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Q1 Ans- Homeostasis is a biological mechanism which ensures the maintenance of body fluid compositions to establish a constant internal environment. It is a dynamic process that requires constant monitoring of all body systems to detect changes, overlook operations that react to those changes and restore stability. This helps the organism to function without being influenced by external environmental changes. A constant body temperature, pH and water potential within the body are necessary to prevent the inactivation or denaturation of enzymes and to allow smooth enzymatic reactions. Homeostasis accomplishes so as a result of incorporating feedback loops into its procedure.

There are two kinds of feedback loops - negative feedback loop and positive feedback loop. Negative feedback loops react antagonistically to any changes detected to achieve equilibrium. It consists mainly of five aspects: a set-point, a stimulus, a receptor, a control centre and a corrective mechanism. A set-point is the state that is to be maintained. A stimulus is a change or variation in the body. Sense organs such as eyes, ears, nose, tongue and skin, also known as receptors, identify the stimulus and send the information to the control centre i.e the brain and its associating parts. The corrective mechanism through responding organs produces the reverse effect of the stimulus until the set-point is returned. Examples of a negative feedback loop are thermoregulation and blood sugar regulation. The second type of feedback loops is positive feedback loops where any change detected is amplified instead of being opposed, usually when a process needs to be pushed to completion. Examples include during childbirth and lactation.

Q2 Ans- The major homeostatic organs in mammals are the lungs, the skin, the muscles, the kidneys, the liver, the pancreas, the hypothalamus and the pituitary gland of the brain.

The exchange of gases, maintenance of the pH and the water potential in the blood are all functions of the lungs. Oxygen is inhaled and carbon dioxide is exhaled at a constant rate. Carbon dioxide reacts with water to form bicarbonate ions. The enzyme, carbonic anhydrase, catalyzes bicarbonate ions and hydrogen ions to create carbonic acid. Carbonic acid(decreases blood pH) is then converted to water vapors and carbon dioxide which are exhaled by the lungs. The numerous alveoli in lungs and the tiny capillaries surrounding them assist in the rapid procedure. This is how the pH and water potential of the blood is kept under control. During exercise, the body requires more energy and thus, more oxygen. The lung compensate for the lack of oxygen by increasing the breathing rate. Under any circumstances where the blood pH is falling outside of the optimum range, hydrogen ions may be utilized to decrease the pH or bicarbonate ions may be utilized to increase the pH, either of the two to return blood pH to normal depending on the situation. When the blood water potential is high, higher amounts of water vapors are exhaled out and when it is low, reduced amounts of water vapors are exhaled. Lungs play a remarkable role in homeostasis in coordination with the rest of the respiratory system.

# data[].attributes.body
Q1) Homeostasis is the maintenance of a constant internal environment. It is the process of keeping the composition of the  body fluids within narrow limits by ensuring a relatively stable environment and providing the organism with a certain degree  of independence from the variations in external environmental conditions. The concentration, acidity and temperature of this fluid are being adjusted all the time. A feedback loop is a biological occurrence wherein the output of a system amplifies the system (positive feedback) or inhibits the system (negative feedback). In negative feedback stimulus is changed back to normal is adjusted and brought back to normal. Anything which gets higher or lower than the normal is adjusted and brought back to normal by the three parts (stimulus, control center and responding organ) of typical feedback playing major role to return back to normal. Whereas, in positive feedback the stimulus detected by the receptors cannot be changed back to normal and homeostasis does not take place.

Q2) The main homeostatic organs are lung, liver, kidney and skin. Lungs carry out two important homeostatic functions; exchange of gases and maintenance of pH. One of the main homeostatic functions of the respiratory system is the gas exchange that occurs in the alveoli in the lungs. As blood passes through the tiny capillaries in the alveolar sacs, changing pressure gradients allow oxygen and carbon dioxide to diffuse in and out of the blood. To maintain the carbon concentration in the blood, excess carbon is removed from the blood. Carbon dioxide is transported in the blood as bicarbonate ions. These ions are converted into carbonic acid which is the converted into carbon dioxide and water by the action of carbonic anhydrase. The carbon dioxide is removed by the alveolar spaces in the lungs. Secondly, the pH of the blood is maintained by the lungs because the presence of carbonic acid causes the blood pH to decrease affecting the cell activities and vice versa. Therefore, the breathing rate is adjusted accordingly.

