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A-Level Biology > 8 Transport in animals > Flashcards

8 Transport in animals Flashcards

1
Q

Why are specialised transport systems needed?

A

1) The metabolic demands of most multicellular animals are high, so diffusion over the long distances is not enough to supply the quantities needed.
2) The surface area to volume ratio gets smaller as multicellular organisms get bigger so diffusion distances get bigger and the amount of surface area available to absorb or remove substances becomes relatively smaller.
3) Molecules such as hormones or enzymes may be made in one place but needed in another.

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2
Q

What features do most circulatory systems have in common?

A

1) A liquid transport medium that circulates around the system (blood).
2) Vessels that carry the transport medium.
3) A pumping mechanism to move the fluid around the system.

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3
Q

What are mass transport systems?

A

A transport system where substances are being transported in a mass of fluid.

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4
Q

What is an open circulatory system?

A

A circulatory system with a heart but a few vessels to contain the transport medium.

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5
Q

What happens in the open circulatory system?

A

1) The heart is segmented and contracts in a wave, starting from the back, pumping the blood in a single main artery.
2) That artery opens up into the body cavity- haemocoel.
3) The haemolymph (insect blood) comes into direct contact with the tissues and the cells, which is where exchange takes place.

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6
Q

What type of organisms have an open circulatory system?

A

Invertebrates (e.g insects)

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7
Q

What does the circulatory system supply the insects calls?

A
  • It supplies it with nutrients
  • Transports hormones around the body
  • However it doesn’t supply the insect’s cells with oxygen, this is done by the tracheal system
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8
Q

What is a closed circulatory system?

A

A circulatory system where the blood is enclosed in blood vessels and does not come into direct contact with the cells

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9
Q

Where are single circulatory systems found?

A

E.g fish

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10
Q

What is a single closed circulatory system?

A
  • A circulatory system where the blood flows through the heart and is pumped out to travel all around the body before returning to the heart.
  • Blood travels only once through the heart for each complete circulation of the body.
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11
Q

What does the blood pass through in a single closed circulation?

A
  • The blood passes through two sets of capillaries before it returns to the heart.
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12
Q

What happens in a double circulatory system?

A
  • Blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide, and then returns to the heart.
  • Oxygenated blood flows through the heart and is pumped out to travel all around the body before returning to the heart again.
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13
Q

What is a double circulatory system?

A
  • A circulatory system where the blood travels twice through the heart for each complete circulation of the body.
  • Each circuit only passes through one capillary network, which means a relatively high pressure and fast flow of blood can be maintained.
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14
Q

What are the five types of blood vessels?

A

1) Arteries
2) Arterioles
3) Capillaries
4) Venules
5) Veins

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15
Q

What do arteries do?

A
  • Arteries carry blood away from the heart to the tissues of the body.
  • All arteries carry oxygenated blood except the pulmonary arteries which take deoxygenated blood to the lungs.
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16
Q

What do artery walls contain?

A
  • Artery walls contain elastic fibres, smooth muscle and collagen.
  • The elastic fibres enable them to withstand the force of the blood pumped out of the heart and stretch to take the larger blood volume.
  • In between the contractions of the heart, the elastic fibres recoil and return to their original length.
  • This helps to even out of the surges of blood pumped from the heart to give a continuous flow.
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17
Q

What are arterioles and what do they do?

A
  • Arterioles link the arteries and the capillaries.
  • They have more smooth muscle, which allows them to expand or contract, thus controlling the amount of blood flowing to tissues.
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18
Q

What are capillaries?

A
  • Capillaries are microscopic blood vessels that link the arterioles with the venules.
  • They form an extensive network through all the tissues of the body.
  • Substances are exchanged through the capillary walls between the tissue cells and the blood.
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19
Q

How are capillaries adapted for their role?

A
  • They provide a very large surface area for the diffusion of substances into and out of the blood.
  • The walls are a single endothelial cell thick, giving a very thin layer of diffusion.
  • The relatively slow movement of blood through capillaries give more time for the exchange of materials by diffusion between the blood and the cells.
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20
Q

What do veins do?

A
  • Veins carry blood towards the heart and away from the cells of the body
  • They carry deoxygenated blood, except for the pulmonary veins which carries oxygenated blood from the lungs to the heart.
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21
Q

What are the features of veins?

A
  • They have valves to prevent the backflow of blood.
  • The walls contain lots of collagen and little elastic fibre.
  • The vessels have a wide lumen and a smooth, thin lining so the blood flows easily.
  • Very low blood pressure
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22
Q

What are venules?

A
  • Smaller veins.

- Several venules join to form a vein.

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23
Q

What are functions of blood?

