3.3.4.1 mass transport in animals

Question 1

Circulatory system

Answer 1

General pattern of blood circulation in a mammal

Question 2

Closed double circulatory system

Answer 2

Blood passes through heart twice for each complete circulation of body

Pulmonary circulation - deoxygenated blood in right side of heart pumped to lungs > oxygenated blood returns to left side of heart

Systemic circulation - oxygenated blood in left side of heart pumped to tissues/organs of body > deoxygenated blood returns to right side

Question 3

Importance of closed double circulatory system in mammals

Answer 3

Prevents mixing of oxygenated and deoxygenated blood > so blood pumped to body is fully saturated with oxygen > efficient delivery of oxygen and glucose for respiration

Blood can be pumped at a higher pressure > substances taken to and removed from the body cells quicker and more efficiently.

Question 4

Coronary arteries

Answer 4

Deliver oxygenated blood to cardiac muscle

Question 5

Aorta

Answer 5

Takes oxygenated blood from heart > respiring tissues

Question 6

Vena cava

Answer 6

Takes deoxygenated blood from respiring tissues > heart

Question 7

Pulmonary artery

Answer 7

Takes deoxygenated blood from the heart > heart

Question 8

Pulmonary vein

Answer 8

Takes oxygenated blood from the lungs > heart

Question 9

Renal arteries

Answer 9

Takes deoxygenated blood > kidneys

Question 10

Renal veins

Answer 10

Takes deoxygenated blood > vena cava from the kidneys

Question 11

Atrioventricular valves

Answer 11

Prevents back flow of blood from ventricles to atria

Question 12

Semi lunar valves

Answer 12

Prevent back flow of blood from arteries to ventricles

Question 13

How the structure of heart relates to function

Answer 13

Atrioventricular valves

Semi lunar valves

Left has a thicker muscular wall

• generates higher blood pressure
• oxygenated blood has to travel greater distance around the whole body

Right has a thinner muscular wall

• generates lower blood pressure
• for deoxygenated blood to travel a small distance to the lungs where high pressure would damage alveoli

Question 14

Arteries

Answer 14

Carry blood from heart to rest of body at high pressure

Question 15

Arteries structure

Answer 15

Thick smooth muscle layer

• contracts pushing blood along
• maintains blood pressure

Elastic tissue layer

• stretches as ventricles contract (when under high pressure) and recoil as ventricle relaxes (when under low pressure)
• evens out blood pressure and maintains high pressure

Thick wall
- withstands high pressure and prevents artery bursting

Smooth and thin endothelium
- reduces friction

Narrow lumen
- increases and maintains high blood pressure

Question 16

Arterioles

Answer 16

Division of arteries to smaller vessels which can direct blood to different capillaries

Question 17

Arterioles structure

Answer 17

Thicker muscle layer than arteries

• constricts to reduce blood flow by narrowing lumen
• dilates to increase blood flow by enlarging lumen

Thinner elastic layer as lower pressure surges

Question 18

Veins

Answer 18

Carry blood back to heart under lower pressure

Question 19

Veins structure

Answer 19

Wider lumen than arteries

Very little elastic and muscle tissue

Valves prevent back flow of blood

Contraction of skeletal muscles squeezes veins, maintaining blood flow

Question 20

Structure of capillaries and importance of capillary beds as exchange surfaces

Answer 20

Capillary wall is 1 cell thick > short diffusion path > rapid diffusion

Capillary bed is made of a large network of branched capillaries > increased SA > rapid diffusion

Narrow lumen > reduces flow rate so more time for diffusion

Capillaries permeate tissues > short diffusion pathway

Pores in walls between cells > allows substances to escape

Question 21

Capillaries

Answer 21

Allow the efficient exchange of gases and nutrients between blood and tissue fluid

Question 22

Tissue fluid

Answer 22

Fluid surrounding cells/tissues

Provides respiring cells with water/glucose/amino acids

Enables waste substances to move back into blood

Question 23

Formation of tissue fluid

Answer 23

At atrioles at end of capillaries

• higher hydrostatic pressure inside capillaries (due to contraction of left ventricle)
• forces fluid out of capillaries, into spaces around cells
• large plasma proteins remain in capillary as too large to leave

Question 24

Return of tissue fluid to the circulatory system

Answer 24

Towards venue end of capillaries

Hydrostatic pressure reduces as fluid leaves capillary

(Due to water loss) an increasing concentration of plasma proteins lowers water potential in capillary below the water potential of the tissue fluid

Water re-enters capillaries from the tissue fluid by osmosis down a water potential gradient

Excess water taken up by lymph system and is returned to the circulatory system through veins in the neck

Question 25

Causes of accumulation of tissue fluid

Answer 25

Low concentration of protein in blood plasma - water potential in capillary not as low so water potential gradient is reduced - more tissue fluid formed at arteriole end High blood pressure can lead to an accumulation of tissue fluid - high blood pressure = high hydrostatic pressure - increases outward pressure from arterial end of capillary - so more tissue fluid formed - and the lymph system is not able to drain tissues fast enough

Question 26

Atrial systole

Answer 26

Atria contract > decreasing volume and increasing pressure inside atria Atrioventricular valves forced open - when pressure inside atria > pressure inside ventricles, atrioventricular valves open Blood pushed into ventricles

Question 27

Ventricular systole

Answer 27

Ventricles contract from the bottom up > decreasing volume and increasing pressure inside ventricles Semilunar valves forced open - when pressure inside ventricles > pressure inside arteries Atrioventricular valves shut - when pressure inside ventricles > pressure inside atria Blood pushed out of heart through arteries

