CSIR NET Life Sciences and Biotechnology Unit 7 covers system physiology – animal. These topic-wise notes explain essential concepts in simple language for examination preparation.
Select a topic below to read its explanation, remember the key distinctions, and open the detailed notes for further study.
Unit 7 Topic-wise Notes
1. Blood and hemostasis
Blood contains red cells, white cells and platelets. Hemoglobin carries oxygen; platelet activation and coagulation produce a stable clot.
For CSIR NET, begin by identifying the main components involved in blood and hemostasis and the order in which they interact. Explain what changes when one component is removed, inhibited, overexpressed or exposed to different conditions. This approach is especially useful for interpreting experiments rather than recalling isolated facts.
When solving a question, distinguish the underlying mechanism from its observable outcome. Compare the normal situation with the altered condition, and check whether the evidence supports a direct effect or only an association. The central distinction to retain is: a left shift of the hemoglobin oxygen curve indicates increased affinity.
Hemostasis begins with vascular responses and platelet adhesion, followed by activation and aggregation at injured vessels. Coagulation reactions generate thrombin, which converts fibrinogen to fibrin; factor XIII stabilizes the clot by cross-linking fibrin. Antithrombin, protein C and other controls restrict clot formation. Fibrinolysis involves plasmin-mediated fibrin degradation. Platelet count, bleeding time and coagulation assays assess different components, so an abnormal result should be mapped to the pathway it measures rather than treated as a general failure of clotting.
Important: A left shift of the hemoglobin oxygen curve indicates increased affinity.
Read Detailed Notes →2. Heart and ECG
The cardiac cycle includes filling and ejection; ECG reflects cardiac electrical activity.
For CSIR NET, begin by identifying the main components involved in heart and ecg and the order in which they interact. Explain what changes when one component is removed, inhibited, overexpressed or exposed to different conditions. This approach is especially useful for interpreting experiments rather than recalling isolated facts.
When solving a question, distinguish the underlying mechanism from its observable outcome. Compare the normal situation with the altered condition, and check whether the evidence supports a direct effect or only an association. The central distinction to retain is: cardiac output = heart rate × stroke volume.
The sinoatrial node normally initiates electrical activity, which passes through the atria, atrioventricular node and ventricular conduction system. On an ECG, the P wave reflects atrial depolarization, the QRS complex ventricular depolarization and the T wave ventricular repolarization. Cardiac output equals heart rate multiplied by stroke volume. Preload, afterload and contractility influence stroke volume through different mechanisms. A changed ECG interval cannot alone establish a change in cardiac output; electrical and mechanical measurements must be interpreted separately.
Important: Cardiac output = heart rate × stroke volume.
Read Detailed Notes →3. Respiratory physiology
Gas exchange follows partial-pressure gradients; hemoglobin carries O₂ and most CO₂ travels as bicarbonate.
For CSIR NET, begin by identifying the main components involved in respiratory physiology and the order in which they interact. Explain what changes when one component is removed, inhibited, overexpressed or exposed to different conditions. This approach is especially useful for interpreting experiments rather than recalling isolated facts.
When solving a question, distinguish the underlying mechanism from its observable outcome. Compare the normal situation with the altered condition, and check whether the evidence supports a direct effect or only an association. The central distinction to retain is: higher CO₂ and lower pH usually promote oxygen unloading.
Ventilation moves air through pressure gradients, whereas gas exchange occurs by diffusion across the alveolar–capillary interface. Oxygen transport depends on hemoglobin saturation, partial pressure and dissolved oxygen; CO2 is transported largely as bicarbonate. The oxyhemoglobin dissociation curve shifts with pH, CO2, temperature and 2,3-BPG. Ventilation–perfusion mismatch can impair oxygenation even when total ventilation is preserved. In respiratory calculations, distinguish minute ventilation from alveolar ventilation because anatomical dead space does not contribute to alveolar exchange.
Important: Higher CO₂ and lower pH usually promote oxygen unloading.
Read Detailed Notes →4. Nervous system
Voltage-gated Na⁺ and K⁺ channels generate action potentials; Ca²⁺ triggers transmitter release at chemical synapses.
