Topic 1 - Heart and Circulation

Question 1

Define mass flow

Answer 1

The transport of substances in bulk from one part of an organism to another

Question 2

Why can larger organisms not rely only on diffusion

Answer 2

Low surface area to volume ratio

Question 3

Mass transport allows organisms to overcome:

Answer 3

The limitations of diffusion

Question 4

Main function of exchange surfaces?

Answer 4

To establish and maintain differences in conc and pressure

Question 5

Two examples of mass flow systems

Answer 5

Xylem and phloem in a plant

Question 6

Name 4 features of a mass flow system

Answer 6

1. A system of vessels to carry substances
2. A means of making sure substances are moving in right direction
3. A means of maintaining conc gradient so that substances move fast enough to meet organisms needs
4. Suitable transport medium

Question 7

2 types of circulatory system

Answer 7

Closed - mammals

Question 8

Summary of open circulation

Answer 8

1. Simple heart pumps blood into cavities surrounding insects organs
2. Substances diffuse in/out of cells directly into blood
3. Heart relaxes, blood is drawn back into heart though small calves along length of heart

Question 9

Closed circulatory systems are generally for…

Answer 9

Larger animals that are more active

Question 10

Critical structural difference between open and closed circulation

Answer 10

Closed: blood is enclosed in tubes (arteries, veins, capillaries)

Question 11

Main advantage of closed system

Answer 11

Blood is forced along narrow channels, creating higher blood pressure

Question 12

Why is higher blood pressure better

Answer 12

Blood travels faster so more efficient at delivering substances around the body

Question 13

What type of circulatory system do fish have

Answer 13

Single

Question 14

What’s the main feature of single circulation

Answer 14

Blood only flows through heart once for each circulation

Question 15

3 steps of single circulation

Answer 15

1. Heart pumps deoxygenated blood to gills
2. Gas exchange takes place as blood passes through gills (large SA)
3. Blood leaves gills, oxygenates body, returns to heart

Question 16

Describe simply double circulation

Answer 16

1) right ventricle pumps deoxygenated blood to lungs to be oxygenated
2) blood returns to heart, pumped a second time from left ventricle to rest of body

Question 17

Advantages of double circulation

Answer 17

• blood can be pumped at power pressure to lungs, reducing risk of vessel damage
• blood returning from lungs gets an extra boost, speeding circulation around the body

Question 18

Two types circulation in humans:

Answer 18

Pulmonary circulation- low pressure, from heart to lungs, (40mmHg)

Systemic circulation- high pressure, carries blood from heart to body and back, (120mmHg)

Question 19

Structure of capillaries

Answer 19

Smaller diameter means RBCs have to flex to pass though, slows down so more time for diffusion
-
Endothelium is permeable to water and dissolved substances
-
Small pores in walls

Question 20

Structure of arteries near the heart

Answer 20

Middle layer is composed of elastic fibres, allowing them to dilate then elastically recoil

Question 21

Structure of arteries further from the heart

Answer 21

Supplied with neurones that can stimulate vasodilation/constriction

Question 22

Structure of arterioles

Answer 22

Smallest type of arteries, consist of endothelium with a few muscle fibres wrapped around them

Question 23

Structure of veins

Answer 23

Much less muscle and elastic fibres in middle layer, so wall is thinner 
-
Diameter of lumen is greater
-
Valves to prevent back-flow

Question 24

How do skeletal muscles help to circulate blood?

Venous return

Answer 24

Contract, squeezing veins, create higher pressure in vein

Question 25

What coronary arteries

Answer 25

Supply the heart with blood - Can not get from 4 chambers directly

Question 26

Cardiac cycle =

Answer 26

One complete sequence of contraction and relaxation

Question 27

2 main stages of cardiac cycle

Answer 27

Systole: heart contracts, pumps blood through Aorta and pulmonary artery - Diastole: heart relaxes, fills with blood

Question 28

What happens in atrial systole

Answer 28

``` Atria contract - This pushes blood into ventricles - Opens atrio-ventricular valves ```

Question 29

What happens in ventricular systole

Answer 29

``` Ventricles contract - Atria relax - A/V valves close - Blood enters aorta and pulmonary vein, opening semi-lunar valves ```

Question 30

What happens in ventricular diastole

Answer 30

``` Ventricles relax - Semi-lunar valves close - Pressure in ventricles fall so blood flows into them from atria - A/V valves open ```

Question 31

What is cardiac diastole

Answer 31

When both atria and ventricles are relaxed at the same time

Question 32

What artery takes blood from heart to body at high pressure

Answer 32

Aorta

Question 33

How is the left ventricle structural adapted for us function

Answer 33

Has thicker more muscular walls

Question 34

What is the function of atrioventricular valves?

Answer 34

Link atria to ventricles - Stop backflow when ventricles contract

Question 35

Where are semi-lunar valves found?

Answer 35

Pulmonary artery - Aorta

Question 36

What’s the function of semi lunar valves

Answer 36

Stop blood flowing back into the heart

Question 37

Four structural features of an artery

Answer 37

``` Elastic tissue - Thick muscle layer - Lumen - Folded endothelium ```

Question 38

4 features of a vein

Answer 38

``` Large lumen - Think muscle wall - Valves - Endothelium ```

Question 39

What are capillaries for?

Answer 39

Metabolic exchange- substances are exchanged between cells and capillaries

Question 40

Contraction is...

Answer 40

Systole

Question 41

Relaxation is of the heart is...

Answer 41

Diastole