Respiration System

Question 1

Define pulmonary ventilation.

Answer 1

Movement of air into and out of the lungs.

Question 2

Give a brief description of what internal respiration means.

Answer 2

Internal respiration refers to the use of oxygen inside mitochondria to generate ATP (in the process of oxidative phosphorylation), and the generation of carbon dioxide as a waste product.

Question 3

Give a brief description of what external respiration means.

Answer 3

This respiration refers to the exchange of oxygen and carbon dioxide between the atmosphere and body tissues, which is occurs via the respiratory and circulatory systems.

Question 4

External respiration refers to the movement of oxygen and carbon dioxide between the atmosphere and body tissues and this can be broken down into 4 processes. What are they?

Answer 4

1. Pulmonary ventilation.
2. Gas exchange between lungs and blood.
3. Movement of oxygen and carbon dioxide between the lungs and body tissues via the blood.
4. Gas exchange between the blood and body tissues.

Question 5

Lobes are structures that makes up the lungs. How many lobes is each lung divided into?

Answer 5

Right lung has 3 lobes, and left lungs has 2 lobes.

Question 6

What are the upper airways referring to into the respiratory system?

Answer 6

The air passages in the head and neck. This includes how air can enter through the oral cavity and nasal cavity, and how both airways leads to the pharynx.

Question 7

What is the pharynx?

Answer 7

The pharynx is a muscular tube found in the throat, that is a passageway for both food and air.

Question 8

Describe the movement of air (to alveoli) in the human gas exchange system.

Answer 8

> Nose
Nasal cavity
Trachea
Bronchi
Bronchioles
Alveoli

Question 9

How is the nasal cavity adapted to taking in air?

Answer 9

> The nasal cavity has a large surface area with a good blood supply, which warms the air to body temperature.
It has a hairy lining that secretes mucus to trap dust and bacteria (protecting lung tissue from irritation and infection).

Question 10

How is the trachea in humans adapted to its function?

Answer 10

The trachea carries air from the nasal cavity to bronchi.
> The trachea is supported with C-shaped rings of cartilage, to prevents the trachea from collapsing down on itself. It is C-shaped as it allows for movement of food down the adjacent pipe, the oesophagus.
> The trachea is lined with goblet cells and ciliated epithelium. The goblet cells secretes mucus (made of glycoproteins) which traps any bacteria and pathogens in the trachea, stopping them from reaching the lungs. The cilia then sweeps this mucus back up to be coughed up.
> The tracheal walls are made of smooth muscle. The trachea is able to contract and recoil due to the elastic fibres in trachea wall. The contraction of smooth muscle reduces the size of the lumen in the trachea, possibly to reduce airflow to the lungs in the presence of harmful substances.

Question 11

How are the bronchioles adapted to its function?

Answer 11

The bronchioles carries air from the bronchi to alveoli.
> The bronchioles also contains some smooth muscles in its walls, so when it constricts, it is able to reduce airflow to the lungs.
> The walls of the bronchioles is made up of a thin layer of flattened epithelium, making some gas exchange possible.

Question 12

How are the alveoli adapted to its function?

Answer 12

The alveoli is the site of gas exchange is humans.
> The alveoli has high surface area. Each individual alveoli is very small in size, giving a high SA:V. But with millions of alveoli in the lungs, this increases the surface area greatly, giving a faster diffusion rate.
> Short diffusion distance - Each alveoli has one layer of squamous epithelial cells in its walls.
> Maintained concentration gradient- Each alveoli is surrounded by a network of capillaries, with a good blood supply that is constantly exchanging gases.
> Elastic tissues in the walls of the alveoli allows the alveoli to expand as air is drawn in (and then recoil).

Question 13

When we breath in through our mouth (Oral cavity), it is normally during exercise (to get more in an air intake) or when our nose is blocked. However, relative to the air breathed in via the nasal cavity, the air breathed in through the oral cavity is cold and dry. Why is this?

Answer 13

The nasal cavity or nose is able to warm and moisturise the air we take in. It is able to warm the air because the nose has a sufficient blood supply that radiates heat. The hairy lining in the nose also secretes mucus that moisturises the air.

