3.2 Transport in Animals

Question 1

Why do multicellular organisms require transport systems ?

Answer 1

• Large size (small surface area to volume ratio), 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 heart 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 pressure surges.
Narrow lumen to maintain pressure.
- carry oxygenated blood (except in the pulmonary artery)

Question 4

Relate the structure of veins to their function

Answer 4

Thin walls due to lower pressure.
Require valves to ensure blood doesn’t flow backwards. Have less muscular and elastic tissue as they don’t have to control blood flow.
Carry deoxygenated blood (except the pulmonary vein)

Question 5

Relate the structure of capillaries to their function

Answer 5

• microscopic blood vessels that link the arterioles with the venules
  • 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 a 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 and 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= the pressure exerted by the proteins in the blood plasma. proteins in the blood ,such as albumin, create an osmotic pressure that draws water back into the capillaries

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 the capillaries. It then exchanges substances with the cells

Question 10

How does tissue fluid differ from blood and lymph ?

Answer 10

• 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 it becomes lymph, and therefore this contains less oxygen and nutrients and more waste products

Question 11

What does blood consist of ?

Answer 11

Plasma

carries a wide variety of components: dissolved glucose and amino acids ,red blood cells , platelets and more

Question 12

Functions of the blood

Answer 12

• oxygen to, and carbon dioxide from, the respiring cells
• digested food from the small intestine
• nitrogenous waste products from the cells to the excretory organs
• chemical messages (hormones)
• food molecules from storage compounds to the cells that need them
• platelets to damaged areas
• cells and antibodies involved in the immune response.

Question 13

What is Lymph ?

Answer 13

Lymph is similar in composition to plasma and tissue fluid but has less oxygen and fewer nutrients. Along the lymph vessels are the lymph nodes. Lymphocytes build up here when necessary and produce antibodies , which are the passed into the blood.

Question 14

Human heart diagram with names of chambers , vessels and valves

Question 15

Describe what happens during cardiac diastole

Answer 15

The heart is relaxed . Blood enters the atria, increasing the pressure and pushing open the atrioventricular 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 16

Describe what happens during atrial systole (first part of the systolic phase)

Answer 16

The atria contract, pushing any remaining blood into the ventricles

Question 17

Describe what happens during ventricular systole (second part of the systolic phase)

Answer 17

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

Question 18

how to calculate Cardiac Output

Answer 18

Heart rate x stroke volume

Question 19

What does myogenic mean ?

Answer 19

The ability of the heart to generate its own electrical impulses.

Question 20

Explain how the heart beat is initiated and how the contractions of the four chambers are coordinated

Answer 20

• a wave of electrical excitation /depolarisation begins in the right atrium in the area called the pacemaker (SAN)
  • SAN initiates and spreads impulse across the atria, so they contract.(atrial systole)
  • AVN receives, delays, and then conveys the impulse down where it is split up into left and right branches
• the heart is myogenic - it has the ability to generate its own electrical impulses
• the impulse travels down these branches , on the side of these branch are purkinje tissue (fibres)
• purkinje fibres are found on the walls of the ventricles and stimulate the ventricles to contract
• therefore, forcing blood out the ventricles - ventricular systole

Question 21

What is an electrocardiogram(ECG) ?

Answer 21

A graph showing the amount of electrical activity in the heart during the cardiac cycle (the mechanic event of one heart beat)

Question 22

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

Answer 22

• Tachycardia= fast heartbeat (over 100bpm)
• Bradycardia= slow heartbeat (under 60bpm)
• Fibrillation= irregular, fast heartbeat
• Ectopic= early or extra heartbeats

Question 23

Describe the role of haemoglobin

Answer 23

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 24

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

Answer 24

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 25

What do oxyhaemoglobin dissociation curves show ?

Answer 25

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

Question 26

Describe the Bohr effect

Answer 26

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 27

Explain the role of carbonic anhydrase in the Bohr effect

Answer 27

• Carbonic anhydrase is present in red blood cells. • Converts carbon dioxide 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 28

Explain the role of bicarbonate ions in gas exchange

Answer 28

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

Question 29

Describe the chloride shift

Answer 29

The intake of chloride ions across a red blood cell membrane, this repolarises ( returning to its resting state) the cell after bicarbonate ions have diffused out

Question 30

How does fetal haemoglobin differ from adult haemoglobin?

