Unit 1: Section 5 - Transport in Animals

Question 1

How does a fish’s circulatory system work?

Answer 1

The heart pumps blood to the gills to pick up oxygen and then through the rest of the body in a single circuit.

Question 2

How does a mammals circulatory system work?

Answer 2

1) The right side of heart pumps blood to the lungs to collect oxygen
2) From lungs it travels to the left side of the heart, which pumps it to the rest of the body
3) When blood returns to the heart, it enters the right side again

Question 3

What is the pulmonary system?

Answer 3

The system that sends blood to the lungs

Question 4

What is the systemic system?

Answer 4

The system that sends blood to the rest of the body

Question 5

What do the atrioventricular and semi lunar valves do?

Answer 5

atrioventricular links the atria to the ventricles and the semi lunar valves link the ventricles to the pulmonary artery and aorta

Question 6

When is a valve forced open/shut

Answer 6

Open - when the pressure behind a valve is higher than in
front
Closed - when the pressure behind a valve is lower than in front

Question 7

Which ventricle is thicker and why?

Answer 7

Left is thicker than right because it needs to contract powerfully to pump blood all the way around the body so it is under higher pressure than the right.

Question 8

Outline the three stages of the cardiac cycle

Answer 8

1) Ventricles relax, atria contract - The atria fill with blood increasing the pressure within them. The higher pressure causes the atrioventricular valves to open allowing blood to flow into the ventricles. The atria then contract, forcing the remaining blood out
2) Ventricles contract, atria relax - The pressure is higher in the ventricles than the atria, so the atrioventricular vales close. The high pressure in the ventricles open the semi-lunar valves - forcing blood into the pulmonary artery and aorta
3) Ventricles and atria relax. Lowers pressure in both, this means that higher pressure in aorta and pulmonary artery causes semi-lunar valves to close. The atria then fills with blood and cycle starts again.

Question 9

What is the sino-atrial node and where is it found?

Answer 9

Its sets the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls. It is found in the wall of the right atrium.

Question 10

Why is the cardiac muscle known as ‘myogenic’?

Answer 10

Because it can contract and relax without receiving signals from nerves.

Question 11

What does the band of non-conducting collagen tissue do?

Answer 11

Prevents the waves of electrical activity from being passed directly from the atria to the ventricles.

Question 12

What does the atrioventricular node do?

Answer 12

The impulse is transferred from the SAN to the atrioventricular node. The AVN is responsible for passing the waves of electrical activity onto the bundle of His.

Question 13

Why is there a slight delay before the AVN reacts?

Answer 13

To make sure that the ventricles contract after the atria has emptied.

Question 14

What is the bundle of His?

Answer 14

A group of muscle fibres responsible for conducting the waves of electrical activity to the purkyne tissue in the right and left ventricle walls.

Question 15

What does the purkyne tissue do?

Answer 15

Carries the waves of electrical activity into the muscular walls of the right and left ventricles, causing them to contract simultaneously, from the bottom up.

Question 16

What does an electrocardiograph do?

Answer 16

Records the electrical activity of the heart.

Question 17

What happens to a hearts electric activity when it contracts and relaxes?

Answer 17

When it contracts its depolarises (loses charge)

When it relaxes it repolarises (gains charge)

Question 18

What does it mean if your heartbeat is too fast?

Answer 18

During exercise a high heart rate is fine, but at rest it shows that the heart isn’t pumping blood efficiently.

Question 19

What does it mean if the atria are contracting but sometimes the ventricles are not?

Answer 19

There may be a problem with the AVN - impulses aren’t travelling from the atria to the ventricles

Question 20

What is fibrillation?

Answer 20

A really irregular heartbeat. The atria or ventricles completely lose their rhythm and stop contracting properly.

Question 21

What do arteries do and what is their structure?

Answer 21

Carry blood from the heart to the rest of the body. Their walls are thick and muscular and have elastic tissue to cope with the high pressure produced by the heartbeat. The inner lining is folded, allowing the artery to expand - again helping to cope with high pressure.

Question 22

What type of blood do all arteries carry and what is the exception?

Answer 22

Oxygenated blood and the pulmonary arteries carry de-oxygenated to the lungs.

Question 23

What do capillaries do and what is their structure?

