acids, hormones)

Functions:

• Maintains osmotic balance
• Transports nutrients, hormones, and waste products
• Regulates body temperature
• Participates in immune responses
• Forms a blood clot to prevent excessive bleeding

Blood Cells:

• Red Blood Cells (Erythrocytes): Reference: NCERT Biology Book 1, Chapter 17. Blood

• Most abundant type of blood cells
• Contain hemoglobin for oxygen transport
• Biconcave shape increases surface area for oxygen absorption
• Lack a nucleus and other organelles
• Approximately 5 million RBCs per cubic millimeter of blood

• White Blood Cells (Leukocytes): Reference: NCERT Biology Book 1, Chapter 17. Blood

• Less abundant than RBCs
• Involved in immune defense and protection
• Different types include neutrophils, lymphocytes, monocytes, eosinophils, and basophils
• Respond to infections, allergies, and foreign particles

• Platelets (Thrombocytes): Reference: NCERT Biology Book 1, Chapter 17. Blood

• Smallest and least abundant type of blood cells
• Involved in blood clotting
• Release substances that initiate the formation of a blood clot
• Prevent excessive bleeding

Hemoglobin:

• Protein in red blood cells that carries oxygen
• Consists of four polypeptide chains (globin) and four heme groups
• Each heme group contains an iron ion that binds to oxygen
• Oxygen-saturation curve sigmoid-shaped

Factors affecting oxygen affinity of hemoglobin (Bohr effect):

• Partial pressure of carbon dioxide
• pH
• Temperature
• 2,3-Bisphosphoglycerate (BPG)

Hematocrit:

• Percentage of red blood cell volume compared to total blood volume
• Normally around 45% in men and 42% in women
• High hematocrit may indicate dehydration, polycythemia, or heart disease
• Low hematocrit may indicate anemia

Blood Vessels and Circulation:

Types of Blood Vessels:

• Arteries: Carry blood away from the heart
• Capillaries: Tiny vessels where exchange of nutrients and wastes occur
• Veins: Carry blood back to the heart

Structure of Blood Vessels:

• Arteries: Thick, muscular walls to withstand high blood pressure
• Capillaries: Thin, single-layer walls for easy diffusion
• Veins: Thin walls with valves to prevent backflow of blood

Blood Pressure and its Regulation:

• Blood pressure: force exerted by blood on blood vessel walls
• Influenced by heart rate, stroke volume, blood vessel resistance, blood viscosity, and blood volume
• Regulated by various mechanisms including renin-angiotensin-aldosterone system, sympathetic nervous system, and vasodilator hormones

Capillary Exchange:

• Fluid movement occurs through filtration, reabsorption, and osmotic balance
• Filtration: movement of fluid out of capillaries into interstitial fluid due to hydrostatic pressure
• Reabsorption: movement of fluid from the interstitial fluid back into capillaries due to osmotic pressure created by proteins and other solutes
• Osmotic balance: net balance between filtration and reabsorption

Cardiac Muscle Structure:

• Striated muscle tissue found only in the heart
• Composed of interconnected cardiomyocytes
• Contains gap junctions for rapid spread of electrical signals

Structure of the Heart:

• Chambers: Four chambers (two atria and two ventricles) with valves to regulate blood flow
• Septa: Walls that separate the chambers
• Coronary arteries: Supply blood to the heart muscle

Cardiac Conduction System:

• Specialized tissue that coordinates the heart’s contractions
• Consists of the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, and Purkinje fibers

Cardiac Cycle:

• Systole: Contraction of the heart
• Diastole: Relaxation of the heart
• Heart sounds: Lubb-dupp sounds produced by the closing of heart valves

Electrical Events During Cardiac Cycle (ECG):

• Electrocardiogram (ECG) is a recording of the electrical activity of the heart
• P wave: Atrial contraction
• QRS complex: Ventricular contraction
• T wave: Ventricular relaxation

Heart Function:

Cardiac Output:

• Amount of blood pumped by the heart per minute
• Determined by heart rate and stroke volume
• Normal cardiac output: (70 beats/minute) x (70 mL/beat) = 4900 mL/minute or 4.9 L/minute

Regulation of Heart Rate:

• Intrinsic factors: SA node, AV node, and refractory periods
• Extrinsic factors: Sympathetic and parasympathetic inputs

Cardiac Contractile Force:

• Influenced by calcium dynamics, Starling’s law, and Frank-Starling mechanism
• Calcium dynamics: Calcium ions bind to troponin, causing a conformational change that allows myosin to interact with actin
• Starling’s law: Increase in preload and afterload increases the force of contraction
• Frank-Starling mechanism: As the heart muscle is stretched, it contracts with more force

Circulatory System:

Pulmonary and Systemic Circulation:

• Pulmonary circulation: The circulation of blood between the heart and lungs
• Systemic circulation: The circulation of blood between the heart and the rest of the body

Regulation of Blood Flow to Different Tissues:

• Vasodilation: Blood vessels dilate (widen) to increase blood flow
• Vasoconstriction: Blood vessels constrict (narrow) to decrease blood flow
• Local chemical factors: Metabolic needs, adenosine, nitric oxide

Microcirculation:

• Structure and Functions of Microvessels:
• Arterioles: Connect arteries to capillaries
• Capillaries: Sites of exchange between blood and tissues
• Venules: Connect capillaries to veins

Lymphatic System:

• Network of vessels and tissues that collect and return fluid to the bloodstream
• Plays a role in fluid balance and immune responses
• Contains lymph nodes, which filter out foreign substances and pathogens