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Alevel Biology OCR > 3.1.2 - Transport in Animals > Flashcards

3.1.2 - Transport in Animals Flashcards

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1
Q

Why do multicellular organisms need transport systems?

A
  • larger organisms so have a high SA:V -can not transport everything by diffusion alone
  • molecules (eg. oxygen, waste products, food absorbed in intestine, hormones and enzymes produced in the body) need to be transported to other areas of the body
  • have a high metabolic rate
  • very active -have a high demand for glucose and oxygen
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2
Q

What do all circulatory systems need?

A

a pumping mechanism (eg. heart)
a fluid substances can be transported in (eg. blood, haemolymph)
vessels which the fluid can flow in (eg. blood vessels)

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3
Q

What is an open circulatory system?

A

a circulatory system where the fluid (haemolymph) is not always enclosed in the vessels
eg. insects’ circulatory system

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4
Q

What happens in an open circulatory system?

A
  • heart pumps haemolymph (fluid) through short vessels into the haemocoel (large cavity containing organs and tissues)
  • when the heart relaxes, the haemolymph is sucked back in via ostia (pores)
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5
Q

What are the advantages and disadvantages of an open circulatory system?

A

✔️requires less energy
✔️low pressure
❌difficult to increase haemolymph concentration
❌can’t maintain steep concentration gradient
❌haemolymph only carries food and nitrogenous waste (no oxygen or carbon dioxide)

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6
Q

What is a closed circulatory system?

A

a circulatory system where the blood is fully enclosed in the blood vessels at all times

  • can be either a single or double system
    eg. mammal or fish’s circulatory system
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7
Q

What happens in a closed circulatory system?

A
  • heart pumps blood into progressively smaller vessels

- blood returns in progressively larger vessels

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8
Q

What is a single circulatory system?

and name an example

A

a circulatory system where the blood only passes through the heart once in a complete circuit
eg. in fish the blood flows from the heart to the gills to the rest of the body and back to the heart

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9
Q

What is a double circulatory system?

and name an example

A

a circulatory system where the blood passes through the heart twice in a complete circuit ∴ the heart is split in two (the right contains deoxygenated blood and the left contains oxygenated blood)
eg. in mammals (like humans) the blood flows from the right side of the heart to the lungs and back into the left side of the heart, and then to the rest of the body and back into the right side of the heart

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10
Q

What is the function and structure of the arteries like?

A

carry oxygenated blood away from the heart under high pressure
Structure:
-narrow lumen -maintains pressure
-think layers of elastic fibres -stretch and recoil to provide arteries with flexibility and to withstand pressure of blood
-thick muscle layers -contracts and relaxes to allow lumen to change size
-smooth endothelium -blood can flow easily over it
-roughly 0.4cm wide

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11
Q

What is the function and structure of the arterioles like?

A

carry oxygenated blood from the arteries to the capillaries
Structure:
-generally the same as arteries but has less elastic fibres and more muscle -muscle prevents vasoconstriction (blood flowing into capillary bed)
-roughly 30μm wide

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12
Q

What is the function and structure of the capillaries like?

A

forms a network of vessels through all body tissues for exchange of substances
links the arterioles and venules
Structure:
-one cell thick endothelium capillary wall -short distance for diffusion
-roughly 10μm wide

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13
Q

What is the function and structure of the venules like?

A

carry deoxygenated blood from the capillaries to the veins
Structure:
-thin walls
-no elastin or smooth muscle, just collagen -provides structural support to maintain shape and volume of vessel
-roughly 0.1mm wide

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14
Q

What is the function and structure of the veins like?

A

carry deoxygenated into the heart
very low pressure -do not have a pulse
Structure:
-large lumen -maintain low pressure
-doesn’t have much elastin or smooth muscle
-a lot of collagen in walls -provides structural support to maintain shape and volume of vein
-have valves -prevent back flow of blood

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15
Q

How is tissue fluid formed?

A
  • blood flows into the arteriole end of the capillary at high hydrostatic pressure
  • high pressure forces fluid through fenestrations
  • this fluid (with dissolved oxygen and nutrients) fills the space between the cells in the tissue and is known as tissue fluid
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16
Q

What happens at the venous end of the capillaries?

A
  • some proteins (like albumins) have an osmotic effect (causes water to have low water potential) and creates oncotic pressure
  • causes fluid to move back into the blood via osmosis
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17
Q

What happens to the excess tissue fluid that doesn’t go back into the capillaries?

