unit 3b Flashcards
1
Q
how is tissue fluid formed?
A
- at the start of the capillary (arteriole end) the hydrostatic pressure inside capillaries is greater than the hydrostatic pressure in the tissue fluid
- difference in hydrostatic pressure means an overall outward pressure forces liquid out of capillaries and into spaces around cells forming tissue fluids
2
Q
how is water reabsorbed into capillaries?
A
- hydrostatic pressure reduced in capillaries as fluid leaves- hydrostatic pressure lower at venule end
- due to fluid loss and an increasing conc of plasma proteins, the water potential at venule end is lower than water potential in tissue fluid
- water re-enters the capillaries from venule end by osmosis
3
Q
what happens to any excess tissue fluid?
A
drained into lymphatic system which transports this excess fluid from the tissues and dumps it back into circulatory system
4
Q
Hb structure
A
- quaternary structure
- soluble
- globular protein
- 4 polypeptide chains
- 2 beta and 2 alpha chains
- each haem group contains an iron ion
- each haemoglobin carries 4 O2 molecules
5
Q
what does Hb have a high affinity for?
A
oxygen
6
Q
equation for Hb
A
Hb + 402 ⇋ Hb08
7
Q
xylem vessels
A
- part of xylem tissue
- transports water and ions
- very long, tube-like structures formed from dead cells making an uninterrupted tube allowing water to pass up the middle easily
8
Q
what do xylem tissues do
A
transport water and mineral ions in solution and these substances move up the plant from roots to leaves
9
Q
cohesion tension theory
A
- water evaporates from the leaves at the top of xylem (transpiration)
- creates tension (suction) pulling water into leaf
- water molecules are cohesive (stick together) whole column of water in xylem from leaves to roots (moved upwards)
- adhesion of water to the xylem vessels also aids in resisting gravity
- water enters the stem through the roots
10
Q
transpiration
A
- water evaporates from the moist cell walls and accumulated in spaces between cells in leaf
- when stomata open it moved out the leaf down the concentration gradient (more water inside than outside air)
11
Q
cohesion
A
a force resulting from attraction between molecules of the same substance
12
Q
adhesion
A
a force resulting from attraction between molecules of different substances
13
Q
four main factors affecting transportation rate
A
light
humidity
temperature
wind
14
Q
light
A
- lighter means faster transpiration rate stomata open for co2 for photosynthesis
- when it’s dark the somata are usually closed, so less transpiration
15
Q
temperature
A
- higher the temp the faster transpiration rate
- warmer water molecules have more energy so they evaporate faster
- increases conc gradient between inside and outside of leaf, making water diffuse out the leaf faster
16
Q
humidity
A
- the lower the humidity the faster the transpiration rate
- if air around the plant is dry, the conc gradient between the leaf and the air is increased which increases transpiration
17
Q
wind
A
- the windier it is the faster the transpiration rate
- lord of air movement blows away water molecules from around the stomata
- increases the conc gradient which increases the rate of transpiration
18
Q
dissociation curve for adult human haemoglobin
A
- where pO2 is high (eg lungs) Hb has a high affinity for oxygen (readily combine with O2 so high saturation of O2)
- where pO2 is low (eg respiring tissues)Hb has low affinity for oxygen (releases oxygen rather than combining with it- low saturation of O2)
19
Q
why is a dissociation graph S-shaped?