A

The transport of:

  • Oxygen to, and carbon dioxide from the respiring cells
  • Digested food from the small intestines
  • Chemical messages (hormones)
  • Platelets to damaged areas
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24
Q

What are the main cellular components of blood?

A
  • Plasma
  • Erythrocytes
  • Platelets
  • Leucocytes
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25
Q

What is tissue fluid?

A
  • Tissue fluid is the solution surrounding the cells of multicellular animals.
  • It’s made from substances that leave the blood plasma e.g oxygen, water and nutrients
26
Q

What is haemoglobin?

A
  • The red, oxygen carrying pigment of red blood cells.
  • It is a very large globular conjugated protein made up of four peptide chains, each with an iron-containing haem prosthetic group.
27
Q

What is oxyhaemoglobin?

A
  • In the lungs, oxygen joins to the iron in the haemoglobin to form oxyhaemoglobin.
  • The reaction is reversible.
  • Hb+4O2-> Hb(O2)4
28
Q

What is the partial pressure of oxygen (pO2)?

A
  • It is a measure of oxygen concentration.

- The greater the concentration of dissolved oxygen in cells, the higher the partial pressure.

29
Q

What does haemoglobin’s affinity for oxygen vary depending on?

A
  • Haemoglobin’s affinity for oxygen varies depending on the partial pressure of oxygen.
  • Oxygen loads onto haemoglobin to form oxyhaemoglobin where there’s a high pO2.
  • Oxyhaemoglobin unloads its oxygen where there’s a lower pO2.
  • High pO2, loads: ALVEOLI
  • Low pO2, unloads: RESPIRING TISSUE
30
Q

What does an oxygen dissociation curve show?

A

It shows how saturated the haemoglobin is with oxygen at any given partial pressure.

31
Q

When pO2 is high, what is the saturation like?

A
  • Where pO2 is high, haemoglobin has a high affinity so it has a high saturation of oxygen.
  • Where pO2 is low, haemoglobin has a low affinity for oxygen which means it releases oxygen. Thats why it has a low saturation of oxygen.
32
Q

Does adult or fetal haemoglobin have a higher affinity for oxygen?

A

Fetal haemoglobin has a higher affinity for oxygen at the same partial pressure.

33
Q

Why does fetal haemoglobin have a higher affinity for oxygen?

A

1) The fetus gets oxygen from its mother’s blood across the placenta.
2) By the time the mother’s blood reaches the placenta, its oxygen saturation has decreased (because some has been used up by the mother’s body)
3) For the fetus to get enough oxygen to survive, its haemoglobin has to have a higher affinity for oxygen (so it takes up enough)
4) If its haemoglobin had the same affinity for oxygen as adult haemoglobin, its blood wouldn’t be saturated enough.

34
Q

What is the Bohr effect?

A

As the partial pressure of carbon dioxide rises, haemoglobin gives up oxygen more easily.

35
Q

What are atrioventricular valves?

A
  • The atrioventricular valves link the atria to the ventricles.
36
Q

What are semi-lunar valves?

A
  • The semi-lunar valves link the ventricles to the pulmonary artery and the aorta.
37
Q

How do the valves work?

A

1) The valves only open one way- whether they’re open or closed depends on the relative pressure of the heart chambers.
2) If there’s higher pressure behind a valve, it’s forced open.
3) If pressure is higher in front of the valve, its forced shut.

38
Q

How does blood travel around the heart?

A

1) Deoxygenated blood enters the right atrium of the heart

39
Q

How does blood travel around the heart?

A

1) Deoxygenated blood enters the right atrium via the vena cava.
2) As blood flows in, slight pressure builds up until the tricuspid valve opens to let blood pass into the right ventricle.
3) When both the atrium and ventricle are filled with blood, the atrium contracts, forcing all the blood into the right ventricle.
4) The right ventricle contracts fully and pumps deoxygenated blood through the semilunar valves into the pulmonary artery.
5) Oxygenated blood from the lungs enters the left atrium from the pulmonary vein.
6) As pressure in the atrium builds, the bicuspid valve opens between the left atrium and the left ventricle so the ventricle also fills with oxygenated blood.

40
Q

What is the cardiac cycle?

A

The events of a single heartbeat, composed of diastole and systole.

41
Q

What happens in diastole?

A
  • The heart relaxes
  • The atria and then the ventricles fill with blood in the heart build as the heart fills.
  • Pressure in the arteries is at minimum
42
Q

What happens in systole?

A
  • The atria and ventricles contract
  • The pressure inside the heart increases dramatically and blood is forced out of the right side of the heart to the lungs, and from the left side to the main body circulation.
  • The blood pressure in the arteries is at a maximum.
43
Q

What does myogenic mean?

A

Muscle (e.g cardiac muscle) which has its own intrinsic rhythm (60beatspermin)

44
Q

What is tachycardia?