A

excess drains into the lymphatic system, where it forms lymph

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18
Q

What are the differences between blood, tissue fluid and lymph?

A

are the same as blood except…
tissue fluid doesn’t have red blood cells, platelets or proteins and only a few white blood cells
lymph doesn’t have red blood cells, platelets or proteins (except antibodies)
lymph has more lipids than tissue fluid

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19
Q

Why are there no red blood cells or proteins in tissue fluid?

A

they are too large to pass through fenestrations in the capillary walls so can not leave the blood to become tissue fluid

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20
Q

What are the specialised features of erythrocytes?

A
  • biconcave shape (larger SA)
  • no nuclei (more room for haemoglobin)
  • contains haemoglobin
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21
Q

What is haemoglobin?

A

a globular protein with four polypeptide chains, each with a prosthetic haem group

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22
Q

How does haemoglobin carry oxygen?

A

each haemoglobin can bind to 4 oxygen molecules to form oxyhaemoglobin (in a reversible rxn)

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23
Q

Hb + 4O2 ⇌

A

HbO8

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24
Q

What does an oxygen dissociation curve show?

A

how saturated haemoglobin is with oxygen at any given partial pressure

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25
Q

What does the positive cooperativity of oxygen binding to haemoglobin mean?

A

when an oxygen molecule binds to haemoglobin, the haemoglobin changes shape slightly which makes it easier for more oxygen molecules to bind
-causes a steep gradient on oxygen dissociation curve

26
Q

How does haemoglobin’s affinity for oxygen vary depending on the partial pressure of oxygen?

A
  • where there’s a low partial pressure of oxygen, haemoglobin has a low affinity for oxygen -oxyhaemoglobin unloads its oxygen
  • where there’s a high partial pressure of oxygen, haemoglobin has a high affinity for oxygen -oxygen binds to the haemoglobin readily
27
Q

What is the Bohr effect/shift?

A

when the partial pressure of carbon dioxide increases, haemoglobin releases more oxygen
-this is because haemoglobin changes shape making it harder for oxygen to bind so reduces its affinity for oxygen
✓ beneficial because it increases how much oxygen is unloaded at tissues (where its needed for respiration)

-oxygen dissociation curve shifts to the right

28
Q

Does an adult or fetus’ haemoglobin have a higher affinity for oxygen?

A

fetus

29
Q

Why does a fetus’ haemoglobin have a higher affinity for oxygen?

A
  • fetus gets its oxygen from its mother’s blood (from the placenta)
  • when the mother’s blood reaches the placenta, some of the oxygen has already been used up, meaning the oxygen saturation has decreased
  • for the fetus to get enough oxygen to survive, it needs to have a higher affinity for oxygen so that it takes up enough and is saturated enough to survive

-oxygen dissociation curve shifts to the left

30
Q

How is carbon dioxide transported?

A
  • dissolved in the plasma (5%)
  • combined with amino groups in the polypeptide chains of haemoglobin to form carbaminohaemoglobin (10-20%)
  • converted into hydrogen carbonate ions in the cytoplasm of red blood cells (75-85%)
31
Q

Describe the main way that carbon dioxide is transported

A

-in erythrocytes, carbon dioxide reacts with water to form carbonic acid
-carbonic acid dissociates to form hydrogen ions and hydrogen carbonate ions
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
-carbonic anhydrase catalyses this reaction
-lots of hydrogen carbonate ions move out of the erythrocytes by diffusion
-to maintain the electrical balance of the cell, chloride ions move into the erythrocyte (the chloride shift)
-when the blood reaches the lungs, there is a low concentration of carbon dioxide so carbonic anhydrase catalyses the reverse reaction to produce carbon dioxide which diffuses into the lungs
-the chloride ions diffuse back into the plasma

32
Q

What is the chloride shift?

A

when Cl- ions move into the erythrocyte to maintain the electrical balance of the cell (maintains balance of charge) after the HCO3- ions move out of the cell

33
Q

How does haemoglobin act as a buffer in erythrocytes?

A

prevents changes in pH (from H+ ions increasing the acidity) by accepting free hydrogen ions in a reversible reaction to form haemoglobinic acid
-this causes oxyhaemoglobin to release its oxygen (causing the Bohr effect)

34
Q

Which side of the heart pumps oxygenated blood?

A

the left side

pumps oxygenated blood to the body

35
Q

Which side of the heart pumps deoxygenated blood?

A

the right side

pumps deoxygenated blood to the lungs

36
Q

Where are the atrioventricular valves?

