Modue 3: Transport In Animals

Question 1

What is transport?

Answer 1

The movement of oxygen, nutrients, hormones, waste

and heat around the body.

Question 2

Describe the need for transport systems in multicellular animals.

Answer 2

All organisms need oxygen and nutrients to survive. They also must remove waste products as they can become toxic.

Very small organisms do not need a transport system to do this as all of their cells are close to the environment in which they live ‐ diffusion will be sufficient to supply and remove these things.

In larger organisms, diffusion will be too slow to provide sufficient oxygen and nutrients to meet the requirements of the organisms ‐ they need transport systems.

Question 3

What factors affect the need for transport systems?

Answer 3

• Size
• Level of activity
• SA:VOL

Question 4

Explain how 3 factors affect the need for transport systems.

Answer 4

Size:
Any oxygen or nutrients diffusing from the environment would be used up by outer layers of cells of the organism. They would not reach the cells deeper in the body.

SA:VOL:
Larger organisms have a smaller surface‐area‐to‐volume‐ratio.
Outer surface is not large enough to enable oxygen etc. to exchange via diffusion fast enough into the body to keep all the cells alive.

Level of Activity:
The more active an animal, the more glucose and oxygen it needs for aerobic respiration to release enough energy to move around.
Some animals like mammals also need energy to keep themselves warm. Diffusion would not be able to supply enough oxygen and glucose to cells to active organisms.

Question 5

Explain two reasons why mammals need a circulatory system whilst unicellular organisms, such as that shown in the diagram, do not. (4)

Answer 5

(mammals) larger / AW;
cells deep in the body;
regions requiring materials separated by a distance / need to get materials to all parts;
diffusion too slow / AW;
activity
(mammals) more (metabolically) active / AW;
need more materials / more rapid supply / more removal of wastes;
SA:V ratio
(mammals) surface area:volume ratio reduced / AW;
diffusion alone not effective / AW; must be linked to SA:V max 4.

Question 6

A good transport system must have…

Answer 6

1) A fluid ‐ blood
2) A pump to create pressure ‐ heart
3) Exchange surfaces

Question 7

What is an open circulatory system?

Answer 7

The blood is not always in vessels e.g. insects.

Question 8

What is a closed circulatory system?

Answer 8

The blood always remains inside vessels e.g.

fish and mammals.

Question 9

What are features of an open circulatory system?

Answer 9

An open circulatory system consists of a heart that pumps
blood through short vessels and into a large body cavity.

The blood bathes the cells and tissues where substances are exchanged with the cells.

The blood then returns to the heart through pores called ostia.

Question 10

Why do insects have an open system but not e.g. fish and

mammals?

Answer 10

Insects are small ‐ blood doesn’t have to travel far.

Larger organisms use blood to transport O2 and CO2 (insects don’t) ‐ the blood is at very low pressure and so flows too slowly to provide enough O2 to more active organisms like mammals.

Question 11

What are features of a closed circulatory system?

Answer 11

From the heart, blood is pumped through a series of progressively smaller vessels. In the smallest, the capillaries, substances exchange by diffusing in and out of the blood and into cells (and waste visa versa).

Blood is then returned to the heart via a series of progressively larger vessels.

Question 12

Why is a closed system more suitable for larger organisms like fish and mammals?

Answer 12

Blood stays at a higher pressure in the vessels and so flows faster ‐ delivering e.g. oxygen and removing waste more quickly.

Tissue fluid bathes cells instead.

Question 13

Explain the meaning of a single circulatory system.

Answer 13

Blood passes through the heart once for each

circuit of the body e.g. fish.

Question 14

Explain the meaning of a double circulatory system.

Answer 14

Blood flows twice through the heart for one circuit of the body. Contains a pulmonary circuit and a systemic circuit e.g. mammals.

Question 15

Pulmonary circuit

Answer 15

Carries blood to lungs to become oxygenated.

Question 16

Systemic circuit

Answer 16

carries blood containing oxygen and nutrients to the body’s cells.

Question 17

Advantages of double circulatory systems

Answer 17

• Blood can be maintained at a higher pressure in the systemic circuit, so it is delivered more quickly.
• A slightly lower pressure can be maintained in the pulmonary circuit to prevent damage to capillaries of the lungs.
• Mammals are much more active than fish and also maintain their own body temp ‐ both requiring a lot of energy and therefore a good and quick supply of oxygen and glucose to cells.
• As fish are less active and don’t maintain their body temp, a single circulatory system is sufficient to supply enough oxygen and glucose to meet their energy requirements.

