KPK Board 12th Class Biology Ch 15 Homeostasis Short Questions Answers

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define the external and internal environment of an organism?

the external environment  the surroundings of the organism in which the organism lives is called its external environment .

internal environment  The internal environment of organisms is that environment in which the tissue of the body lives .

What is homeostasis?

The production of the internal environment of an organism for the harms of change in the external environment is called homeostasis.

What is the mechanism to maintain homeostasis?

Osmoregulation is the mechanism in which solute and water balance is maintained called osmoregulation.

Excretion  which eliminates nitrogen waste from the body of the organism is called excretion.

Thermoregulation is the maintenance of internal temperature in tolerable range.

How does the homeostasis mechanism operate like a physical control system?

a static mechanism operates just like a physical control system.

Components  receptors, control Centre, effectors.

Receptors,  receptors are sense organs that detect changes in variables and give information to the control centre.

control Centre brain the control Centre put together data from sensors and store set point data .

effectors This part has an effect  on variables according to the orders of the control centre.

What is a feedback mechanism?

A feedback mechanism is a process through which the level of one substance influences the level of another increase of heart rate and respiratory rate due to exercise on muscular activity.

What is a negative feedback mechanism?

negative feedback results in a reversal of direction of changes.  In this mechanism the system tends to decrease the output.

For example , controlling the water content of the body when the body is deficient in water hypothalamus stimulates more ADH that helps in the reabsorption of water in collecting tubules and more water is retained in the body the reverse occurred during more water intake.

What is positive feedback?

A positive feedback mechanism improves the output created by stimulus that had activated previously in this mechanism; the system tends to increase output.

Example  positive feedback mechanism are rare in Biology but a good example is production of construction when a woman is in labour.oxytocin causes uterine muscles to contract and the baby to descend into birth Canal this signals from stretch receptors are detected by hypothalamus which in turn signals  pituitary gland to secrete more oxytocin leading to more construction and for the movement of baby.

What do you know about harmful positive feedback?

Sometimes the positive feedback becomes harmful for the body.

Example during high fever  the metabolic changes push fever higher and higher due to positive feedback.

inhaling high carbon dioxide content, the Co2 receptors increased the breathing rate so the person breathe faster taking in carbon dioxide does making breath faster and faster.

What are osmoregulators?

Osmoregulation are those animals which have solute concentrations different from the external environment. They  use energy to control water loss or water gain to keep the balance of water and solute.  Their cells cannot survive without water,  all land animals  most Marine vertebrates.

define osmoconformers?

osmoconformers are those animals which have solute concentration equal to the external environment the animal body fluids are kept isotonic, sea animals.

write down some waste products of humans?

The following waste products  are produced in the human body during metabolism.

urea is produced by metabolism of amino acids.

uric acid is produced from nucleic acid.

Bilirubin is the end product of haemoglobin.

toxin produced pesticides drug  food additives.

How do freshwater animals maintain osmoregulation?

Almost  all of the freshwater animals are osmo regulator’s having body solute concentration more than external environments.

problems more water can enter to their body because the body has less water and the surroundings has more water as a result their cell can swell.

body solutes are more concentrated so having a risk of being lost in water.

Solution,  these problems are solved by producing large volumes of dilute urine. Their Kidneys reabsorbed the required salts they are actively transporting through special cells called monocytes in gills.

How Marine animals maintain osmoregulation?

Marine  animals are osmoconformers the solute concentration in the body is low as compared to external.  Example,  isotonic plasma:  cartilaginous fishes are isotonic to seawater e.g  shark.

hypotonic plasma,  fishes are hypotonic to seawater teleosts.

Solution:  the osmoregulation is maintained by these fishes through.

Drinking large amounts of water to replace water loss.

Some fishes have special salt secreting glands in rectum.

How terrestrial animals are adapted to avoid water loss from their body?

Land  animals have the following adaptation to prevent their bodies from dehydration.

arthropods have chitinous exoskeleton to avoid water loss.

Reptiles birds and mammals,  they have keratinized skin to reduce the water loss by their body.

What do you know about any hydrobiosis?

It is a process where organisms can survive in situations of extreme dehydration. For example desert animals importance anhydrobiosis is an adaptation to live in extreme conditions.

Define amonotectic animals?

Animals that excrete Ammonia as their major nitrogenous waste product are called Ammonotelic animals, for example most fish protozoans sponge coelenterates.

Reasons ammonia is highly soluble in water these organisms have sufficient so what is so they can supply excrete Ammonia as 1 gram of Nitrogen in Ammonia requires 500ml water to be excreted.

define ureotelic animals?

These organisms which excrete urea as the major waste product are called ureotelic animals.

example of some marine and all Terrestrial animals.reasons urea is less toxic than Ammonia and water Needed for its removal so these organisms excrete urea to avoid water loss.

What are ureotelic animals?

Those animals which excrete uric acid are called ureotelic example Birds Seasons as Birds. Most time in air and they excrete uric acid to avoid loss because one gram nitrogen in uric acid requires just 1 ml of water .