A

between the ventricles and atria in the heart

37
Q

Where are the semi-lunar valves?

A

between the ventricles and pulmonary artery/aorta in the heart

38
Q

How do valves stop blood flowing the wrong way?

A

they open/close depending on the relative pressure around them

  • when there’s pressure behind a valve, it is forced open
  • when there’s pressure in front of a valve, it is forced closed
39
Q

What is the cardiac cycle?

A

the control and co-ordination of the heart through the ongoing process of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating around the body

40
Q

What are the three stages of the cardiac cycle?

A
  • atrial systole
  • ventricular systole
  • diastole
41
Q

What is a systole?

A

heart contraction

42
Q

What is a diastole?

A

heart relaxation

43
Q

What happens in the diastole stage of the cardiac cycle?

A
  • the whole heart relaxes (both the atria and ventricles)
  • the atria fill with blood
  • as the ventricles continue to relax, their pressure falls to become lower than the pressure in the atria, causing the atrioventricular valves to open so that the blood starts to flow into the ventricles
44
Q

What happens in the atrial systole stage of the cardiac cycle?

A
  • the atria contract (decreasing their volume but increasing their pressure)
  • pushes blood into ventricles
  • slight increase in pressure and volume in the ventricles as more blood enters them
45
Q

What happens in the ventricular systole stage of the cardiac cycle?

A
  • ventricles contract (and atria relax)
  • high pressure in ventricles -forces atrioventricular valves shut and forces semi-lunar valves open
  • blood leaves heart (either via pulmonary artery or aorta)
46
Q

cardiac output =

A

heart rate x stroke volume
(heart rate = beats per minute
stoke volume = volume of blood pumped each heartbeat in cm³)

47
Q

Why is the cardiac muscle described as being myogenic?

A

the heart can beat without the nervous system

48
Q

Describe how heart action is initiated and coordinated

A
  • the sino-atrial node (SAN) sends an electrical impulse
  • this causes atria to contract (simultaneously), initiating heart beat
  • the atrioventricular node (AVN) picks up electrical activity from SAN and after a slight delay, stimulates bundle of His to penetrate through the septum
  • the bundle of His splits into two branches -conducts the electrical waves to the apex (bottom) of the heart
  • purkyne fibres spread out through ventricle walls on both sides of the heart
  • this causes the ventricles to contract (starting at bottom -allows for more efficient emptying of ventricles)
49
Q

What does the sino-atrial node do?

A

sends an electrical impulse
-causes atria to contract simultaneously
-initiates heart beat
acts as pacemaker

50
Q

Where does the electrical impulse start in the heart?

A

in the sino-atrial node (SAN) located in the right atrium

51
Q

What does the atrio-ventricular node do?

A

detects electrical activity from SAN

imposes a slight delay before stimulating the bundle of His -which penetrates through the septum

52
Q

What is the bundle of His in the heart?

A

a bundle of conducting tissue made up of Purkyne fibres

53
Q

What does the bundle of His do?

A
  • penetrates down the septum

- splits in two and conducts wave of electricity to the apex of the heart

54
Q

What do the Purkyne fibres do?

A

spreads out the electrical impulse through the walls of the ventricles on both sides of the heart
-triggers ventricles to contract starting from the apex

55
Q

What is an electrocardiogram (ECG)?

A

a machine which records the electrical activity of the heart
-picks up any irregularities (eg. a heart attack)

56
Q

When does the heart depolarise?

A

the heart depolarises (loses electrical charge) when it contracts

57
Q

When does the heart polarise?

A

the heart polarises (gains electrical charge) when it relaxes

58
Q

heart rate (bpm) =

A

60/time taken for one heart beat

59
Q

What is tachycardia?

A

when the heart beat is very rapid (over 100bpm)

  • this is normal when you exercise, have a fever, etc
  • abnormal when it’s caused by electrical control of heart
60
Q

What is bradycardia?

A

when the heart rate slows down (under 60bpm)

61
Q

What is fibrillation?

A

a type of arrythmia (abnormal rhythm of heart)

  • rapid electrical impulses are generated in the atria and contract very fast up to 400 times a minute however they don’t contract properly and only some impulses are passed to the ventricles
  • as a result the heart doesn’t pump blood efficiently
62
Q

What is ectopic heartbeat?

A

extra heart beats out of the normal rhythm

-often happen once a day for most people but when they are frequent it can be serious

Alevel Biology OCR (26 decks)

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