3. Heart & Circulation

Question 1

2 factors determining whether an organism needs a transport system

Answer 1

1. SA to volume ratio: could nutrients reach all parts of the organism by diffusion alone?
2. How active is the organism?

Question 2

6 important common features of transport systems

Answer 2

1. Suitable medium to carry nutrients - usually a liquid (blood)
2. Closed system of tubes (blood vessels)
3. Form of mass transport in which liquid is moved in bulk over large distances/faster than diffusion (heart)
4. Mechanisms to maintain movement in one direction (valves, maintaining a high pressure)
5. Means of controlling the flow to different parts of the organisms (constriction/dilation of blood vessels)
6. Mechanisms for gas exchange

Question 3

What is meant by a closed circulatory system?

Answer 3

Blood stays/is contained within the blood vessels

Question 4

What is the advantage of a double circulatory system?

Answer 4

Blood goes through the heart twice

Different pressures: high in systemic circuit, low in pulmonic circuit

Question 5

What is the blood vessel going from the heart to the gut called?

Answer 5

Mesenteric artery

Question 6

What does the hepatic portal vein do?

Answer 6

Blood goes to the liver so that excess glucose can be removed & stored as glycogen
Toxins can also be removed

Question 7

All the layers of a blood vessel (innermost to outermost)

Answer 7

Lumen
Endothelium
Elastic tissue
Muscle layer
Tough fibrous outer layer

Question 8

Describe the endothelium

Answer 8

Smooth & flat

Question 9

Function of the tough fibrous outer layer

Answer 9

Prevents damage

Question 10

Why do veins have a lower pressure than arteries?

Answer 10

Pressure comes from the heart, so by the time blood gets to the veins the pressure is much lower

Question 11

Function of thick muscular layer in arteries

Answer 11

Allows them to constrict & dilate to control the volume of blood flowing to particular organs

Question 12

Do veins need to constrict or dilate?

Answer 12

No

Question 13

Function of thick elastic layer in arteries

Answer 13

Allows for stretch & recoil as the heart beats

Question 14

Function of gaps between cells in capillary wall

Answer 14

Allows WBCs to leave capillaries and enter tissues (esp. phagocytes)

Question 15

How thick is the endothelial cell wall in capillaries?

Answer 15

One cell thick; short diffusion distance!

Question 16

Elaborate on the narrow lumen in capillaries?

Answer 16

• RBCs pushed up against the capillary wall: reducing diffusion distance
• Whole blood vessel is narrow: it can fit between cells in the tissue. No cell is far from a capillary.

Question 17

What is tissue fluid?

Answer 17

Fluid that bathes the cells. Water with solutes such as glucose, amino acids etc dissolved in it.

Question 18

How is tissue fluid formed?

Answer 18

High hydrostatic pressure in arteriole end of the capillary: water & small molecules are forced out of the capillaries through the small pores in the capillary walls (ultrafiltration).
Plasma forced out of capillaries to become tissue fluid.

Question 19

What happens in the venules (tissue fluid)?

Answer 19

Lower hydrostatic pressure in venule end of capillary than in tissue fluid, so fluid moves back into capillaries.
Low WP in capillaries because lots of water was forced out at the arteriole end. This means water moves from the tissue fluid into the blood vessel by osmosis.

Question 20

What is meant by excess tissue fluid, and where does it go?

Answer 20

Tissue fluid that didn’t move back into the capillaries

It drains into the lymphatic system

Question 21

What do heartstrings do?

Answer 21

Stop the valves from opening the wrong way

Question 22

Why is the wall of the left ventricle thicker than the right?

Answer 22

Needs to be able to contract with enough force to produce enough pressure to push blood around the body

Question 23

Is the right AV valve the tricuspid or bicuspid?

Answer 23

Tricuspid

Question 24

Do the left and right sides of the heart contract together or separately?

Answer 24

TOGETHER

Question 25

What is diastole?

Answer 25

When the heart relaxes

Question 26

What is systole?

Answer 26

When a particular chamber contracts (e.g. atrial/ventricular systole)

Question 27

Ultimately, what does the cardiac cycle rely on?

Answer 27

Changes in PRESSURE!

Question 28

What happens in diastole?

Answer 28

Blood flows in from the veins into the atria. Blood also starts to trickle down into the ventricles (due to gravity)

Question 29

What are the semi-lunar valves doing in diastole?

Answer 29

They are closed! | Pressure in arteries > pressure in ventricles, preventing backflow of blood from arteries into ventricles

Question 30

What happens in atrial systole?

