SECTION - A: GENERAL HUMAN PHYSIOLOGY

I. ELABORATE ON (10 Marks)

Q1. Define Blood Pressure. Normal values of Systolic and Diastolic BP. Factors affecting BP. Short-term Regulation of Blood Pressure.

• Systolic BP (SBP): 120 mmHg (pressure during ventricular systole)
• Diastolic BP (DBP): 80 mmHg (pressure during ventricular diastole)
• Pulse Pressure = SBP - DBP = 40 mmHg
• Mean Arterial Pressure (MAP) = DBP + 1/3 Pulse Pressure = ~93 mmHg

BP = Cardiac Output × Peripheral Vascular Resistance

• Stroke Volume (ventricular filling pressure/preload)
• Heart Rate (controlled by sympathetic α- and β-adrenergic systems)
• Myocardial contractility

• Vessel diameter (radius) - most important (Poiseuille's law: resistance ∝ 1/r⁴)
• Blood viscosity
• Length of blood vessels
• Vasoconstrictors: Angiotensin II, catecholamines, endothelin
• Vasodilators: Kinins, prostaglandins, nitric oxide (NO)

• Baroreceptors are stretch-sensitive mechanoreceptors located in the walls of the carotid sinus and aortic arch.
• They continuously monitor arterial pressure.
• Afferent pathway: Glossopharyngeal nerve (IX) from carotid sinus; Vagus nerve (X) from aortic arch - both go to the Nucleus Tractus Solitarius (NTS) in the medulla.
• When BP rises: Baroreceptors fire more → NTS activates → vagal tone increases, sympathetic tone decreases → HR decreases, vasodilation occurs → BP falls back to normal.
• When BP falls: Baroreceptor firing decreases → sympathetic activity increases → vasoconstriction, increased HR and contractility → BP rises back to normal.
• This reflex allows rapid adjustments in blood pressure in response to abrupt changes in posture, blood volume, cardiac output, or peripheral resistance during exercise.
• In chronic hypertension, the baroreceptor reflex is "reset" to maintain elevated pressure.

• Peripheral chemoreceptors (carotid and aortic bodies) respond to hypoxia, hypercapnia, and acidosis.
• Stimulation causes reflex vasoconstriction and rise in BP.

• When blood flow to the vasomotor center is reduced, marked sympathetic stimulation occurs.
• Causes intense vasoconstriction and rise in BP - an emergency response.

• Type B atrial receptors respond to increased venous return (atrial distension).
• Cause vasodilation and reduced BP, but heart rate increases (unlike baroreceptors).

II. WRITE NOTES ON (5 Marks each)

1. Functions of the Liver

• Liver produces 600-1000 mL of bile per day.
• Bile contains bile salts, bile pigments (bilirubin), cholesterol, lecithin, and electrolytes.
• Bile salts emulsify fats and aid fat digestion and absorption.

• Glycogen storage (glycogenesis)
• Conversion of galactose and fructose to glucose
• Gluconeogenesis (from amino acids, lactate, glycerol)
• Glucose buffer function - removes excess glucose post-prandially and releases it when blood glucose falls; liver failure causes hypoglycemia.

• Fatty acid oxidation (beta-oxidation) for energy
• Synthesis of lipoproteins (VLDL, HDL)
• Conversion of carbohydrates and amino acids to fat for storage
• Synthesis and metabolism of cholesterol; conversion of excess cholesterol to bile acids

• Synthesis of all major plasma proteins: albumin, fibrinogen, prothrombin, clotting factors (I, II, V, VII, IX, X), acute-phase proteins, hormone-binding proteins
• Deamination of amino acids (urea cycle - conversion of ammonia to urea)
• Transamination reactions

• Phase I reactions: Oxidation, hydroxylation via cytochrome P450 enzymes
• Phase II reactions: Conjugation (esterification/glucuronidation)
• Kupffer cells phagocytose bacteria and particulate matter
• Metabolism of all steroid hormones; liver disease causes hormone excess

• Stores vitamins A, D, E, K, B12, and iron (as ferritin)

• Kupffer cells (hepatic macrophages) provide immune surveillance

• Liver is the main source of body heat due to intense metabolic activity

2. Structure and Function of the Juxta-Glomerular Apparatus (JGA)

• Modified smooth muscle cells (myoepithelial cells) in the media/wall of the afferent arteriole as it enters the glomerulus.
• Contain membrane-lined secretory granules packed with renin.
• Act as baroreceptors - sense pressure in the afferent arteriole.

• A specialized region of the tubular epithelium at the beginning of the distal convoluted tubule, where the tubule touches the arterioles.
• Cells are tall, closely packed, and have prominent nuclei.
• Functions as a chemoreceptor - senses NaCl concentration (and flow) in tubular fluid.

• Located at the junction between the afferent and efferent arterioles.
• Also contain some renin but function not fully understood.
• May serve as a communication/signaling link between macula densa and JG cells.