Question 14

What is the conducting and respiratory zone and how do they differ?

Answer 14

The conducting zone refers to the passageway that travels from the upper parts of the respiratory system to the bronchioles.

The respiratory zone refers to the air in the lower parts of the respiratory system- this includes the terminal bronchioles and alveoli.

Apart from the locations of these zones, the zones also differ by the fact that the air in the respiratory zone takes place in gas exchange, while the air in the conducting zone does not.

Question 15

Where is the larynx located and what is its function?

Answer 15

The larynx is found in throat and is part of the respiratory tract. The larynx contains our vocal cords, that generates sound as air passes over them.
The larynx is also responsible for ensuring food or drink does not enter the respiratory tract. The top or opening of the larynx is called the glottis and the glottis is capable of being covered by a flap of tissue called the epiglottis. During swallowing, the epiglottis is forced down, and this prevents food from entering the respiratory tract.

Question 16

List the structures of the conducting zone, starting from the trachea.

Answer 16

Trachea, primary bronchi, secondary bronchi, tertiary bronchi, bronchioles, terminal bronchioles and alveoli.

Question 17

What is the trend in cartilage and diameter going from the trachea to alveoli?

Answer 17

Going from the trachea to the alveoli, there is a decrease in cartilage and diameter, which means the trachea has the most cartilage and greatest diameter. The trachea needs a lot of cartilage to support its structure.

Question 18

What is the trend in smooth muscle going from the trachea to the alveoli?

Answer 18

Going from the trachea to the alveoli, there is an increase in smooth muscle. The presence of the smooth muscle in the tract helps gives the function of contraction to reduce diameter of the lumen to stop the passage of air, in the case of anything harmful being in the air (poisonous air).

Question 18

Where are goblet cells found?

Answer 18

The larynx and trachea.

Question 19

What is the purpose of cilia lining the trachea?

Answer 19

The cilia sweeps mucus up towards the glottis, which allows the mucus to be swallowed or coughed up.

Question 20

What part of the respiratory tract does smoking affect, so much that smokers are coughing constantly?

Answer 20

Smokers cough a lot due to the damage sustained to the epithelial cell wall, more specifically, the cilia. The cilia is damaged and so does not have enough propulsion to move the mucus up the trachea. To compensate this, people who smoke cough a lot to provide propulsion to push the mucus up the trachea.

Question 21

What is ‘dead space’?

Answer 21

Dead space refers to air that was last breathed in, and this air will also be the air we next breathe out. The volume of air in each breath that is dead space is around 150ml, and this air never reaches the alveoli for gas exchange.

Question 22

When we do exercise, is it more effective to breathe more frequently or breathe in more air in each breath to gain sufficient oxygen?

Answer 22

Breathing in more air with each breath is more effective because it ensures a higher volume of air actually reaches the alveoli for gas exchange of oxygen, even if we still have the same volume of dead space. Breathing more frequently means that the same volume of air is restricted to reaching the alveoli in each breath, so limited (and definitely not the maximum) gas exchange occurs.

Question 23

What are the functions of the conducting zone?

Answer 23

Provides a passageway for air to enter respiratory zone.
Adjustment of air temperature.
Humidifying the air.

Question 24

What structures make up the respiratory zone?

Answer 24

Respiratory bronchioles, alveolar ducts, alveoli and alveolar sacs (alveolar sacs is a structure that is made from many alveoli).

Question 25

Around how much alveoli is in the lungs?

Answer 25

Around 300 million alveoli in the lungs, but this can change with age and size.

Question 26

What are alveolar pores? What is the purpose of alveolar pores in the alveoli?

Answer 26

Alveolar pores are holes in the alveoli, which connects adjacent alveoli. The alveolar pores serves as a passageway for air flow between adjacent alveoli, so each alveoli is not completely independent. Since air flows between all the alveoli, there is an equilibration of pressure throughout the lungs.

Question 27

There are two types of cells in the alveoli. Where are Type 1 cells located and what is their function?

