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z - A Level Biology > 3.1.2: Transport in animals > Flashcards

3.1.2: Transport in animals Flashcards

1
Q

Why do multicellular organisms require a transport system?

A
  • Most have high metabolic demands
  • Substance absorbed in one part of the organism need to be transported to another –> distance is too great for diffusion/diffusion alone would be too slow
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2
Q

Types of transport system

A

• Open
• Closed
⟶ Single closed
⟶ Double closed

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3
Q

Open circulatory system found in:

A

Invertebrates

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4
Q

Features of an open circulatory system

A
  • Few vessels
  • Haemolymph pumped straight from heart into body cavity (haemocoel)
  • Haemolymph comes into direct contact with tissues and cells
  • Very low pressure
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5
Q

What is haemolymph?

A

The transport medium found in the open circulatory systems of invertebrates. Carries food, nitrogenous waste products and cells to defend against disease. DOES NOT CARRY GAS EXCHANGE PRODUCTS.

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6
Q

What are the limitations of an open circulatory system?

A

✘ Steep diffusion gradients cannot be maintained.

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7
Q

Closed circulatory system found in:

A

• Cephalopod molluscs, annelid worms, echinoderms, vertebrates.

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8
Q

Features of a closed circulatory system:

A
  • Transport medium (blood) enclosed within vessels –> does not directly contact body cells
  • Blood pigment (haemoglobin) carries respiratory gases
  • Substances enter and leave blood by diffusion through walls of the blood vessels
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9
Q

Benefits of a closed circulatory system:

A

✔︎ High pressure enables steep concentration gradient to be maintained

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10
Q

Single closed circulatory system found in:

A
  • Fish

* Annelid worms

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11
Q

Double circulatory system found in:

A
  • Birds

* Mammals

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12
Q

Benefits of a double circulatory system:

A

✔︎ Each circuit only passes through 1 set of capillaries

∴ High pressure and steep concentration gradient can be maintained

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13
Q

Limitations of a single circulatory system:

A

✘ Lower pressure than double circulatory system

∴ Cannot maintain as steep a concentration gradient

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14
Q

How are the limitations of a single circulatory system overcome in fish?

A
  • Lower metabolic demands

* Gills very good at removing oxygen from water so blood carries comparatively more oxygen

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15
Q

Single circulatory system (closed)

A
  • Blood pumped straight from heart, to gas exchange surface, to body cells
  • Blood travels through 2 sets of capillaries before returning to heart
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16
Q

Double circulatory system (description)

A
  • Blood pumped from heart, to gas exchange surface, to heart, then to body cells
  • Blood travels through 1 set of capillaries before returning to the heart
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17
Q

Bicuspid valve

A
  • Left atrioventricular valve

* Consists of two flaps

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18
Q

Tricuspid valve

A
  • Right atrioventricular valve

* Consists of three flaps

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19
Q

Atrial systole

A
  • Walls of atria contract
  • Push remaining blood from atria into ventricles
  • Through atrioventricular valves
  • Semilunar valves are closed
  • Ventricles fill with blood
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20
Q

Ventricular systole

A
  • Walls of ventricles contract
  • Blood pressure inside ventricles increases
  • Atrioventricular valves are forced shut
  • Blood is pumped out into the aorta and pulmonary artery
  • Through the semilunar valves
  • Atria start to refill as they collect blood from the veins
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21
Q

Diastole

A

• Heart relaxes
• Pressure inside heart decreases
• Semilunar valves close
⟶ preventing backflow of blood into ventricles from the aorta and pulmonary artery
• When pressure of blood in ventricles falls below pressure of blood in atria, atrioventricular valves open
• Blood from atria flows into ventricles

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22
Q

Myogenic

A

Contraction is initiated from within the muscle itself rather than from external nerve impulses.

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23
Q

Why would a hole in the septum be a problem?

A
  • Mixing of deoxygenated and oxygenated blood would occur.
  • Deoxygenated blood may never reach lungs
  • Lack of oxygenated blood to body cells (which need it in order to carry out aerobic respiration)
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24
Q

Why does the left ventricle have such a thick wall?

A
  • To pump blood at v. high pressure into the aorta

* Needs to exert high pressure –> needs to circulate to body cells a great distance away from the heart

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25
Q

How does cardiac muscle differ to other muscles in the body?

A
  • Myogenic

* Does not get fatigued and require rest

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26
Q

Why must contractions of 4 chambers of the heart be synchronised?

A

To avoid fibrillation.

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27
Q

What is the SAN?

A

Sino-atrial node: patch of tissue which generates electrical activity.
• Initiates wave of electrical excitation at regular intervals
• Causes atria to contract

28
Q

Controlling the heart beat

A

1) Excitation spreads over the walls of both atria causing contraction (atrial systole)
2) Disc of tissue at the base of the atria is insulating; contraction cannot pass to ventricles
3) Atrioventricular node is the only route for the excitation ⟶ slight delay before ventricles contract allows all the blood from the atria to empty into the ventricles
4) AVN stimulates the bundle of His
5) Purkyne fibres spread through the spread out through the ventricle walls causing contraction starting at the apex (spreads base up)

29
Q

Bundle of His

A

Conducting tissue made up of Purkyne fibres

30
Q

AVN

A

Atrio-ventricular node: path by which electrical excitation passes from the atria to the ventricles

31
Q

Why is it beneficial that the electrical activity initiated from the SAN passes across the tops of the atria and then down across the atria?