Answer 30

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

Question 31

what three different ways is carbon dioxide transported from the tissues to the lungs ?

Answer 31

• About 5% is carried dissolved in the plasma. • 10-20% is combined with the amino groups in the polypeptide chains of haemoglobin to form a compound called carbaminohaemoglobin. • 75-85% is converted into hydrogen carbonate ions in the cytoplasm of the red blood cells.

Question 32

Compare the circulatory systems of mammals and fish

Answer 32

Similarities: - Both are closed systems , meaning blood is confined to vessels - Both have a heart - Both carry oxygen using haemoglobin - Both have arteries/veins/capillaries

Question 33

Contrast the circulatory systems of mammals and fish

Answer 33

Differences: - Fish has a single circulation, blood through heart once. Mammals have a double circulation , blood through heart twice. - one atrium and 1 ventricle , 2 chambers ( in heart of fish). Two atria and 2 ventricles , 4 chambers (in heart of mammals). - in fish blood passes through 2 sets of capillaries (blood returning to the heart ). In mammals blood passes through one set of capillaries (blood returning to the heart) - in fish blood pressure in lower. In mammals blood is maintained at high pressure -fish are less efficient at transporting oxygen to tissues . Mammals are more efficient in transporting oxygen to tissues

Question 34

Outline how the difference between lumen size of arteries and veins is related to their function

Answer 34

- Arteries have a narrow lumen to maintain high pressure -veins have a wide lumen to ensure easy blood flow at low pressure - same flow rate is achieved by having a larger volume/cross sectional area

Question 35

Explain why the oncotic pressure of the blood depends only on the concentration of large plasma proteins

Answer 35

- large plasma proteins cannot pass out through capillary wall/leave the blood, but other solutes can -imbalance of large plasma proteins between blood and tissue fluid results in oncotic pressure

Question 36

Describe the similarities between ultrafiltration and the formation of tissue fluid

Answer 36

• Small molecules diffuse out of the blood. - Both processes our in capillaries. % Large molecules/proteins/ cells, remain in the blood. • High (hydrostatic) pressure in both processes. ・Many molecules (e.g. water, sugars, ions) are reabsorbed back into capillaries.

Question 37

Describe the differences between ultrafiltration and the formation of tissue fluid

Answer 37

-Molecules that are not reabsorbed by capillaries form urine in the kidney, but molecules that are not reabsorbed from tissue fluid will, enter cells / form lymph. • Blood filtered through 3(named) layers in ultrafiltration, but only 1 (named) layer in formation of tissue fluid • knot of capillaries in ultrafiltration but a network of capillaries in formation of tissue fluid

Question 38

Which subdivision of the peripheral system supplies the SAN ?

Answer 38

Autonomic

Question 39

Describe and explain why people with a hole in the septum of the heart can easily become tired

Answer 39

- deoxygenated blood passes into left ventricle (during atrial systole) - less oxygenated blood pumped around the body - less oxygen available for aerobic respiration

Question 40

Describe the events taking place at the points marked W, X, Y and Z and explain how these events are related to the changes in pressure shown in the diagram. ( look and relate to diagram )

Answer 40

Chambers: ventricles begin to contract at Y ventricles are relaxing between W and Y .. atria relaxed at W, X, Y and Z atrial contraction completed before Y. Valves: • A-V / bicuspid, valve closes at Y and opens at X • semilunar / aortic, valve opens at Z and closes at W. Pressure: • At W ventricular pressure falls below aortic pressure • At X ventricular pressure falls below atrial pressure • At Y ventricular pressure rises above atrial pressure • At Z ventricular pressure rises above aortic pressure.

Question 43

What is cooperative binding and how does it relate to haemoglobin?

Answer 43

Cooperative binding is when the binding of one oxygen molecule to haemoglobin increases the affinity of the remaining subunits for oxygen. Haemoglobin has 4 subunits, and each oxygen molecule that binds causes a conformational change, making it easier for the next one to attach. This explains the S-shaped oxygen dissociation curve, showing efficient oxygen loading in the lungs and unloading in tissues.