🧬 Biology — Human Physiology
1. Nutrition in Animals
NUTRIENTS
- Carbohydrates: Energy yielding (glucose, fructose, starch)
- Proteins: Structural material (keratin, renin, trypsin)
- Lipids: Structural and energy giving (fatty acids + glycerol)
- Vitamins: Biochemical functions — hormones (D), antioxidants (E), co-enzymes (B-complex)
VITAMINS AND DEFICIENCY DISEASES
| Vitamin | Chemical Name | Solubility | Deficiency Disease |
|---|---|---|---|
| A | Retinol | Fat | Night blindness |
| B1 | Thiamine | Water | Beri-beri |
| B3 | Niacin | Water | Pellagra |
| B12 | Cyanocobalamin | Water | Megaloblastic anaemia |
| C | Ascorbic acid | Water | Scurvy |
| D | Calciferol | Fat | Rickets, Osteomalacia |
| E | Tocopherol | Fat | Anaemia (newborns) |
| K | Phylloquinone | Fat | Bleeding diathesis |
2. Digestion in Humans
DIGESTIVE ENZYMES
| Region | Secretion | Enzyme | Product |
|---|---|---|---|
| Mouth | Saliva | Salivary amylase | Starch → Maltose |
| Stomach | Gastric juice | Pepsinogen | Protein → Peptone |
| Pancreas | Pancreatic juice | Trypsin, Amylase, Lipase | Protein → Polypeptide |
| Small intestine | Intestinal juice | Peptidase, Maltase, Lipase | Amino acids, Glucose, Fatty acids |
DISORDERS
- Vomiting: Expulsion of food from mouth
- Diarrhoea: Loose frequent bowel
- Jaundice: Yellow colouration of skin
- Gall stones: Cholesterol crystallisation
- Constipation: Difficulty in defecation
- Appendicitis: Inflammation of appendix
3. Respiration in Humans
RESPIRATORY SYSTEM
- Pathway: Nostril → Nasal cavity → Larynx → Trachea → Bronchi → Bronchioles → Alveoli
- Diaphragm: Dome-shaped muscle for breathing
- Inhalation: Diaphragm flattens, rib cage moves outward
- Exhalation: Diaphragm relaxes, rib cage moves inward
GAS TRANSPORT
- Oxygen transport: 98.5% by haemoglobin (1 Hb carries 4 O₂ molecules)
- CO₂ transport: 70% as bicarbonate, 23% as carbamino-haemoglobin, 1% dissolved in plasma
- Respiratory Quotient (RQ): Volume of CO₂ released / Volume of O₂ absorbed
- RQ of carbohydrate = 1; Protein = 0.80
- RQ determined by Ganong's respirometer
DISORDERS
- Asthma: Airway blockage, coughing, breathing difficulty
- Pneumonia: Inflammation of alveoli
- Tuberculosis: Inflammation of lungs/pleural membrane
4. Transportation in Humans
CIRCULATORY SYSTEM
- Heart: 4-chambered (2 atria + 2 ventricles); weight: 280-340g (male), 230-280g (female)
- Pericardium: Outer covering of heart
- Heart beat: Systole (contraction) + Diastole (relaxation) = 0.8 seconds
- Blood pressure: Systolic (120 mm Hg) / Diastolic (80 mm Hg)
- Arteries: Carry blood away from heart (except pulmonary artery)
- Veins: Carry blood towards heart (except pulmonary vein)
BLOOD COMPONENTS
- Plasma: Liquid matrix with proteins, salts, hormones
- RBC: Contains haemoglobin
- WBC: Immune function
- Platelets: Blood clotting
CARDIOVASCULAR DISEASES
- Arteriosclerosis: Hardening of arteries
- Atherosclerosis: Cholesterol deposition in arteries
- Heart attack: Decreased blood supply to heart
- Angina pectoris: Chest pain due to insufficient oxygen
5. Excretion in Humans
EXCRETORY SYSTEM
- Waste product: Urea (nitrogenous waste)
- Kidneys: Bean-shaped, made of nephrons
- Nephron: Glomerulus + Bowman's capsule + Convoluted tubules + Collecting duct
URINE FORMATION
- Glomerular filtration: Movement of blood/ minerals from glomerulus to Bowman's capsule
- Tubular reabsorption: 99% of water, vitamins, glucose reabsorbed
- ADH (Antidiuretic hormone): Opposes urine formation, conserves water
DISORDERS
- Kidney stones: Crystals of salts precipitate
- Diabetes insipidus: Low ADH secretion
- Uremia: Excess urea in blood
- Haemodialysis: Artificial kidney for filtering blood
6. Skeletal System
BONES
- Axial skeleton: Skull (22 bones), Vertebral column (33), Sternum, Ribs (24)
- Appendicular skeleton: Pectoral girdle, Pelvic girdle, Forelimbs, Hindlimbs
- Total bones: 206
DISORDERS
- Arthritis: Joint inflammation