Question 18

Describe the external features of the heart

Answer 18

• Made out of cardiac muscle.
• Most of heart is the 2 ventricles ‐ very thick walls of muscle.
• Above the ventricles are the atria with thinner walls.
• Coronary arteries lie over the surface of the heart ‐ supply the cardiac muscle with oxygen for aerobic respiration.
• If the coronary artery becomes blocked it restricts blood flow and therefore delivery of oxygen to the muscle. This can cause myocardial infarction (heart attacks).
• At the top of the heart are the arteries (carry blood away) and veins (carry blood towards).
• The bottom of the heart that comes to a point is called the apex.

Question 19

Describe the internal features of the heart

Answer 19

Semi-lunar valves:
- At base of arteries:
‐ prevents blood flowing backwards into the heart when ventricles relax (as the pressure would be lower there).

AVV:
Prevents blood flowing backwards from ventricles to atria.

Ventricular septum:

• Stops oxygenated and deoxygenated blood mixing;
• Ensures oxygenated blood gets to the body
• There would be a possible drop in blood pressure if hole present.

Question 20

Explain the differences in thickness of the walls of the different chambers of the heart in terms of their functions.

Answer 20

• The muscle in the walls of each chamber contracts to increase the pressure in the blood.
• The higher the pressure, the further the blood will travel.
• The pressure in the arteries is produced by the contraction of the left ventricular walls.
• Atrial walls ‐ thinnest ‐ don’t need to create high pressure as the blood only needs to be pushed into the ventricles.
• Right ventricular wall ‐ thicker than atria ‐ needs to create enough pressure to pump blood to lungs (pulmonary system). Pressure must not be too high otherwise thin capillary walls in lungs could burst.
• Left ventricular wall ‐ thickest ‐ needs to create most pressure to pump blood through aorta to whole body (systemic system) which is a much greater distance than any other chamber.

Question 21

What is the cardiac cycle?

Answer 21

The sequence of events in 1 heart beat.

Question 22

What are the 3 stages of the cardiac cycle?

Answer 22

• Diastole (atria and ventricles relax)
• Atrial systole (atria contract)
• Ventricular systole (venticles contract)

Question 23

Describe Diastole

Answer 23

• atria and ventricles relax and recoil.
• blood flows from veins into atria.
• pressure in ventricles is lower than in atria.
• blood flows through open A‐V valves into ventricles.
• volume in atria and ventricles increase.
• pressure in atria and ventricles slowly increases.

Question 24

Describe Atria systole

Answer 24

Both atria contract.

Causes further increase in pressure in the atria.

Increase in pressure causes blood to be pumped through the open A‐V valves into the ventricles.

Causing the volume in the ventricles to increase.

Question 25

Describe ventricular systole

Answer 25

When the ventricles are full, they begin to contract (from apex upwards).

The pressure in the ventricles increases above the pressure in the atria A‐V valves snap shut ‐ stops blood returning to atria.

At this point the semilunar valves are also shut as the pressure in the major arteries is higher than in the ventricles.

The pressure in the ventricles increases quickly as the blood can’t escape.

When the pressure in the ventricles exceeds the pressure in the major arteries, the semilunar valves open and the blood is pumped out the heart due to this pressure

The volume in the ventricles drops quickly.

This causes pressure to drop in the ventricles, below the pressure of the major arteries ‐ semilunar valves pushed closed by blood in arteries and stop blood flowing back into ventricle.

Question 26

Explain how the pressure changes in the cardiac cycle.

Answer 26

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Question 27

How do you calculate cardiac output?

Answer 27

Cardiac output = heart rate x stroke volume

Question 28

What does myogenic mean?

Answer 28

Muscle that generates it’s own contractions.

Cardiac muscle is myogenic.

Question 29

What does fibrillation mean?

Answer 29

The chambers of the heart contracting out of rhythm.

Question 30

What is the role of the SAN

Answer 30

The sinoatrial node (SAN) is the heart’s own pacemaker.

It sits on top of the right atrium.

It sends out waves of electrical excitation at regular intervals to initiate the heart’s contractions.

Question 31

Describe how the cardiac cycle is coordinated with reference to the SAN.

