transport in animals

Question 1

When is oxygen released by erythrocytes?

Answer 1

Oxygen is not released by erythrocytes until they reach the capillaries.

Question 2

Why do erythrocytes have no nuclei or membrane-bound organelles?

Answer 2

This leaves more space for haemoglobin and allows them to squeeze through capillaries easily.

Question 3

What are the disadvantages of erythrocytes lacking nuclei and organelles?

Answer 3

They have a limited life span, cannot reproduce or undergo mitosis, cannot do protein synthesis or repair, and lack mitochondria for respiration.

Question 4

Do erythrocytes use the oxygen they carry?

Answer 4

No, erythrocytes do not use the oxygen they carry as it is bound to haemoglobin and they lack mitochondria.

Question 5

How do erythrocytes move?

Answer 5

Erythrocytes are moved by mass flow and require less ATP for metabolic processes due to the lack of organelles.

Question 6

Why does blood offload more oxygen to actively respiring tissues?

Answer 6

Higher levels of carbon dioxide in actively respiring tissues lower the affinity of haemoglobin for oxygen, leading to more oxygen release.

Question 7

What are the similarities between frog and mammalian circulation?

Answer 7

Both frogs and mammals have double circulations.

Question 8

What are the differences between frog and mammalian circulation?

Answer 8

Mammalian heart transports blood separately to lungs and body, preventing mixing of oxygenated and deoxygenated blood, while frog heart does not.

Question 9

Which is more effective: frog or mammalian circulation?

Answer 9

The mammalian system is more effective as it provides maximum available O2 for higher metabolic rates.

Question 10

How is electrical activity in the heart controlled?

Answer 10

It is controlled by a wave of depolarisation from the AVN moving along the Purkyne fibres.

Question 11

What follows systole in the mammalian heart?

Answer 11

Diastole follows systole because cardiac muscle takes time to repolarise after stimulation.

Question 12

What is a double circulatory system?

Answer 12

In a double circulatory system, blood flows twice through the heart for one heartbeat.

Question 13

What causes cell death in relation to blood pressure?

Answer 13

High blood pressure can cause small blood vessels to burst, leading to localized pressure build-up and cell death.

Question 14

What are the two circuits in the circulatory system?

Answer 14

The two circuits are the pulmonary and systemic systems.

Question 15

What effect does a toxin that slows conduction down the Purkyne fibres have?

Answer 15

It slows down heart rate by delaying ventricular systole and increasing the time the heart is in diastole.

Question 16

Why is the left ventricle larger than the right ventricle?

Answer 16

The left ventricle has a thicker wall of cardiac muscle to generate higher pressure for pumping blood around the body.

Question 17

Why is the left ventricle thicker than the left atrium?

Answer 17

It has more muscle to create more force for higher pressure against greater resistance in systemic circulation.

Question 18

When do the atrioventricular valves close?

Answer 18

They close during ventricular systole when ventricular pressure exceeds atrial pressure.

Question 19

What is a single circulatory system?

Answer 19

In a single circulatory system, blood passes through the heart once per circuit of the body.

Question 20

What is a closed circulatory system?

Answer 20

In a closed circulatory system, blood is maintained inside vessels.

Question 21

How does the heartbeat initiate?

Answer 21

The sinoatrial node initiates the excitation, causing atrial contraction.

Question 22

Where is cardiac muscle found?

Answer 22

Cardiac muscle is found in the walls of the heart chambers.

Question 23

What causes pressure inside the heart chambers?

Answer 23

Ventricular and atrial systole cause pressure inside the heart chambers.

Question 24

How do arteries differ from veins?

Answer 24

Arteries have no valves, thicker muscle and elastic tissue, and a more folded endothelium.

Question 25

What does histamine do?

Answer 25

Histamine stimulates smooth muscle contraction and makes capillary walls more permeable.

Question 26

What is hydrostatic pressure in the arteries generated by?

Answer 26

It is generated by the contraction of the ventricle muscle wall in the heart.

Question 27

What happens to hydrostatic pressure as blood moves away from the heart?

Answer 27

Hydrostatic pressure drops due to increased vessel number and larger total lumen.

Question 28

What occurs at the arterial end of the capillary?

Answer 28

Plasma moves out of the capillary, forming tissue fluid due to higher hydrostatic pressure.

Question 29

What are the advantages of keeping blood in vessels?

Answer 29

It maintains higher blood pressure for increased flow and allows for directed flow.

Question 30

How is the artery adapted to withstand pressure?

Answer 30

The artery has a thick wall with collagen for strength and a folded endothelium to stretch.

Question 31

How does the artery maintain pressure?

Answer 31

The thick elastic tissue allows the artery to recoil back to its original size.

Question 32

What causes pressure fluctuations in the aorta?

Answer 32

Systole increases pressure via left ventricle contraction, while diastole decreases pressure.

Question 33

What is the pulse/heart rate?

Answer 33

The number of pressure fluctuations per minute is the pulse/heart rate.

Question 34

Why is it important that blood pressure changes as blood flows from the aorta to the capillaries?

Answer 34

High pressure could damage capillary walls, so lower pressure reduces the risk of tissue fluid build-up.

Question 35

How does oxygen enter red blood cells?

Answer 35

Oxygen enters red blood cells by diffusion.

Question 36

Why is there a delay between atrial and ventricular excitation?

Answer 36

The delay allows time for the atria to fully contract and for the ventricles to fill with blood.

Question 37

How does the excitation wave travel in the heart?

Answer 37

It travels down the septum to the apex, causing ventricular contraction from the apex upwards.

Question 38

How do people with sickle cell anaemia benefit from fetal haemoglobin?

Answer 38

Fetal haemoglobin may not crystallise at low pO2, preventing shape change of red blood cells.

Question 39

How do substances dissolve in blood plasma enter tissue fluid?

Answer 39

They enter via diffusion from high to low concentration as hydrostatic pressure in the capillary is higher.

Question 40

Why aren’t erythrocytes found in tissue fluid?

Answer 40

Erythrocytes are too large to fit through the gaps between endothelial cells.

Question 41

What is the affinity of haemoglobin for oxygen?

Answer 41

Haemoglobin has a high affinity for oxygen, binding it in the alveoli where pO2 is high.

Question 42

How are hydrogencarbonate ions produced in erythrocytes?

Answer 42

Carbon dioxide diffuses into erythrocytes and reacts with water to form hydrogencarbonate ions.

Question 43

What is the Bohr effect?

Answer 43

Carbon dioxide reduces the affinity of haemoglobin for oxygen, facilitating oxygen release in respiring tissues.

Question 44

What happens if the ventricles contract twice for every atrial contraction?

Answer 44

Less blood leaves the heart for each ventricular contraction due to insufficient filling time.

Question 45

Why is there a hole in the septum between heart chambers in a fetus?

Answer 45

The hole allows blood to bypass the non-functioning lungs and be oxygenated in the placenta.

Question 46

What is unique about fetal haemoglobin?

Answer 46

Fetal haemoglobin contains gamma subunits, giving it a higher affinity for oxygen than adult haemoglobin.

Question 47

How many blood vessels carry blood away from the heart in mammals?

Answer 47

There are two blood vessels: one for the pulmonary circuit and one for the systemic circuit.

Question 48

What can a weak irregular heartbeat result in?

Answer 48

It may result in fatigue due to slow blood flow and lower oxygen delivery to cells.