# data[].attributes.body
Q1)it is the method of maintaining the composition of body fluids within narrow limits and is typical of a system that regulates its internal atmosphere and seeks to retain a steady and fairly constant level of pH , temperature, water potential and concentration gradient. Given changes such as pH or temperature in the external environment these conditions remain more or less constant. Regulation of homoestasis requires a

major principle, called negative feedback.s There needs to be a stimulus for homeostasis control to occur which is a transition in the internal or external environment.
TThere are receptor cells

that can sense the stimulus.

There is an automated or self-regulating

corrective mechanism which results in negative feedback.

A feedback loop is a biochemical phenomenon in which a

system's output amplifies (positive feedback) or inhibits the system (negative feedback).

Positive Feedback is a mechanism in which the end effects of an

action in a feedback loop trigger more of the action to happen.

This amplifies the

action originally taken.

It is compared with negative feedback which is where the end effects of an action prevent the activity from continuing to continue In positive feedback a shift in a given direction induces incremental change in the same direction

Q2)  there are four homeostatic organs. lungs, liver, kidney and skin

lungs are responsible for transferring molecules and for preserving

the pH and the blood 's water potential. To reduce the concentration of carbon in the

blood excess carbon is eliminated from the blood. Carbon dioxide is transportex  as bicarbonate ions through the plasma.

These ions are converted by the action of carbonic anhydrase

to carbonic acid which is converted into carbon dioxide and oxygen.The alveolar spaces in the

lung absorb the carbon dioxide.

Second, the lungs retain the pH of the blood as the presence of carbonic acid allows the pH of the blood to decrease affecting cell function and vice versa.

The respiration rate

is then modified accordingly.

In fact, the conservation of blood 's water potential relies also on the lungs. Water is removed

as vapours after expiration.

If the water potential is elevated in blood, more water vapors will be

exhaled and if the water potential is low, fewer water vapors will be exhaled.

The lungs perform essential

homeostatic roles over all.

# data[].attributes.body
Q1) Homeostasis is the maintenance of a constant internal environment.It is the process of keeping the composition of the body fluids within narrow limits and is characteristic of a system that regulates its internal environment and tends to maintain a stable and relatively constant limit of pH, temperature, water potential and concentration gradient. These conditions remain more or less constant despite changes such as pH or temperature in the external environment. Homoestasis control involves an important principle called the negative feedback. For homeostasis control to occur there must be a stimulus which is a change in the internal or the external environment. There are receptor cells which can detect the stimulus. There is an automatic or self regulatory corrective mechanism that brings about a negative feedback.  A feedback loop is a biological occurrence wherein the output of a system amplifies the system (positive feedback) or inhibits the system (negative feedback). Positive Feedback is a process in which the end products of an action cause more of that action to occur in a feedback loop. This amplifies the original action. It is contrasted with negative feedback which is when the end results of an action inhibit that action from continuing to occur  In positive feedback a change in a given direction causes additional change in the same direction.
Q2) The main homeostasis organs are the lungs, liver, kidney and skin.
Homeostasis is maintained by lungs in two ways that is gaseous exchange and the regulation of blood pH.
The exchange of gases is done in the lungs between the air (we took in by breathing) and the blood vessels surrounding the alveoli. This gaseous exchange maintains the concentration of oxygen and carbon dioxide in the blood. This is very essential for the survival of the human body. Carbon dioxide is a metabolic waste product and thus has to be removed from the body as it can have undesirable effects. The carbon dioxide gas travels as bicarbonate ions in the body. So first the bicarbonate ions and hydrogen ions are converted to carbonic acid and then to carbon dioxide and water and are removed when we exhale.
The pH of the blood is regulated by the lungs.The carbon dioxide in the blood dissolves in water to form carbonic acid. This lowers the pH of the blood and this does not allow the cells and the enzymes of the body to work at optimum efficiency; as the cells do not survive and the non-acidic enzymes are denatured. A low pH in the blood can even cause death. If the concentration of carbon dioxide rises in the blood, then the rate of breathing is increased so more carbon dioxide gas is removed from the body. If the concentration of carbon dioxide is too low in the blood and the blood has become alkaline, then the rate of breathing is slowed to prevent the fast removal of carbon dioxide from the body.