A
  • Ensures both atria contract together

* Ensures the atria contract top to bottom (this pushes blood towards and into the ventricles)

32
Q

Advantage of the short delay in transmission of electrical activity through the AVN?

A

• Ensures atria ave time to empty blood into ventricles BEFORE the ventricles contract

33
Q

Advantage of impulse passing down the bundle of His then spreading up from the apex?

A
  • Means that ventricular contraction occurs apex to top of heart
  • Blood is pushed up to the semilunar valves –> leading to aorta/pulmonary artery
34
Q

Why is it beneficial for heart rate to increase during exercise?

A
  • Higher heart rate = higher cardiac output = quicker circulation of blood delivering oxygen to cells
  • Increased rate of O₂ delivery –> increases rate of aerobic respiration to release ATP for muscle contraction
  • Reduces anaerobic respiration
  • Removal of waste products of anaerobic respiration
35
Q

Electrocardiagrams

A
  • Measure the electrical activity of the heart

* Used to diagnose heart problems

36
Q

Cardiac output

A

the volume of blood pumped by one ventricle of the heart in 1 minute.

37
Q

Formula for cardiac output

A

Cardiac output = heart rate x stroke volume

38
Q

Heart rate

A

Number of cardiac cycles per minute

39
Q

Stroke volume

A

Volume of blood pumped out of the ventricle during one cardiac cycle (one beat)

40
Q

Endurance athletes (heart)

A

Higher stroke volume –> lower heart rate at rest

41
Q

Blood composition

A

~55% plasma
~1% WBCs
~45% erythrocytes

42
Q

Erythrocytes contents

A
  • Full of haemoglobin (millions of molecules per cell)
  • 4 polypeptide chains (2 alpha globin, 2 beta globin)
  • Haem groups (1 prosthetic group per chain)
  • Each group can bind reversibly to 1 O₂
  • Each haemoglobin can carry 4O₂ molecules
43
Q

Erythrocyte flattened biconcave shape

A
  • Increases SA:V ratio, enables more efficient diffusion

* All haemoglobin close to surface –> short diffision pathway

44
Q

Erythrocyte structure

A
  • Flattened biconcave disc
  • Small (~7µm diameter)
  • Contains haemoglobin
  • No organelles
  • Thin centre
45
Q

Erythrocyte small (~7µm diameter)

A
  • Can pass through capillary

* Touches the side of the capillary: reduce distance for oxygen fo diffuse

46
Q

Erythrocyte lack of organelles

A

• Maximise space for haemoglobin

47
Q

Erythrocyte thin centre

A
  • Flexible (can squeeze through narrow capillary)

* Short diffusion pathway centre of cell

48
Q

Formula for the partial pressure of oxygen

A

Air pressure x 0.21 = pO₂

49
Q

At a high pCO₂ …

A
  • Haemoglobin has a lower affinity for oxygen

* Releases oxygen from oxyhaemoglobin

50
Q

3 ways in which CO₂ is transported

A
  • Dissolved in plasma (5%)
  • Binds to amino groups of polypeptide chains of haemoglobin (10-20%)
  • Converted to hydrogen carbonate ions in RBCs (75-85%)
51
Q

Large vein diameter

A

Larger than 1cm

52
Q

Medium vein diameter

A

Less than 1cm

53
Q

Venule diameter

A

0.1mm

54
Q

Composition of large vein

A

Elastin
Smooth muscle
Collagen

55
Q

Composition of medium vein

A

Elastin
Smooth muscle
Collagen
(all less than large vein)

56
Q

Composition of venule

A

Collagen

57
Q

Aorta diameter

A

2.5 cm

58
Q

Medium sized artery diameter

A

0.4 cm

59
Q

Arteriole diameter

A

30 um

60
Q

Aorta composition

A 
Elastin fibres (many)
Smooth muscle (little)
Collagen (moderate-high)
61
Q

Medium artery composition

A 
Elastin fibres (many)
Smooth muscle (lots; more than aorta)
Collagen (very little)
62
Q

Arteriole composition

A 
Elastin fibres (few)
Smooth muscle (moderate - highest of alll 3)
Collagen (moderate)
63
Q

Why do arteries need smooth muscle?

A

Contract for vasoconstriction

64
Q

Why do arteries need elastin?

A

Faciliates relaxation of smooth muscle, evens out pressure changes (more in lungs)

65
Q

How is the heart action coordinated?

A 
Vagus nerve (parasympathetic nervous system) connects from the cardiovascular centre in medulla oblongata to SAN
Action potentials from the vagus nerve slow the heart rate
66
Q

Why might actions potentials be sent via vagus nerve?

A

To slow heart rate
e.g. if baroreceptors detect high blood pressure
or
chemoreceptors detect low CO₂, high pH

z - A Level Biology (25 decks)

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