NDA Biology · Teaching notes
Human Physiology — NDA Biology
Human Physiology is the largest chapter in NDA Biology — 52 PYQs across 2017–2026, almost all EASY or MODERATE, and almost all pure named-fact recall. The trick is not derivation; it is knowing the right table cold. The chapter teaches in nine movements, building from the body's raw materials up to whole organ systems: (1) Body tissues — the four tissue types and the connective-tissue family (blood, cartilage, tendon, ligament) that every later system is built from; (2) Digestion and enzymes — the enzyme-substrate-source-pH table and the gland chain that processes food; (3) Nutrition — the vitamin-deficiency table (the single highest-yield table in the chapter), balanced diet, and minerals; (4) Circulation — heart chambers and valves, arteries vs veins, blood, lymph and clotting; (5) Respiration — the airway, gas exchange in the alveoli, and lung volumes; (6) Excretion and reproduction — the nephron and spermatogenesis; (7) Nervous system and sense organs — the nerve impulse, the reflex arc and brain, and the eye; (8) Endocrine system — the hormone-gland-function table; (9) Immune system — which cells make antibodies. 23 concepts, every PYQ tagged. Most concepts are reference tables: memorise the table, win the marks.
Subtopic notes
Body Tissues — the Building Blocks
8 PYQsA tissue is a group of similar cells doing one job; the body builds every organ from four tissue types — epithelial (covering), connective (support), muscle (movement), and nervous (signalling).
Open note
Digestion and Enzymes
7 PYQsDigestion breaks food into absorbable molecules using enzymes — each enzyme acts on one substrate, comes from one gland, and works best at one pH.
Open note
Nutrition, Vitamins and Minerals
8 PYQsA balanced diet supplies seven components; vitamins and minerals are the micronutrients whose deficiency causes specific named diseases.
Open note
Circulation — Heart, Vessels and Blood
6 PYQsThe heart pumps blood through arteries and veins in a double circuit; blood is a connective tissue, lymph resembles plasma, and clotting seals wounds with fibrin.
Open note
The Respiratory System
5 PYQsAir travels down a branching airway to the alveoli, where gas exchange happens; the volumes of air moved are named, with tidal volume the smallest.
Open note
Excretion and Reproduction
3 PYQsThe nephron filters blood at Bowman's capsule to make urine; the kidney also releases renin to control blood pressure; sperm form through meiosis from the primary spermatocyte.
Open note
Nervous System and Sense Organs
8 PYQsNerve cells carry electrical signals using sodium and potassium ions; the reflex arc and brain coordinate responses; and the eye converts light into images.
Open note
The Endocrine System and Hormones
5 PYQsEndocrine glands release hormones into the blood; each hormone has a gland of origin and a specific job, and the menstrual cycle is run jointly by the ovary and pituitary.
Open note
The Immune System
2 PYQsWhite blood cells defend the body; lymphocytes are the cells that produce antibodies against foreign antigens.
Open note
PYQ weightage by concept
23 concepts · 52 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
23 concepts · 52 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| The connective-tissue family — tendon, ligament, cartilage, bone | 4 | 8% |
| The four types of animal tissue | 2 | 4% |
| Epithelium and skin | 2 | 4% |
| Levels of organization — cells to organ systemsfoundation | — | — |
| Concept | PYQs | Share |
|---|---|---|
| Digestive enzymes — substrate, source, and pH | 3 | 6% |
| Digestive glands and their secretions | 3 | 6% |
| The ruminant (four-chambered) stomach | 1 | 2% |
| Concept | PYQs | Share |
|---|---|---|
| Vitamins — chemical name, deficiency, and source | 4 | 8% |
| Balanced diet and macronutrients | 3 | 6% |
| Minerals and metabolic waste | 1 | 2% |
| Concept | PYQs | Share |
|---|---|---|
| Blood, lymph, and clotting | 3 | 6% |
| Heart chambers, valves, and blood flow | 2 | 4% |
| Arteries vs veins | 1 | 2% |
| Concept | PYQs | Share |
|---|---|---|
| The airway and gas exchange in the alveoli | 3 | 6% |
| Lung volumes and capacities | 2 | 4% |
| Concept | PYQs | Share |
|---|---|---|