Answer 27

Type 1 cells are epithelial cells overlying a basement membrane. Type 1 cells are primarily responsible for efficient gas exchange between the alveoli and the blood.

Question 28

In the lungs there is a fused basement membrane between the alveolar epithelium and capillary endothelium. What is this fused membrane structure, and how is it formed?

Answer 28

Alveoli has epithelium cells that sits on a basement membrane, and blood vessels have endothelium cells that is underlying on a basement membrane. In many places in the lungs, the basement membrane of the alveoli and capillaries are so close together that they fuse and become one basement membrane.

Question 29

Gas exchange occurs over the respiratory membrane in the lungs. What is the reseparatory membrane comprised of?

Answer 29

Alveolar epithelium, a fused basement membrane and a capillary endothelium.

Question 30

What are the functions of Type 2 cells in the alveoli and where are they located?

Answer 30

Type 2 cells are found along the lining of the epithelial wall in the alveoli. The primary function of Type 2 cells is to secrete surfactant. Surfactant is a solution which contains a mixture of lipids and proteins, and this reduces the surface tension in the alveoli. The function of this is to prevent the alveoli from collapsing and holding their structure during exhalation. Another function of these type 2 cells is that they are capable of differentiating into type 1 cells (epithelial cells), so it has a function of regenerating damaged alveolar tissue.

Question 31

What is the purpose of alveolar macrophages?

Answer 31

Alveolar macrophages have the function on engulfing and digesting foreign material and pathogens that have made it pass through the other defense systems and barriers. These macrophages are not bound to anything and free to move around in the alveoli.

Question 32

What bones are found in the thoracic cavity (chest cavity)?

Answer 32

Ribcage, sternum (elongated bone in the centre of the chest- breastbone) and thoracic vertebrae (bones in the chest region found in the backbone).

Question 33

What muscles are found in the thoracic cavity, essential to respiration?

Answer 33

Internal and external intercostal muscles.

Question 34

What are the functions of the thoracic cavity?

Answer 34

Protects the lungs and facilitates ventilation.

Question 35

Where are the intercostal muscles located in the thoracic cavity?

Answer 35

Intercostal muscles are located in between the ribs.

Question 36

What is the pleural sac?

Answer 36

The pleural sac is a thin fluid filled membrane that surrounds each lungs, and separates the lungs from the ribs and intercostal muscles.

Question 37

What is the function of the pleural sac?

Answer 37

The pleural sac connects the lungs and ribcage constantly; so it makes them inseparable. The pleural sac provides flexibility as it allows the lungs to slide past the ribcage. It keeps them lubricated as well.

Question 38

State the names of the inner and outer membranes of the pleural sac.

Answer 38

The membrane (inner?) that is connected with the lungs is called the visceral pleura. The membrane that is in contact with the ribs (outer?) is called the parietal pleura. The interior of the pleural sac is called the intrapleural space.

Question 39

What is pneumothorax?

Answer 39

Pneumothorax is when there is a puncture or damage in the pleural sac (which can be from a wound or due to a lung health condition), which allows air to escape from the lungs and enter the thoracic cavity. This causes the lung to lose its structure and shape, due to a decrease in pressure in the lungs, as well as the pressure exerted on the lungs from the outside (in the chest cavity) from the released air.

Question 40

Describe the pulmonary pressures at rest.

Answer 40

The lungs and the chest wall are both elastic and tend to recoil back to their normal position. A rest, the chest wall is compressed but the lungs are stretched. At rest, there is also a negative pressure in the intrapleural space.

Question 41

What are the different pulmonary pressures?

Answer 41

Atmospheric pressure, intra-alveolar pressure (0 at rest) and intrapleural pressure (always negative and smaller than intra-alveolar pressure).

Question 42

Describe the process of inspiration in humans.

Answer 42

> The diaphragm contracts and moves downwards. > External intercostal muscles contract. > Ribcage is pulled upwards and outwards. > The volume of thorax (chest cavity) increases. > The pressure in the thorax drops below atmospheric pressure. > Causes air to flow in the lungs.

Question 43

Describe the process of expiration in humans.

