Animal Transport

Question 1

What is an open circulatory system?

Answer 1

A circulatory system with a heart or pump but few vessels to contain the transport medium.

Question 2

What is a closed circulatory system?

Answer 2

A circulatory system where blood is enclosed in blood vessels and does not come into direct contact with body cells.

Question 3

What is a single circulatory system?

Answer 3

A circulatory system where the blood flows through the heart once with each full circuit.

Question 4

What is a double circulatory system?

Answer 4

A circulatory system where the blood flows through the heart twice with each full circulation.

Question 5

What is haemolymph?

Answer 5

The transport medium found in insects.

Question 6

What is a mass transport system?

Answer 6

A transport system where substances are transported in a mass of fluid.

Question 7

What is oncotic pressure?

Answer 7

The tendency of water to osmose into the blood from surrounding tissues.

Question 8

At which ends are oncotic pressure and hydrostatic pressure higher?

Answer 8

Hydrostatic pressure highest at arterial end, oncotic pressure higher at venous end.

Question 9

What causes oncotic pressure? Why does it remain constant (3.3kPa)?

Answer 9

Large, dissolved proteins decrease the water potential of blood. These proteins cannot diffuse out, too large.

Question 10

What is the role of tissue fluid?

Answer 10

Bathes cells in required nutrients/reactants for metabolic processes e.g oxygen and glucose. Waste diffuses into it.

Question 11

How does the tissue fluid composition compare to plasma composition?

Answer 11

Less dissolved substances (e.g large proteins), higher proportion of it is water. No blood structures can move across (e.g erythrocytes), some leukocytes can.

Question 12

What % of tissue fluid returns to the capillary? Why?

Answer 12

Oncotic pressure begins to overcome hydrostatic pressure as the blood in the capillary travels toward the venous end, so fluid moves back in. 90% returns. The other 10% becomes lymph.

Question 13

Why is the lymphatic system so important?

Answer 13

Prevents accumulation of unnecessary tissue fluid. Contains leukocytes. Drainage system, gets rid of cellular waste products.

Question 14

Relate the structure of arteries to their function.

Answer 14

Thick muscular walls to maintain high pressure without tearing. elastic tissue allows recoil to prevent pressure surges. Narrow lumen to maintain pressure.

Question 15

Relate the structure of veins to their function.

Answer 15

Thin walls due to low pressure. Valves to ensure blood doesn’t flow backwards. Less muscular and elastic tissue as they don’t have to control blood flow.

Question 16

Relate the structure of capillaries to their function.

Answer 16

One cell thick walls; short diffusion pathway. Very narrow, so can permeate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues. Numerous and highly branched to provide a large SA.

Question 17

Relate the structure of arterioles and venues to their function.

Answer 17

Branch off of arteries and veins in order to feed blood into capillaries. Smaller than arteries and veins so that the change in pressure is more gradual as blood passes through increasingly small vessels.

Question 18

How does tissue fluid differ from blood and lymph?

Answer 18

• Tissue fluid is formed from blood, but does not contain red blood cells, platelets, and various other solutes usually present in blood.
• After tissue fluid has bathed cells 10% becomes lymph, and therefore this contains less oxygen and nutrients and more waste products.

Question 19

Describe what happens during cardiac diastole.

Answer 19

• Ventricles and atria relax.
• Pressure inside the chambers drops below that in the arteries because they are not contracted (higher volume).
• Blood under high pressure in arteries cause semi-lunar valves to shut. (DUB).

Question 20

Describe what happens during atrial systole.

Answer 20

The atria contract, pushing any remaining blood into the ventricles. 70% has already passively flowed down. Atrioventricular valves open due to pressure against them.

Question 21

Describe what happens during ventricular systole.

Answer 21

The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent back flow (LUB), and opening the semilunar valves. Blood flows into the arteries (aorta from left ventricle, pul.artery from right ventricle).

Question 22

How do you calculate cardiac output?

Answer 22

Heart rate x stroke volume.

Question 23

What does myogenic mean?

Answer 23

The heart’s contraction is initiated from with the muscles itself, rather than by nerve impulses.

Question 24

Explain how the heart contracts.

Answer 24

• SAN initiates and spreads impulse across atria, so they contract.
• AVN receives, delays, and then conveys the impulse down the bundle of His.
• Impulse travels into the Purkinje fibres which branch across the ventricles, sending the impulse from the apex of the heart (bottom) upwards.