Answer 30

- Atrial walls contract - This increases atrial pressure - Pressure in atria > pressure in ventricles - This pushes the AV valves open and pushes blood into ventricles

Question 31

What happens in ventricular systole?

Answer 31

- Ventricular walls contract, increasing the pressure in the ventricles - Pressure in ventricles > pressure in atria - This pushes AV valves closed - This also pushes semi-lunar valves open, and pushes blood into arteries

Question 32

In a heartbeat, what is the lub and what is the dub?

Answer 32

``` Lub = AV valves closing during ventricular systole Dub = semi-lunar valves closing ```

Question 33

Valves open and close because of...

Answer 33

pressure differences!

Question 34

Formula for cardiac output

Answer 34

Cardiac output = heart rate x stroke volume

Question 35

Cardiac output

Answer 35

Volume of blood pumped by one ventricle per minute

Question 36

Heart rate

Answer 36

Number of heartbeats per minute

Question 37

Stroke volume

Answer 37

Volume of blood pumped by one ventricle per heartbeat

Question 38

P wave on an EKG

Answer 38

Excitation of the atria

Question 39

QRS complex on an EKG

Answer 39

Excitation of the ventricles

Question 40

T wave on an EKG

Answer 40

Diastole

Question 41

Heart muscle can be described as...

Answer 41

myogenic

Question 42

What does myogenic mean?

Answer 42

Contractions of the heart muscle are initiated within the heart muscle itself, not the nervous system

Question 43

The role of the nervous system is...

Answer 43

to speed up or slow down heart rate

Question 44

Which contracts first: atria or ventricles?

Answer 44

Atria!

Question 45

Where is the sinoatrial node (SAN)?

Answer 45

In the wall of the right atrium

Question 46

What does the sinoatrial node do?

Answer 46

Initiates an impulse which spreads out through the atrial walls, stimulating them to contract

Question 47

What does the atrioventricular node (AVN) do?

Answer 47

Conducts the impulse from the SAN into the ventricles (the only route for the ventricular walls to receive the impulse)

Question 48

What does the non-conducting layer in the heart wall between the atria and ventricles do?

Answer 48

Stops the impulse spreading down into the ventricular walls

Question 49

Where do the impulses go to after passing through the AVN?

Answer 49

Pass down the Purkinje fibres in the bundle of His to the heart apex

Question 50

What happens after impulses pass down the Purkinje fibres?

Answer 50

They spread up through the ventricle walls causing contraction from the apex upwards. Blood is squeezed into the arteries.

Question 51

What is the role of the coronary arteries?

Answer 51

Supply oxygen and glucose to the heart muscle for aerobic respiration

Question 52

What is atherosclerosis?

Answer 52

Narrowing of the blood vessels

Question 53

What can atherosclerosis lead to?

Answer 53

Angina: pain in the heart caused by lactic acid from anaerobic respiration Heart attacks: part of the cardiac muscle stops respiring

Question 54

What causes the lumen to have a reduced volume?

Answer 54

Build up of saturated fats & cholesterol in the blood vessel wall

Question 55

What is an atheroma?

Answer 55

The buildup itself causing atherosclerosis

Question 56

What is coronary heart disease (CHD)?

Answer 56

Disease caused by atherosclerosis in the coronary arteries

Question 57

Risk factors for CHD

Answer 57

1. Smoking 2. Genetics 3. Diet (high in saturated fats & cholesterol) 4. Lack of exercise 5. Age 6. Gender (men more likely to get it) 7. High blood pressure 8. Blood cholesterol (HDLs & LDLs)

Question 58

How is cholesterol transported around the body?

Answer 58

In lipoproteins

Question 59

Types of lipoproteins

Answer 59

High or low density (HDL & LDL)

Question 60

Is LDL bad or good?

Answer 60

Bad - made of saturated fats - transport cholesterol to the body, so much more likely to end up in a blood vessel & cause atherosclerosis

Question 61

Is HDL bad or good?

Answer 61

Good - made of unsaturated fats - transports cholesterol to the liver which uses it in useful ways (e.g. making bile)

Question 62

What is a thrombosis?

Answer 62

A blood clot that forms inside the blood vessels, and it can block blood flow

Question 63

What can thrombosis in the brain do?

Answer 63

Cause a stroke

Question 64

Link between atherosclerosis & thrombosis

Answer 64

1. Atherosclerosis disrupts blood flow, so making thrombosis more likely 2. Atherosclerosis narrows blood vessels: thrombosis could block the blood vessel/get stuck. Basically thrombosis becomes more of a problem.