Circulatory system in mammals

Question 2

Describe the pathway of blood through the heart

Answer 2

Vena cava, right atrium, right ventricle, pulmonary artery, lungs,
pulmonary vein, left atrium, left ventricle, aorta, body

Question 3

Name the valves in the heart and describe their location

Answer 3

Atrioventricular valves (between atrium and ventricle on
both side). Semi-lunar valves (in the arteries as they leave
the heart)

Question 4

Compare single and double circulation

Answer 4

Single - blood passes through heart once on each circuit of the body.
Double - blood passes through heart twice on each circuit of the body

Question 5

What does diastole mean?

Answer 5

relaxing

Question 6

What does systole mean?

Answer 6

contracting

Question 7

What is cardiac diastole?

Answer 7

• atria and ventricles relax
• elastic recoil of the heart lowers the pressure inside the heart chambers and blood returns to the heart and fills the atria.
• Pressure increases in the atria until the atrioventricular valves open and blood flows into the ventricles.
  -The relaxed atria and ventricles means that the semi-lunar valves are closed.

Question 8

What is atrial systole?

Answer 8

The atria then contract forcing any remaining blood into the ventricles

Question 9

What is ventricular systole?

Answer 9

• contraction of the ventricles causes the atrioventricular valves to close
• semi-lunar valves open
• blood leaves the heart

Question 10

Explain the volume and pressure changes which take place in the heart during the cardiac cycle

Answer 10

In Atrial systole, the pressure in the heart increases, this remains high in ventricular systole. As the blood leaves the heart and cardiac diastole occurs, the pressure in the heart is lowered. As the heart fills with blood this pressure increases.

Question 11

How are the atria adapted for their function?

Answer 11

thin walls and elastic so they can stretch when filled with blood

Question 12

How are ventricles adapted for their function?

Answer 12

thick and muscular walls pump blood under high pressure. Left ventricle is thicker- has to pump blood all around the body

Question 13

What are the layers that make up blood vessels?

Answer 13

• lumen
• endothelium
• elastic layer
• muscle layer
• tough fibrous outer layer

Question 14

How are arteries adapted for their function?

Answer 14

• have a thicker elastic layer and thinner (compared to arterioles) muscle layer, as they have to withstand blood flowing at high pressures . Walls are thicker- to prevent tearing

Question 15

How are arterioles adapted for their function?

Answer 15

Have thinner elastic layer and thicker muscle layer (when compared to arteries) so they can control blood flow.

Question 16

How are veins adapted for their function?

Answer 16

• have thinner walls as blood is moving at a lower pressure
• have valves to prevent backflow

Question 17

Why is a double circulatory system needed in mammals?

Answer 17

To maintain blood pressure throughout the body. Otherwise, pressure would drop too low (after being in the lungs) and blood would be unable to flow to all areas of the body

Question 18

How are capillaries adapted for their function?

Answer 18

• walls only one cell thick- short diffusion distance
• very narrow- RBC pushed flat against walls, increasing SA and time for diffusion
• numerous and highly branched- large SA

Question 19

What is tissue fluid?

Answer 19

a watery liquid containing glucose, amino acids, oxygen and other molecules. It provides these to the cells whilst also removing waste materials

Question 20

How is tissue fluid formed?

Answer 20

• blood flows through a capillary, there is high hydrostatic pressure at the arterial end
• This forces water and small molecules (oxygen, amino acids, glucose etc.) out of the capillary, leaving behind cells and proteins (ultra-filtration)

Question 21

Explain how water from tissue fluid is returned to the circulatory system

Answer 21

• proteins remain (in blood plasma)
• (Creates) water potential gradient (lower in the blood)
• Water moves (to blood) by osmosis
• Returns (to blood) by lymphatic system

Question 22

Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin

Answer 22

• causes O2 to disassociate more easily
• by changing/ lowering pH and therefore changing the shape of the haemoglobin

Question 23

Explain how the atrioventricular valve maintains a unidirectional flow of blood

Answer 23

• Pressure in atrium is higher than in ventricle causing valve to open
• Pressure in ventricle is higher than in atrium causing valve to close

Question 24

Explain why the binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind

Answer 24

-Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin
-This uncovers a second binding site

Question 25

Explain the role of the heart in the formation of tissue fluid

Answer 25

• Contraction of ventricle(s) produces high
  blood/hydrostatic pressure;
• (This) forces water (and some dissolved
  substances) out (of blood capillaries)

Question 26

What are 4 features of a mammalian circulatory system?

Answer 26

• A suitable medium; for example the blood, which is water based and can therefore dissolve substances
• Means of moving the medium; animals often have a pump known as the heart to maintain pressure differences around the body
• Mechanism to control flow around the body; valves are used in veins to prevent any backflow
• Closed system of vessels; form a branching network to deliver substances all around the body

Question 27

What 2 factors impact whether an organism will have a transport system/pump?

Answer 27

• SA to volume ratio
• how active the organism is

Question 28

How could more red blood cells lead to a heart attack?

Answer 28

• blood thickening
• can block arteries/clot/slows blood flow