Excretion and Control
NCERT Class 10 • Science • Chapter "Life Processes" | NCERT Class 10 • Science • Chapter "Control and Coordination"
Excretion and Control
Excretion is the removal of harmful nitrogenous waste produced by the body's chemical activity. If these wastes accumulated they would poison the body, so every organism has a way of separating them from useful substances and sending them out.
The Human Excretory System
- The excretory system has two kidneys, two ureters, a urinary bladder and a urethra.
- The nephron is the basic filtering unit of the kidney, and each kidney has a very large number of them.
- Blood entering the nephron is filtered under pressure in a cup like structure, and the filtrate contains water, glucose, salts and urea.
- As the filtrate travels along the tubule, useful substances such as glucose, amino acids, most salts and most water are reabsorbed into the blood.
- What remains is urine, which is collected and passed through the ureter to the bladder.
- The amount of water reabsorbed depends on how much excess water there is and how much dissolved waste has to be excreted.
- Dialysis is an artificial process used when the kidneys fail, in which blood is cleaned by passing it through a machine.
Excretion in Plants and Control in Animals
- Plants have no special excretory organ; they release oxygen and carbon dioxide through stomata and excess water by transpiration.
- Plants store waste in vacuoles, old leaves and bark, which are then shed, and secrete gum and resin.
- Control and coordination in animals is handled by the nervous system and the endocrine system together.
- The nervous system works through electrical impulses and gives a fast, short lived response, as in a reflex action.
- A reflex arc passes through the spinal cord rather than the brain, which is why the response is so quick.
- The endocrine system works through hormones carried in the blood, giving a slower but longer lasting response.
- Important glands are the pituitary, thyroid, pancreas, adrenal and the reproductive glands, each with its own hormone.
| System | Message Carried By | Speed and Duration |
|---|---|---|
| Nervous | Electrical impulse | Very fast, short lived |
| Endocrine | Hormones in blood | Slower, long lasting |
Nephron — the basic filtering unit of the kidney, in which blood is filtered and useful substances are reabsorbed.
Exam me kaise aata hai
- The filtering unit of the kidney is the — nephron
- Artificial cleaning of blood is called — dialysis
- A reflex action is controlled by the — spinal cord
- Hormones are carried to their target by the — blood
UPSC/State PSC ke liye
- The reflex arc passes through the spinal cord because sending the signal to the brain first would cost time the body cannot afford in danger.
- Reabsorption is what makes the kidney efficient: filtration is indiscriminate, so the useful substances must be deliberately taken back.
Yahan confuse hote hain
✗ Urine is simply filtered blood | Useful substances are reabsorbed before urine is formed | ✓
✗ Reflex action is controlled by the brain | It is controlled by the spinal cord | ✓
✗ Plants have a special excretory organ | Plants have no such organ and use other routes | ✓
Ek nazar me
- Excretion removes nitrogenous waste; kidneys are the main organ.
- The nephron filters blood and reabsorbs useful substances.
- Dialysis substitutes for failed kidneys.
- Nervous system gives fast responses; hormones give slower, lasting ones.
Ab practice karein
Life processes se har exam me seedhe diagram aur factual questions bante hain. ExamAtlas ke mock test se abhi jaanchein.