Answer 43

> The diaphragm relaxes. > External intercostal muscles relax. > Internal intercostal muscles can contract, if air is being pushed out forcefully (forceful expiration). > Ribcage is pulled inwards and downwards. > The volume of the thorax decreases. > The pressure in the lungs increases and rises above atmospheric pressure. > Air moves out of the lungs.

Question 44

What is the difference between normal expiration and forcefully exhaling (like during exercise, sneezing or coughing)?

Answer 44

Normal expiration is a passive process, where the internal intercostal muscles do not contract. When someone forcefully exhales, the intercostal muscles contracts which requires energy- it is not passive.

Question 45

Describe how a floating chamber spirometer works.

Answer 45

> A floating chamber spirometer consists of a chamber of air or medical grade oxygen floating on top of a tank of water. > During inspiration, air is drawn from the chamber so the lid moves down. > During expiration, air returns to the chamber, raising the lid. These movements are recorded by a data logger.

Question 46

What precautions should be taken when using a spirometer?

Answer 46

> The subject should be healthy (free from asthma). > Soda lime should be fresh and functioning. > There should be no air leaks in the apparatus (it can give inaccurate results). > Sterilised mouthpiece. > Water chamber should not be overfilled.

Question 47

What is Boyle's law?

Answer 47

Boyle's law calculates the pressure in the lungs P= nRT/ V. It basically encompasses the fact that when volume increases, the pressure decreases (and when volume decreases, the pressure increases).

Question 48

What is intra-alveolar pressure dependent on?

Answer 48

Quantity of air (moles) and volume of air.

Question 49

Describe the pressure and volume changes during inspiration.

Answer 49

During inspiration, the lung volume increases, so then the pressure decreases (relative to atmospheric pressure). This causes air to rush into the lungs.

Question 50

Describe the pressure and volume changes during expiration.

Answer 50

During expiration, the lung volume decreases causing an increase in pressure (relative to atmospheric pressure). This causes air to flow out of the lungs to outside the body.

Question 51

What is lung compliance?

Answer 51

Lung compliance is how easily the lungs can expand and stretch when air is inhaled. It can be calculated with the formula: Change in volume / Change in (alveolar pressure - interpleural pressure) A high lung compliance means the lungs can expand easily with little effort, while a low lung compliance means the lungs are stiff, and requires a lot of energy to expand.

Question 52

What is lung compliance dependent on?

Answer 52

> Elasticity of the lungs > Surface tension of fluid lining the alveoli (the work required to increase surface area).

Question 53

What is surface tension?

Answer 53

Surface tension is when the surface of a liquid is able to resist an external force. This is able to happen due to the cohesion of like molecules (bonding between these molecules).

Question 54

Is surface tension an inwards or outwards force? How does it work?

Answer 54

Surface tension is an inwards force because the molecules at the surface of a liquid is more attracted and form more bonds with the other surface molecules, rather than the air molecules above. The interactions between molecules at the surface brings the liquid inwards and closer together (almost like a spherical shape) causing it to decrease in volume. This surface tension force is always present due to the normal forces of air that can act on a liquid. There can also be the surface tension of gas molecules, due to interactions of gas molecules that are enclosed in a membrane.

Question 55

The alveoli's shape and structure, as well as the water film lining the alveoli, causes the force of surface tension to work on the alveoli. What affect does surface tension have on alveoli?

Answer 55

The surface tension is an inwards force acting on the alveoli (due to the hydrogen bonding bringing water molecules closer together; water molecules from the water lining the alveoli). The inwards force suppresses the air pressure inside the alveoli causing to collapse.

Question 56

How are the alveoli prevented from collapsing as a result of surface tension?

Answer 56

Type 2 cells in the alveoli secrete surfactant, which decreases the surface tension. The surfactant is amphipathic molecule which interacts with molecules at the surface of the liquid (or surface of the gas) where the force of the surface tension is the most. The interaction between the surfactant and surface molecules causes a disruption of cohesive forces, causing a decrease in surface tension. Now the alveoli do not need to try compensate with a larger air pressure inside to stop it collapsing, instead the surfactant helps with that.