Question 25

What is an electrocardiogram ((ECG)?

Answer 25

A graph showing the amount of electrical activity in the heart during the cardiac cycle.

Question 26

Describe types of abnormal activity that may be seen on an ECG.

Answer 26

• Tachycardia = fast heartbeat (over 100bpm)
• Bradycardia = slow heartbeat (under 60bpm)
• Atrial fibrillation = fast, irregular heartbeat caused by quivering atrial muscles.
• Ectopic = early or extra heartbeats.

Question 27

Describe the role of haemoglobin.

Answer 27

Present in red blood cells. Oxygen molecules bind to the haem groups and are carried around the body, they dissociate when needed in respiring tissues. The first and last oxygen molecules are more difficult to bind than the second and third.

Question 28

How does partial pressure of oxygen affect oxygen-haemoglobin binding?

Answer 28

• Low ppO2, fewer Hb molecules have 02 molecules bound. Low affinity for oxygen, will readily dissociate at respiring tissues.
• High ppO2, more haem groups bound to oxygen, making it easier for more O2 to be picked up. Will readily associate.

Question 29

Why is it advantageous for Hb to have a higher affinity for oxygen at high oxygen partial pressures and vice versa?

Answer 29

Will readily associate with oxygen at the lungs (high ppO2), will readily dissociate at respiring tissues (low ppO2).

Question 30

Describe the Bohr effect.

Answer 30

As partial pressure of carbon dioxide increases, the conditions becomes acidic causing haemoglobin to change shape. The affinity of haemoglobin for oxygen therefore decreases, so oxygen is therefore released from Hb more readily. The O2 dissociation curve shifts to the right.

Question 31

Why is the Bohr effect advantageous?

Answer 31

At tissues with high ppCO2, oxygen will more readily dissociate.

Question 32

Explain the role of carbonic anhydrase in the Bohr effect.

Answer 32

• C.A is present in RBCs.
• Converts CO2 to carbonic acid, which dissociates to produce H+ ions.
  These combine with the Hb to form haemoglobinic acid.
• Encourages oxygen to dissociate from Hb.

Question 33

Explain the role of HCO3- ions in gas exchange.

Answer 33

Produced by dissociation of carbonic acid. 70% of CO2 is carried in this form. In the lungs, HCO3- ions are converted back into CO2 which we breathe out.

Question 34

Describe the chloride shift.

Answer 34

The intake of chloride ions across a RBC membrane. This repolarises the cell after HCO3- ions have diffused out, balancing the H+ ions.

Question 35

How does foetal Hb differ from adult Hb.

Answer 35

The ppO2 of oxygen is low by the time it reaches the foetus, therefore foetal haemoglobin must have a higher affinity from oxygen so that foetal blood can be transferred oxygen from the mother’s blood at the placenta. Allows for both the mother’s and child’s oxygen needs to be met.

Question 36

What are the properties and functions of myoglobin?

Answer 36

• Myoglobin will only release its O2 at very low ppO2.
• Oxymyoglobin will only dissociate when O2 levels are low.
• Found in muscles cells, acts as a reserve for oxygen.

Question 37

Why is the cardiac muscle described as ‘myogenic’?

Answer 37

• It can initiate its own contractions without the need for nervous stimulation. Impulse originates from within the heart.

Question 38

What is the role of the SAN?

Answer 38

• Muscle cells (myocytes) in the heart have a slight electrical charge across their membranes (polarised). When they become depolarised (charge reversed) they contract. A wave of depolarisation/excitation is initiated in the SAN where there are specialised fibres collectively known as the ‘pacemaker of the heart’.

Question 39

What happens after the SAN initiates the wave of excitation?

Answer 39

• Depolarisation spreads through the atria, where they contract. The electrical wave cannot speed directly to the ventricles due to the region of nonconductive tissue, known as annulus fibrosis, at the base of the atria. This channels the wave of excitation down the septum.

Question 40

What happens after the atria contract?

Answer 40

• The AVN is stimulated by the wave of excitation. Causes a slight delay in the waves transmission, then passes the wave of excitation down to the bundle of His which consists of Purkinje fibres which are conductive. There is only one pathway for the wave of the SAN.

Question 41

What happens after the wave of excitation is passed into the AVN and the bundle of His?

Answer 41

• The bundle of His splits into two branches of Purkinje fibres, based in the apex, which carry the wave to the apex and upwards to the ventricles. This delay enables the ventricles to fill with a sufficient amount of blood before contracting.