3.1.2 transport in animals

Question 1

Why is there a need for specialised transport system in animals?

Answer 1

Metabolic demands of most multicellular organisms are too high so diffusion over long distances is not enough to supply quantities needed.
SA:V ratio gets smaller as the organism gets bigger.
Molecules e.g. hormones or enzymes, may be made in one place but needed in another.
Food will be digested in one organ system but needs to be transported to every cell for respiration.
Waste products need to be removed.

Question 2

What is an open circulatory system?

Answer 2

Pumped straight from the heart into the body cavity (haemocoel) of the animal.
Found mainly in invertebrate animals.

Question 3

What is insect blood?

Answer 3

Haemolymph- doesn’t carry oxygen or carbon dioxide.

Question 4

a

Question 5

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

Answer 5

Single- blood passes through two sets of capillaries before returning to the heart.
Only goes through the heart once in a circuit.
Double- two separate circulations, blood is pumped from the heart to the lungs and then through the heart and the rest of the body before returning to the heart.

Question 6

What is the structure and function of an artery?

Answer 6

Carry deoxygenated blood.
Artery walls contain elastic fibres, smooth muscle, and collagen.
Elastic fibres allow it to withstand force of the blood pumped out the heart and stretch to take larger blood volumes.
The lining of an artery is smooth so blood flows easily over it.

Question 6

What are arterioles?

Answer 6

Arterioles link arteries and capillaries.
They have more smooth muscle and less elastin in their walls than arteries, they have little pulse surge, but can constrict and dilate to control flow of blood.
When the smooth muscle contracts it constricts the vessel and prevents blood flowing into the capillary bed (vasoconstriction).
When smooth muscle relaxes, blood flows through into the capillary bed (vasodilation).

Question 7

What is the structure and function of capillaries?

Answer 7

Capillaries are microscopic blood vessels linking arterioles to venules.
They form an extensive network throughout the body.
The lumen is so small so red blood cells have to travel single file.
Substances are exchanged in and out the capillary walls.
Gaps between endothelial cells are large so many substances can pass out the capillaries into fluid surrounding cells.

Question 8

How are capillaries adapted to their role?

Answer 8

Large SA:V ratio for the diffusion of substances in and out the blood.
Total cross-section of capillaries is always greater than the arteriole supplying them, so rate of blood flow falls. Slow time gives time for exchange of material by diffusion.
The walls are a single endothelial cell thick, thin layer for diffusion.

Question 9

What is the structure and function of a vein?

Answer 9

Veins carry blood away from cells to the heart, deoxygenated blood.
Valves to prevent backflow.
Walls contain lots of collagen and little elastic fibre, and the vessels have a wide lumen and a smooth, thin lining so blood flows easily.

Question 10

What are venules?

Answer 10

Venules link capillaries with veins.
They have thin walls with a little smooth muscle.
Several venules join together to form a vein.

Question 11

What adaptations assist returning deoxygenated blood towards the heart?

Answer 11

Veins have one-way valves at intervals which prevent blood from flowing backwards.
Many big veins run between big active muscles, when the muscles contract it squeezes the veins forcing blood towards the heart (valves stop backflow when relaxing).
Breathing movements of the chest act as a pump.

Question 12

What is transported in blood?

Answer 12

Oxygen and carbon dioxide- from respiring cells.
Digested food- from small intestine.
Nitrogenous waste- from cells to excretory organs.
Chemical messages (hormones).
Food molecules- from storage cells to other cells.
Platelets- to damaged areas.
Cells and antibodies involved in the immune response.

Question 13

What is plasma?

Answer 13

Plasma is a yellow liquid which carries the other components in blood.
Makes up 55% of blood by volume.

Question 14

What is meant by oncotic pressure?

Answer 14

The tendency for water to move into the blood by osmosis.

Question 15

Why does water have a tendency to move into the blood?