Question 57

Describe the relationship between surface tension and radius of the alveoli.

Answer 57

Surface tension and radius of alveoli is inversely proportional, so a smaller alveolus has greater surface tension. Consider two alveoli with the same concentration of air molecules, but one has a smaller radius. The alveolus with a smaller radius would have a greater pressure, as well as the air molecules being packed closer together. The packing of molecules closer together allows more cohesive forces and bonding to occur between these molecules (that pulls the alveoli inwards), leading to a greater surface tension.

Question 58

What is airway resistance?

Answer 58

Airway resistance is the total resistance experienced in the respiratory tract.

Question 59

How is airway resistance regulated?

Answer 59

> Smooth muscles (contraction or relocation) in the walls of the bronchioles. > extrinsic (neuronal, hormonal) > Intrinsic (oxygen and carbon dioxde)

Question 60

What is the formula to calculate air flow?

Answer 60

Air flow= (atmospheric pressure - alveolar pressure) / resistance

Question 61

How do we know when airway resistance in the repiratory tract has increased?

Answer 61

We know when: There is the same normal change in volume of air but a bigger change in pressure OR The same change in pressure, but a smaller change in volume.

Question 62

What are some diseases that are associated with an increased airway resistance?

Answer 62

Asthma and COPD (chronic obstructive pulmonary disease)

Question 63

What is tidal volume?

Answer 63

The air inhaled and exhaled when at rest.

Question 64

What is vital capacity?

Answer 64

A measurement of maximum volume of air an individual can breathe in after strongest possible exhalation.

Question 65

What is inspiratory reserve volume?

Answer 65

The maximum volume of air you can breathe in over and above normal inhalation.

Question 66

What is expiratory reserve volume?

Answer 66

The extra amount of air you can force out of your lungs at the end of a normal expiration.

Question 67

What is residual volume?

Answer 67

The maximum volume of air that remains in the lungs so they don't collapse.

Question 68

What is total lung capacity?

Answer 68

This is the sum of vital capacity and residual volume.

Question 69

What in inspiratory capacity?

Answer 69

While the inspiratory reserve volume is the maximum volume of air that can be inhaled after a normal inspiration, the inspiratory capacity is the maximum volume of air that can be inhaled after a normal expiration. So basically, it is the total volume of air including the normal inhalation and air breathed in above this inhalation, while inspiratory reserve volume just encompasses the volume of air breathed in above the normal inhalation.

Question 70

What is the functional residual capacity?

Answer 70

Volume of air remaining in the lungs at the end of a tidal expiration. This is not the same a residual volume; in fact the value of functional residual capacity is greater than residual volume.

Question 71

What is minute ventilation?

Answer 71

The total amount of air that flows into or out of the respiratory system in a minute. Calculated by doing: Tidal volume x number of breaths every minute

Question 72

What is minute alveolar ventilation?

Answer 72

The amount of fresh air that reaches the alveoli each minute (excludes dead space). Alveolar ventilation: (tidal volume x ventilation rate) - (dead space x ventilation rate)

Question 73

What is ventilation rate?

Answer 73

Number of breaths per minute

Question 74

What is the approximate volume of dead space?

Answer 74

150mL

Question 75

What determines the partial pressures of oxygen and carbon dioxide in the arteries?

Answer 75

The partial pressures of oxygen and carbon dioxide in the alveoli.

Question 76

What 3 factors determines the partial pressure of oxygen and carbon dioxide in the alveoli?

Answer 76

> Partial pressure of oxygen and carbon dioxide of inspired air (but is assumed to be constant). > Minute alveolar ventilation (volume of fresh air that reaches the alveoli every minute). > Rate of oxygen consumption and carbon dioxide in respiring tissues.

Question 77

Although partial pressure of oxygen and carbon dioxide of inspired air is indeed a factor of their alveolar partial pressures, why do we in most cases dismiss this factor?

