Transport systems

Question 1

Why are specialised transport systems needed??

Answer 1

The metabolic demands of multicellular organisms is high- diffusion alone is not enough to supply quantities needed over long distances
SA:V ratio gets smaller
Waste products will be needed to transported to excretory organs
Molecules (hormones/ enzymes) may be needed in one place and made in another

Question 2

What is a mass transport system?

Answer 2

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

Question 3

What is the difference between an open and closed circulatory system?

Answer 3

Open- few vessels to contain the transport medium so it comes directly into contact with cells to exchange substances
Closed- transport medium is enclosed within vessels and does not come directly into contact with cells

Question 4

What is the difference between a single and double circulatory system?

Answer 4

Single- blood travels once through the heart for each complete circulation of the body
Double- blood travels twice through the heart for each complete circulation of the body
Double is more effective- especially for land animals
as high pressure and fast blood flow can be maintained

Question 5

Arteries and arterioles

Answer 5

Carry oxygenated blood away from the heart
Blood is under higher pressure than in the veins
Elastic fibres enable them to stretch and take larger blood volumes, then recoil and return to original size
When smooth muscle contracts, it constricts the vessel and prevents blood flow
Arterioles link arteries and capillaries

Question 6

Capillaries

Answer 6

Blood vessels that link arterioles with venules
Substances are exchanged through the capillary walls between tissues and the blood
When blood enters, it is oxygenated and by the time it leaves it has less oxygen

Question 7

What are the ways in which capillaries are adapted for their role?

Answer 7

Large surface area for diffusion
Slow movement of blood through the capillary allows more time for exchange
Walls are a single cell thick- shorter diffusion distance

Question 8

Veins and venules

Answer 8

Carry blood to the heart
Vessels have a wide lumen (larger volume)
Venules link the capillaries with the veins

Question 9

How do veins prevent the backflow of blood?

Answer 9

Low pressure blood going against gravity
Have valves to prevent the backflow of blood, if blood goes the wrong way valves shut
Many veins run between active muscles so that when the muscle contracts they squeeze the vein and force blood upward
Breathing movements of chest act as a pump

Question 10

What is the composition of blood?

Answer 10

Plasma, which carries components such as RBC, WBC, platelets, amino acids, glucose etc.

Question 11

What is the function of blood?

Answer 11

Transport of: oxygen to cells, carbon dioxide from cells, hormones, platelets, antibodies

Question 12

What is the role of tissue fluid?

Answer 12

Exchange of substances between the blood and cells occurs via the tissue fluid
It has the same composition as plasma, but fewer proteins
At the arterial end of a capillary, tissue fluid is forced out as the hydrostatic pressure (4.6kPa) is greater than the oncotic pressure (-3.3kPa)
At the venous end of a capillary, tissue fluid is forced in as the hydrostatic pressure (2.3kPa) is smaller than the oncotic pressure (-3.3kPa)

Question 13

What is lymph

Answer 13

The tissue fluid that does not return to the capillaries drains into the lymph capillaries
It is similar in composition to plasma but has less oxygen and nutrients
They also have valves to prevent the backflow of lymph

Question 14

Lymph nodes

Answer 14

Lymphocytes build up at the lymph nodes, where they produce antibodies
Bacteria is also intercepted here, which is ingested by phagocytes

Question 15

What adaptations do RBCs have for their role?

Answer 15

Biconcave shape- increases the SA available for diffusion of gases and help them pass through narrow capillaries
No nuclei- maximum amount of haemoglobin can fit
haemoglobin + oxygen = oxyhaemoglobin

Question 16

What is positive cooperativity ?

Answer 16

As soon as one oxygen molecule binds to a haem group the molecule changes shape, making it easier for the next oxygen molecule to bind
The free oxygen concentration in the erythrocyte stays low, maintaining a steep concentration gradient

Question 17

What does an oxygen dissociation curve show?

Answer 17

Shows the affinity of haemoglobin for oxygen- at higher partial pressures of oxygen haemoglobin is loaded with it, until it levels off as all the haem groups are saturated

Question 18

What is the Bohr effect?

Answer 18

As the partial pressure of CO2 rises, haemoglobin gives up oxygen more easily
In the lungs, where CO2 levels are low, oxygen binds to the haemoglobin molecules easily
In active tissues, oxygen is released more quickly

Question 19

What is the difference between fetal and adult haemoglobin

Answer 19

Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin
This is vital as it allows a foetus to obtain oxygen from its mother’s blood at the placenta
Fetal haemoglobin can bind to oxygen at lower partial pressures

Question 20

How is carbon dioxide transported?

Answer 20

Dissolved in the plasma
Combined with haemoglobin to form carbaminohaemoglobin
Converted into hydrogen carbonate ions

Question 21

How are hydrogen carbonate ions formed?

Answer 21

CO2 diffuses into red blood cells from the plasma, where it reacts with water to form carbonic acid
This reaction is catalysed by carbonic anhydrase
Carbonic acid dissociates to form hydrogen carbonate and hydrogen ions

Question 22

What is the chloride shift?

Answer 22

Hydrogen carbonate ions diffuse out of the red blood cell and into the plasma
To maintain the electrical balance of the cells, negatively charged chloride ions diffuse into the cell

Question 23

Why is it important for the carbon dioxide to be converted?

Answer 23

To maintain a steep concentration gradient for the diffusion of more CO2 into RBCs
When blood reaches the lung tissue, the whole process is undone

Question 24

Describe the pathway of blood in the heart

Answer 24

Vena Cava- Right atrium- Tricuspid valve- Right ventricle- Semilunar valve- Pulmonary artery- Lungs- Left atrium- Bicuspid valve- Left ventricle- Semilunar valve- Aorta

Question 25

Why is the muscular wall of the left side of the heart thicker than the right?

Answer 25

The right side has to pump blood a relatively short distance- to the lungs
The left side has to pump it further- through the whole body

Question 26

What is the difference between a diastole and a systole ?

Answer 26

Diastole- relaxing of the heart
Atria and ventricles fill with blood
Pressure in arteries at minimum
Systole- atria contraction then ventricular contraction
Blood is forced out of the right side to the lungs, and from the left side to the rest of the body
Blood pressure in arteries is at a maximum

Question 27

Why is cardiac muscle described as myogenic ?

Answer 27

It has its own intrinsic rhythm, preventing the body from wasting resources maintaining a basic heart rate

Question 28

Describe the events in the cardiac cycle

Answer 28

1- Wave of electrical excitation begins in the SAN
2- Atrial contraction
3- Wave of excitation travels to the AVN
4- Wave of excitation travels to the bundle of His (made up of purkyne fibres) after a short delay
5- This takes the wave to the apex of the heart
6- Stimulates ventricular contraction
The delay is important to ensure the ventricles contract after that atria

Question 29

Describe the different types of ECGs

Answer 29

Tachycardia- rapid heartbeat
Bradycardia- slow heartbeat
Ectopic heartbeat- extra heart beats out of normal rhythm
Atrial fibrillation