What is the role of lungs in homeostasis?

lungs are respiratory organs of Terrestrial vertebrates role in homeostasis during cellular respiration and CO2 and H2O are produced as by products which are not used by the body so they must be eliminated from the body so this your to dissolve in blood plasma and reads the long for removal along some water .

What is the role of skin in homeostasis?

skin is the outer covering of the body that protects the internal parts.

The role of homeostasis skin is an important role in homeostasis during cold season the blood supply to the skin is reduced so as to provide more heat to the body well in summer season blood supply to the skin increases to radiate the excess heat from the body.

sweat glands do sweat glands of the skin excrete sweat and also provide a cooling effect to the body.

What is excretion and write down components of the human excretory system?

excretion is a process during which metabolic wastes are removed from the body of organism.excretory system:  consists of all the all those which in removing organ include.

skin, lungs, liver ,kidney.

Write down the external morphology of Kidneys?

Kidneys are excretory organs of vertebrates colour and shape Kidneys are dark red slightly flattened Bean shaped organ size Kidneys of human are 12 cm long six and white 4cm thick weight of each kidney is about 150 gram hilus  a deep notch is present on the inner side of kidney  called notch .

the large collecting ducts emerge from hilus.

Write down the anatomy structure of the kidney?

The transverse section of the kidney shows two distinct region cortex cortex; it is the outer region of the kidney that contains the corpuscles and convoluted tubules of nephron.

medula it is the inner region of the kidney that contains conical pyramids.

nephron nephron is the structural and functional unit of kidney the kidney contains millions of nephrons.

write on the structure of nephrons?

nephron the structural and functional unit of kidney is nephron structure structure of nephron consists of following two components renal corpuscles and renal tubules.

Renal corpuscle is composed of glomerulus and bowman’s capsule which is the initial filtering component of nephron.

The tubes used are divided into the following three parts:  proximal convoluted tubule, loop of henle ,distal convoluted tubule, collecting duct.

write down types of nephrons?

nephron is the structural and functional unit of kidney types nephron is of following to general types according to their location cortical nephron, and juxtamedullary nephrons.

Cortical nephrons are found in the cortex; they have a short loop of henle and constitute 70 to 80% of the total nephron.

Function : under normal conditions the cortical nephron deals with control of blood volume.

Juxtamedullary  nephrons have renal corpuscles close to the junction of cortex and medulla, they have a long loop of henle extending deep into medulla constituting 20- 30% of the nephron function these are responsible for the concentration of urine.

Why does filtration take place only at the glomerulus part of the nephron?

The blood is filtered in the glomerulus region of nephron it is due to the porous walls of glomerulus that act  sieve filter the waste material from the blood that is why the blood is filtered at glomerulus and where else.

What do you know about ultrafiltration?

ultrafiltration refers to the filtration of blood under pressure in the glomerulus process during this process large molecules that are essential to the body are filtered out so that they can be  re- absorbed site  ultrafiltration occurs in the bowman’s capsule arterioles and capillaries.

write down the blood circulation through the kidney?

following blood vessels are responsible for blood circulation through kidney renal artery blood enters the kidney by renal artery Afferent  divided and redivided  before entering glomerulus as

afferent  arterial.

Efferent arteriole: Filter blood leaves the glomerulus by different arteriole peritubular capillaries around the proximal and distal convoluted tubules this network Vasa recta it Run anti parallel to loop of henle and the collecting ducts in medulla.

What does glomerular filtrate how it is formed?

glomerular filtrate is the liquid that after filtering problem errorless components it contains water and Na, H Cl, Mg, Ca, H, bicarbonate Urea, uric acid, drug used.

Discuss pressure filtration in the kidney?

pressure filtration occurs at the glomerulus part of the nephron.

Pressure:  the pressure is provided by the arterial blood from the heart.  Filtration:  the walls of glomerulus are porous for everything that is smaller than the pores of glomerulus filtered out of the blood.

Filtrate:  filtration of through result infiltration with dissolved salt sugar medicine and nitrogen waste all these filters to Bowman’s capsule . what is called the bowman ‘s  filtrate.

what do you know about selective reabsorption?

The proximal convoluted tubules of nephrons, some useful substances reabsorbed by the blood this is called selective reabsorption.

Substances:  the substances that are selected for reabsorption include water nutrients glucose amino acid and salt.

discuss tubular secretion in nephrons?

This  process takes place at the distal convoluted part of nephron.

Process: During this process hydrogen and NH3 and present in the interstitial fluid enter to the lumen of distal and this is known as popular secretion.

Importance is important for removing unwanted substances from secretion. 

How does urine pass from nephron to the outside of the body?

urine is produced by filtration of blood and then collected in the central cavity of the kidney called pelvis then it passes to the outside the following way.

Ureter:  it is a tube arising from pelvis.

Urinary bladder:  The writings of both kidney drains into the urinary bladder through urethral orifice.

Urethra:  the opening of the urinary bladder is called urethra guarded by the sphincter  muscles.

What is meant by micturition?

The involuntary urination in children is called micturition; it is the act of emptying the bladder .

Reason:  the muscles of urethra are involuntary in children under the age of about three years after which they are regulated voluntarily so the infants cannot stop their urination due to this reason it can also be caused in adults during injuries.

