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Biology > 3.1 > Flashcards

3.1 Flashcards

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1
Q

What are the three main factors that affect the need for an exchange system?

A
  • Size
  • Surface area to volume ratio
  • Level of activity
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2
Q

How does size affect the need for an exchange system?

A

In very small organisms, all the cytoplasm is very close to the environment in which they live. Diffusion will supply enough oxygen and nutrients to keep the cells alive and active.

However, multicellular organisms may have several layers of cells. Here, any oxygen or nutrients diffusing in from the outside have a longer diffusion pathway. Diffusion is too slow to enable a sufficient supply to the innermost cells.

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3
Q

How does SA:V affect the need for an exchange system?

A

Small organisms have a large surface area to volume ratio. This means that their surface area is large enough to supply all their cells with sufficient oxygen.

Larger organisms have a small surface area to volume ratio. This means that their surface area is NOT large enough to supply all their cells with sufficient oxygen.

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4
Q

How does Activity level affect the need for an exchange system?

A

Some organisms are more active than others. Metabolic activity uses energy from food and requires oxygen to release the energy in aerobic activity.

The cells of an active organism need good supplies of nutrients and oxygen to supply the energy for movement.

This need for energy is increased in those animals, such as mammals, that keep themselves warm.

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5
Q

What are the three main features of a good exchange surface?

A
  • A large surface area to provide more space for molecules to pass through. This is often achieved by folding walls.
  • A thin permeable barrier to reduce diffusion distance.
  • A good bloody supply. This can bring fresh supplies of molecules to one side, keeping the concentration gradient. This ensures diffusion can occur rapidly.
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6
Q

What is pathway of air in mammals?

A

Trachea, Bronchi, Bronchioles, Alveoli

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7
Q

How does gas exchange in the alveoli?

A

Gases pass by diffusion through the thin walls of the alveoli.

Oxygen passes from the air in the alveoli to the blood in the capillaries.

Carbon dioxide passes from the blood to the air in the alveoli.

The lungs maintain a steep concentration gradient in each direction in order to ensure that diffusion can continue.

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8
Q

How do the lungs ensure a large surface area for diffusion?

A

The individual alveoli are very small, however, they are so numerous that the total surface area of the lungs is much larger than that of our skin.

The alveoli are also lined by a thin layer of moisture, which evaporates and is lost as we breathe out. The lungs must produce a surfactant that coats the internal surface of the alveoli to reduce the cohesive forces between the water molecules as these forces could force the alveoli to collapse.

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9
Q

How do the lungs ensure a thin barrier for diffusion?

A
  • Both walls consist of squamous (flattened) cells.
  • The alveolus and the capillary wall are one cell thick
  • The capillaries are in close contact with the alveolus walls
  • The capillaries are so narrow that the red blood cells are squeezed against the capillary walls. This makes them closer to the air in the alveoli and reduces the rate of flow.
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10
Q

How do the lungs ensure a good blood supply for diffusion?

A

The blood supply helps to maintain a steep concentration gradient so that the gases continue to diffuse.

  • The blood system transports carbon dioxide from the tissues to the lungs. This ensures that the concentration of carbon dioxide in the blood is higher than that in the air of the alveoli. Therefore, carbon dioxide diffuses into the alveoli.
  • The blood also transports oxygen away from the lungs. This ensures that the concentration of oxygen in the blood is kept lower than that in the alveoli. Therefore, oxygen diffuses into the blood.
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11
Q

What is ventilation?

A

The refreshing of air in the lungs, so that there is a higher oxygen concentration than in the blood, and a lower carbon dioxide concentration.

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12
Q

What are the intercostal muscles?

A

Muscles beween the ribs.

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13
Q

What is the diaphragm?

A

A layer of muscle beneath the lungs

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14
Q

What is the process of Inspiration?

A
  1. The diaphragm contracts to move down and becomes flatter - this displaces the digestive organs downwards
  2. The external intercostal muscles contract to move the ribs upwards and outwards
  3. The volume of the chest cavity is increased
  4. The pressure in the chest cavity drops below atmospheric pressure
  5. Air moves into the lungs
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15
Q

What is the process of Expiration?

A
  1. The diaphragm relaxes and is pushed up by the displaced organs underneath
  2. The external intercostal muscles relax and the ribs fall. The internal intercostal muscles contract to help push air out more forcefully.
  3. The volume of the chest cavity is decreased
  4. The pressure in the chest cavity increases above atmospheric pressure.
  5. Air moves out of the lungs
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16
Q

What is Cartillage?