Answer 77

The partial pressures of oxygen and carbon dioxide in inspired airs is assumed to be constant. Their PP is lowered due to intense humidification (so, it is not the same as their natural pressures in the atmosphere). The exception to this is if there is a change in altitude, or if a person were to undergo artificial breathing (breathing in a mixture of air that is 95% oxygen and 5% carbon dioxide).

Question 78

Assuming a person is at ground level and there is no use of artificial breathing, what factors would determine their alveolar partial pressures of oxygen and carbon dioxide?

Answer 78

We would look at minute alveolar ventilation as well as oxygen consumption and carbon dioxide production in respiring tissues. More specifically, we would look at minute alveolar ventilation relative (or in response to) oxygen consumption and carbon dioxide production.

Question 79

What is it called when the minute alveolar ventilation increases with rate of oxygen consumption and carbon dioxide production (and in this case, alveolar ventilation is matching the demands of the tissue)?

Answer 79

Hypernea.

Question 80

How is hyperventilation brought about (in terms of the partial pressure and alveolar ventilation)? What does it cause for arterial pressures?

Answer 80

Hyperventilation is brought about when the minute alveolar ventilation exceeds the demands for respiring tissues. Minute alveolar ventilation > rate of oxygen consummation and carbon dioxide production For arterial partial pressures, carbon dioxide decreases (below its standard 40 mm Hg) and oxygen increases (above its standard 100 mm Hg).

Question 81

How is hypoventilation brought about (in terms of the partial pressure and alveolar ventilation)? What does it cause for arterial pressures?

Answer 81

In hypoventilation, the minute alveolar ventilation is insufficient to meet the demands of the respiring tissues. Minute alveolar ventilation < rate of oxygen consumption and carbon dioxide production For arterial partial pressures, carbon dioxide increases (above normal value of 40 mm Hg) and oxygen decreases (100 mm Hg).

Question 82

What factors allow us to regulate our ventilation?

Answer 82

Regulation of minute alveolar ventilation (frequency and volume of breaths), central regulation, chemoreceptors and local regulation.

Question 83

What are chemoreceptors?

Answer 83

They detect changes in chemical concentrations.

Question 84

Where are central chemoreceptors found, and what do they respond to?

Answer 84

Central chemoreceptors are neurons found in the medulla oblongata (brain), and they respond to changes of H+. (When CO2 reacts with H20, we get H2CO3. When H2CO3 dissociates we get HCO3- and H+). This receptor is not sensitive to partial pressure changes in oxygen.

Question 85

Where are peripheral chemoreceptors found, and what do they respond to?

Answer 85

Specialised sensory cells located in carotid bodies near the carotid sinus. This neuron responds to changes in arterial partial pressure of oxygen (only when it is below 60 mm Hg), and it can respond to pH changes (due to partial pressure changes of carbon dioxide).

Question 86

What is the blood brain barrier?

Answer 86

Separates CSF (cerebrospinal fluid) from blood; H+ ions cannot cross this barrier. Instead CO2 crosses and is converted to H+ and HCO3-.

Question 87

Describe the stages to regulation of ventilation when hypoventilation occurs (in terms of chemoreceptor activity).

Answer 87

If hypoventilation occurs, there is an increase in arterial partial pressure of carbon dioxide, and hence an increase of H+ concentration in cerebrospinal fluid. There is also a decrease is arterial partial pressure of oxygen. As chemoreceptors respond to increases of CO2 partial pressure, there is an increase in chemoreceptor activity. This increases the ventilation (minute alveolar ventilation) so that the ventilation meets the demands of respiring tissues. This is an example of negative feedback.

Question 88

Describe the stages to regulation of ventilation when hyperventilation occurs (in terms of chemoreceptor activity).

Answer 88

If hyperventilation occurs, there is a decrease in arterial partial pressure of carbon dioxide, and hence a decrease of H+ concentration in cerebrospinal fluid. However, there is an increase in arterial partial pressure of oxygen. As chemoreceptors respond to increases of CO2 partial pressure, there is a decrease in chemoreceptor activity. This decreases the ventilation (minute alveolar ventilation) so that the ventilation matches the activity of respiring tissues. This is an example of negative feedback.

