3.1.2 - Transport in animals

Question 1

What are the three main factors that influence the need for a transport system?

Answer 1

1) Size
2) Surface area to volume ratio
3) Level of metabolic activity

Question 2

Describe how the size of an organism determines whether it needs a transport system or not.

Answer 2

In small organisms, their cells are surrounded by (or very close to) the external environment.
Therefore they can rely on diffusion to supply them with enough oxygen and nutrients to keep the cell alive.

HOWEVER:
In large organisms = diffusion distance is too big.
- some cells are deep within the organism, very far from the external environment.
- diffusion would be too slow.

• also the outer layers of cells use up the supplies, so that less will reach the cells deep inside the body.

Question 3

Describe how surface area to volume ratio affects the need for a transport system.

Answer 3

Small animals like the flat worm have a LARGE surface area to volume ratio.

(for each gram of tissue in their body they have a sufficient area of the body surface through which exchange can occur.)

Large animals = small SA to VOL. ratio.
- each gram of tissue has a smaller area of body surface for exchange.

Question 4

Describe how the level of metabolic activity of an organism affects need for transport system.

Answer 4

animals = need energy from food (to move around)

aerobic respiration needs oxygen to release energy.

animal v active = cells need good supplies of nutrients and oxygen to supply the energy for movement.

Animals that keep themselves warm, e.g. mammals, need even more energy.

Question 5

What are the features of a good transport system?

Answer 5

1) A fluid or medium to carry nutrients, oxygen, and wastes around the body - this is the blood
2) A pump to create pressure that will push the fluid around the body - this is the heart.
3) Exchange surfaces that enable substances to enter the blood and leave it again where they are needed - capillaries.
4) tubes or vessels to carry blood by mass flow
5) two circuits - one to pick up oxygen and another to deliver oxygen to the tissues.

Question 6

Describe a single circulatory system.

Answer 6

Blood only passes through the heart once for each complete circuit of the body.

Question 7

State an organism that has a single circulatory system and how that works. (route)

Answer 7

Fish

heart > gills > body > heart

In fish, the heart pumps blood to gills (to pick up oxygen) and then on through the rest of the body (to deliver the oxygen) in a single circuit.

Question 8

Describe a double circulatory system.

Answer 8

Blood passes through the heart twice for each complete circuit of the body.

Question 9

State a group of organisms that have a double circulatory system and how that works. (route)

Answer 9

Mammals

heart > body > heart > lungs > heart

Blood flows through the heart twice for each circuit of the body.
The system has two separate circuits. One circuit carries blood to the lungs to pick up oxygen = pulmonary circulation.

Other circuit carries oxygen and nutrients around body to tissues = systematic circulation.

Question 10

Describe how the pressure of the blood changes during the circulation of fish and why their single system works for them and fish are not very metabolically active?

Answer 10

• blood pressure drops as blood passes through the tiny capillaries of gills
• blood has a low pressure as it flows towards body, and own’t flow very quickly
• rate at which oxygen and nutrients are delivered to respiring tissues, and carbon dioxide and urea are removed = limited.

Fish aren’t very metabolically active - they do not maintain their body temp. They need less energy. Their system works for their needs.

Question 11

Describe why the double circulatory system works for mammals.

Answer 11

• blood pressure mustn’t be too high in pulmonary circulation, otherwise it may damage the delicate capillaries in the lungs.
• the heart can increase the pressure of blood after it has passed through the lungs
  ∴ blood is under higher pressure as it flows to the body = flows more quickly.
• the systemic circulation can carry blood dat a higher pressure than the pulmonary circulation.

Question 12

Are mammals active or less active?
Do they need to maintain their body temp. or not?
Do they need a lot of energy or little energy?
How do mammals get this energy?

Answer 12

• mammals are active animals
• they maintain their body temp.
• supplying the energy for activity and heat needed to keep body warm requires energy from FOOD.

> energy is released from food in the process of respiration.
to release a lot of energy
= cells need good supply of nutrients & oxygen, as well as removal of waste products.

Question 13

What is an open circulatory system?

Answer 13

One in which the blood is not held in vessels.

> the blood fluid circulates through the body cavity, so that the tissues and cells are bathed directly in the blood.