A

When the heartbeat is very rapid, over 100bpm. This is often normal happens when ur angry or during a fever

45
Q

What is bradycardia?

A

When the heart rate slows down below 60bpm. Many people have bradycardia because they are fit- training makes the heart beat more slowly and efficiently

46
Q

What is an ectopic heartbeat?

A

Extra heartbeats that are out of the normal rhythm. Most people have them at least one a day.

47
Q

What is atrial fibrillation?

A
  • An example of arrhythmia, which means an abnormal rhythm of the heart.
  • Rapid electrical impulses are generated by the atria and contract very fast up to 40 times a minute
  • They dont contract properly and so heart doesn’t not pump blood effectively.
48
Q

How does the cardiac muscle control regular beating of the heart?

A

1) A wave of electrical excitation begins in the pacemaker area called the sino-atrial node (SAN), causing the atria to contract and so initiating the heartbeat. A layer of non-conducting tissue prevents the excitation passing directly to the ventricles.
2) The electrical activity from the SAN is picked up by the atrio-ventricular node (AVN). The AVN imposes a slight delay before stimulating the bundle of His, a bundle of conducting tissue made up of Purkyne fibres, which penetrate through the septum between ventricles.
3) The bundle of His splits into two branches and conducts the wave of excitation to the apex (bottom) of the heart.
4) At the apex the Purkyne fibres spread out through the walls of the ventricles on both sides. The spread of excitation triggers the contraction of the ventricles, starting at the apex. Contraction starting at the apex allows more efficient emptying of the ventricles.
5) The way in which the wave of excitation spreads through the heart from the SAN, with AVN delay, makes sure that the atria have stopped contracting before the ventricles start.

49
Q

What is oncotic pressure?

A

The tendency of water to move into the blood by osmosis. It is about -3.3kPa

50
Q

What is hydrostatic pressure?

A

The pressure created by water in an enclosed system.

51
Q

What is tissue fluid?

A

The solution surrounding the cells of multicellular animals.

52
Q

At which end of the capillary is hydrostatic pressure high?

A

At the arterial end of the capillary, the hydrostatic pressure forcing fluid out of the capillaries is relatively high (around 4.6kPa)

53
Q

At which end of the capillary is hydrostatic pressure low?

A

At the venous end the hydrostatic pressure falls to around 2.3kPa as fluid has moved out.

54
Q

Why does fluid flow back into the capillary at venous end?

A

Water moves back into the capillaries by osmosis because the oncotic pressure is stronger than the hydrostatic pressure.

55
Q

How much tissue fluid is back in the blood vessels?

A

90%

56
Q

Where does the 10% of tissue fluid go?

A

It drains into a system of lymph capillaries (basically known as lymph).

57
Q

How is fluid transported through the lymph vessels?

A

Fluid is transported through the lymph vessels by the squeezing of body muscles.

58
Q

Why do lymph vessels have valves?

A

To prevent the backflow of lymph

59
Q

What are the lymph nodes?

A
  • Along the lymph vessels are the lymph nodes.
  • Lymphocytes build up in the lymph nodes when necessary and produce antibodies which then passes into the blood.
  • Lymph nodes intercept bacteria and other debris from the lymph, which are ingested by the phagocytes.
60
Q

How are hydrogencarbonate ions formed?

A

1) As carbon dioxide DIFFUSES into the blood, some of it enters the RED BLOOD CELLS.
2) From here, the carbon dioxide combines with water to form a weak acid called CARBONIC ACID
3) .This is then CATALYSED by an enzyme called CARBONIC ANHYDRASE
4) The CARBONIC ACID dissociates to release HYDROGEN IONS (H+) and HYDROGENCARBONATE IONS (HC03-)
5) The HYDRO CARBONATE Ions DIFFUSE out of the RED BLOOD CELL and into the PLASMA
6) Charge inside the RED BLOOD CELL is MAINTAINED by the movement of CHLORIDE IONS (CL-) from the PLASMA into the RED BLOOD CELL

7) H+ binds to haemoglobin (oxyhemoglobin dissociates because of this).

61
Q

Describe the role of haemoglobin in transporting oxygen around the body.

A
  • haemoglobin has high affinity for oxygen
  • oxygen binds to haemoglobin in, lungs / alveoli / high pO2 to form oxyhaemoglobin (loading)
  • oxygen released, in tissues / where needed / where pO2 is low / where respiration is occurring (unloading)
62
Q

ecg

A
  • Wave P = excitation of atria
  • QRS = excitation of ventricles
  • T = diastole

records electrical activity in heart

  • measure tiny electrical differences in skin which result from electrical activity of heart
  • helpful to identify arrhythmias (abnormal heart rhythms)

A-Level Biology (41 decks)

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