Question 89

What is Dalton's Law?

Answer 89

Total pressure is the sum of the partial pressures of individual gases. Ptotal = P1 + P2 + P3 +... +Pn

Question 90

What is the partial pressure of any gas dependent on?

Answer 90

The fractional concentration of the gas (i.e. fraction of its moles over total moles for all gases present) and the total pressure exerted by the gas mixture.

Question 91

The partial pressure of oxygen and carbon dioxide is relatively constant in the alveolar air, pulmonary veins and systematic arteries. What are the partial pressures of oxygen and carbon dioxide in these areas?

Answer 91

Oxygen- 100 mm Hg Carbon dioxide- 40 mm Hg

Question 92

The partial pressures of oxygen and carbon dioxide is relatively constant in the systematic veins and pulmonary arteries. What are the partial pressures of oxygen and carbon dioxide in these areas?

Answer 92

Oxygen- 40 mm Hg Carbon dioxide- 46 mm Hg

Question 93

The partial pressures of oxygen and carbon dioxide in the atmosphere are 160 mm Hg and 0.23 mm Hg, respectively. However, partial pressures of these gases in the alveolar air is 100 mm Hg and 40 mm Hg. What factors cause this change in partial pressures?

Answer 93

Gas exchange Dead Space Water Vapour (Water vapour is a gas, and having another gas present reduces the partial pressure of the other two gases, as their molar fraction of the total gas decreases).

Question 94

What is the partial pressures of oxygen and carbon dioxide at cells of respiring tissues?

Answer 94

Oxygen less than or equal to 40 mmHg. Carbon dioxide greater than or equal to 46 mm Hg.

Question 95

Talk about gas exchange in the respiratory system; where it happens, what causes it, what components further facilitates gas exchange.

Answer 95

Gas exchange can take place in the lungs (between blood alveoli), or at respiring tissues (between blood and cells). Gas exchange is driven by a pressure difference between gases (and via process of simple diffusion); for example, in the alveoli, oxygen has a partial pressure of 100 mm Hg, whereas in the veins at the lungs oxygen has a pressure of 40 mm Hg. This concentration gradient in pressure different causes oxygen to diffuse from alveoli to blood. The components that further facilitates this gas exchange is the thinness of the membranes, high surface areas and, as mention above, a pressure gradient.

Question 96

What is Henry's Law?

Answer 96

Henry's Law is all about the solubility of a gas in a liquid, and states that at equilibrium, the concentration of the dissolved gas is proportional to the partial pressure of the gas and solubility of the gas. c = kp c = concentration of dissolved gas k = Henry's Law constant (changes at different temperatures). p = partial pressure of the gas At equilibrium of the dissolving of a gas in a liquid, the number of gas molecules dissolving into the liquid is equal to the number of gas molecules leaving the liquid.

Question 97

Different types of gases have different solubility. Which is generally more soluble, oxygen or carbon dioxide?

Answer 97

Carbon dioxide is generally more soluble than oxygen.

Question 98

Describe the structure of haemoglobin?

Answer 98

In haemoglobin's structure, there are 2 alpha polypeptides chains, and 2 beta polypeptide chains. Each chain holds a co-factor called a haem group (carbon and nitrogen molecule centered around a Fe2+). The haem group is what oxygen can bind to reversibly.

Question 99

What is it called when oxygen has bonded to haemoglobin? What is it called oxygen is not bonded?

Answer 99

Oxyhaemoglobin- oxygen bonded to haemoglobin Deoxyhemoglobin- Oxygen is not bonded to haemoglobin

Question 100

How many oxygen molecules can a haemoglobin molecule transport?

Answer 100

Can transport 4 oxygen molecules, as each haemoglobin molecule has 4 haem groups.

Question 101

Why are haemoglobin's essential to the transport of oxygen?

Answer 101

As said before, the solubility of oxygen is very low. Although it can easily diffuse into the blood, it cannot easily dissolve in the blood (like how carbon dioxide dissolves in the blood?). For this reason, the binding of oxygen to haemoglobin in red blood cells, is very helpful with transporting oxygen around the body.