- Osteomalacia: Insufficient Ca and P in bones
- Osteoporosis: Loss of minerals and fibres from bone matrix
- Sprain: Ligament damage due to twisting
7. Neural Co-ordination
NEURON & SYNAPSE
- Synapse: Junction between two neurons with a synaptic cleft
- Neurotransmitters: Dopamine, Acetylcholine (transmit signals)
BRAIN FUNCTIONS
- Cerebrum: Thinking, intelligence, memory, will power, reasoning
- Hypothalamus: Body temperature regulation (thermostat), appetite, emotions
- Cerebellum: Muscular co-ordination, posture, equilibrium
- Medulla oblongata: Heart rate, involuntary breathing, blood pressure
DISORDERS
- Meningitis: Inflammation of brain meninges
- Parkinson's disease: Destruction of dopamine-producing neurons
- Alzheimer's disease: Destruction of neurons in hippocampus; acetylcholine deficiency
8. Endocrine System
HORMONES AND THEIR FUNCTIONS
| Gland | Hormone | Function |
|---|---|---|
| Pituitary (Posterior) | ADH, Oxytocin | Water resorption, labour, milk ejection |
| Thyroid | Thyroxine (T4) | Metabolism, blood pressure, tissue growth |
| Pancreas | Insulin, Glucagon | Blood sugar regulation |
| Adrenal medulla | Epinephrine | Stress response (fight or flight) |
| Testis | Testosterone | Reproductive maturation, sperm production |
| Ovary | Oestrogen, Progesterone | Reproductive maturation, menstrual cycle |
| Pineal | Melatonin | Circadian rhythm |
| Thymus | Thymosin | T-lymphocyte development |
KEY POINTS
- Hypothalamus: Controls pituitary gland
- Parathyroid: Increases blood calcium levels
- Adrenal cortex: Glucocorticoids, Mineralocorticoids (stress response)
Summary: Human Physiology at a Glance
| System | Key Function | Key Fact |
|---|---|---|
| Digestive | Breakdown of food | Salivary amylase → Starch to Maltose |
| Respiratory | Gas exchange | O₂ transport by haemoglobin |
| Circulatory | Transport | Blood pressure = 120/80 mm Hg |
| Excretory | Waste removal | Urea is main waste product |
| Skeletal | Support and protection | 206 bones in human body |
| Endocrine | Chemical co-ordination | Hypothalamus controls pituitary |
KEY TAKEAWAYS FOR UPSC
- Vitamins: A (Fat, Night blindness), C (Water, Scurvy), D (Fat, Rickets)
- Digestion: Salivary amylase (mouth), Pepsin (stomach), Trypsin (pancreas)
- Respiratory: RQ carbohydrate = 1, Protein = 0.80
- Blood pressure: 120/80 mm Hg
- Blood groups: O = Universal donor, AB = Universal recipient
- Urine formation: Glomerular filtration + Tubular reabsorption
- Brain: Cerebrum (thinking), Hypothalamus (thermostat), Cerebellum (co-ordination)
- Hormones: Insulin (blood sugar), ADH (water balance), Thyroxine (metabolism)
- Haemodialysis: Artificial kidney for blood filtration
- Total bones: 206
High-Yield Interactive UPSC Quiz (Biology — Human Physiology)
Q1. Which vitamin deficiency causes scurvy?
Correct Answer: C. Vitamin C (ascorbic acid) deficiency causes scurvy.
Q2. Where does protein digestion begin in humans?
Correct Answer: B. Protein digestion begins in the stomach with pepsinogen (pepsin).
Q3. The respiratory quotient (RQ) of carbohydrate is:
Correct Answer: B. The RQ of carbohydrate is 1.0.
Q4. What is the normal blood pressure of a healthy human?
Correct Answer: B. Normal blood pressure is 120/80 mm Hg.
Q5. Which blood group is the universal donor?
Correct Answer: D. Blood group O is the universal donor.
Q6. Which hormone regulates blood sugar level?
Correct Answer: B. Insulin regulates blood sugar level (decreases it).
Q7. Which part of the brain is called the thermostat of the body?
Correct Answer: B. Hypothalamus regulates body temperature (thermostat).
Q8. What is the total number of bones in the human body?
Correct Answer: C. The human body has 206 bones.
Q9. Which enzyme converts starch into maltose?
Correct Answer: C. Salivary amylase converts starch into maltose.
Q10. ADH (Antidiuretic hormone) is secreted by which gland?
Correct Answer: C. ADH is secreted by the posterior pituitary gland.