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.

Gaseous Exchange Short Answers - 2

·         Effect of Smoking on Teeth:

Smoking is responsible for:

1- The weakening and staining of teeth.

2- It can lead to plaque.

3- Tooth loss is 2 to 3 times higher in smokers than in non-smokers.

·         Pneumonia Symptoms:

The infection of lungs in which causative organisms enter the alveoli, break the lung tissues and area becomes filled with fluid and pus is called pneumonia. 
Symptoms: Cold followed by a high fever, shivering, cough with sputum production, shortness of breath, patient’s skin color may change to dusky or purplish due to poor oxygenation of blood.

·         Arteriosclerosis:

Hardening of blood vessels is called arteriosclerosis.  
Cause: The chemicals present in smoke increase the production of blood platelets. When platelets are more than the normal numbers, they make the blood viscous and it can lead to arteriosclerosis.

·         Stomata vs Lenticels:

Stomata are the living pores formed by the turgor pressure in guard cells while lenticels are the dead pores formed in the bark (when young stem turns into mature stem).

Stomata are present in leaves and young stems while lenticels are present in mature stems and mature roots.

Stomata are not raised while lenticels are the raised pores.
Stomata open during day time and close during night time while lenticels remain open all the time.

·         Respiratory Centre:

The point in medulla oblongata of the brain which controls the rate of breathing is called respiratory Centre.

Significance/Role: It is sensitive to the concentration of carbon dioxide in the blood. Greater than normal concentration of carbon dioxide in blood as a result of increased cellular respiration by muscle cells stimulates the respiratory Centre of brain which sends messages to rib muscles and diaphragm to increase rate of breathing so that excess carbon dioxide present in blood can be removed out of the body. Thus during exercise, breathing rate may increase up to 30-40 times per minute.

·         Bad Effects of Smoking:

1- Tobacco smoke contains 4,000 different chemicals and about 50 carcinogens.

2- Smoking can lead to lung cancer.

3- It can also cause various other cancers of the body e.g. in kidney, oral cavity, larynx, breast and pancreas etc.

4- Chemicals in smoke can cause emphysema and other respiratory disorders.

5- Carbon monoxide in tobacco smoke lessens oxygen carrying capacity of hemoglobin.

6- It leads to increase in number of platelets leading to arteriosclerosis.

7- Smoking can cause greater risk of developing infections in lungs e.g. tuberculosis.

8- Smoking is also responsible for weakening and staining of teeth and tooth loss.

·         Acute vs Chronic Bronchitis:

1- Acute bronchitis occurs for less time span while chronic bronchitis occurs for longer time span.

2- Acute bronchitis usually lasts about two weeks while chronic bronchitis lasts for 3 months to two years.

3- In acute bronchitis, patients recover with no permanent damage to bronchi or bronchioles while in chronic bronchitis, the bronchi develop chronic inflammation leading to permanent damage.

·         Nostrils:

A pair of openings through which air moves into or out of the nasal cavity is termed as nostrils. There are two types of nostrils:

1- External Nostrils: Openings through which nasal cavity opens to the outside.

2- Internal Nostrils: Openings through which nasal cavity opens to the pharynx.

·         Glottis vs Epiglottis:

Glottis: The narrow opening at the floor of pharynx which leads into the larynx is called glottis. The air goes from the pharynx into the larynx through glottis.

Epiglottis: The flap of cartilage which guards the glottis (opening) is called epiglottis. It closes the glottis when food is being swallowed.

·         Gaseous exchange in Roots:

The gases are found in the soil surrounding the roots which can diffuse in or out of the roots.

Young Roots: In young roots, gases diffuse in and out of the general surface.

Mature Roots: The surface of mature roots is covered by bark and is thus impervious to gases or water. However there are certain pores called lenticels which allow the air to pass through them.

Gaseous Exchange Short Answers - 1

Chapter # 10:

Gaseous Exchange

·         Inspiration/Inhalation:

The process of taking fresh air inside the lungs for gaseous exchange is called inspiration.

Mechanism: During inspiration, the rib muscles and diaphragm both contract thus increasing the area of thoracic cavity and thereby reducing the pressure on lungs. As a result, the lungs expand and pressure within them decreases and air from outside rushes into the lungs to equalize pressure on both sides.

·         Expiration/Exhalation:

The process of expelling the impure air outside the lungs into the environment after gaseous exchange takes place in the lungs is called expiration.

Mechanism: During expiration, the rib muscles and diaphragm both relax thus decreasing the area of thoracic cavity and thereby increasing the pressure on lungs. As a result, the lungs contract and air is expelled out of them into the environment.

·         Bronchitis:

The inflammation of bronchi or bronchioles resulting in excessive secretions of mucus into the tubes and leading to the swelling of tubular walls and narrowing of the tubes is called bronchitis.

Cause: It is caused by viruses, bacteria or exposure to chemical irritants e.g. tobacco smoke.

·         Cellular Respiration:

The process in which C-H bonds in food containing high potential energy are broken by oxidation reduction reactions and the energy released is transformed into ATP for various activities is called cellular respiration. It occurs inside the cell.

Aerobic Respiration: Oxygen is required for the complete oxidation of food and is termed as aerobic respiration.

·         Breathing vs Respiration:

Breathing is the process through which animals take air in their bodies to get oxygen from it and then give out air for getting rid of carbon dioxide. While, respiration is the process in which both gaseous exchange (breathing) and cellular respiration occurs i.e. C-H bonds are broken by oxidation reduction reactions and energy is released and stored in the form of ATP. Carbon dioxide formed during the process, moves out of the body.

Breathing is only a mechanical process of exchange of gases while respiration involves both mechanical (external respiration/gaseous exchange) and biochemical (cellular respiration) processes.

·         Diaphragm:

The muscular sheet made up of skeletal muscles which separates the thoracic cavity from the abdominal cavity is called diaphragm.

Significance: It helps in inspiration and expiration. In normal or relaxed position, it is dome shaped thus reducing the area of thoracic cavity for expiration while when contracted, it becomes horizontal thus increasing the area of thoracic cavity for inspiration.

·         Symptoms of Emphysema:

The destruction of the walls of alveoli resulting in larger sacs but with less area for gaseous exchange is called emphysema. Following are the main symptoms:

Shortness of breath, fatigue, recurrent respiratory infections and weight loss. (In Points)

·         Trachea and structure:

The 12 cm long tube through which air passes, which continues from larynx and lies in front of the esophagus is called trachea. It is also called windpipe.

Structure: There are C-shaped cartilaginous rings in the wall of trachea which prevent its collapsing. It is also lined with ciliated and glandular cells for the filtration of air passing through it. On entering the chest cavity, the trachea divides into two smaller tubes called bronchi.

·         Passive Smoking Injurious:

The inhalation of smoke from another person’s smoking is called passive smoking. It can be injurious to health as:

1- It is capable of causing Lung Cancer.

2- The smoke from the burning end of a cigarette is more dangerous than the smoke from the filter end.

3- Heart disease risk of passive smokers increases by 25-30%.

4- Lung cancer risk increases by 20-30%.

5- Many people are allergic to cigarette smoke thus it causes asthma.

6- Passive smokers can also develop other disorders like regular active smokers e.g. CO poisoning, Increase in blood platelets, developing of lung infections etc.