A

A form of connective tissue

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17
Q

What is Ciliated Epithelium?

A

A layer of cells that have many hair-like extensions called cilia.

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18
Q

What are Elastic Fibres?

A

Protein fibres that can deform and then recoil to original size

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19
Q

What are Goblet Cells?

A

Cells that secrete mucus

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20
Q

What is Smooth Muscle?

A

Involuntary muscle that contracts without the need for conscious thought.

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21
Q

What is lung tisssue comprised of?

A

The alveolus walls contain elastic fibers that stretch during inspiration but then recoil to help push out the air during expiration

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22
Q

What requirements must airways meet to be effective?

A
  • Large enough to allow sufficient air to flow without obstruction
  • Be supported to prevent collapse when the air pressure inside is low during inspiration
  • Be flexible in order to allow movement
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23
Q

What is the role of cilliated epithelium and goblet cells?

A

The airways are lined by ciliated epithelium, which contributes to keeping the lungs healthy.

Goblet cells in the epithelium release mucus, which traps pathogens.

The cilia then move the mucus up to the top of the airway, where it is swallowed. The glandular tissue in the loose tissue also produces mucus.

24
Q

What is the trachea and bronchi comprised of?

A

The trachea and bronchus walls have a similar structure. However, the bronchi are narrower than the trachea.

These airways are supported by rings of cartilage which prevent collapse during inspiration. The rings of cartilage in the trachea are C-shaped rather than a complete ring which allows flexibility and space for food to pass down the esophagus.

25
Q

What are the bronchioles comprised of?

A

The bronchioles are much narrower than the bronchi. The larger bronchioles may have some cartilage, but the smaller ones have no cartilage.

The wall is comprised mostly of smooth muscle and elastic fibers. The smallest bronchioles end in clusters of alveoli.

26
Q

What is the role of smooth muscle and elastic tissue?

A

The action of smooth muscle will constrict the airway. This makes the lumen of the airway narrower.

Controlling the flow of air to the alveoli might be important if there are harmful substances in the air. This can also occur if someone is having an allergic reaction.

Once smooth muscle has contracted it must be elongated again by the elastic fibres when they recoil to their original shape and size. This acts to dilate the airways.

27
Q

What is Breathing Rate?

A

The number of breaths per minute

28
Q

What is Oxygen Uptake?

A

The volume of oxygen absorbed by the lungs in one minute

29
Q

What is total lung volume made up of?

A

Vital capacity and residual volume

30
Q

What is Vital Capacity?

A

The greatest volume of air that can be expelled from the lungs after taking the deepest possible breath. (ERV)

This is approximately 2.5-5.0 dm^3

31
Q

What does Vital Capacity depend upon?

A
  • The size of a person (height)
  • Their age and gender
  • Their level of regular exercise
32
Q

What is Tidal Volume?

A

The volume of air inhaled or exhaled in one breath, usually measured at rest.

This is approximately 0.5 dm^3

33
Q

What is Residual Volume?

A

The volume of air that remains in the lungs even after forces expiration. The air remains in the airways and alveoli.

This is approximately 1.5dm^3.

34
Q

Why are we unable to exhale the residual volume?

A

Alveoli are held open by elastic fibres and airways are held open by cartilage - the space inside is filled by air.

35
Q

What is a Spirometer?

A

A device that can measure the movement of air into and out of the lungs

36
Q

How does a Spirometer work?

A

A float-chamber spirometer consists of a chamber of air or medical-grade oxygen floating on a tank of water.

During inspiration, air is drawn from the chamber so that the lid moves down.

During expiration, the air returns to the chamber raising the lid.

The movement is displayed on a data logger.

37
Q

What precautions must be taken when using a spirometer?

A
  • The subject should be healthy and, in particular, free from asthma.
  • The soda lime should be fresh and functioning.
  • There should be no air leaks in the apparatus, as this would give invalid or innacurate results
  • The mouthpiece should be sterelised.
  • The water chamber must not be overfillled (or water may enter the air tubes)
38
Q

What are the benefits and drawbacks of modern spirometer traces?

A
  • Modern spirometers may be small and simple hand-held devices
  • However, they cannot measure the rate of oxygen consumption
39
Q

What will increase oxygen uptake?

A
  • Increasing breathing rate
  • Deeper breaths
40
Q

How can Oxygen uptake be measured from a spirometer trace?

A

As a person breaths from the spirometer, oxygen is absorbed by the blood and replaced by carbon dioxide.

