Adaptation For Transport In Animals

Question 1

Types of circulatory systems

Answer 1

Open, closed, single, double

Question 2

Open circulatory system

Answer 2

Blood is pumped into a haemocoel where it
bathes organs and returns slowly to the heart
with little control over direction of flow. Blood
is not contained in blood vessels.

Question 3

Closed circulatory system

Answer 3

Blood is pumped into a series of vessels;
blood flow is rapid and direction is controlled.
Organs are not bathed by blood but by tissue fluid that leaks from capillaries

Question 4

Single circulatory system

Answer 4

Blood passes through the heart once in each
circulation.

Question 5

Double circulatory system

Answer 5

Blood passes through the heart twice in each
circulation – once in the pulmonary (lung)
circulation and then again through the
systemic (body) circulation.

Question 6

Insect circulatory system

Answer 6

Open circulatory system.Dorsal tube-shaped heart. No respiratory pigment in blood as lack of respiratory gases in blood due to tracheal gas exchange system

Question 7

Earthworms

Answer 7

Closed circulatory.
5 pseudohearts.
Respiratory pigment haemoglobin carries respiratory gases in blood

Question 8

Fish circulatory system

Answer 8

Closed, single circulatory system.
Blood pumped to and oxygenated in the gills continues around body tissues.
This means a lower pressure and slower flow around the body

Question 9

Mammals circulatory system

Answer 9

Closed, double circulatory system.
High blood pressure to body delivers oxygen quickly.
Lower pressure to lungs prevents hydrostatic pressure forcing tissue fluid into and reducing efficiency of alveoli

Question 10

Structure of arteries

Answer 10

Thick layer of smooth muscle that contracts and relaxes to alter blood flow to different organs.
Thick layer of elastic tissue recoils to propel blood forward and even out flow.
Tough collagen outer coat to prevent overstretching.
Small lumen surrounded by smooth endothelium to prevent friction.

Question 11

Structure of veins

Answer 11

Larger lumen as blood is under lower pressure.
This gives less resistance to blood flow.
Less muscle and elastic fibres. Instead, veins contain semilunar valves to prevent backflow of blood

Question 12

Structure of capillaries

Answer 12

A single layer of endothelium giving a short
diffusion path

Question 13

The mammalian heart

Answer 13

Superior vena cava, atrium left ventricle, right atrium, right ventricle, aorta, pulmonary valve pulmonary artery, by cuspid and tricuspid valves, septum and apex

Question 14

Superior vena cava

Answer 14

Returns deoxygenated blood to the heart

Question 15

Right atrium

Answer 15

Contracts and pumps the oxygenated blood into the right ventricle

Question 16

Tricuspid valve

Answer 16

Pressure of contraction of the atrium opens his valve which then closes, preventing the backflow to the right atrium when the ventricles contract.

Question 17

Right ventricle

Answer 17

Thinner muscular wall compared to left ventricle as less pressure is produced on contraction

Question 18

Aorta

Answer 18

Carries oxygenated blood from the left ventricle to the body

Question 19

Pulmonary artery

Answer 19

Takes deoxygenated blood to lungs from right ventricle

Question 20

Semilunar valves

Answer 20

In aorta and pulmonary arteries they prevent blood flowing back into the ventricles between heartbeats

Question 21

Bicuspid valve

Answer 21

Prevents backflow of blood into the left atrium when the ventricles contract

Question 22

Left ventricle

Answer 22

Thicker muscular wall than right ventricle to produce a higher pressure to push oxygenated blood rapidly around body

Question 23

Septum

Answer 23

wall dividing oxygenated blood and deoxygenated blood side of heart

Question 24

The cardiac cycle

Answer 24

Atrial systole, ventricular systole, ventricular diastole, diastole

Question 25

Atrial systole

Answer 25

Atrial contract.
Pressure opens atrio-ventricular valves.
Blood flows into ventricles.

Question 26

Ventricular
systole

Answer 26

Ventricles contract.
Atrio-ventricular valves close due to pressure in
ventricles being higher than that in the atria.
Semilunar valves in aorta and pulmonary artery open.
Blood flows into arteries.

Question 27

Ventricular
Diastole

Answer 27

Ventricle muscle relaxes.
Semilunar valves close to prevent backflow of
blood into the ventricles.