For CSIR NET, begin by identifying the main components involved in nervous system and the order in which they interact. Explain what changes when one component is removed, inhibited, overexpressed or exposed to different conditions. This approach is especially useful for interpreting experiments rather than recalling isolated facts.
When solving a question, distinguish the underlying mechanism from its observable outcome. Compare the normal situation with the altered condition, and check whether the evidence supports a direct effect or only an association. The central distinction to retain is: action potentials are all-or-none.
Neurons maintain membrane potential through ion gradients and selective conductances. An action potential results from voltage-dependent changes in sodium and potassium permeability, followed by repolarization and refractory periods. Myelin increases conduction efficiency by concentrating regenerative currents at nodes of Ranvier. Synaptic transmission depends on calcium-triggered vesicle fusion and receptor-mediated postsynaptic responses. Excitatory and inhibitory effects depend on the reversal potential of the activated conductance, not simply on whether the transmitter is labeled excitatory or inhibitory.
Important: Action potentials are all-or-none.
Read Detailed Notes →5. Sensory systems
Rods and cones transduce light; cochlear hair cells detect mechanical vibrations.
For CSIR NET, begin by identifying the main components involved in sensory systems and the order in which they interact. Explain what changes when one component is removed, inhibited, overexpressed or exposed to different conditions. This approach is especially useful for interpreting experiments rather than recalling isolated facts.
When solving a question, distinguish the underlying mechanism from its observable outcome. Compare the normal situation with the altered condition, and check whether the evidence supports a direct effect or only an association. The central distinction to retain is: light generally hyperpolarizes vertebrate photoreceptors.
Sensory transduction converts physical or chemical stimuli into changes in membrane potential. Photoreceptors respond to light through a G-protein cascade that changes cyclic GMP-gated channel activity; in vertebrate rods, illumination typically hyperpolarizes the receptor. Auditory hair cells detect mechanical deflection through mechanically gated channels. Receptive fields, adaptation and lateral inhibition shape sensory coding. A larger stimulus does not necessarily produce a larger receptor potential indefinitely because responses can saturate or adapt.
Important: Light generally hyperpolarizes vertebrate photoreceptors.
Read Detailed Notes →6. Kidney and excretion
Glomerular filtration, tubular reabsorption and secretion determine urine composition. ADH helps regulate water retention.
For CSIR NET, begin by identifying the main components involved in kidney and excretion and the order in which they interact. Explain what changes when one component is removed, inhibited, overexpressed or exposed to different conditions. This approach is especially useful for interpreting experiments rather than recalling isolated facts.
When solving a question, distinguish the underlying mechanism from its observable outcome. Compare the normal situation with the altered condition, and check whether the evidence supports a direct effect or only an association. The central distinction to retain is: clearance = urine concentration × urine flow / plasma concentration.
Glomerular filtration generates a protein-poor filtrate, while tubular segments selectively reabsorb and secrete solutes. The loop of Henle contributes to the medullary osmotic gradient, enabling water conservation when collecting-duct water permeability increases under vasopressin. Aldosterone enhances sodium reabsorption and potassium secretion in appropriate nephron segments. Clearance calculations relate urine concentration, flow and plasma concentration; clearance equal to GFR suggests filtration without net reabsorption or secretion for an ideal marker. Osmolarity and urine volume must be considered together.
Important: Clearance = urine concentration × urine flow / plasma concentration.
Read Detailed Notes →7. Digestion and endocrinology
Digestive enzymes break down food; hormones coordinate metabolism and reproduction through feedback loops.
For CSIR NET, begin by identifying the main components involved in digestion and endocrinology and the order in which they interact. Explain what changes when one component is removed, inhibited, overexpressed or exposed to different conditions. This approach is especially useful for interpreting experiments rather than recalling isolated facts.
When solving a question, distinguish the underlying mechanism from its observable outcome. Compare the normal situation with the altered condition, and check whether the evidence supports a direct effect or only an association. The central distinction to retain is: the LH surge triggers ovulation in a typical menstrual cycle.