This carbon dioxide is absorbed by the soda lime in the spirometer, so that the volume of air in the chamber decreases. This decrease can be observed and measured on the spirometer trace.

We can assume that the volume of carbon dioxide released and absorbed by the soda lime equals the volume of oxygen absorbed by the blood.

Therefore, measuring the gradient of the decrease in volume enables us to calculate the rate of oxyfen uptake.

41
Q

How can breathing rate be measured from a spirometer trace?

A

The breathing rate can also be measured from a spirometer trace. Simply count the number of peaks in each minute.

Breathing rate at rest is usually about 12-14 breaths per minute.

42
Q

What is the name for a fishes mouth?

A

Buccal Cavity

43
Q

What makes up each gill?

A

Each gill consists of two rows of gill filaments (primary lamellae), which are slender branches of tissue, attached to a bony arch.

The filaments are very thin, and their surface is folded into many secondary lamellae (gill plates). This provides a very large surface area for gas exchange to take place.

44
Q

How many pairs of gills do bony fish tend to have?

A

5 Pairs of gills

45
Q

What covers a fishes gills?

A

A bony flap called the operculum covers and protects the gills

46
Q

What are the steps for a fish dissection?

A
  1. Find the operculum on either side of the fish’s head
  2. Lift the operculum and observe the gills
  3. Cut away one operculum to view the gills.
47
Q

What is countercurrent flow in fish?

A
  • Where two fluids flow in opposite directions.

Blood flows along the gill arch and out along the filaments to the secondary lamellae.

The blood then flows through capillaries in the opposite direction to the flow of water over the lamellae.

This arrangement creates a countercurrent flow that absorbs the maximum amount of oxygen from the water.

48
Q

How does ventillation in bony fish occur?

A

The buccal cavity can change volume.

The floor of the mouth moves downwards, drawing water into the buccal cavity due to the decrease in pressure.

The mouth closes and the floor is raised again pushing water through the gills due to the increase in pressure.

Movements of the operculum are coordinated with the movements of the buccal cavity.

As water is pushed from the buccal cavity, the operculm moves outwards. This movement reduces the pressure in the opercular cavity, helping water to flow through the gills.

49
Q

What type of circulatory system do insects have?

A

Insects do not transport oxygen in blood or blood vessels.

Insects have an open circulatory system in which the body fluid acts as both blood and tissue fluid.

50
Q

What is the trachael system?

A

An air-filled system that supplies air directly to all the respiring tissues. It is made up of pipes called trachea, which branch into smaller pipes called tracheoles. Tracheoles are supported by chitin and contain tracheal fluid.

51
Q

How does ventillation in insects occur?

A

Air enters and leaves the system via pores known as spiracles.

Gaseous exchange occurs between the air in the tracheoles and the tracheal fluid at the end of the tracheoles.

The walls of the tracheoles are also very thin so some gas is also exchanged across the walls.

This system supplies all of the bodily cells with oxygen directly.

52
Q

How do insects keep up with an increased demand in oxygen?

A

When tissues are active, the tracheal fluid can be withdrawn into the body fluid in order to increase the surface area of the tracheole wall exposed to air. This allows more oxygen to be absorbed when the insect is active.

53
Q

Why is tracheal fluid withdrawn into the body when tissue is very active?

A

Oxygen can diffuse through the walls at the end of the tracheoles into the tissue fluid, withdrawing fluid from the end of the tube increases the surface area over which exchange can occur.

54
Q

How can larger insects ventilate their tracheal system?

A

Movements in the body

  • Sections of the tracheal system are expanded and have flexible walls. These act as air sacs that can be squeezed by the action of the flight muscles. Repetitive expansion and contraction of these sacs ventilate the tracheal system.
  • In some insects, the movement of the wings alters the volume of the thorax.
  • Locusts can alter the volume of their abdomen by specialized breathing movements. These are coordinated with the opening and closing valves in the spiracles.

As the abdomen expands, spiracles at the front end of the body open, and air enters the tracheal system.

As the abdomen reduces in volume, the spiracles at the rear end of the body open and air can leave the tracheal system.

55
Q

Why do insects have a separate tracheal system instead of relying on blood to transport oxygen around the body?

A

With an open circulation, an insect cannot easily direct the flow of blood to the tissues that need it most; the flow is also affected by body movements.

Using separate air-filled tubes allows development of a system that can bring more air to the tissues that need it. If the insect relies on diffusion to some extent, the oxygen can diffuse more quickly through air than through blood fluid.

Biology (6 decks)

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