# data[].attributes.body
Q1) Homeostasis is the maintenance of constant internal environment. It refers to the fact that the composition of tissue fluid in the body is kept within the narrow limits. The concentration, acidity and temperature of this fluid are being adjusted all the time to function efficiently.

A feedback loop is a biological occurrence wherein the output of a system amplifies the system (positive feedback) or inhibits the system (negative feedback). In negative feedback stimulus is changed back to normal. Anything which gets highs or lower than the normal is adjusted and brought back to normal by the three parts (stimulus,control center and responding organ) of typical feedback playing major role to return back to normal. Whereas, in positive feedback the stimulus detected by receptors cannot be changed back to normal and homeostasis does not take place.

Q2) There are four major homeostatic organs: lungs, liver ,kidney and skin.

Lungs are one of major homeostatic organs, playing vital role in exchange of gases, maintenance of pH in blood and regulating water potential in blood.

The gaseous exchange maintains concentration of oxygen and carbon dioxide in the blood. Carbon dioxide is transported in blood as bicarbonate ions in the body. Bicarbonate and hydrogen ions are converted to carbonic acid and then to carbon dioxide which is then removed through exhalation.

Carbon dioxide dissolved in blood forming carbonic acid and lowering the pH of the blood, due to which the cells and enzymes can not function efficiently. The rate of breathing is adjusted according to the concentration of carbon dioxide in the blood by lungs, thus maintaining the pH.

Water not leaves our body only through sweat, urine, vomiting it also leaves through lungs by the process of exhalation. During exhalation, water vapours are also removed along with carbondioxide from the body. If the water potential is high more water vapours are exhaled and vice versa.

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A1) Homeostasis is the process of keeping the composition of the body fluids within narrow limits by ensuring a relatively stable environment and providing the organism with a certain degree of independence from the variations in external environmental conditions. The homostatic control involves a corrective mechanism after a stimulus is detected by the receptors. There are two types of feedback loops: Positive and negative feed back. In negative feedback, the observed stimulus can be changed and fixed back to normal. For example if the water potential of the blood increases above the norm, the body will correct this and bring it down to normal condition. And if it decreases below the norm, the body will respond and cause the water potential to rise the normal condition again. In positive feedback, the stimulus detected by receptos cannot be changed. This can cause dangers in the boys like hyperthermia.

A2) There are four major homeostatic organs: skin, lungs, liver and kidney. Lungs maintain homeostasis in two ways: gaseous exchange and regulation of blood pH. To maintain the carbon concentration in blood, lungs remove the excess carbon. Carbon dioxide is first transported in the blood as bicarbonate ions. The ions are converted into carbonic acid and then to carbon dioxide which is removed from our body during exhalation. Secondly, the pH of the blood is also maintained by the lungs. Presence of the carbonic acid causes pH of blood to decrease which in turn affects the cell activities. If the concentration of  carbon dioxide is low in the blood and the blood has become alkaline then the rate if breathing is lowered to prevent the fast removal of carbon dioxide from the body as it lowers the pH of the blood and do not allow the enzymes and cells to get dentured rather enable them to work properly in low pH. Lungs also help in the maintenance of the blood's water potential. Like during expiration water in our body is removed as water vapors. If water potential in our blood is high than more water vapors are exhaled and if water potential is low then fewer water vapors get exhaled out.

