Heart

Question 1

The heart rate of a sleeping person is low. Explain how nerves supplying the heart may produce a low heart rate in a sleeping person.

Answer 1

Impulses;
	Along parasympathetic/vagus;
OR	Fewer impulses;
	Along sympathetic/(cardiac)accelerator;
	Slows activity from SAN/pacemaker;

Question 2

why are both the heart and arteries are described as organs

Answer 2

Contain different/more than one tissue/type of cell;

Question 3

what is the formula for cardiac output?

Answer 3

heart rate x stroke volume

Question 4

Suggest two ways in which prolonged high blood pressure may affect the arteries.

Answer 4

Muscle in artery walls becomes thicker;
Aneurysm / ballooning of artery walls may occur;
Damage to endothelium (so foam cells enter);

Question 5

which blood vessels in the heart contain oxygenated blood?

Answer 5

aorta and pulmonary vein

Question 6

why is there more pressure in the aorta than in the pulmonary artery?

Answer 6

left ventricle with thicker wall/more muscle / (muscle in) left ventricle
contracts more forcefully/beats more strongly;

Question 7

what causes the difference in pressure bewteen the fet and right ventricle

Answer 7

Left ventricle has thicker / more muscle;

Question 8

When may the atrioventricular valves shut?

Answer 8

when the pressure in the ventricle is greater than the pressure in the atrium

Question 9

explain how the structures of the walls of arteries, veins and capillaries are related to their functions.

Answer 9

Artery:
1. thickest wall, enabling it to carry blood at high pressure
2. most elastic tissue, which maintains pressure;
3. most muscle which also maintains pressure;
4. muscle in wall to control blood flow;
Vein:
5. thin wall does not have to withstand high pressure;
Capillary:
6. thin wall, allowing diffusion
7. only endothelium present, allowing short diffusion pathway;
All vessels
8. have endothelium that reduces friction;

Question 10

Explain why a pulse cannot be felt when the fingers are placed over a vein which is close to the surface.

Answer 10

Pressure constant / smooth in vein / only have pressure

surges in artery

Question 11

Describe how

this tissue fluid is returned to the circulatory system.

Answer 11

1. Hydrostatic pressure is lower in capillary
2. So Water returns
3. By osmosis.
4. Water potential is lower in the capillary and higher in the tissue fluid
5. Due to protein in blood;
6. So the tissue fluid returns via lymph system

Question 12

An arteriole is described as an organ. Explain why

Answer 12

Made of different tissues

Question 13

An arteriole contains muscle fibres. Explain how these muscle fibres reduce blood flow
to capillaries.

Answer 13

1. Muscle contracts;

2. Arteriole reduces size of lumen which is vasoconstriction;

Question 14

A capillary has a thin wall. This leads to rapid exchange of substances between the
blood and tissue fluid. Explain why.

Answer 14

Short diffusion pathway;

Question 15

Blood flow in capillaries is slow. Give the advantage of this

Answer 15

More time for exchange of

substances

Question 16

Explain why a lack of protein in the blood causes a build up of tissue fluid

Answer 16

1. Water potential in capillary is higher so
2. Less water moves back into the capillary
3. By osmosis

Question 17

A leaf is an organ. What is an organ?

Answer 17

a group of TISSUES