Answer 31

1) SAN initiates a wave of excitation which spreads over atrial walls causing them to contract simultaneously (atrial systole).
2) A band of fibres between the atria and ventricles stops the wave of excitation passing over the ventricular walls.
3) The wave of excitation reaches the atrioventricular node (AVN) on the septum.
4) The AVN delays the wave of excitation for 0.1 seconds to allow the atrial systole to complete before ventricular systole.
5) Wave of excitation spreads down the septum to the bundle of His and then to the Purkyne fibres.
6) Ventricles contract simultaneously.
7) Ventricles contract from the apex upwards into the arteries to completely empty the ventricles.

Question 32

Electrocardiograms (ECG)

Answer 32

Aim: To monitor the electrical activity of the heart.

In a healthy person:
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P wave- shows excitation of atria (atria systole)

QRS complex- shows excitation of ventricles (ventricular systole)

T wave- shows diastole

Question 33

How would you use an ECG to calculate heart rate?

Answer 33

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Question 34

Abnormal heart activities

Answer 34

Arrythmia- irregular heart beats:

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Ventricular fibrilation- uncoordinated heart beats:

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Elevated ST section - myocardinal infraction:

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Brachycardia- slow heart rate:

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Tachycardia- fast heart rate:

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Question 35

Blood

Answer 35

Liquid in blood vessels

1) Erythrocytes
2) Leucocytes
3) Platelets (thrombocytes)
4) Plasma ‐ dissolves:
‐ O2 and CO2
‐ salts
‐ glucose
‐ urea
‐ fatty acids
‐ amino acids
‐ hormones
‐ plasma proteins

Question 36

Tissue fluid

Answer 36

Bathes the cells of tissues to transport O2 and glucose etc. to cells and take CO2 and other waste back to the blood.

Question 37

Explain how tissue fluid is formed from the plasma.

Answer 37

artery ‐‐> arteriole ‐‐> capillary ‐‐> venule ‐‐> vein

• Due to the contraction of the heart, blood is at high hydrostatic pressure at the arteriole end of the capillaries.
• Between the cells of the capillary walls there are small gaps.
• The hydrostatic pressure is greater than the ocotic pressure.
• This forces fluid out of the capillaries carrying plasma and dissolved substances, e.g. oxygen and glucose (and some small WBCs ‐ neutrophils) with it ‐ this is the tissue fluid.
• RBCs, proteins and some WBCs can’t leave the capillaries because they are too large.
• Hydrostatic pressure is lower at the venule end.
• Oncotic pressure (in direction of capillary) is now greater.
• Due to presence of plasma proteins in the blood (lowers ψ).
• Fluid moves back into the capillary taking dissolved waste e.g. CO2 with it.

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Question 38

Substances in the blood, tissue fluid and lymph

Answer 38

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Question 39

Explain how lymph is formed

Answer 39

• Not all the tissue fluid returns to the capillaries.
• Pores allow fluid to leave the tissue fluid and enter lymph vessels.
• It will remove proteins (made by cells) out of the tissue fluid.
• It will remove neutrophils from tissue fluid.
• Low in O2 and glucose (used by cells).
• More CO2 and waste (made by cells).
• A lot of fats absorbed from intestines.
• Contains lymphocytes (WBCs produced in lymph nodes) which engulf and digest bacteria in the lymph fluid ‐ part of the immune system.

Question 40

Arteries

Answer 40

• Carry blood away from the heart.
• Have a small lumen to maintain the high pressure.
• Thick walls made of collagen to provide strength.
• Walls have elastic tissue - allows stretch when heart pumps and then allows recoil to maintain high pressure when heart relaxes.
• Walls have smooth muscle - can contract and constrict the artery to narrow the lumen (e.g. in vasoconstriction to redirect blood flow).

Question 41

Veins

Answer 41

• Carry blood towards the heart.
• Large lumen to make flow of blood easier.
• Walls are thinner (have thinner layers of collagen, elastic tissue and smooth muscle) as they do not need to withstand high pressure and are not used to constrict blood flow.
• Contain valves ‐ stop blood flowing in wrong direction and help it back to the heart.

Question 42

Capillaries

Answer 42

• allow exchange of materials between blood and cells.
• thin walls of flattened endothelial cells (squamous epithelial) to reduce diffusion distance.
• lumen is narrow to squeeze RBCs up next to the wall to reduce diffusion distance further.

Question 43

How does the pressure in the blood vessels change, as you get further away from the heart?

Answer 43

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