Digestive enzymes hydrolyze macromolecules into absorbable products, and different intestinal regions specialize in nutrient uptake. Gastrin, secretin and cholecystokinin coordinate acid secretion, pancreatic output and gallbladder contraction. Endocrine feedback maintains glucose, calcium and other regulated variables. Insulin promotes nutrient storage and uptake in responsive tissues, whereas glucagon supports hepatic glucose production. A rise in blood glucose can result from impaired insulin secretion, reduced tissue responsiveness or increased glucose production; these are distinct physiological mechanisms.
Important: The LH surge triggers ovulation in a typical menstrual cycle.
Read Detailed Notes →8. Thermoregulation and stress
Neural and endocrine responses balance heat production and loss and support adaptation to stress.
For CSIR NET, begin by identifying the main components involved in thermoregulation and stress and the order in which they interact. Explain what changes when one component is removed, inhibited, overexpressed or exposed to different conditions. This approach is especially useful for interpreting experiments rather than recalling isolated facts.
When solving a question, distinguish the underlying mechanism from its observable outcome. Compare the normal situation with the altered condition, and check whether the evidence supports a direct effect or only an association. The central distinction to retain is: homeostasis means dynamic regulation, not constant values.
Thermoregulation integrates peripheral and central temperature signals with effectors such as sweating, shivering and changes in skin blood flow. The hypothalamus coordinates many responses, while endocrine and autonomic systems alter metabolic heat production. Stress responses involve rapid sympathetic–adrenal signaling and slower hypothalamic–pituitary–adrenal regulation. Fever reflects a regulated change in the temperature set point, unlike uncontrolled hyperthermia. Compare core temperature, heat production and heat loss when interpreting a thermoregulatory experiment.
Important: Homeostasis means dynamic regulation, not constant values.
Read Detailed Notes →9. Gut microbiome and holobionts
Gut microbes affect metabolism, immunity and signaling; germ-free models help test causal roles.
For CSIR NET, begin by identifying the main components involved in gut microbiome and holobionts and the order in which they interact. Explain what changes when one component is removed, inhibited, overexpressed or exposed to different conditions. This approach is especially useful for interpreting experiments rather than recalling isolated facts.
When solving a question, distinguish the underlying mechanism from its observable outcome. Compare the normal situation with the altered condition, and check whether the evidence supports a direct effect or only an association. The central distinction to retain is: an association between microbes and disease does not prove causation.
The gut microbiome contributes to fermentation of otherwise inaccessible substrates, metabolite production and immune education. Short-chain fatty acids can influence epithelial physiology and host signaling. Microbiome composition varies with diet, age, medication and sampling methods, making association studies vulnerable to confounding. Germ-free and colonization experiments can help test causality, but host developmental differences must be considered. The holobiont concept emphasizes host–microbe interactions without implying that every microbial species is essential to every host.
Important: An association between microbes and disease does not prove causation.
Read Detailed Notes →Key Concepts and Quick Revision
- Blood and hemostasis: A left shift of the hemoglobin oxygen curve indicates increased affinity.
- Heart and ECG: Cardiac output = heart rate × stroke volume.
- Respiratory physiology: Higher CO₂ and lower pH usually promote oxygen unloading.
- Nervous system: Action potentials are all-or-none.
- Sensory systems: Light generally hyperpolarizes vertebrate photoreceptors.
- Kidney and excretion: Clearance = urine concentration × urine flow / plasma concentration.
- Digestion and endocrinology: The LH surge triggers ovulation in a typical menstrual cycle.
- Thermoregulation and stress: Homeostasis means dynamic regulation, not constant values.
- Gut microbiome and holobionts: An association between microbes and disease does not prove causation.
Practice and Revision Resources
Frequently Asked Questions
What topics are covered in Unit 7?
This unit covers system physiology – animal, including the key topics explained above.
How should I study this unit?
Read each explanation, revise the Remember points, and solve topic-wise questions and analytical problems.
Are these notes useful for Part C?
They establish the concepts needed for analytical questions; practice data interpretation and multi-step reasoning separately.
What is the best way to revise?
Use the quick revision notes and return to detailed explanations for difficult concepts.