Homeostasis Short Answers

Short Questions

Chapter # 11:

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 Homeostasis:

The maintenance of internal conditions of the body at equilibrium, despite changes in the external environment is called homeostasis.

For example: Core temperature of human body remains at about 37 C despite fluctuations in the surrounding air temperature. The blood glucose level remains at about 1g per litre despite eating a meal rich in carbohydrates.

Main processes involved in maintaining the stable internal conditions are: 

Osmoregulation (maintenance of the amount of water and salts in body fluids)

Thermoregulation (maintenance of internal body temperature)

Excretion (elimination of metabolic wastes from the body)

·         Osmoregulation:

The process of maintaining the amounts of water and salts in the body fluids (i.e. blood and tissue fluids) at equilibrium, despite changes in the external environment is called Osmoregulation.

Significance: Relative amount of water and salts in body fluids and inside the cells control the processes of diffusion and osmosis, essential for the functioning of cells.

·         Transpiration at Night:

The loss of water from the plant surfaces in the form of vapors is called transpiration.

At Night: Transpiration usually does not occur at night because most plants have their stomata closed at that time.

Guttation: At night, if there is high water content in soil, water enters the roots and is accumulated in xylem vessels. Some plants force this water through special pores present at leaf tips or edges and form drops, another process known as guttation.

·         Thermoregulation:

The process of maintaining the internal body temperature at equilibrium (i.e. 37 C in human body) despite the changes in external environment is called thermoregulation.

Significance: Particular temperature (Optimum temperature) is required for the body enzymes to work best. Any change in body temperature will affect their functioning.

·         Tubular Secretion:

The secretion of different ions, creatinine, urea etc. from blood into the filtrate in the renal tubule is called tubular secretion.

Significance: It is donein order to maintain the normal pH of blood (7.35-7.45).

Urine Formation: Tubular Secretion is the third and the last step in functioning of the nephron and after that, filtrate present in renal tubules is knows as urine which moves into collecting ducts and then into the renal pelvis.

·         Hydrophytes mechanism:

The plants which live completely or partially submerged in freshwater are termed as hydrophytes.

They do not face the problem of water shortage. They have developed mechanisms for the removal of extra water from their cells.

Modifications: 

1- They have broad leaves 

2- The leaves have a large number of stomata

3- Most stomata are on the upper surfaces of leaves directly facing the sunlight.

Thus these characteristics help them to remove extra amount of water with increased transpiration.

Example: Water lily and hydrilla.

·         Removal of Kidney Stones:

The hard deposits formed due to incapability of large crystals of many salts e.g. calcium oxalate, calcium and ammonium phosphate, uric acid etc. (formed when urine becomes concentrated) to pass in urine are called Kidney Stones. Most stones start in kidney and some may travel to ureter or urinary bladder.

Following are the removal methods.

1- Water: 90% or all kidney stones can pass through the urinary system by drinking plenty of water.

2- Lithotripsy: The bombardment of non-electrical shock waves from outside on the stones in the urinary system is called lithotripsy. These waves hit the dense stones and break them thus making them sand like and easy to pass through urine.

3- Surgery: In surgical treatment, the affected area is opened and stones are removed.

·         Formation of Hypotonic Urine:

The dilute urine formed when there is excess water in the body fluids is called hypotonic urine.

Mechanism: 

1- Kidneys filter more water from glomerular capillaries into Bowman’s capsule

2- Less water is reabsorbed and abundant dilute urine is produced.

Significance: It brings down the excess volume of body fluids to normal.

·         Causes of Kidney Failure:

A complete or partial failure of kidneys to perform their regular function of urine formation and osmoregulation is called kidney failure.

Following are the causes.

1- Diabetes mellitus

2- Hypertension

3- Interruption in blood supply to kidney

4- Drug overdoses

·         Kidney Transplant:

The replacement of patient’s damaged kidney with a donor healthy kidney as a treatment for the end-stage kidney failure is called kidney transplant.

Donation: The kidney can be donated by a deceased donor or a living donor and donor may not be a relative of the patient. Before transplant, the tissue proteins of donor and patient are matched. Average lifetime for a donated kidney is ten to fifteen years.

·         Dialysis:

The process of cleaning of blood by artificial means after a kidney failure is called dialysis.

Principle: It works on the principle of diffusion of solutes across a semipermeable membrane. There are two methods of dialysis.

Peritoneal Dialysis: In this type, dialysis fluid is pumped into the peritoneal cavity and waste materials diffuse from peritoneal blood vessels into the dialysis fluid which is then drained out.

Hemodialysis: Patient’s blood is pumped through the long tubes of dialyzer while dialysis fluid flows around the tubes. Waste materials and extra water diffuse from water to the dialysis fluid and cleansed blood is returned back to body.

·         Goosebumps:

The bumps like condition appearing on the skin due to the contraction of small muscles in dermis are called Goosebumps.

Significance: It creates an insulating blanket of warm air in cold environment thus playing a role in thermoregulation.

·         Metabolic Wastes:

The waste materials produced as a result of body metabolism which may harm the body and are thus needed to be excreted from the body are called metabolic wastes.

Example:

In Animals: Urea, Uric acid, Carbon dioxide etc.

In Plants: Calcium oxalate, resins, gums, oxygen etc.