ISC Class 11 Biology Flashcards

24 sample cards from the Biology deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. Define tidal volume, vital capacity and residual volume.

   Tidal volume (TV): air inhaled/exhaled in normal breathing (~500 mL). Vital capacity (VC): maximum air a person can breathe out after maximum inspiration (ERV+TV+IRV). Residual volume (RV): air remaining in lungs after forceful expiration (~1100–1200 mL).

2. What is the composition of human blood?

   Blood is a fluid connective tissue made of plasma (~55%, fluid matrix) and formed elements (~45%): erythrocytes (RBCs), leucocytes (WBCs) and thrombocytes (platelets). Plasma is ~90–92% water with proteins, ions and nutrients.

3. Trace the path of blood through the human heart (double circulation).

   Deoxygenated blood: body → vena cava → right atrium → right ventricle → pulmonary artery → lungs. Oxygenated blood: lungs → pulmonary veins → left atrium → left ventricle → aorta → body. This is double circulation (pulmonary + systemic).

4. What is the cardiac cycle and normal heart rate?

   The cardiac cycle is one complete heartbeat consisting of atrial systole, ventricular systole, and joint diastole, lasting about 0.8 seconds. The normal resting heart rate is about 72 beats per minute, pumping ~70 mL per beat (cardiac output ~5 L/min).

5. What is the role of the SA node in the heart?

   The sino-atrial (SA) node, located in the right atrium, is the pacemaker of the heart; it generates the action potential that initiates and regulates the heartbeat. The impulse then passes to the AV node, bundle of His and Purkinje fibres.

6. Name the main nitrogenous excretory products and classify organisms by them.

   Ammonia (ammonotelic — most toxic, e.g., bony fishes, aquatic animals), Urea (ureotelic — e.g., mammals, terrestrial amphibians), and Uric acid (uricotelic — least toxic/least water, e.g., birds, reptiles, insects).

7. What is the structural and functional unit of the kidney, and its main parts?

   The nephron is the structural and functional unit of the kidney. Its parts: Bowman's capsule (with glomerulus = Malpighian/renal corpuscle), proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

8. What are the three main processes of urine formation?

   (1) Glomerular filtration (ultrafiltration of blood in the glomerulus), (2) Tubular reabsorption (selective reabsorption of useful substances like glucose, water, ions), and (3) Tubular secretion (active secretion of wastes like H+, K+, ammonia into the filtrate).

9. What is the role of ADH in kidney function?

   Antidiuretic hormone (ADH/vasopressin), from the posterior pituitary, increases water reabsorption in the distal tubule and collecting duct, producing concentrated urine and preventing diuresis. Its absence causes diabetes insipidus.

10. What are the three types of muscle tissue and their characteristics?

    Skeletal (striated, voluntary, multinucleate — attached to bones), Cardiac (striated, involuntary, branched with intercalated discs — heart), and Smooth/visceral (non-striated, involuntary, spindle-shaped — walls of internal organs).

11. State the sliding filament theory of muscle contraction.

    During contraction, the thin actin filaments slide over the thick myosin filaments toward the centre of the sarcomere. Cross-bridges of myosin heads attach to actin and pull it; the H-zone and I-band shorten while the A-band length stays constant. It requires Ca2+ and ATP.

12. How many bones are in the human skeleton, and what are the two divisions?

    The adult human skeleton has 206 bones, divided into the axial skeleton (80 bones: skull, vertebral column, ribs, sternum) and the appendicular skeleton (126 bones: limbs and girdles).

13. Name the three types of joints with an example of each.

    Fibrous/immovable (e.g., skull sutures), Cartilaginous/slightly movable (e.g., joints between vertebrae), and Synovial/freely movable (e.g., ball-and-socket joint of the shoulder/hip, hinge joint of the knee/elbow).

14. What is a neuron and its three main structural parts?

    A neuron is the structural and functional unit of the nervous system. Its parts are the cell body (cyton/soma with nucleus), dendrites (receive impulses), and the axon (conducts impulses away from the cell body to the synapse).

15. Explain how a nerve impulse is transmitted across a synapse.

    At a chemical synapse, the arriving impulse triggers Ca2+ influx, causing synaptic vesicles to release neurotransmitters (e.g., acetylcholine) into the synaptic cleft. These bind to receptors on the post-synaptic membrane, generating a new impulse in the next neuron.

16. What is a resting potential and an action potential in a neuron?

    Resting potential is the polarized state (~ -70 mV, negative inside) maintained by the Na+/K+ pump when the neuron is not conducting. An action potential is the rapid depolarization (Na+ influx) and repolarization (K+ efflux) wave that travels along the axon as a nerve impulse.

17. What are the divisions of the human nervous system?

    Central Nervous System (CNS: brain and spinal cord) and Peripheral Nervous System (PNS: cranial and spinal nerves). The PNS is further divided into somatic (voluntary) and autonomic (involuntary) systems; autonomic = sympathetic + parasympathetic.

18. Name the three main parts of the human brain and one function of each.

    Forebrain (cerebrum — intelligence, memory, voluntary actions), Midbrain (relay of visual/auditory reflexes), and Hindbrain (cerebellum — balance/coordination; medulla oblongata — controls heartbeat, breathing, blood pressure; pons).

19. What is the difference between endocrine and exocrine glands?

    Endocrine (ductless) glands secrete hormones directly into the blood (e.g., pituitary, thyroid, adrenal). Exocrine glands secrete their products through ducts onto a surface or cavity (e.g., salivary, sweat, sebaceous glands).

20. What is the role of insulin and glucagon in blood sugar regulation?

    Both are secreted by the islets of Langerhans of the pancreas. Insulin (beta cells) lowers blood glucose by promoting its uptake and conversion to glycogen. Glucagon (alpha cells) raises blood glucose by breaking down glycogen (glycogenolysis). Insulin deficiency causes diabetes mellitus.

21. Why is the pituitary gland called the 'master gland'?

    The pituitary gland (hypophysis) is called the master gland because it secretes hormones (like TSH, ACTH, FSH, LH) that control and regulate the secretions of many other endocrine glands. It is itself controlled by the hypothalamus.

22. What hormones does the thyroid gland secrete and what is their function? Name a deficiency disorder.

    The thyroid secretes thyroxine (T4) and triiodothyronine (T3), which regulate basal metabolic rate, growth and development; it also secretes calcitonin (lowers blood calcium). Iodine deficiency causes goitre; deficiency in children causes cretinism.

23. What are the hormones of the adrenal medulla and their effect?

    The adrenal medulla secretes adrenaline (epinephrine) and noradrenaline — the 'emergency'/'fight-or-flight' hormones. They increase heart rate, blood pressure, blood glucose, alertness and breathing rate during stress.

24. Differentiate hormones from enzymes.

    Hormones are chemical messengers secreted by endocrine glands, transported by blood, that regulate body functions and are not reused. Enzymes are biological catalysts (mostly proteins) that speed up biochemical reactions, act at the site of production, and are reusable/unchanged.

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