Question 14

Some animals use body ………………… to help circulate the blood. If this stops - what effect does this have on the blood?

Answer 14

• movements of the body help to circulate the blood

∴ without movement the blood stops moving, so the transport of oxygen & nutrients stops.

Question 15

Describe how the open circulatory system works in insects that are smaller and less active.

Answer 15

> have muscular pumping organ similar to a heart
= a long, muscular tube that lies just under the dorsal (upper) surface of the body.

> blood enters heart through pores called OSTIA

> heart then pumps blood towards head by peristalsis
at the forward end of heart (nearest head), blood pours into the body cavity.

> circulation can continue when insect is resting, but body movements may still affect circulation.

Question 16

Describe how the open circulatory system works in insects that are larger and more active.

Answer 16

> have open-ended tubes attached to the heart.

= these direct the blood towards active parts of the Boyd e.g. leg & wing muscles

Question 17

Give two disadvantages of open circulatory systems.

Answer 17

• blood pressure is low and blood flow is slow

- circulation of blood may be affected by body movements or lack of body movements

Question 18

What is a closed circulatory system?

Answer 18

One in which the blood is held in vessels.

> a separate fluid, called tissue fluid, bathes the tissues and cells

Question 19

Give four advantages of closed circulatory systems.

Answer 19

• higher pressure
  ∴ blood flows more quickly
• more rapid delivery of oxygen and nutrients
• more rapid removal of carbon dioxide and other wastes
• transport is INDEPENDENT of body movements

Question 20

All types of blood vessel have an inner layer or lining, made of a single layer of cells called…

Answer 20

the endothelium.

Question 21

What does the right side of the heart do?

Answer 21

Pumps deoxygenated blood to the lungs to be oxygenated.

Question 22

What does the left side of the heart do?

Answer 22

Pumps oxygenated blood to the rest of the body.

Question 23

Why does the heart make the pumping action?

Answer 23

On both sides, the heart squeezes the blood, putting it under pressure.
- this pressure forces the blood along the arteries and through the circulatory system.

Question 24

What do coronary arteries do? Why are they so important?

Answer 24

Supply oxygenated blood to the heart muscle.
- important because if they become constricted, it would restrict the blood flow to the heart muscle.
∴ the delivery of oxygen and nutrients such as fatty acids and glucose would be reduced.
> may cause angina or a heart attack (myocardial infarction).

Question 25

What does the pulmonary vein do?

Answer 25

• oxygenated blood from the lungs flows through the pulmonary vein into the left atrium.

Question 26

What do tendinous cords do?

Answer 26

Prevent valves from turning inside out when the ventricle walls contract.

Question 27

What does the septum do? Why is it important?

Answer 27

The septum is a wall of muscle that separates the ventricles from each other.
- ensures that the oxygenated blood and the deoxygenated blood don’t mix.

Question 28

What does the pulmonary artery do?

Answer 28

Takes deoxygenated blood to the lungs

Question 29

What does the aorta do?

Answer 29

Carries blood to a no. of arteries that supply all parts of the body.

Question 30

What are semilunar valves?

Answer 30

Valves that are found at the base of the major arteries.

- prevent blood returning to the heart as the ventricles relax.

Question 31

Why are the walls of the atria thin?

Answer 31

• because these chambers do not need to create much pressure.
• their function is to receive blood from the veins and push it into the ventricles.

Question 32

How thick are the walls of the right ventricle? Why is this important?

Answer 32

• thicker than the walls of the atria
• enables the right ventricle to pump deoxygenated blood out of the heart to the lungs.
  > the lungs are in the chest cavity beside the heart so that the blood does not need to travel very far.
• the alveoli in the lungs are very delicate and could be damaged by very high blood pressure.

Question 33

How thick are the walls of the left ventricle? Why is this important?

Answer 33

• the walls of the left ventricle can be two or three times thicker than those of the right ventricle.
• blood from the left ventricle is pumped out through the aorta & needs sufficient pressure to overcome the resistance of the systemic circulation.

Question 34

Describe the first stage of the cardiac cycle.

Answer 34

Ventricles RELAX, atria CONTRACT.

• ventricles are relaxed
• atria contract, which decreases their volume and increases their pressure
• this pushes the blood into the ventricles through the atrioventricular valves.
  > slight increase in ventricular pressure and volume as ventricles receive the ejected blood from contracting atria.