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Q1) homeostasis is the maintenance of a constant internal environment.
Homeostasis is there for needed because cells in the bodies of animals such as mammals and birds are efficient but demanding.They have to be kept at right temperature and must be bathed in tissue fluid of the correct PH and water potential. This means that these animals which includes humans have to keep the composition of tissue fluid with very narrow limits.The homeostatic control includes a stimulus (external or internal change) and a receptor to detect stimulus.There are two types of feedback loops,a negative feedback and a positive feedback.Positive feedback is the process in which stimulus  cannot be homeostatically controlled and is rather reinforced.Negative feedback is a reaction which always bring opposite effect to the change,it plays a vital role in achieving homeostasis by reversing the stimulus.It is to adjust a stimulus to return back to normal if the stimulus occurs within narrow limits.

Q2)There are four major homeostatic organs:lungs,liver,skin and kidney. Lungs are one of the most important homeostatic organ as it carries out to main homeostatic functions which includes gaseous exchange and maintenance of the pH and the water potential of blood. However as cells respire they produce carbon dioxide which isn't useful.As carbon dioxide is a waste product and has little use in our body we have to dispose it of. carbon dioxide is transported in the blood as a bicarbonate ions these ions are converted to carbonic acid and then to carbon dioxide which when we exhale is removed out of our body
Furthermore,the second most important function of lungs is to maintain the pH of bloof.The presence of carbonic acid causes the blood pH to decrease affecting the cell activities and causing non acidic enzymes to denature which may lead to death.
Moreover lungs also help in the maintainance of water potential of blood.When we exhale, not only we remove carbon dioxide, but we also remove lots of water vapor.So , as water leaves our body through lungs, it is involved in keeping the right balance of water (along with sweat and urine). As one area increases or decreases, all the other ways of removing water will adjust to balance it out.

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Q1)Homeostasis is the tendency of biological systems to maintain relatively constant conditions in the internal environment while continuously interacting with and adjusting to changes originating within or outside the system. feedback loop is biological process through which homeostasis is maintained. there are two types of feedback loop positive and negative feedback loop. In a positive feedback mechanism, the output of the system stimulates the system in such a way as to further increase the output. Negative feedback occurs when a system’s output acts to reduce or dampen the processes that lead to the output of that system, resulting in less output. In general, negative feedback loops allow systems to self-stabilize. Negative feedback is a vital control mechanism for the body’s homeostasis. The stimulus is first detected by receptor (sensory organ) which send signal brain and its associated parts. which later transmits the information to the responding organ that bring  about a reverse effect of stimulus  the information that homeostasis have been achieved is sent to the receptor. hence the corrective mechanism ends

Q2) the main homeostatic organs are lung, liver, kidney and skin. Lungs carry out two important homeostatic functions; exchange of gases and maintenance of pH.  One of the main homeostatic functions of the respiratory system is the gas exchange that occurs in the alveoli in the lungs. As blood passes through the tiny capillaries in the alveolar sacs, changing pressure gradients allow oxygen and carbon dioxide to diffuse in and out of the blood. To maintain the carbon concentration in the blood, excess carbon is removed from the blood. Carbon dioxide is transported in the blood as bicarbonate ions. These ions are converted into carbonic acid which is the converted into carbon dioxide and water by the action of carbonic anhydrase. The carbon dioxide is removed by the alveolar spaces in the lungs. Secondly, the pH of the blood is maintained by the lungs because the presence of carbonic acid causes the blood pH to decrease affecting the cell activities and vice versa. Therefore, the breathing rate is adjusted accordingly.

