B3.2 - transport in mammals (6d)

Question 1

What is the role of capillaries?

Answer 1

Capillaries carry blood through tissues and allow exchange of materials between blood and the internal or external environment.

Question 2

How is the structure of the capillaries adapted for their function?

Question 3

What are the features of veins on a micrograph in terms of:
- Muscle walls
- Elastic fibre layer
- Impact on shape
- Lumen to wall ratio
- Valves

Answer 3

Muscle walls - Thinner
Elastic fibre layer - Thinner
Impact on shape - Does not maintain a ring shape
Lumen to wall ratio - Larger
Valves - Yes (may not be visible)

Question 4

What is the role of the arteries?

Answer 4

Arteries convey blood at high pressure away from the heart to tissues.

Question 5

How is the structure of arteries adapted for their function?

Answer 5

• Thick layers of muscle tissues in the walls of arteries help them to withstand high blood pressures, preventing rupturing.
• Narrow lumen maintains a high blood pressure.
• Thick elastic tissue allows artery to stretch and recoil to maintain sufficiently high blood pressure and help push the blood.
• Muscle layers contract to increase and control blood flow.
• Folding in the endothelium allow stretching.
• Smooth endothelium reduces friction.

Question 6

What is the role of veins?

Answer 6

Veins collect blood at low pressure from the tissues in the body and return it to the heart.

Question 7

How is the structure of veins adapted for their function?

Answer 7

• Wide lumens reduce resistance to blood flow.
• Valves to prevent backflow.
• Flexibility of the wall to allow it to be compressed by muscle action to move blood through the vessels, particularly against gravity.

Question 8

How can we determine the heart rate using traditional methods?

Answer 8

Traditional methods involve using fingertips to feel the pulse within the arteries that are close to the skin’s surface, and counting the number within a minute.
- carotid pulse at the side of the neck
- radial pulse at the wrist

Question 9

How can we determine heart rate using digital methods?

Answer 9

• pulse rate = using infrared light to detect the expansion of arteries blood as pumped through them (pulse oximeters and fitness trackers)
• heart rate = detecting small electrical currents generated by pacemaker cells in the heart during the cardiac cycle

Question 10

What are the risk factors for occlusion of coronary arteries?

Answer 10

• Age
• Ethnicity
• Genetics
• Fatty diet (high LDL/HDL, transfats or saturated fats)
• Lifestyle
• Comorbidities (obesity, diabetes)

Question 11

How does coronary heart disease develop?

Answer 11

1. Risk factors.
2. Plaque formation in arteries.
3. Artery walls harden and become less flexible.
4. Plaque breaks off or ruptures.
5. Damage to artery walls.
6. Activates blood clot formation.
7. Clots may block a coronary artery.
8. Reduced blood flow and oxygen supplied to heart muscle.
9. May cause heart muscle death = heart attack.

Question 12

What is plaque?

Answer 12

Plaque is a substance, including cholesterol and lipids, that builds up on artery walls.

Question 13

What does epidemological mean?

Answer 13

Relating to disease prevalence in a population

Question 14

What are the positives of epidemological data?

Answer 14

• Large sample sizes are often possible

Question 15

What are the negatives of epidemological data?

Answer 15

• Causes of death may be misattributed, both risking under and over reporting figures
• Most analyses rely on data reported from several different sources which may not be reliable
• Researcher bias may be introduced when selecting data to analyze from very large sets

Question 16

How can we use error bars to determine the strength of a correlation?

Answer 16

The positive correlation between age and CHD prevalence is stronger than the negative correlation between habitual exercise and cardiovascular mortality risk as the error bars are relatively small for the age data.

Question 17

How can we use correlation coefficients to determine strength of a correlation?

Answer 17

The negative correlation between raised cholesterol and cardiovascular mortality is stronger than the positive correlation between BMI and cardiovascular mortality because the correlation coefficients has a larger absolute value than cholesterol data.

Question 18

How do correlation coefficients inform us about the data?

Answer 18

Low correlation coefficients or lack of any correlation could provide evidence against a hypothesis.

Question 19

What is a limitation of using correlation coefficients?

Answer 19

Even strong correlation (r=0.92) does not prove a causal link.

Question 20

How can we distinguish between arteries and veins on a micrograph in terms of:
- Muscle walls
- Elastic fibre layer
- Impact on shape
- Lumen to wall ratio
- Valves