3.2 - Transport In Animals

Question 1

Why do multicellular animals need a transport system?

Answer 1

They have a small SA:V ratio (cannot exchange enough substances to supply the large volume of animal through a relatively small outer surface.
Cannot supply cells deep within the body as there’s a large distance between them and the outside.
High metabolic rate, so they use oxygen and glucose faster than single-celled organisms.

Question 2

What is an open circulatory system?

Answer 2

Blood is not kept within the vessels all the time. It flows freely in body cavity.
E.g. insects - but it supplies the insect with nutrients and transports hormones, it doesn’t supply the insect with oxygen; this is done with the tracheal system.

Question 3

What is an closed circulatory system?

Answer 3

The blood is maintained inside vessels.

E.g. fish or mammals.

Question 4

What are the advantages of a closed circulatory system?

Answer 4

Flow can be directed and moved faster if necessary. Higher blood pressure can be maintained.

Question 5

What is a single circulatory system?

Answer 5

Blood passes through the heart once for each circulation of the body - uses a two-chambered heart. E.g. in fish - blood travels from the heart to the gills and then to the organs and tissues in the rest of the body, and back to the heart.

Question 6

What is a double circulatory system?

Answer 6

Blood passes through the heart twice for each circulation of the body. One circuit is from the heart to the lungs and back and then from the heart to the rest of the body and back.

Question 7

What are the advantages of a double circulatory system?

Answer 7

The heart can give an extra push between the lungs and the rest of the body making blood travel faster and deliver oxygen to the tissues more quickly.

Question 8

What structures enable arteries to withstand pressure?

Answer 8

Wall is thick and made of collagen to provide strength. Folded endothelium prevents damage to artery as it stretches.

Question 9

What structures enable arteries to maintain pressure?

Answer 9

Elastic tissue to recoil and return to original size. Smooth muscle constricts the lumen to allow pressure to be maintained elsewhere.

Question 10

How is the structure of arteries different to veins?

Answer 10

Arteries have folded endothelium – more muscle (thicker walls), more elastic tissue and more collagen than veins and no valves.

Question 11

What is tissue fluid and what is it made of?

Answer 11

Fluid that surrounds the cells in tissues. Made from plasma fluid and small molecules dissolved in the fluid such as glucose and oxygen.

Question 12

How is tissue fluid different to blood?

Answer 12

It does not contain red blood cells (RBC) or big proteins as they are too large to be pushed through capillary walls.

Question 13

What are the gaps between the capillary endothelial cells called?

Answer 13

Fenestrations.

Question 14

How is hydrostatic pressure generated?

Answer 14

In the heart by the contraction of the ventricle wall.

Question 15

How is oncotic pressure generated?

Answer 15

By plasma proteins present in the capillaries, which lower the water potential.

Question 16

What is a capillary bed?

Answer 16

The network of capillaries in an area of tissue.

Question 17

What happens at the arteriole end of a capillary bed?

Answer 17

Hydrostatic pressure inside the capillary is greater than the hydrostatic pressure in the tissue fluid. The difference in hydrostatic pressure forces fluid out of the capillaries and into the spaces around cells, forming tissue fluid.

Question 18

What happens at the venule end of a capillary bed?

Answer 18

Hydrostatic pressure inside the capillary is low (as fluid been forced out). The water potential inside the capillaries is lower than the water potential in the tissue fluid (due to fluid loss from the capillaries and the remaining plasma proteins inside the capillary). Water moves from the tissue fluid (high water potential) into the capillaries (low water potential) by osmosis.

Question 19

How do oxygen and glucose dissolved in blood plasma enter the tissue fluid from the capillaries?

Answer 19

Some is dissolved in the plasma and is forced out of the capillary along with the plasma fluid moving down the pressure gradient from high to low pressure. Some moves by diffusion from high concentration to low concentration, down concentration gradient.

Question 20

Why does blood pressure drop as it moves away from the heart?