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Ans2)There are 4 major homeostatic organs which play an important role in maintaining a constant internal environment which includes skin,lungs,kidney and liver.Homeostasis in lungs is maintained in 3 ways.Lungs are responsible for the gaseous exchange,regulation of blood pH and maintaining the water potential in body.In order to maintain the carbon concentration in blood,excess carbon is removed from the blood.The carbondioxide is transported in the form of bicarbonate ions in the blood stream.The bicarbonate ions are converted into carbonic acid(HCO₃)  which is then broken down into water vapours and carbondioxide by the action of carbonic anhydrase. The carbondioxide is diffused through alveolar spaces and is removed as we exhale.This gaseous exchange maintains the concentration of oxygen and carbondioxide in blood and is essential for survival of human body.Other then that the lungs maintain the pH of blood as the carbonic acid  dissolved in the blood lowers the pH  of blood.It affects the activities of cells and enzymes as it do not allow the cells and enzymes to work at their optimum efficiency.As the pH becomes acidic,the enzymes which work at alkaline pH get denatured and the cells cease to work.Low pH of blood can lead to serious conditions like death.As the concentration of carbondioxide increases in blood,in response the rate of breathing is increased thus the excess carbondioxide can be removed from the system.Similarly if the concentration of carbondioxide is too low,then the rate of breathing is slowed to prevent removal of carbondioxide from blood.When we exhale,we also remove a huge amount of water vapours.Thus water leaves our body through urine,sweat,tears and alo via lungs.

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Q1) Homeostasis is the mechanism of maintaining the composition of  the body fluids within a narrow limit ie. under control.In simpler words it can be defined as the maintenance of a constant internal environment as it tends to maintain a stable and comparatively constant limit of pH,temperature,water potential and concentration gradient.The homeostatic control includes a stimulus(external or internal change),a receptor as well as corrective mechanism.
A feedback loop is a biological process or occurrence where in the output of the body system that amplifies positive feedback or inhibits negative feedback.The negative feedback loop bring about an opposite change to stimulus detected or when the change occurred can return back to normal despite the external change and the body becomes calm again.Negative feedback system is characterized by the distinctive ability to increase or decrease the stimulus according to the demand of body..This reaction causes a decrease in function in response to any kind of stimulus usually causing the output of system to be lessened eg. if the body has a low blood sugar,negative feedback rises it to normal.Whereas in positive feedback the stimulus can't be controlled homeostatically rather in response the stimulus is reinforced.Positive feedback loop will continue to amplify the initial change until the stimulus is removed.The receptor detects the change and an effector is activated to induce the further change.
Q2)

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Ans.1) Homestasis is the process of keeping the composition of the body fluids under control. It maintains the internal environment of the body and ensures that the environment is according to the functions of the body cells. Homeostasis can only be achieved with the help of feedback.There are two types of feedback; negative and positive. In negative feedback the stimulus observed can be changed and fixed back to normal. For example, if, the pH of the blood rises, body will correct it and bring it back to normal. And if the pH decreases the body will bring it back to its normal pH. When the body provides an opposite action to an effect its called negative feedback. When a stimulus is observed and sensed by the receptor(sensory organs) the designed organ brings about a change called the negative feedback. In positive feedback, the stimulus detected by the receptor can not be changed. This can cause dangers in the body like hyperthermia.
Ans.2) The homeostatic organs are lung, liver, kidneys and skin. Lungs are responsible for maintaining the concentration of the gaseous exchange that takes place during breathing. Carbon dioxide produced as the product of reparation is transported into the blood by dissolving into the water and forming carbonic acid in presence of carbonic anhydrase. This presence of carbonic acid decreases the pH of the blood which denatures non-acidic enzymes and can even cause death.This is detected by chemoreceptors and sent to medula oblongata. So to get the pH to normal, breathing rate is increased and more carbon dioxide is exhaled out by the breakdown of carbonic acid into bicarbonate and then into carbon dioxide and hydrogen. If the concentration of carbon dioxide decreases in blood, breathing rate increases so more carbon dioxide gets dissolved in blood in form of carbonic acid and the pH of the blood does not become alkaline, in absence of carbonic acid. So the lungs also control the pH of the blood. The liver also maintains the water potential in blood. Water vapour, a product of respiration is also exhaled by lungs. The water vapour is collected from the body cells and dissolved in blood. And is then exhaled out with carbon dioxide.