Question 35

Describe the second stage of the cardiac cycle.

Answer 35

Ventricles CONTRACT, atria RELAX.

• the atria relax
• ventricles contract (decreasing their volume), increasing their pressure
• pressure becomes higher in ventricles than the atria, which forces the atrioventricular valves shut to PREVENT back-flow.
  > the high pressure in the ventricles opens the semi-lunar valves - blood is forced out into the pulmonary after and aorta.

Question 36

Describe the third stage of the cardiac cycle.

Answer 36

The ventricles and atria BOTH RELAX.
- higher pressure in the pulmonary artery & aorta causes semi-lunar valves to close, preventing back-flow

• the atria fill with blood (increasing their pressure) due to higher pressure in the vena cava & pulmonary vein.
• as ventricles continue to relax, their pressure falls below pressure in the atria.
• causes atrioventricular valves to open & blood flows passively (without being pushed by atrial contraction) into ventricles from the atria.

Question 37

Bradycardia definition.

Answer 37

A slow heart rhythm.

Question 38

Ectopic heart beat definition.

Answer 38

An extra beat or an early beat to of the ventricles.

Question 39

Fibrillation defintion.

Answer 39

Uncoordinated contraction of the atria and ventricles.

Question 40

Myogenic muscle:

Answer 40

Muscle that can initiate its own contraction

Question 41

Electrocardiogram:

Answer 41

A trace that records the electrical activity of the heart.

Question 42

Tachycardia:

Answer 42

A rapid heart rhythm.

Question 43

Purkyne tissue:

Answer 43

Consists of specially adapted muscle fibres that conduct the wave of excitation from the AVN excitation at regular intervals in order to initiate contractions.

Question 44

Sino-atrial node (SAN)

Answer 44

the heart’s pacemaker.
A small patch of tissue that sends out waves of electrical excitation at regular intervals in order to initiate contractions.

Question 45

Why is the heart myogenic?

Answer 45

Because it can initiate its own contraction.

(the muscle would contract and relax rhythmically even if it was not connected to the body.

Question 46

Do the atrial muscle and the ventricular muscle contract at the same frequency?

Answer 46

No.

The atrial muscle tends to contract at a higher frequency than the ventricular muscle.

Question 47

Why does the heart need a mechanism that can coordinate the contractions of all four chambers?

Answer 47

Because otherwise the muscle could start inefficiently pumping because the contractions of the chambers would not be synchronised.
> condition known as fibrillation.

Question 48

What is the Sino-atrial node (SAN).

Answer 48

A small patch of tissue that generates electrical activity.

- at the top of the right atrium, near the point where the vena cava empties blood into the atrium.

Question 49

What is another term for the SAN?

Answer 49

the pacemaker

Question 50

What does the SAN do?

Answer 50

Initiates a wave of excitation at regular intervals.

- in a human, this occurs 55-80 times a minute.

Question 51

List the first four points of the contraction of the atria.

Answer 51

• wave of excitation quickly spreads OVER the walls of both atria
• travels along membranes of muscle tissue.
• wave of excitation passes, causes the cardiac muscle cells to contract
• this is an atrial systole.

Question 52

Describe what happens after the first four points of contraction of the the atria.

Answer 52

> tissue at base of atria = unable to conduct the wave of excitation
∴ it cannot spread directly down tot he ventricle walls.

> top of interventricular septum (septum separating two ventricles) = another node - the atria-ventricular node (AVN).

> only route that can conduct the wave of excitation through to the ventricles.
- the wave of excitation is delayed in the node.
∴ allows time for the atria to finish contracting and for the blood to flow down into the ventricles before they begin to contract.

Question 53

List the six steps of contraction of the ventricles.

Answer 53

> after this short delay in the node, the wave of excitation is carried away from the AVN and down specialised conducting tissue called the Purkyne tissue.

> this runs down the interventricular septum
at the base of the septum, the wave of excitation spreads out over the walls of the ventricles.

> as the excitation spreads upwards from the base (apex) of the ventricles = causes muscles to contract

> means the ventricles contract from base upwards
pushes blood up towards major arteries at top of heart