Answer 20

Arteries divide into many smaller vessels which together have a larger total cross sectional area – resulting in less resistance to blood flow. Arteries stretch and expand. Plasma is forced through the capillary fenestrations to form tissue fluid.

Question 21

Why is the wall of the left ventricle thicker than the right?

Answer 21

More muscle is needed to create more force and higher pressure. Has to push blood against greater resistance and pumps blood all around the body.

Question 22

Explain how pressure changes in the heart bring about closure of the atrioventricular valve.

Answer 22

Ventricle wall contracts (ventricular systole) and increase ventricular pressure higher than the atrial pressure. The increased pressure of the blood pushes the valve shut. Tendinous cords prevent inversion of the valves.

Question 23

Describe the role of the SAN and AVN in the coordination of the heart.

Answer 23

SAN initiates heart beat send impulse over atria walls (making them contract).
AVN delays impulse and sends impulse down bundle of His to the Purkyne fibres.
This causes the ventricles to then contract from the base (apex) up.

Question 24

What does the P wave represent in an ECG?

Answer 24

Atrial systole (contraction).

Question 25

What does the QRS wave represent in an ECG?

Answer 25

Ventricular systole (contraction).

Question 26

What does the T wave represent in an ECG?

Answer 26

Diastole (relaxation).

Question 27

What does the P-QRS-T wave represent in an ECG?

Answer 27

One ‘beat’ of the heart.

Question 28

What term is given to a patient with a slow heart rate?

Answer 28

Bradycardia.

Question 29

What term is given to a patient with a fast heart rate?

Answer 29

Tachycardia.

Question 30

What is fibrillation?

Answer 30

Uncoordinated contraction of the atria and ventricles resulting in a really irregular heartbeat.

Question 31

What term is given to an extra beat or an early beat of the ventricles?

Answer 31

An ectopic heartbeat.

Question 32

What is the scientific term for a red blood cell?

Answer 32

Erythrocyte.

Question 33

What is haemoglobin (Hb)?

Answer 33

A large protein consisting of 4 polypeptide chains.

Question 34

How many oxygen molecules can each haemoglobin (Hb) molecule carry?

Answer 34

4.

Question 35

How do red blood cells carry oxygen from the lungs to the tissues?

Answer 35

Red blood cells contain Hb. Hb has high affinity for oxygen. In the lungs Hb associates with oxygen to form oxyhaemoglobin. In respiring tissues, Hb dissociates with oxygen.
Do not say oxygen dissociates as this implies oxygen is forming ions.

Question 36

How can the amount of oxygen released be increased?What is this called?

Answer 36

In the presence of more carbon dioxide, carbonic acid, H+ ions or HCO 3- ions.
The Bohr effect.

Question 37

Describe and explain the oxygen dissociation curves for fetal and adult Hb.

Answer 37

The partial pressure of oxygen (ppO2) at the placenta is low (as some O2 used up by the mothers body). Adult Hb will dissociate with Hb in low ppO2. Fetal Hb has a higher affinity for oxygen and is able to take up oxygen at lower ppO2.

Question 38

How is carbon dioxide transported from respiring tissues?

Answer 38

Carbon dioxide diffuses into RBC and combines with water to form carbonic acid. This reaction is catalysed by the enzyme carbonic anhydrase. Carbonic acid dissociates to form hydrogencarbonate (HCO 3-) ions and hydrogen (H+) ions (85%). HCO 3- ions diffuse out of RBC into the blood plasma. A small amount (10%) of CO2 can also combine with Hb to form carbaminohaemoglobin (CO2Hb).

Question 39

What happens at the same time as HCO 3- ions leaving the RBC to maintain electrical neutrality and what is this called?

Answer 39

Chloride (Cl- ) ions diffuse into the RBC. It is called the chloride shift. It prevents any change in pH that could affect the cells.

Question 40

What happens to the (H+) ions?

Answer 40

React with Hb to make haemoglobinic acid (HHb). This prevents a fall in pH and so has an overall buffering effect.