Answer 15

Plasma proteins give the blood in the capillaries a relatively high solute potential compared to surrounding fluid, and so water had a tendency to move into the blood in capillaries.

Question 16

What is meant by hydrostatic pressure?

Answer 16

The pressure from the surge of blood that occurs every time the heart contracts.

Question 17

How does tissue fluid occur?

Answer 17

The hydrostatic pressure at the arterial end of the capillaries is relatively high at 4.6kPa. It is higher than the oncotic pressure attracting water in by osmosis, so fluid is forced out of the capillaries.
Tissue fluid is the fluid which fills the space between the cells.

Question 18

What happens as the blood moves through the capillaries towards the venous system?

Answer 18

The hydrostatic pressure falls to around 2.3kPa in the vessels as fluid has moved out and the pulse is lost.
The oncotic pressure is still -3.3kPa, so it is stronger than the hydrostatic pressure, so water moves back into the capillaries by osmosis.

Question 19

What is the difference in composition for blood, tissue fluid, and lymph?

Answer 19

Blood- made up of plasma, erythrocytes, platelets, leucocytes.
Tissue fluid- plasma, BUT no red blood cells or plasma proteins.
Lymph- same as blood and tissue fluid but less oxygen and fewer nutrients, also contains fatty acids.

Question 20

What are lymphocytes?

Answer 20

Lymphocytes build up in the lymph node when necessary and produce antibodies.

Question 21

What is the reaction with the reactants: oxygen and haemoglobin?

Answer 21

4O2 + Hb -><- Hb(O2)4
oxygen + haemoglobin -> oxyhaemoglobin.

Question 22

What is haemoglobin?

Answer 22

Haemoglobin is the red pigment that carries oxygen.
It is a very large globular conjugated protein made up of four peptide chains, each with an iron-containing haem prosthetic group.

Question 23

How does oxygen bind with haemoglobin?

Answer 23

When erythrocytes enter the capillaries in the lungs, the oxygen levels in the cells are relatively low.
This makes a steep concentration gradient between the inside of the erythrocytes and the air in the alveoli.
Oxygen moves into the erythrocytes and binds with the haemoglobin.

Question 24

What is positive cooperativity in blood?

Answer 24

The arrangement of the haemoglobin molecule means that 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.

Question 25

How does oxygen separate from haemoglobin?

Answer 25

The concentration of oxygen in the cytoplasm of the body cells is lower than in erythrocytes.
Oxygen moves out of the erythrocytes down a concentration gradient.

Question 26

What do oxygen dissociation curves show?

Answer 26

Oxygen dissociation curves show the affinity of haemoglobin for oxygen.

Question 27

How is an oxygen dissociation curve graph plotted?

Answer 27

The percentage saturation haemoglobin in the blood is plotted against the partial pressure of oxygen (pO2).

Question 28

Why is the Bohr effect important in the body?

Answer 28

In active tissues with a high partial pressure of carbon dioxide, haemoglobin gives up its oxygen more readily.
In the lungs where the proportion of carbon dioxide in the air is relatively low, oxygen binds to the haemoglobin molecules easily.

Question 29

What is the Bohr effect?

Answer 29

As the partial pressure of carbon dioxide rises, haemoglobin gives up oxygen more easily.

Question 30

How does fetal haemoglobin differ from adult haemoglobin?

Answer 30

Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin at each point along the dissociation curve.
So it removes oxygen from the maternal blood as they move past each other.

Question 31

How is carbon dioxide transported from the tissues to the lungs?

Answer 31

About 5% is dissolved in the plasma.
10-20% is combined with the amino groups in the polypeptide chains of haemoglobin to form a compound (carbaminohaemoglobin).
75-85% is converted into hydrogen carbonate ions (HCO3^-) in the cytoplasm of the red blood cells.

Question 32

What does carbonic anhydrase do?