Discuss some disorders of the kidney?

Due to some external and internal factors the normal working off kidney may be disturb this situation are called renal disorders.

The following are two common disorders of kidney renal failure, kidney stone.

What do you know about renal failure?

when the nephrons of the kidney are unable or disturb due to some internal or external factors and they become unable to work normally then the kidney fail to remove the nitrogen waste which are harmful for the body is not remove this condition of kidney is known as kidney failure it is also known as renal insufficiency.

What is kidney stone?

It is a disorder in which a heart stone like mass is collected in the Kidney.

Which causes obstruction in the urinary tract causing severe pain cause kidney stones are formed by the crystallization of salt in bowman’s filtrate.

Type:  kidney stones are of the following three types: calcium oxalate stone, calcium phosphate stone, urete are uric acid stones.

What are two metabolic altered States caused by kidney stones?

The two metabolic ulta States are caused by kidney stones following hyperoxaluria, hypercalcemia.

Hyperoxaluria;  above normal state, it is high blood level of oxalate-  which are present in green vegetables and tomato.

Hypercalcemia is the high level of the circulating calcium in blood it may cause by other diseases.

What is the role of ADH in osmoregulation?

antidiuretic hormones:  site it is the hormone of anterior pituitary gland.

Function: it increases the permeability of renal tubules.

Hyper- secretion:  in case of less water intake more ADH is secreted which increases the permeability so the volume of urine decrease and water is conserved in the body hypo- secretion:  in case of excess supply of water are secretion is reduced that reduces the reabsorption of water so urine is produced with excess water from the body thus ADH maintain water balance in the body.

What are pyrogens?

During viral or bacterial infection the leukocytes increase in number and produce chemicals called pyrogens.

importance the pyrogens set the point of the hypothalamus above the normal 37 resulting in increasing the body temperature which is helpful in stimulating the protective mechanism against the pathogens.

discuss the role of kidney in homeostasis?

The kidney is the organ of excretion in Terrestrial vertebrates.

The most important organ of homeostasis is to filter out the nitrogen waste from the blood and excrete it from the body.

In case of Limited supply of water the kidney retains water and in case of more water urine is produced by the kidney to remove excess water and maintain homeostasis.

What do you know about kidney transplantation?

It is a method of treatment during which a kidney from one person is taken and connected to the urinary system of another person.

Donor: the person who gave the kidney to another person is known as Donor. Recipient:  the person to whom the Kidneys given is known as recipient.

Precaution:  matching of blood groups of Donor and recipient is necessary for kidney transplant otherwise tissue rejection can cause death.

How are kidney stones removed?

Many methods of removing kidney stones are used in the world some of which are as under medicines some plant extract like alloy, bryophyllum, chanca piedra  are successfully being used around the world to remove kidney stones.

Laser therapy kidney stones can be broken down by laser therapy. Surgery:  when the stone is small it can easily pass without pain well large stones are removed surgically.

What do you know about ESWL?

ESWL is the abbreviation of extracorporeal shock wave Lithotripsy it is known as invasive treatment of kidney stones biliary,  calcull .

History was for the first time introduced by the company in Germany in 1980 breaking stone by high intensity acoustic  pulse.

What is dialysis?

It is a process in which the blood is cleaned with the help of an artificial kidney machine known as dialyzer mechanism. During this process the blood is temporarily diverted from an artery in the arm and after filtration in the dialyzer it is returned to the vein in the arm.

Time required dialyzers usually takes 2 to 3 hours. It is done three times in a week depending on the condition of the patient.

What is peritoneal dialysis?

It is the treatment for patients with chronic kidney disease process During this process the patient’s peritoneum in the abdomen is used as a membrane across which the fluid and dissolved substances, Urea, glucose, album and other small molecules are exchanged from the blood.

Complication:  its primary complication is infection due to the presence of a permanent tube in the abdomen.

What do you know about donor recipient matches?

the donor kidney must match the recipient as closely as possible in following three ways Donor and recipient must have same blood group Donor and recipient must match human leukocyte antigen which are Surface  protein of leukocytes every person has 6 at (HLAs) the more the (HLAs) that match the higher the likelihood that the recipient’s body will accept the donor kidney the donors blood must not initiate and antibody response called  and negative crossmatch.

What are the risks and complications for kidney recipients?

Bleeding:  the risk of transplantation in bleeding during or after the operation.

Infection:  there is also a risk of infection.

Protection:  that transplanted kidney is lower than native kidney so it lacks the protection of rib organ rejection:  there is always a risk of organ rejection that is treated by various medicines. 

What isPCNL is?

PNL is  percutaneous nephrolithotripsy it is a process of removing large stones it is a procedure during which large stones are broken down and removed from the kidney without surgery.

What do you know about UTIs?

UTLs stand for urinary tract infections these are the infections that can happen and where along the urinary tract.

types following are the types of UTLs  depending upon the site.




What is hemodialysis?

is a process of process due car that membrane catheter  is inserted into blood vessel usually in ARM the blood from artery is diverted to dialyzer after cleaning the blood is returned from vein in many nephrologist feel that the process of hemodialysis is more effective than the peritoneal dialysis.

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