Transport In Animals

Question 1

Why do multocellular organisms require transport systems

Answer 1

Large size (small SA:V) subsequently high metabolic rates
Demand for oxygen is high, so need a specialised system to ensure a strong supply to all respiring tissues

Question 2

Summarise the different types of circulatory system

Answer 2

Open = blood can diffuse out of vessels e.g. insects
Closed = blood confined to vessels e.g. fish, mammals
- Single = blood passes through pump once per circuit of the body
- Double = blood passes through heart twice per circuit of the body

Question 3

Relate the structure of arteries to their function

Answer 3

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

Question 4

Relate the structure of veins to their functions

Answer 4

Thin walls due to lower pressure
Requires valves to ensure blood doesnt flow backwards. Have less muscular and elastic tissue as they dont have to control blood flow

Question 5

Relate the structure of capillaries to their functions

Answer 5

Walls only one cell thick, 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 providing large surface area

Question 6

Relate the structure of arterioles and venules to their function

Answer 6

Branch off 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 7

What is tissue fluid

Answer 7

A watery substance containing glucose, amino acids, oxygen, and other nutrients. It supplies these to the cells, while also removing any waste materials

Question 8

What types of pressure influence formation of tissue fluid

Answer 8

Hydrostatic pressure- higher at arterial end of capillary than venous end
Oncotic pressure - changing water potential of the capillaries as water moves out, induced by proteins in the plasma

Question 9

How is tissue fluid formed

Answer 9

As blood is pumped through increasingly small vessels, hydrostatic pressure is greater than oncotic pressure, so fluid moves out of capillaries. It then exchanges substances within the cells

Question 10

How does tissue fluid differ from blood and lymph

Answer 10

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

Question 11

Describe what happens during cardiac diastole

Answer 11

The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the atriovetricular valves. This allows blood to flow into the ventricles. Pressure in the heart is lower than in the arteries, so semilunar valves remain closed

Question 12

Describe what happens during atrial systole

Answer 12

The atria contract, pushing any remaining blood into the ventricles

Question 13

Describe what happens during ventricular systole

Answer 13

The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves. Blood flows into the arteries

Question 14

How do you calculate cardiac output?

Answer 14

Cardiac output = heart rate x stroke volume

Question 15

What does myogenic mean?

Answer 15

The heart’s contraction is initiated from within the muscle itself, rather than by nerve impulses

Question 16

Explain how the heart contracts

Answer 16

SAN initiates and spreads impulse across the 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 so they contract from the bottom up

Question 17

What is an electrocardiogram (ECG)

Answer 17

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

Question 18

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

Answer 18

Tachycardia = fast heartbeat (>100 bpm)
Bradycardia = slow heart beat (<60 bpm)
Fibrillation = irregular, fast heartbeat
Ectopic = extra or early heartbeat

Question 19

Describe the role of haemoglobin

Answer 19

Present in red blood cells. Oxygen molecules bind to the haem groups and are carried around the body, then released where they are needed in respiring tissues

Question 20

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

Answer 20

As partial pressure of oxygen increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. When partial pressure is low, oxygen is released from haemoglobin

Question 21

What do oxyhaemoglobin dissociation curves show?

Answer 21

Saturation of haemoglobin with oxygen (in %), plotted against partial pressure of Oxygen (in kPa). Curves further to the left show the haemoglobin has a higher affinity for oxygen

Question 22

Describe the Bohr effet

Answer 22

As partial pressure of carbon dioxide increases, the conditions become acidic causing haemoglobin to change shape. The affinity of haemoglobin for oxygen therefore decreases, so oxygen is released from haemoglobin

Question 23

Explain the role of carbonic anhydrase in the Bohr effect

Answer 23

Carbonic anhydrase is present in RBCs
Converts CO2 to carbonic acid, which dissociates to produce H+ ions
These combine with the haemoglobin to form haemoglobinic acid
Encourages oxygen to dissociate from haemoglobin

Question 24

Explain the role of bicarbonate ions (HCO3 -) in gas exchange

Answer 24

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

Question 25

Describe the chloride shift

Answer 25

The intake of chlorine ions across a RBC membrane. This repolarises the cell after bicarbonate ions have diffused out

Question 26

How does foetal haemoglobin differ from adult haemoglobin

Answer 26

The partial pressure of oxygen is low by the time it reaches the foetus, therefore foetal haemoglobin has a higher affinity for oxygen than adult. Allows both mothers and childs oxygen needs to be met