1. Renin Secretion - The primary function. Renin is released when:
   • Blood pressure in the afferent arteriole decreases (sensed by JG cells as baroreceptors)
   • Reduced NaCl delivery/concentration at macula densa
   • Increased sympathetic nervous activity via β1 adrenoreceptors
   • Prostaglandins stimulate renin release
   • Renin is inhibited by increased Na⁺/Cl⁻ reabsorption at macula densa, Angiotensin II (negative feedback), vasopressin
2. Renin-Angiotensin-Aldosterone System (RAAS) Activation:
   • Renin cleaves angiotensinogen → Angiotensin I → (ACE) → Angiotensin II
   • Angiotensin II: causes vasoconstriction, stimulates aldosterone (Na⁺ retention), stimulates ADH, raises blood pressure
3. Tubuloglomerular Feedback (TGF):
   • When GFR increases, more NaCl reaches macula densa → triggers vasoconstriction of afferent arteriole → reduces GFR back to normal (autoregulation of GFR)

3. Functions of Growth Hormone (GH)

• GH is the principal endocrine regulator of growth.
• Stimulates growth of all body tissues - bone, muscle, cartilage, viscera.
• On Bone: Stimulates proliferation of chondrocytes at epiphyseal plates → increases length of long bones (in children). After puberty (epiphyseal plate closure), it causes thickening of bones.
• Deficiency in childhood → Pituitary Dwarfism (normal proportions, short stature)
• Excess in childhood → Gigantism (e.g., Alton giant: >2.7 m)
• Excess after puberty → Acromegaly (enlargement of hands, feet, jaw, soft tissue hypertrophy)

• Most growth-promoting effects of GH are mediated indirectly through Insulin-like Growth Factor-1 (IGF-1), produced by the liver.
• IGF-1 stimulates cell proliferation and differentiation.

• ↑ lean body mass, ↓ body fat
• Stimulates immune system
• Mild sodium retention
• Stimulates erythropoiesis (↑ RBC production)
• GH replacement in adults with GH deficiency: increases lean body mass, decreases body fat, improves sense of well-being

• GH secreted in pulses, mainly during slow-wave sleep (stage 3 and 4 NREM)
• Measured to diagnose hypopituitarism, acromegaly, gigantism
• Recombinant GH available clinically

III. SHORT ANSWERS (2 Marks each)

1. Define Active Transport. Give an Example.

• Primary Active Transport: Directly coupled to ATP hydrolysis.
  • Example: Na⁺-K⁺ ATPase pump (Sodium-Potassium pump) - pumps 3 Na⁺ out and 2 K⁺ into the cell per cycle, against concentration gradients, using ATP. Found throughout the renal tubule and all body cells.
• Secondary Active Transport: Uses energy from an ion gradient (created by primary active transport) to drive another solute against its gradient.
  • Example: Glucose reabsorption by renal proximal tubule - Na⁺-glucose cotransporter (SGLT) uses the Na⁺ gradient to move glucose against its gradient. Also: Na⁺-amino acid cotransport.

2. Functions of Oestrogen

1. Female Secondary Sexual Characteristics:
   • Development of breasts, widening of pelvis, female fat distribution (hips, thighs, breasts)
   • Growth of pubic and axillary hair
2. Female Reproductive Tract:
   • Proliferation of endometrium (proliferative phase of menstrual cycle)
   • Growth and development of uterus, vagina, fallopian tubes
   • Maintains vaginal epithelium and acidity
3. Ovarian Function:
   • Stimulates follicular development (synergistic with FSH)
4. Skeletal Effects:
   • Stimulates bone growth; closes epiphyseal plates at puberty
   • Protects against osteoporosis (post-menopause, estrogen loss → osteoporosis)
5. Metabolic Effects:
   • Lowers LDL cholesterol, raises HDL cholesterol → cardioprotective
   • Promotes sodium and water retention (mild)
6. CNS Effects:
   • Maintains libido; may have neuroprotective roles
   • Increases CNS sensitivity to serotonin
7. Positive Feedback at Pituitary/Hypothalamus:
   • High estrogen levels at mid-cycle trigger the LH surge → ovulation

3. Types of White Blood Cells (WBCs / Leukocytes)

4. Functions of Cerebrospinal Fluid (CSF)

1. Mechanical Protection (Cushioning):
   • Acts as a "water jacket/hydraulic cushion" - protects the brain and spinal cord from mechanical shock and trauma by buoyancy effect. Brain weighs ~1400 g in air but only ~50 g in CSF.
2. Buoyancy:
   • Reduces the effective weight of the brain, preventing compression of blood vessels and nerve roots at the base of the brain.
3. Chemical Protection (Homeostasis):
   • Maintains a constant ionic environment for neurons (stable pH, ionic composition)
   • Brain is sensitive to changes in K⁺, Ca²⁺, Mg²⁺, H⁺ concentration
4. Nutrient Supply:
   • Carries glucose, amino acids, and oxygen to brain tissue not directly supplied by capillaries
5. Waste Removal:
   • Removes metabolic waste products and CO₂ from brain tissue
6. Intracranial Pressure Regulation:
   • Helps maintain constant intracranial pressure; adjustments in CSF volume compensate for changes in brain volume or blood volume
7. Acts as Pathway for Neuroactive Substances:
   • Hormones and neurotransmitters may be distributed to various parts of the CNS via CSF

5. Define Tidal Volume. What is the Normal Value?

• 500 mL (0.5 L) in a healthy adult at rest
• Also written as approximately 6-8 mL/kg of body weight

Note: Section B (Biochemistry) questions are not visible in the image. If you share the full paper, I can provide those answers too. Draw the labeled diagrams as instructed - especially the Baroreceptor Reflex Arc, JGA diagram, and Lung Volumes spirogram - to score full marks in TNMGRMU exams.