Answer 32

The enzyme catalyses the reversible reaction between carbon dioxide and water to form carbonic acid (which dissociates to form hydrogen carbonate ions and hydrogen ions).

Question 33

What is the chloride shift?

Answer 33

The negatively charged hydrogen carbonate ions move out the erythrocytes into the plasma by diffusion down a concentration gradient and negatively charged chloride ions move into the erythrocytes, which maintains the electrical balance of the cells.

Question 34

What role does haemoglobin play in erythrocytes during the chloride shift?

Answer 34

It acts as a buffer and prevents changes in the pH by accepting free hydrogen ions in a reversible reaction to form haemoglobinic acid.

Question 35

What is the function of the heart?

Answer 35

Deoxygenated blood enters the right atrium from vena cava. As blood flows in, pressure builds up to open to the atrio-ventricular valve.
The right ventricle contracts fully and pumps deoxygenated blood through the semilunar valves into the pulmonary artery.
At the same time oxygenated blood from the lungs enters the left atrium from the pulmonary vein. As pressure in the atrium builds the bicuspid valve opens between the left atrium and the left ventricle. The left ventricle then contracts and pumps oxygenated blood through semilunar valves into the aorta.

Question 36

What is the structure of the heart?

Answer 36

The heart is made up of cardiac muscle, and surrounded by inelastic pericardial membranes which help prevent the heart from over-distending with blood.
The muscular wall of the left side is much thicker, the right side only has to pump a relatively short distance to the lungs. The left has to produce sufficient force to overcome the resistance of the aorta.
The septum is the inner dividing wall of the heart.

Question 37

What happens in diastole?

Answer 37

In diastole the heart relaxes. The atria and then the ventricles fill with blood.
The volume and pressure of the blood in the heart build as the heart fills, but the pressure un the arteries is at a minimum.

Question 38

What happens at systole?

Answer 38

In systole the atria contract (atrial systole), followed by the ventricles (ventricular systole).
The pressure inside the heart increases and blood is forced out the right side of the heart to the lungs and from the left side to the main body circulation.
The volume and pressure of the blood in the heart are low at the end of systole, and the blood pressure in the arteries is at a minimum.

Question 39

What is the average resting heart rate for an adult?

Answer 39

Around 70bpm.

Question 40

What is the sino-atrial node (SAN)?

Answer 40

The pacemaker.

Question 41

How is the basic rhythm of the heart maintained?

Answer 41

-A wave of electrical excitation begins in the sino-atrial node, causing the atria to contract and so initiating the heartbeat. A layer of non-conducting tissue prevents the excitation passing directly to the ventricles.
-The electrical activity from the SAN is picked up by the atrio-ventricular node (AVN). The AVN imposes a slight delay before stimulating the bundle of His, a bundle of conducting tissue made up of fibres (Purkyne fibres), which penetrate through the septum between ventricles.
-The bundle of His splits into two branches and conducts the wave of excitation to the apex of the heart.
-At the apex the Purkyne fibres spread out through the walls of the ventricles on both sides. The spread of excitation triggers the contraction of the ventricles, starting at the apex. Contraction starting at the apex allows more efficient emptying of the ventricles.

Question 42

What do electrocardiogram (ECG) measure?

Answer 42

The tiny electrical differences in the skin, which result from the electrical activity of the heart.

Question 43

What is Tachycardia?

Answer 43

When the heartbeat is very rapid, over 100 bpm.

Question 44

What is Bradycardia?

Answer 44

When the heart rate slows down to below 60 bpm.

Question 45

What is an Ectopic heartbeat?

Answer 45

Extra heartbeats that are out of the normal rhythm.

Question 46

What is Atrial fibrillation?

Answer 46

An example of arrhythmia, which means an abnormal rhythm of the heart.
Rapid electrical impulses are generated in the atria.
They contract very fast up to 400 times a minute.

Question 47

What is the equation for cardiac output?

Answer 47

cardiac output = heart rate x stroke volume.