Transport in animals

Question 1

What is the role of the circulatory system

Answer 1

To transport gases and nutrients around and organism in a transport liquid. This liquid is transported around in vessels and there is a pump to move the liquid (e.g the heart)

Question 2

Name the types of circulatory system

Answer 2

Open system
Closes system
Double system
Single system

Question 3

What is an open circulatory system

Answer 3

Had by invertebrates such as insects
Transport medium (haemolymph) pumped to an open body cavity (haemocoel)
Very few transport vessels
Transport medium is pumped at low pressure, transports food and nitrogenous waste (not gases which are transported via the tracheal system)
Once the exchange has occurred in cells and tissues, the transport medium returns to the heard via an open ended vessel

Question 4

What is a close circulatory system

Answer 4

Had by vertebrates (e.g fish and mammals) and some invertebrates (annelid worms)
Transport medium (blood) remains inside of the blood vessels
Gases and small molecules can leave blood by diffusion or due to high hydrostatic pressure
Transport oxygen and carbon dioxide, oxygen is usually transported by a pigmented protein (haemoglobin)

Question 5

What is a single closed circulatory system

Answer 5

Had by fish
Blood only passed through heart once per cycle
Blood passes through two sets of capillaries immediately after the heart, blood flows through capillaries in gills to be oxygenated then flows through capillaries delivering blood to the body before returning to the heart
This system works for fish due to the counter current flow mechanism in gas exchange

Question 6

What is a double closed circulatory system

Answer 6

Had by birds and most mammals
Blood passes through heart twice per cycle
One circuit of blood vessels carry blood from heart to lungs for gas exchange and the second carry blood from heart to body to deliver oxygen and nutrients and to collect waste

Question 7

Properties of arteries

Answer 7

The smooth muscle layer is thicker than in veins so that constriction and dilation can occur to control volume and pressure of the blood
The elastic layer is thicker to help maintain blood pressure because these walls can stretch and recoil in response to the heart beat
The collagen outer layer provides structural support
The wall is generally thicker to help maintain the blood pressure

Question 8

Properties of arterioles

Answer 8

The smooth muscle layer is thicker than in arteries to help restrict blood flow into the capillaries
The elastic layer is thinner than in the arteries as the pressure of the blood is lower
The collagen layer is thinner (low pressure means not as much support is needed)
Wall is thinner as the pressure is lower

Question 9

Properties of capillaries

Answer 9

They are one cell thick consisting of only a lining layer (no smooth muscle, elastic or collagen layer) this helps provide a short diffusion distance for exchanging materials

Question 10

Properties of venules

Answer 10

Thin layer of smooth muscle
No elastic or collagen layer
Very thin wall (several venules join to form a vein)
Has valves

Question 11

Properties of veins

Answer 11

Relatively thin smooth muscle layer so it cannot control the blood flow
Relatively thin elastic layer as there is low pressure
Contains a lot of collagen
Thin wall ask risk of vessel bursting is low due to low pressure, thin walls also mean that the vessels are easily flattened which helps the flow of blood up to the heart
Has valves to prevent back flow due to low pressure

Question 12

Describe capillaries

Answer 12

Form capillary beds (many branched capillaries) at exchange surfaces
Have a narrow diameter to slow the blood flow
Red blood cells can only just fit through and are squashed against the walls which maximises diffusion

Question 13

What is tissue fluid

Answer 13

The liquid and small molecules forced out through small gaps in capillaries
Tissue fluid can be formed and reabsorbed due to the interaction between hydrostatic and oncotic pressure

Question 14

What is hydrostatic pressure

Answer 14

The pressure exerted by a liquid

Question 15

What is oncotic pressure

Answer 15

The tendency of water to move into the blood via osmosis

Question 16

How is tissue fluid formed

Answer 16

As blood enters capillaries from attentions, the decreased diameter leads to high hydrostatic pressure, this pressure forces water, glucose, amino acids, fatty acids, ions and oxygen out of the capillaries at the arterial end
This solution that has been forced out is called tissue fluid and bathes the cells in substances that they need

Question 17

How is tissue fluid reabsorbed

Answer 17

Large molecules such as plasma proteins remain in the capillaries and therefore lower the water potential of the blood remaining in the capillary
This lowered water potential will result in higher oncontic pressure
The net movement is back into the capillaries via osmosis
Once equilibrium of the water potential has been reached, no more water from the tissue fluid can be reabsorbed back (the remaining liquid is absorbed into the lymphatic system and will eventually drain back into the bloodstream near the heart)
When the liquid is in the lymphatic system it is called lymph, it is like plasma without the large plasma proteins and less oxygen and nutrients (has been absorbed by cells)

Question 18

Describe features of the mammalian heart

Answer 18

Organ made of cardiac muscle
Responsible for pumping blood around the body
Surrounded by pericardial membranes (inelastic membranes which prevent the heart from filling and swelling with blood)

Question 19

Why is cardiac muscle useful

Answer 19

It is myogenic which means it automatically contracts and relaxes and never fatigues

Question 20

How does the cardiac muscle work

Answer 20

Coronary arteries supply the cardiac muscle with oxygenated blood for aerobic
respiration which provides ATP so the cardiac muscle can continue to contract and relax