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Q1] Homeostasis is the maintenance of a constant internal environment  of a body. its a process which ensures that the composition of body fluid is kept with in a narrow limits and maintain a relatively constant limit of pH, temperature   and water potential.
feedback loop is biological process through which homeostasis is maintained. there are two types of feedback loop positive and negative feedback loop.  positive feedback is the mechanism in which stimulus cannot be controlled is rather reinforced. on the other hand negative feedback loop is characterized by its ability to either  increase or decrease the stimulus. it helps to return the stimulus with in a narrow limit. The stimulus is first detected by receptor (sensory organ) which send signal brain and its associated parts. which later transmits the information to the responding organ that bring  about a reverse effect of stimulus  the information that homeostasis have been achieved is sent to the receptor. hence the corrective mechanism ends
Q2] The main homeostatic organ include  are lungs, kidney, liver and skin. lung carry out two main homeostasis function including gaseous exchange, regulation of blood pH and water potential of blood. To maintain the carbon concentration in blood, lungs remove excess carbon. the blood picks up carbon dioxide from the respiring cell. the carbon dioxide is carried the form of bicarbonate ions. these are later converted to water and carbon by the action of carbonic anhydrous.As blood passes through the tiny capillaries in the alveolar sacs, changing pressure gradients allow oxygen and carbon dioxide to diffuse in and out of blood. Secondly the pH of the blood is maintained by the lungs. the presence of carbonic acid causes the blood pH to decrease affecting the cell activities and vice versa. the breathing is adjusted accordingly. Moreover during expiration water vapors are also released to maintain water potential of blood in a narrow limit. if water potential is high in blood than more vapors are exhaled and if water potential is low than fewer vapors are exhaled. In general lungs carry out major homeostatic function.

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Q1) The maintenance of the internal environment within narrow limits to maintain temperature, pH,concentration and water potential of body fluids is called homeostasis.
A feedback loop is a biological occurrence wherein the output of a system amplifies the system which is a positive feedback or inhibits the system that is a negative feedback. Positive feedback is one in which stimulus cannot be homeostatically controlled and is rather reinforced whereas negative feedback loop is one which occurs in response to some kind of stimulus. It causes a decrease in function and the output of system to be lessened so it tends to stabilize it by returning it back to normal within the narrow limits. The stimulus is first detected by the receptor which sends signal to brain and its associated parts which transfers information to responding organs that brings about a reverse effect of stimulus and a feedback to the receptor hen set point is reached which causes the corrective mechanism to stop.
Q2) The main homeostatic organs are lung, liver, kidney and skin.
Homeostasis is maintained by lungs in two ways: gas exchange and regulation of blood pH.
To maintain the carbon concentration in blood, lungs remove excess carbon.The carbon dioxide is first transported as bicarbonate ion in the blood and these are then converted to water and carbon dioxide by the action of carbonic anhydrase. Carbon dioxide is then removed by the lungs through alveolar spaces.
The presence of the carbonic acid causes pH of blood to decrease which in turn affects the cell activities, therefore it is important that the breathing rate is adjusted.
The lungs also play an important role in maintaining sufficient water content. When we exhale, we not only remove carbon dioxide but also lots of water vapors. If water potential is high in blood, more vapors are exhaled and if water potential is low less vapors are exhaled. So, as water leaves your body via lungs, it is involved in keeping the right balance of water. As one area increases or decreases all other ways of removing water will adjust to balance it out. Thus, lu