Question 102

Describe the shape and axis of a haemoglobin- oxygen dissociation curve.

Answer 102

On the y axis, there is the percentage saturation of haemoglobin with oxygen. On the x axis, there is the partial pressure of oxygen. So this graph investigates how saturated haemoglobin is with oxygen at different partial pressures of oxygen. The curve takes on an S-shape; a sigmoidal shape. We can roughly tell where in the circulation system the graph is talking about based on the partial pressure (of oxygen) axis. We can tell this because different parts of the body have distinct partial pressures of oxygen. If we can tell what part of the body the graph is talking about with the partial pressures, we can tell how much percentage oxygen saturation of haemoglobin occurs in this area of the body.

Question 103

Describe the correlation between percentage saturation and partial pressure of oxygen by looking at an oxygen dissociation curve.

Answer 103

As partial pressure of oxygen increases, the percentage saturation of haemoglobin with oxygen increases.

Question 104

How does temperature affect the percentage saturation of haemoglobin for oxygen?

Answer 104

An increase in temperature, affect the bonds in the tertiary structure of haemoglobin, giving an overall change in structure. This decreases the affinity of haemoglobin for oxygen because, with a change in structure, haemoglobin cannot form the necessary bonds with oxygen to keep it bound. So when the metabolism of a tissue increases (like in exercise), the temperature at respiring tissues increases which causes a decreased affinity of haemoglobin for oxygen, thereby causing the unloading of oxygen. Similarly, as the blood moves back to the lungs, there is a decrease in temperature of the blood, creating an increase in affinity for oxygen, and thereby increasing the loading of oxygen from the alveoli to the blood.

Question 105

An increase in temperature, shifts the graph of a haemoglobin-oxygen dissociation curve in what direction?

Answer 105

Increase in temperature causes a decrease in affinity of haemoglobin for oxygen, hence shifting the graph to the right. Similarly, a decrease in temperature shifts the graph to the left. The increase and decrease in body temperature is speaking with relativeness to the body temperature, 37 degrees.

Question 106

How does a decrease in pH affect the percentage saturation of haemoglobin for oxygen?

Answer 106

A decrease in pH means there is more H+ ions present. H+ ions interrupts the tertiary structures of haemoglobin, by forming hydrogen bonds, ionic bonds and more- this changes the overall structure of haemoglobin. This change in structure renders haemoglobin in being able to form bonds with oxygen to keep it bound- hence there is a decrease in affinity of haemoglobin for oxygen. At respiring tissues, the production is acid (like production of lactic acid during exercises) reduces the pH. Reduced pH decreases affinity of haemoglobin for oxygen, causing more unloading of oxygen into the respiring tissues. THIS IS CALLED THE BOHR EFFECT. An increase in pH increases the affinity of haemoglobin for oxygen.

Question 107

A decrease in pH, shifts the graph of a haemoglobin-oxygen dissociation curve in what direction?

Answer 107

A decrease in pH gives a lower affinity of haemoglobin for oxygen, shifting the graph to the right. Hence, an increase in pH shifts the graph to the left.

Question 108

What is the Bohr effect?

Answer 108

Bohr effect encompasses the idea that a decrease in pH, gives a lower affinity of haemoglobin for oxygen.

Question 109

What is the Carbamino effect?

Answer 109

Carbamino effect encompasses the idea that an increase in carbon dioxide partial pressure, decreases the affinity of haemoglobin for oxygen. Carbon dioxide is a competitive inhibitor to oxygen, as it can also bind to haemoglobin?

Question 110

How can there be the production of H+ ions in the blood?

Answer 110

Carbon dioxide reacts with water and makes H2CO3. H2CO3 dissociates to form H+ and HCO3-.

Question 111

The decrease in pH has proved to greatly affect oxygen transport around the body. How does the body keep the pH of the body at the optimum level (homeostasis)?

Answer 111

Elimination of H+ and HCO3- from the blood via the kidney; this is a relatively slow process to the one below. Removal of carbon dioxide from the blood through the respiration system- relatively quick compared to process above.