Transport in animals

Question 1

What does myogenic mean?

Answer 1

Produce excitations spontaneously, without nerve cell stimulation

Question 2

What is the order of events that cause a heartbeat?

Answer 2

1. Sino-atrial node generates an electrical signal, causing the atria to contract (from the bottom)
2. The atrioventricular valve receives the signal and channels it down the bundle of His.
3. This signal then spreads through the Purkyne fibres and causes the ventricles to contract.

Question 3

What do the heart valves do?

Answer 3

Valves prevent blood flowing backwards and only open when the pressure behind the valve from incoming blood exceeds pressure in the ventricle or arteries.

Question 4

Why is the heart thicker on the left side?

Answer 4

It means that the blood is forced into the atrium under more pressure, thus keeping it travelling quickly.

Question 5

What are the four mains points of interest in an electrocardiogram?

Answer 5

1. The atrioventricular valve closing
2. The semilunar valve opening
3. The semilunar valve closing
4. The AV valve opening

Question 6

How thick is the muscle layer in the:
Arteries
Arterioles
Capillaries
Venules
Veins

Answer 6

Arteries : Thick
Arterioles : Thickest
Capillaries : None
Venules : Thin
Veins : Thin

Question 7

How thick is the elastic layer in the:
Arteries
Arterioles
Capillaries
Venules
Veins

Answer 7

Arteries : Thick
Arterioles : Thin
Capillaries : None
Venules : Thin
Veins : Thin

Question 8

How thick are the following vessels overall:
Arteries
Arterioles
Capillaries
Venules
Veins

Answer 8

Arteries : Thick
Arterioles : Medium
Capillaries : 1 cell thick
Venules : Thin
Veins : Thin

Question 9

Why do only veins have valves? What also helps this reason?

Answer 9

The valves prevent a backflow of blood due to low pressure. Muscle contraction also helps with this.

Question 10

Why do arteries have a thick elastic layer?

Answer 10

They can stretch and recoil, allowing them to withstand the high pressure of blood

Question 11

Why are capillaries so thin?

Answer 11

To maximise rate of diffusion

Question 12

What components can be found in tissue fluid?

Answer 12

Oxygen
Salts
Sugars
Amino acids
Fatty acids
Hormones

Question 13

How does tissue fluid form?

Answer 13

Tissue fluid is a result of two pressures: Hydrostatic and oncotic.
Hydrostatic pressure is due to the contraction of the heart. It pushes the fluid out of the capillaries. It decreases across the tissue fluid.
Oncotic pressure is due to the water potential gradient caused by plasma proteins in the vessels. This means that at the end of the capillary, when oncotic pressure is greater than hydrostatic pressure, water and other substances re-enter the blood stream.

Question 14

What happens to the tissue fluid that does not re-enter the blood?

Answer 14

It drains into the lymph vessels.

Question 15

Why is there a delay between atrial and ventricular systole?

Answer 15

To ensure that all blood has been drained from the atriums

Question 16

Why do animals need specialised transport systems?

Answer 16

1. They have high metabolic demands, and so diffusion is not enough to supply the needed quantities
2. The SA:Volume ratio gets smaller as multicellular organisms get larger, so not only do diffusion distances get bigger but surface area becomes relatively smaller.
3. Molecules such as enzymes may be made in one place but needed in another
4. Food will be digested in one organ system, but needs to be transported to every cell to use for respiration and other aspects of cell metabolism.
5. Waste products need to be removed from the cells.

Question 17

What are the three layers of most blood cells and what is between these layers?

Answer 17

Outmost - Tunica externa
Middle - Tunica media
Internal - Tunica intima
There is a lamina layer between each of these layers

Question 18

What makes up blood?

Answer 18

Red blood cells
White blood cells
Platelets
Blood plasma

Question 19

What are the steps of oxygen dissassociation?

Answer 19

Carbon dioxide diffuses into erythrocytes and is reacted with water by carbonic anhydrase to form carbonic acid

Carbonic acid dissociates into hydrogen carbonate, which diffuses out of the cells, and hydrogen ions

Negative chloride ions diffuse into the cell to balance the positive hydrogen ions – chloride shift.

The hydrogen ions bind to haemoglobin, producing haemoglobinic acid and causing dissociation of oxygen

Question 20

How does partial pressure of oxygen effect dissociation?

Answer 20

The higher the partial pressure, the lower the dissociation