Question 21

Internal structures of the heart

Answer 21

Left ventricle has a thicker muscular wall so it can contract with more force and pump the blood at a higher pressure (this is needed so the book will flow all the way around the body)
The right ventricle only pumps blood to the lungs which is much closer and requires blood to flow slowly to allow time for gas exchange, for this reason the muscular wall is thinner.
Both atria have very thin muscular walls because blood is only pumped from atria to ventricles so minimal pressure is required

Question 22

What are the three key stages of the cardiac cycle

Answer 22

Diastole (relaxing)
Atrial Systole (atria contracting)
Ventricular Systole (ventricles contract)

Question 23

Describe the cardiac cycle

Answer 23

At the start, (diastole) is where both the atria and the ventricles are relaxed so there is a larger volume in the chambers so pressure drops and blood flows in to atria from vena cava and pulmonary vein
As blood flows in pressure increases and atroventricular valves are forced open, atria contract which forces the blood from atria to ventricles
Atria then relax and ventricles contract, high pressure in ventricles causes atroventricular valves to shut, the semi lunar valves will open and blood will be pushed out of the ventricle and into the pulmonary artery and aorta

Question 24

How to find cardiac output

Answer 24

Cardiac output= heart rate X stroke volume

where stroke volume is the volume of blood that leaves the heart each beat and heart rate is how many beats per minute

Question 25

What is the cardiac cycle controlled by

Answer 25

Cardiac cycle contracts on its own accord (it’s myogenic) but the rate of contraction is controlled by a wave of electrical activity
The sinoatrial node
(located in the right atrium and it is known as the pacemaker)
The atroventricular node
(located near the border of the right and left ventricle within the atria)
The bundle of his
(runs through the septum)
The purkyne fibres
(in the walls of the ventricles)

Question 26

How is the cardiac cycle controlled

Answer 26

SAN releases a wave of depolarisation across the atria causing it to contract
AVN releases another wave of depolarisation when the first reaches it
Because there is a non conductive layer between the atria and ventricles which prevents the wave of depolarisation, instead the bundle of his conducts a new wave of depolarisation down the septum and the purkyne finres
This causes the apex and the walls of the ventricles to contract, there is a short delay before this happens whilst the AVN transmits the second waves of depolarisation
This allows enough time for the atria to pump all the blood into the ventricles, finally the cells repolarise and the cardiac muscles relax

Question 27

How do you measure the waves of depolarisation

Answer 27

Using an electrocardiogram (ECG) which measures the differences in electrical activity in your skin (which is caused by the electrical activity of the heart) which allows them to be interpreted to diagnose irregularities in heart rhythms.
Electrodes are stuck onto the skin to detect this electrical activity

Question 28

Types of abnormal heart rhythms

Answer 28

Tachycardia- when the heart is beating at over 100bpm
Bradycardia- when the heart is beating at less than 60bpm
Fibrillation- when there is an irregular rhythm of the heart
Ectopic heartbeat- When there are additional heartbeats that are not in rhythm. If happens regularly it could indicate a serious health condition

Question 29

Features of haemoglobin

Answer 29

Groups of globular proteins found in different organisms. Haemoglobin is a protein with a quaternary structure (4 polypeptide chains). Haemoglobin and red blood cells transport oxygen

Question 30

What is myoglobin

Answer 30

Made of one polypeptide chain and found in muscle tissue in vertebrates

Question 31

What does the oxyhaemoglonin dissociation curve show

Answer 31

Oxygen is loaded in regions with high partial pressure of oxygen (eg alveoli) and is unloaded in regions of low partial pressure of oxygen (eg respiring tissues) this is shown on the oxyhaemoglobin dissociation curve

Question 32

What is the bohr effect

Answer 32

When high carbon dioxide concentrations cause the oxyhaemoglobin curve to shift to the right. The affinity for oxygen decreases because the acidic carbon dioxide changes the shape of the haemoglobin slightly
At low partial pressure of carbon dioxide in the alveoli, curve shifts left which means there is an increased affinity and therefore it uploads more oxygen
At high partial pressure of carbon dioxide at respiring tissue, curve shifts right which means there is a decreased affinity and therefore unloads more oxygen

Question 33

Compare haemoglobin in different animals

Answer 33

Fetal haemoglobin-
shifted to left which means it is more saturated with oxygen (higher affinity), beneficial because the foetus needs to get oxygen from the mothers haemoglobin
Llama haemoglobin-
Live at high altitudes so need higher affinity of oxygen because due to low partial pressure their haemoglobin can still load up and become saturated
Dove haemoglobin-
Lower affinity for oxygen (shifted to the right), they have a faster metabolism and therefore benefit from the faster unloading of oxygen
Earthworm haemoglobin-
Underground so lower partial pressure of oxygen, so beneficial that their haemoglobin has higher affinity for oxygen

Question 34

What are the three modes of transporting carbon dioxide

Answer 34

Dissolved in blood plasma as a haemoglobinic acid
Carbon dioxide can react (reversible) with amino acids in haemoglobin to form haemoglobinic acid
In the cytoplasm of red blood cells in the form of hydrogen carbonate ions

85% is transported as hydrogen carbonate ions in red blood cells, water and carbon dioxide react to form hydrogen ions and hydrogen carbonate ions. Carbonic anhydrase (an enzyme in the cytoplasm of RBC) catalyses this reaction
The carbonic acids can diffuse out of the red blood cells and in exchange, chloride ions diffuse in to RBC, both of these ions are negative so the electrical balance is maintained. This is known as the chloride shift