# data[].attributes.body
Q1. Homeostasis is the mechanism of keeping the composition of the body fluids with in narrow limits and is a characteristic of a system that regulates its internal environment and tends to maintain a table and relatively constant limit of pH ,temperature ,water potential and concentration gradient. The homeostatic control involves a corrective mechanism after a stimulus is detected by the receptors.
Feedback loops is biological occurrence where in the output of a system amplifies the the positive feedback or inhibits the negative feedback.there are two types of feedback.Positive feedback is the process in which the stimulus cannot be homeostatically controlled and is rather reinforced. Negative feedback loop is a reaction that causes a decrease in function . it occurs in response to some kind of stimulus . It helps the  stimulus to return back to normal if the stimulus occurs within narrow limits . At first the stimulus is detected by a sensory organ (receptor) which sends a negative feedback to the brain and its connected parts, which then transmits the information to the responding organ which carries out a certain function to attain homeostasis .the information which is attain by homeostasis is then sent to the receptor. This is how it stabilize the the system.

Q2. The  homeostatic organs include liver, kidney,lungs and skin. Lungs carry out vital homeostasis functions. Lungs are accountable for the the exchange of gases between the air we breath in and blood vessels. This gaseous exchange maintains the concentration of oxygen and carbon dioxide in the blood. To maintain the carbon concentration i the blood lungs remove excess carbon from the blood. The carbon dioxide is transported in the blood as bicarbonate ions. The ions are converted to carbonic acid and then to carbon dioxide which is removed from our body when we exhale. also helps in managing the pH of the blood . If the concentration of carbon dioxide  is low in the blood and the blood has become alkaline then the rate of breathing is slowed to prevent the fast removal of carbon dioxide from the body  as it lowers the pH of blood and do not allow cells and enzymes to denature rather work properly in low pH. Moreover lungs also help in the maintenance of water potential of blood. When expiration occurs water n our body is removed as vapors. If water potential is high in the blood then more vapors of water are exhaled,if water potential is low then fewer vapors of water are exhaled .

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Q.1) Define Homeostasis and Explain Feedback loops. (5 Marks)
Q.2) Name the homeostatic organs and briefly describe the role of lungs (5 Marks)

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Q1. Homeostasis is a mechanism which involves the maintenance of the constant internal environment of the body by keeping the composition of the body fluids within narrow limits to maintain its regular pH, temperature, water potential and concentration. The homeostatic control involves a corrective mechanism after a stimulus (change) is detected by the receptors.
Feedback loops are a very major part of the homeostatic control. There are two kind of feedback loops: positive feedback and negative feedback. A negative feedback plays a vital role in achieving homeostasis by reversing the stimulus. This feedback is used to adjust a stimulus to return back to normal if the stimulus occurs within narrow limits. Firstly, the stimulus (change) is detected by the sensory organ (receptor) which sends a negative feedback to the control center (brain and its associated parts) that transmits the information to the responding organ which carries out a particular function to achieve homeostasis. The information that homeostasis has been achieved is sent to the receptor. This is how a negative feedback loop works. In addition to this, another feedback process is positive feedback in which the stimulus cannot be homeostatically controlled and is instead reinforced.

Q2.  There are four major homeostatic organs: skin, liver, kidney and lungs. Lungs are responsible for the exchange of gases and maintenance of the pH and the water potential of the blood. To maintain the carbon concentration in the blood, excess carbon is removed from the blood. Carbon dioxide is transported in the blood as bicarbonate ions. These ions are converted into carbonic acid which is the converted into carbon dioxide and water by the action of carbonic anhydrase. The carbon dioxide is removed by the alveolar spaces in the lungs. Secondly, the pH of the blood is maintained by the lungs because the presence of carbonic acid causes the blood pH to decrease affecting the cell activities and vice versa. Therefore, the breathing rate is adjusted accordingly. Furthermore, maintenance of water potential of blood is also dependent on lungs. During expiration, water is removed as vapors. If water potential is high in blood, more water vapors are exhaled and if the water potential is low, less water vapors are exhaled. In all, lungs carry out major homeostatic functions.