Answer 23

Substances like glucose and oxygen are exchanged between cells and capillaries, so they’re adapted for efficient diffusion.

Question 24

What do veins do and what is their structure?

Answer 24

Take blood back to the heart under low pressure. They’re wider than arteries with very little elastic or muscle tissue. Veins contain valves to stop blood flowing backwards. Blood flow through veins is also helped by muscle contraction around the veins. All veins carry de-oxygenated blood except for the pulmonary veins which carry oxygenated blood to the heart from the lungs.

Question 25

What is tissue fluid?

Answer 25

The fluid that surrounds cells in tissues. Its made from substances that leave the blood e.g. oxygen, water and nutrients.

Question 26

How do substances move out of the capillaries and into the tissue fluid?

Answer 26

By pressure filtration

Question 27

Outline the steps involved in pressure filtration

Answer 27

At the start of the capillary bed, nearest the arteries, the pressure inside the capillaries is greater than in the tissue fluid, this forces fluid out of the capillaries into the spaces around the cell, forming tissue fluid. As fluid leaves, the pressure reduces in the capillaries - so the pressure is much lower at the end of the capillary bed. Due to fluid loss, the water potential at the end of thhe capillaries nearest the veins is lower than in the tissue fluid, so some water re-enters the capillaries from the tissue fluid at the vein end by osmosis.

Question 28

Why does tissue fluid not contain red blood cells or big proteins?

Answer 28

Because they are too big to be forced out of the capillaries.

Question 29

Outline the steps involved in pressure filtration

Answer 29

At the start of the capillary bed, nearest the arteries, the pressure inside the capillaries is greater than in the tissue fluid, this forces fluid out of the capillaries into the spaces around the cell, forming tissue fluid.

Question 30

What do arteries do and what is their structure?

Answer 30

Carry blood from the heart to the rest of the body

Question 31

How does the fluid not taken into the blood by osmosis eventually get returned to the blood? (name of system)

Answer 31

Through the lymphatic system

Question 32

How does the excess tissue fluid get back into the blood? (procedure)

Answer 32

1) The smallest lymph vessels are the lymph capillaries. 2) Excess tissue fluid passes into lymph vessels. Once inside it is called lymph 3) Valves in the lymph vessels stop the lymph from ging backwards 4) Lymph gradually moves towards the main lymph vessel in the thorax. Here it is returned to the blood, near the heart.

Question 33

See table on page 41

Answer 33

.

Question 34

What is oxygen carried around the body as?

Answer 34

Oxyhaemoglobin

Question 35

Describe the structure of haemoglobin

Answer 35

Large protein with a quaternary structure. It's made up of 4 polypeptide chains. Each chain has a haem group which contains iron and gives haemoglobin its red colour.

Question 36

What does oxygen do when the partial pressure of oxygen is high and when it is low?

Answer 36

High - Oxygen loads onto haemoglobin to form oxyhaemoglobin Low - Oxyhaemoglobin unloads it's oxygen where there's a lower partial pressure of oxygen

Question 37

Which haemoglobin has a higher affinity for oxygen, fetal or adult?

Answer 37

fetal

Question 38

Why does fetal haemoglobin have to have a higher affinity to oxygen?

Answer 38

Because the fetus gets oxygen from it's mothers blood across the placenta, by the time the blood reaches the placenta, its oxygen saturation has decreased, as some of it has been used up by the mothers body. For the fetus to get enough oxygen to survive its haemoglobin has to have a high affinity for oxygen.

Question 39

Why does the concentration of CO2 affect the rate of oxygen unloading?

Answer 39

1) Most of the CO2 produced by respiring tissues is converted into carbonic acid by the enzyme carbonic anhydrase. 2) The carbonic acid splits up to give hydrogen ions and hydrogencarbonate ions. 3) This increase in hydrogen ions causes oxyhaemoglobin to unload its oxygen so that haemoglobin can take up the hydrogen ions. This forms a compound called haemoglobinic acid. 4) The hydrogencarbonate ions diffuse out of the red blood cells and are transported into the blood plasma. 5) When the blood reaches the lungs the low partial pressure of CO2 causes the hydrocarbonate and hydrogen ions to recombine into CO2 6) The CO2 then diffuses into the alveoli and is breathed out.