3.1.2

Question 1

Why do animals need specialised transport systems?

Answer 1

• The metabolic demands of most multicellular organisms are high
• SA:V ratio is very small
• Molecules like hormones or enzymes may be produced in one place but needed in another
• Waste products of metabolism need to be removed

Question 2

What are the common features of a circulatory system?

Answer 2

• They have a liquid transport medium that circulates around the system
• They have vessels that carry the transport medium
• They have a pumping mechanism to move the fluid around the system

Question 3

What is a mass transport system?

Answer 3

When substances are transported in a mass of fluid with a mechanism for moving the fluid around the body

Question 4

What is an open circulatory system?

Answer 4

A circulatory system with very few vessels to contain the transport medium. It is pumped from the heart into the body cavity of the animal. The open body cavity is called the haemocoel. Here, the transport medium is under low pressure, and comes into direct contact with the tissues and the cells. This is where exchange takes place betwee the transport medium and the cells

Question 5

What is the blood in insects called?

Answer 5

Haemolymph

Question 6

In what type of animals are open circulatory systems mainly found in?

Answer 6

Invertebrates, including most insects and some molluscs

Question 7

What does haemolymph carry?

Answer 7

Food and nitrogenous wastes

Question 8

What is a closed circulatory system?

Answer 8

A circulatory system in which the blood is enclosed in blood vessels and does not directly come into contact with the cells of the body. The heart pumps blood around the body under pressure and relatively quickly

Question 9

What is a single circulatory system?

Answer 9

A circulatory system in which the blood flows through the heart once during each circulation

Question 10

Which organisms have single closed circulatory systems?

Answer 10

Fish and annelid worms

Question 11

What is a double circulatory system?

Answer 11

A circulatory system in which the blood flows through the heart twice during each circulation

Question 12

What are the three main components of blood vessels?

Answer 12

Elastic fibres
Smooth muscle
Collagen

Question 13

What is the function of elastic fibres?

Answer 13

Stretch and recoil, providing vessel walls with flexibility, and allowing the vessels to withstand the force of the blood pumped out of the heart and stretch. This evens out the surges of blood pumped from the heart, giving a continuous flow.

Question 14

What is the function of smooth muscle?

Answer 14

Contracts or relaxes, which changes the size of the lumen

Question 15

What is the function of collagen?

Answer 15

Provide structural support to maintain the shape and volume of the vessel

Question 16

What are the functions of the blood?

Answer 16

Transport of oxygen, carbon dioxide, digested food, nitrogenous waste, hormones, food molecules, platelets, and white blood cells and antibodies

Question 17

What is positive cooperativity?

Answer 17

The process by which haemoglobin changes shape each time one oxygen molecule binds to a haem group, making it easier for the next oxygen molecule to bind.

Question 18

What is the shape of an oxygen dissociation curve?

Answer 18

Sigmoidal

Question 19

How does CO2 impact the binding of oxygen with haemoglobin

Answer 19

As the partial pressure of CO2 increases, haemoglobin gives up oxygen more easily. This change is known as the Bohr effect.

Question 20

Why is the Bohr effect important?

Answer 20

In active tissues with a high pCO2, haemoglobin gives up O2 more easily

In the lungs where pCO2 is low, oxygen binds to haemoglobin easily

Question 21

How does foetal haemoglobin compare to adult haemoglobin?

Answer 21

Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin as the foetus is solely reliant on the oxygen provided to it via the placenta

Question 22

How is CO2 transported?

Answer 22

• 5% is carried dissolved in the plasma
• 10-20% is combined with the amino groups in haemoglobin to form carbaminohaemoglobin
• 75-85% is converted into HCO3- in the cytoplasm of red blood cells

Question 23

What is the equation for the formation of carbonic acid?

Answer 23

CO2 + H2O -> H2CO3

Question 24

What catalyses the formation of carbonic acid?

Answer 24

Carbonic anhydrase

Question 25

Where do the HCO3- ions go after being formed?

Answer 25

They move out of the erythrocytes into the plasma by diffusion, and Cl- ions move into the erythrocytes, maintaining the electrical balance of the cell. This is called chloride shift

Question 26

How is the conversion of CO2 to HCO3- useful?

Answer 26

The erythrocytes maintain a steep concentration gradient for CO2 to diffuse from the respiring tissues into the erythrocytes

Question 27

Where does the wave of excitation in the heart begin?

Answer 27

The sinoatrial node, and it causes the atria to contract and so the heartbeat starts. A layer of non-conducting tissue prevents the excitation passing directly to the ventricles

Question 28

Why is there a slight delay imposed by the AVN?

Answer 28

It is to allow the ventricles to completely fill

Question 29

Why does the bundle of His travel to the apex of the heart?

Answer 29

This is to allow more efficient emptying of the ventricles, opposing gravity

Question 30

What is an ECG?

Answer 30

An electrocardiogram, and it detects tiny electrical differences in the skin, which result from the electrical activity of the heart

Question 31

What is tachycardia?

Answer 31

When the heartbeat is very fast, over 100 bpm.

Question 32

What is bradycardia?

Answer 32

When the heart rate slows down to below 60 bpm

Question 33

What is an ectopic heartbeat?

Answer 33

An extra heartbeat out of the normal rhythm

Question 34

What is atrial fibrillation?

Answer 34

Rapid contraction of the atria (up to 400 times per minute) but they do not contract properly, and only some of the impulses are passed on to the ventricles, which contract much less often. This leads to inefficient pumping of the blood.