| The nephron — filtration and renin | 2 | 4% |
| Spermatogenesis — where meiosis happens | 1 | 2% |
| Concept | PYQs | Share |
|---|---|---|
| The eye — parts and photoreceptors | 4 | 8% |
| The nerve impulse — sodium and potassium | 2 | 4% |
| The reflex arc and brain regions | 2 | 4% |
| Concept | PYQs | Share |
|---|---|---|
| Hormones — gland and function | 4 | 8% |
| Reproductive hormones and the menstrual cycle | 1 | 2% |
Formula & revision sheet
0 formulas · 14 reference tables · 23 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
0 formulas · 14 reference tables · 23 gotchas across all subtopics — the exam-eve cheat-sheet
Reference tables (3)
The four types of animal tissue4 rows
| Tissue type | Function | Examples |
|---|---|---|
| Epithelial | Covering and lining of surfaces; protection, absorption, secretion | Skin surface, lining of mouth, oesophagus, intestine, glands |
| Connective | Support, binding, transport; cells in a matrix | Blood, bone, cartilage, tendon, ligament, adipose (fat) Blood is a CONNECTIVE tissue — fluid matrix (plasma) with cells (RBC, WBC, platelets) suspended in it. |
| Muscle | Contraction and movement; contains actin + myosin | Skeletal, smooth, cardiac muscle |
| Nervous | Conducting electrical signals | Neurons (brain, spinal cord, nerves) |
The connective-tissue family — tendon, ligament, cartilage, bone5 rows
| Tissue | Connects / role | Key fact |
|---|---|---|
| Tendon | Muscle to bone | Made of collagen; high tensile strength |
| Ligament | Bone to bone | Elastic; holds joints together |
| Cartilage | Flexible support | In nose, ear, larynx, trachea, knee NOT in the urinary bladder or the bronchioles. |
| Bone | Rigid framework | Calcified; the skeleton |
| Blood | Transport | Fluid matrix (plasma) + cells |
Epithelium and skin4 rows
| Feature | Detail |
|---|---|
| Squamous epithelium | Flat cells; lines the oesophagus, alveoli, blood vessels |
| Columnar epithelium | Tall cells; lines the intestine and stomach (absorption/secretion) |
| Skin pigment | Melanin — gives colour to skin, hair, iris |
| Melanin's role | Absorbs ultraviolet (UV) radiation — not infrared, X-ray or radio NDA 2017 — melanin protects against ULTRAVIOLET radiation specifically. |
Watch out for (4)
- Blood is connective tissue, not 'a fluid' of its own→ The four types of animal tissue
- Tendon ↔ ligament — the direction is the answer→ The connective-tissue family — tendon, ligament, cartilage, bone
- 'Cartilage is NOT found in ___' — know the exceptions→ The connective-tissue family — tendon, ligament, cartilage, bone
- Melanin blocks UV, not infrared or X-rays→ Epithelium and skin
Reference tables (2)
Digestive enzymes — substrate, source, and pH4 rows
| Enzyme | Substrate | Source | Optimum pH |
|---|---|---|---|
| Pepsin | Protein | Stomach wall | ~2 (acidic) NDA 2025 — pepsin works at pH ~2, trypsin at pH ~7.9. Opposite ends. |
| Trypsin | Protein | Pancreas | ~8 (alkaline) |
| Amylase | Starch / carbohydrate | Saliva, pancreas | Slightly alkaline / neutral |
| Lipase | Fat (after bile emulsifies it) | Pancreas | Alkaline |
The ruminant (four-chambered) stomach4 rows
| Chamber | Role |
|---|---|
| Rumen | Largest; microbial fermentation of cellulose |
| Reticulum | Forms the cud; traps foreign objects |
| Omasum | Absorbs water and minerals |
| Abomasum | The 'true' stomach — acid + enzymes |
Watch out for (3)
- Pepsin = acid, trypsin = alkaline→ Digestive enzymes — substrate, source, and pH
- Bile is not an enzyme→ Digestive enzymes — substrate, source, and pH
- The pancreas is an enzyme factory, not a bile store→ Digestive glands and their secretions
Reference tables (3)
Vitamins — chemical name, deficiency, and source6 rows
| Vitamin | Chemical name | Deficiency disease | Source |
|---|---|---|---|
| A | Retinol | Night blindness | Carrots, liver |
| B1 | Thiamin | Beriberi | Whole grains |
| B12 | Cobalamin | Anaemia | Intestinal bacteria, animal foods |
| C | Ascorbic acid | Scurvy | Citrus fruits NDA 2019 — Vitamin C deficiency = scurvy (NOT rickets, which is Vitamin D). |
| D | Calciferol | Rickets | Sunlight |
| K | — | Poor blood clotting | Leafy greens, gut bacteria |
Balanced diet and macronutrients6 rows
| Component | Main role |
|---|---|
| Carbohydrates | Main energy source (glucose) |