Question 28

Diastole

Answer 28

Heart muscle relaxes and atria begin to fill
from vena cava and pulmonary vein

Question 29

Initiating the heartbeat

Answer 29

The heartbeat is myogenic; initiation comes
from the heart itself.
•The sinoatrial node acts as a pacemakers sending waves of excitation across the atria causing them to contract simultaneously.
•A layer of connective tissue prevents the wave of excitation passing down to the ventricles. The wave of excitation passes to the atrio-ventricular node where there is a delay to allow the atria to complete contraction.
•The atrio-ventricular node transmits impulses down the bundle of His to the apex of the heart.
•The impulse then travels up the branched
Purkinje fibres, simulating ventricles to contract from the bottom up. This ensures all the blood is pumped out.

Question 30

Pressure changes in the heart

Answer 30

Contraction of the thick muscular wall
(systole) increases the pressure in the
ventricle. When the pressure in the ventricle
exceeds the pressure in the aorta, the semilunar valve leading to the aorta is forced open and blood enters the aorta, increasing the pressure.
As the ventricle wall relaxes (diastole), the pressure drops in both the ventricle and the aorta. The semilunar valve closes, preventing blood flowing back into the ventricle.
Elastic recoil of the aorta walls increases pressure momentarily. As the ventricles fully relax, contraction in the atria walls causes the atrio-ventricular valves to open and the ventricle to refill with blood. Pressure in atrium increases as it contracts, forcing blood through the atrio-ventricular valves into the ventricles. As the atria empty, the valves snap shut.

Question 31

Electrocardigan

Answer 31

The electrical activity that spreads through the heart during
the cardiac cycle can be detected using electrodes placed
on the skin and shown on a cathode ray oscilloscope. This is
called an electrocardiogram (ECG).

Question 32

Waves on electrocardiogram

Answer 32

P wave Depolarisation of the atria corresponding to atrial systole.
QRS wave Spread of depolarisation through the ventricles resulting in ventricular systole.
T wave Repolarisation of the ventricles resulting in ventricular diastole.

Question 33

Chloride shift

Answer 33

Some CO2 is carried in the blood dissolved in plasma, while
some is carried in the blood as carbaminohaemoglobin.
However, most is carried as hydrogen carbonate ions as
shown below

Question 34

Sequence of chloride shift

Answer 34

1 CO2 diffuses into a red blood cell (RBC).
2 CO2 combines with H2O catalysed by the enzyme carbonic anhydrase, forming carbonic acid.
3 Carbonic acid dissociates into hydrogen ions (H+) and
hydrogen carbonate ions (HCO3-) diffuse out of the RBC
into the plasma.
4 Chloride ions (Cl-) diffuse (facilitated diffusion) into the RBC to maintain electrochemical neutrality – the chloride shift.
5 H+ bind to oxyhaemoglobin, reducing its affinity for oxygen. This is the Bohr effect.
6 Oxygen is released from the haemoglobin.
7 Oxygen diffuses from the RBC into the plasma and body
cells.

Question 35

Formation of tissue fluid

Answer 35

– a link between blood
and cells. This is important as plasma transports nutrients,
hormones and excretory products and also distributes heat.
1. At the arterial end of the capillary bed, hydrostatic
pressure is higher than osmotic pressure.
2. Water and small soluble molecules are forced through
the capillary walls, forming tissue fluid between the cells.
3. Proteins and cells in the plasma are too large to be
forced out.
4. Due to reduced volume of blood and friction, blood
pressure falls and it moves through the capillary.
5. At the venous end of the capillary bed, osmotic pressure
of the blood is higher than the hydrostatic pressure.
6. Most of the water from tissue fluid moves back into
blood capillaries (down its water potential gradient). The
remainder of the tissue fluid is returned to the blood via the lymph vessels

Question 36

Oxygen dissociation curves

Answer 36

Red blood cells transport oxygen. Haemoglobin has a high
affinity for oxygen. Each molecule of haemoglobin can carry
four oxygen molecules, forming oxyhaemoglobin. This
reaction is reversible.

Question 37

Oxygen dissociation curves and how they vhange

Answer 37

A – a sigmoid curve that shows haemoglobin
has a high affinity for oxygen at high partial
pressures of oxygen (the lungs) but releases
it readily at lower partial pressures (respiring
tissues).
B – Where CO2 is present the Bohr shift occurs
and the curve moves to the right, meaning
haemoglobin has a lower affinity for oxygen,
releasing it more readily. This is helpful in respiring
tissues.
Myoglobin - curve shifts to the left. It has a high
affinity for O2 and holds on to it until partial
pressures of O2 are really low, it then releases it
rapidly. It acts as a store of O2 in muscle.
Foetal haemoglobin - curve just to the left, a
higher affinity for O2 than haemoglobin at all
partial pressures so foetus can take O2 from all mothers blood.