Question 28

Diastole

Answer 28

Atria and ventricles relax > increasing volume and decreasing pressure inside chambers Blood from veins fills atria (increasing pressure inside atria) and flows passively to ventricles Atrioventricular valves open - when pressure inside atria > pressure inside ventricles, blood flows passively to ventricles Semilunar valves shut - when pressure inside arteries > pressure inside ventricles

Question 29

Cardiac output calc

Answer 29

= stroke volume x heart rate

Question 30

Cardiac output

Answer 30

Amount of blood pumped out of the heart per minute

Question 31

Stroke volume

Answer 31

Volume of blood pumped by the ventricles in each heart beat

Question 32

Heart rate

Answer 32

Number of beats per minute

Question 33

Calculating heart beat from cardiac cycle

Answer 33

One beat = one cardiac cycle Find length of one cardiac cycle HR = 60 secs / length of one cycle in secs

Question 34

Semilunar valves closed

Answer 34

When pressure in aorta/pulmonary artery is higher than in ventricle > prevents back flow of blood from arteries to ventricles

Question 35

Semilunar valve open

Answer 35

When pressure in ventricle is higher than in aorta/pulmonary artery > blood flows from ventricle to aorta

Question 36

Atrioventricular valve closed

Answer 36

When pressure in atrium is higher than in ventricle > prevents back flow of blood from ventricle to atrium

Question 37

Atrioventricular valve open

Answer 37

When pressure higher in ventricle than atrium > blood flows from ventricle to atrium

Question 38

CHD

Answer 38

Associated with atherosclerosis and atheroma formation

Question 39

How an atheroma can result in a heart attack

Answer 39

Atheroma causes narrowing of coronary arteries Restricts blood flow to heart muscle supplying glucose, oxygen etc Heart anaerobically respires > less ATP produced > not getting enough energy for heart to contract > lactate produced > damages heart tissue

Question 40

Risk factor of CHD/atheroma

Answer 40

Age Diet high in salt or saturated fat High consumption of alcohol Stressful lifecycle Smoking cigarettes Genetic factors High blood pressure increases risk of damage to endothelium of artery wall which increases risk of atheroma which can cause blood clots (thrombosis)

Question 41

Data interpretation questions

Answer 41

Describe overall trend - pos/neg correlation - linear Describe most obvious trend Manipulate data to support your statements - calculations - work out difference from two points - work out how many times greater - work out percentage change

Question 42

Evaluating study design, things to consider

Answer 42

Small sample size Take into account other variables that could have affected results Used similar groups e.g. age, gender Way in which info collected e.g. questionnaires may be unreliable as people lie or give inaccurate information Results reproduced by other scientists by carrying out more studies and collecting more results

Question 43

Correlations and causal relationships

Answer 43

Correlation - relationship between two variables Causation - a change in one variable will directly cause a change in the other variable However, correlation does not mean there’s a causal relationship, may be another variable that causes both of these variables to change

Question 44

Haemoglobin

Answer 44

Group of chemically similar molecules found in many organisms -chemical structure may differ between organisms e.g. due to diff sequence of amino acids in primary structure Found in red blood cells (erythrocytes) - no nucleus for more haemoglobin - biconcave shape increases SA for rapid diffusion of oxygen

Question 45

Haemoglobin structure

Answer 45

Quaternary structured protein - 4 polypeptide chains wound around each other Each polypeptide chain contains a haem group containing an iron ion which combines with oxygen

Question 46

How oxygen is loaded, transported and unloaded in blood

Answer 46

Haemoglobin in red blood cells transports oxygen - can carry 4 oxygen molecules, one at each haem group In lungs, at a high pO2, haemoglobin has a high affinity for oxygen > oxygen readily loads with haemoglobin At respiring tissues, at a low pO2, oxygen readily unloads from haemoglobin - concentration of CO2 is high, increasing the rate of unloading (Bohr effect)

Question 47

Oxyhaemoglobin dissociation curve

Answer 47

At high pO2, haemoglobin is saturated with O2 At low pO2, haemoglobin is less saturated with O2 The cooperative nature of oxygen binding - why the graph is ‘s’ shaped

Question 48

Dissociation curve reasons

Answer 48

Haemoglobin has a low affinity as the 1st oxygen molecule binds - so from 0% saturation, an increase in pO2 results in a slow increase in saturation (shallow gradient) After the 1st oxygen molecule binds, the shape of haemoglobin changes to make it easier for the 2nd and 3rd oxygen molecules to bind (so haemoglobin has a higher affinity for oxygen) - rate of increase in % saturation increases as pO2, further increases (steep gradient) After the 3rd molecule binds, and haemoglobin becomes saturated, shape of haemoglobin changes in a way that makes it harder for other molecules to bind too - at a high pO2, the rate increase in % saturation decreases

Question 49

Effects of CO2 concentration on dissociation of oxyhaemoglobin- Bohr effect

Answer 49

When rate of respiration is high e.g. during exercise > releases CO2 High pCO2 lowers pH and reduces haemoglobins affinity for oxygen as haemoglobin changes shape - increases rate of oxygen unloading Advantageous because provides more oxygen for muscles for aerobic respiration Oxygen dissociation curve for haemoglobin shifts to the right

Question 50

Curve shifted left

Answer 50

Haemoglobin has a higher affinity for oxygen More oxygen associates with haemoglobin more readily (in lungs) at the lower pO2 but dissociates less readily Advantageous to organisms such as a those living in high altitudes, underground or foetuses

Question 51

Curve shifted right

Answer 51

Haemoglobin has a lower affinity for oxygen Oxygen dissociates from haemoglobin more readily to respiring cells at a higher pO2 but associates less readily Advantageous to organisms such as those with high rate of respiration (metabolic rate) e.g. small/active organisms