| Proteins | Growth and repair |
| Fats | Energy store (most energy per gram) |
| Vitamins + Minerals | Micronutrients (from fruits and vegetables) |
| Fibre (roughage) | Aids bowel movement |
| Water | Medium for all reactions |
Minerals and metabolic waste4 rows
| Mineral / waste | Linked to |
|---|---|
| Iodine | Thyroxine synthesis (deficiency → goitre) |
| Iron | Haemoglobin (deficiency → anaemia) |
| Calcium | Bones, teeth, clotting |
| Uric acid | From nucleic acids → high levels cause gout NDA 2017 — gout patients should minimise NUCLEIC-ACID-rich foods (uric acid comes from purines). |
Watch out for (3)
- Not every disease in the options is a deficiency disease→ Vitamins — chemical name, deficiency, and source
- Don't confuse the chemical names→ Vitamins — chemical name, deficiency, and source
- Fibre and water count as diet components→ Balanced diet and macronutrients
Reference tables (1)
Arteries vs veins4 rows
| Feature | Artery | Vein |
|---|---|---|
| Direction | Away from heart | Towards heart |
| Wall | Thick, elastic | Thinner |
| Valves | Absent | Present |
| Usual blood | Oxygenated | Deoxygenated EXCEPTION: pulmonary artery = deoxygenated; pulmonary vein = oxygenated. |
Watch out for (3)
- Bicuspid = left, tricuspid = right→ Heart chambers, valves, and blood flow
- 'Arteries carry oxygenated blood' is only USUALLY true→ Arteries vs veins
- Fibrinogen vs fibrin→ Blood, lymph, and clotting
Reference tables (1)
Lung volumes and capacities5 rows
| Volume | Meaning | Approx. |
|---|---|---|
| Tidal volume | Normal quiet breath | ~500 mL (lowest) NDA 2025/2026 — tidal volume is the air of a normal breath AND the smallest named volume. |
| Expiratory reserve | Extra forced out | ~1100 mL |
| Residual volume | Always remains | ~1200 mL |
| Inspiratory reserve | Extra forced in | ~3000 mL |
| Vital capacity | TV + IRV + ERV | ~4600 mL |
Watch out for (2)
- Bowman's capsule is NOT a breathing structure→ The airway and gas exchange in the alveoli
- Tidal volume is the smallest — not residual→ Lung volumes and capacities
Watch out for (1)
- Bowman's capsule filters; it doesn't carry urine away→ The nephron — filtration and renin
Reference tables (1)
The eye — parts and photoreceptors5 rows
| Part | Role |
|---|---|
| Cornea | Transparent front; light ENTERS here; avascular, proteins + cells NDA 2021 — the cornea is composed of proteins and cells; it is NOT light-sensitive and has NO blood vessels. |
| Iris / Pupil | Iris controls the pupil — the light aperture |
| Lens | Focuses light onto the retina |
| Retina | Light-sensitive screen; IMAGE forms here |
| Cones / Rods | Cones = colour vision; rods = dim-light vision |
Watch out for (4)
- Both ions — not just sodium→ The nerve impulse — sodium and potassium
- A reflex does not go through the brain→ The reflex arc and brain regions
- Cornea vs retina — entry vs image→ The eye — parts and photoreceptors
- Rods vs cones→ The eye — parts and photoreceptors
Reference tables (2)
Hormones — gland and function5 rows
| Hormone | Gland | Function |
|---|---|---|
| Thyroxine | Thyroid | Controls metabolic rate (needs iodine) Iodised salt supplies the iodine the thyroid needs to make thyroxine. |
| Insulin | Pancreas | Lowers blood glucose |
| Adrenaline | Adrenal medulla | Increases heartbeat (fight/flight) |
| Estrogen | Ovary | Female sexual characters |
| FSH / LH | Pituitary | Drive the menstrual cycle / reproduction |
Reproductive hormones and the menstrual cycle2 rows
| Gland | Hormones | Role |
|---|---|---|
| Pituitary | FSH, LH | Trigger follicle growth and ovulation |
| Ovary | Estrogen, Progesterone | Build and maintain the uterus lining |
Watch out for (2)
- Match the hormone to the RIGHT gland→ Hormones — gland and function
- Two glands, not one→ Reproductive hormones and the menstrual cycle
Reference tables (1)
White blood cells and antibody production4 rows
| Cell | Main role |
|---|---|
| Lymphocytes | Produce ANTIBODIES (B-cells → plasma cells) NDA 2024/2025 — the antibody-producing cells are LYMPHOCYTES. |
| Neutrophils | Phagocytosis of bacteria |
| Eosinophils | Parasites, allergy |
| Monocytes | Become macrophages |
Watch out for (1)
- Antibodies = lymphocytes, not other WBCs→ White blood cells and antibody production