2.3 adaptation or transport in animals

Question 1

what are the types of circulatory system?

Answer 1

open, closed, single, double

Question 2

open system

Answer 2

Blood is pumped into a haemocoel where it bathes organs and returns slowly to the heart with little control over direction of flow. Blood is not contained in blood vessels.

Question 3

Closed system

Answer 3

Blood is pumped into a series of vessels; blood flow is rapid and direction is controlled.Organs are not bathed by blood but by tissue fluid that leaks from capillaries.

Question 4

single system

Answer 4

Blood passes through the heart once in each circulation.

Question 5

double system

Answer 5

Blood passes through the heart twice in each circulation - once in the pulmonary (lung) circulation and then again through the systemic (body) circulation.

Question 6

disadvantage of single system

Answer 6

The disadvantage of single circulation is that the blood loses pressure around the circuit, resulting in slower circulation.

Question 7

advantage of double system

Answer 7

The advantage of a double circulation is that the blood is repressurized when it leaves the gas exchange surface, giving a faster and more efficient circulation to the tissues.

Question 8

the cardiac cycle: Atrial systole

Answer 8

• Atrial contract.
• Blood is forced into ventricles making them relax
• Pressure opens AV valves and ventricle fills with blood

Question 9

the cardiac cycle: Ventricular systole

Answer 9

• Ventricles contract.
• AV valves close due to pressure in ventricles being higher than that in the atria which passively fills with blood
• Semilunar valves in aorta and pulmonary artery open.
• Blood is forced into arteries.

Question 10

the cardiac cycle: Ventricular Diastole

Answer 10

• Ventricle muscle relaxes.
• Semilunar valves close to prevent backflow of
  blood into the ventricles.

Question 11

the cardiac cycle: Diastole

Answer 11

Heart muscle relaxes and atria begin to fill from vena cava and pulmonary veins.
- pressure increases to force AV valve to open.
- ventrioles relax and blood passively enters ventrioles from atria

Question 12

the flow of blood through the heart:

Answer 12

both sides of the heart work together. both atria contracts at the same time as well as both ventricles. after contraction and the chamber has been emptied it relaxes to be filled again. the ventricles are more muscular than the atria as they need to generate more pressure. the left ventricular wall is much thicker than the right because it has to pump blood all around the body but the right ventricle only pumps blood to the lungs, a much shorter distance.

Question 13

initiating heartbeat:

Answer 13

• The heartbeat is myogenic; initiation comes from the heart itself.
• The sinoatrial node acts as a pacemaker sending waves of excitation across the atria causing them to contract simultaneously.
• A layer of connective tissue prevents the wave of excitation passing down to the ventricles. The wave of excitation passes to the AV node where there is a delay to allow the atria and ventricle to not contract at the same time.
• The AV node transmits impulses down the bundle of His to the apex of the heart.
• The impulse then travels up the branched Purkinje fibres, simulating ventricles to contract from the bottom up. This ensures all the blood is pumped out.

Question 14

what is meant by the cardiac muscle is myogenic?

Answer 14

It naturally contracts and relaxes of its own accord, it doesn’t need nerve impulses to contract.

Question 15

full sequence of initiating heartbeat:

Answer 15

1. diastole
2. SAN/peacemaker and atrial systole
3. atrioventricular node
4. ventricular systole
5. diastole

Question 16

what does P wave represent in the electrocardiogram?

Answer 16

P wave shows SAN generating electrical impulses causing the depolarisation of the atria which causes contractions of the atrial systole

Question 17

what does QRS wave represent in the electrocardiogram?

Answer 17

QRS shows AVN transmitting electrical impulses that pass through the bundle of his causing the spread of depolarisation through the ventricles resulting in ventricular systole contracting

Question 18

what does T wave represent in the electrocardiogram?

Answer 18

T wave shows the repolarisation of the ventricles which causes ventricular diastole

Question 19

Bohr effect curve: explain how low CO2 levels affect the pH of the blood

Answer 19

as CO2 increases carbonic acid is formed by lowering the pH. when curve is moved to the right more CO2 is produced. haemoglobin changes shape making it harder for oxygen to bind.

Question 20

formation of tissue fluid

Answer 20

This is important as plasma transports nutrients, hormones and excretory products and also distributes heat.

Question 21

What happens at the arterial end of a capillary bed?

Answer 21

• hydrostatic pressure is higher than osmotic pressure.
• Water and small soluble molecules are forced through the capillary walls, forming tissue fluid between the cells.
• Proteins and cells in the plasma are too large to be forced out.
• Due to reduced volume of blood and friction, blood pressure falls and it moves through the capillary.

Question 22

What happens at the venous end of a capillary bed?

Answer 22

• osmotic pressure of the blood is higher than the hydrostatic pressure.
• Most of the water from tissue fluid moves back into blood capillaries (down its water potential gradient). The remainder of the tissue fluid is returned to the blood via lymphatic vessels.