A
- binding of the first O2 molecule causes a change in the tertiary structure of haemoglobin, which uncovers another haem group (binding site)
- this makes it easier for the 2nd + 3rd O2 molecule to bind (cooperative bonding)
- but it is difficult for the 4th O2 to bind (so curve plateaus before 100%)
20
Q
co2 concentrations effect on bonding
A
- when cells respire they produce CO2 raising pCO2
- increases O2 unloading so dissociation curve shifts right
- saturation of blood with oxygen is lower than for a given pO2 meaning more O2 is being released
- bohr effect
21
Q
foetal Hb
A
- foetal Hb has a higher affinity for oxygen than adult Hb
- at same pO2 foetal Hb will load more oxygen
- so foetal Hb can load more oxygen from mothers blood
- foetal Hb dissociation curve is to the left of adult Hb
22
Q
organisms living in environments with low oxygen conc
A
- haemoglobin has higher affinity for oxygen
- even at low pO2 Hb will load more oxygen
- dissociation curve is to the left
23
Q
organisms with high oxygen requirements
A
- haemoglobin has a lower affinity for oxygen
- Hb will unload more oxygen for cells to use in respiration
- dissociation curve is to the right
24
Q
why do multicellular organisms need a circulatory system
A
-they have a low surface area to volume ratio so they require specialised transport system to carry raw materials from specialised exchange organs to their body cells
25
which blood vessel carries deoxygenated blood from kidneys to heart
renal vein
26
which blood vessel carries oxygenated blood to kidneys
renal artery
27
which blood vessel carries deoxygenated blood from liver to heart
hepatic vein
28
blood vessel carrying oxygenated blood from heart to gut and liver
gut= hepatic portal vein
| liver=hepatic artery
29
vena cava
deoxygenated blood to heart
30
aorta
oxygenated blood to body
31
pulmonary artery
deoxygenated blood to lungs
32
arteries structure
-carry blood from heart to body
-walls are thick and muscular and have elastic tissues to stretch and recoil as heart beats- helps maintain high pressure
-endothelium is folded allowing artery to stretch
-
33
arterioles
- directs blood into different areas of demand in body by muscles inside arterioles
- which contract and relax allowing blood to flow fully or to restrict it
34
veins
- take blood back to heart under low pressure
- wider lumen with very little elastic or muscle tissue
- contain valves to stop blood from flowing backwards
- blood flow is helped by contraction of body muscles surrounding them
- carry deoxygenated blood
35
capillaries
- found near cells in exchange tissues- short diffusion pathway
- walls only one cell thick- short diffusion pathway
- large number of capillaries to increase surface area for exchange
- network of capillaries in tissue are called capillary beds
36
why is the left ventricles walls more muscular than the right ventricles
it needs to contract powerfully to pump blood all the way round the body
-right side only needs to get blood to lungs which is close
37
why do ventricles have thicker walls than the atria
-they have to push blood out of heart whereas the atria just need to push blood a short distance into the ventricles
38
atrioventricular valves
-link atria to ventricles and stop blood flowing back into atria when ventricles contract
39
semi-lunar valves
link ventricles to pulmonary artery and aorta and stop blood flowing back into heart after ventricles contract
40
cords
attach AV valves to the ventricle to stop them being forced up into atria when ventricles contract
41
cardiac cycle
an ongoing sequence of contractions and relaxations of atria and ventricles that keep blood continuously circulating round the body
42
cardiac cycle 1 ventricles relax, atria contracts
- ventricles relaxed atria contracts decreasing volume of chambers and increasing pressure inside chambers
- this pushes the blood into the ventricles
- slight increase in ventricular pressure and chamber volume as ventricles receive ejected blood from contracting atria
43
cardiac cycle 2 ventricles contract, atria relax
- atria relax, ventricles contract (decreasing their volume) increasing their pressure
- pressure becomes higher in ventricles than the atria which forces AV valves to shut to prevent backflow
- pressure in ventricles is higher than in aorta and pulmonary artery
- this forces open the SL valves and blood is forced out into these arteries
44
cardiac cycle 3 ventricles relax, atria relaxes
- higher pressure in pulmonary artery and aorta closes SL valves to prevent backflow into ventricles
- blood returns to heart and atria fill again due to higher pressure in vena cava and pulmonary vein
- this starts to increase the pressure of atria
- as ventricles continue to relax their pressure falls down below the pressure of the atria so AV valves open
- allows blood to flow passively into ventricles from atria
- atria contracts cycle repeats
45
atheroma
- endothelium is usually smooth and unbroken damage to it can cause white blood cells and lipids from blood to clump together under lining to form fatty streaks
- increases overtime more white blood cells, lipids and connective tissues build up and harden to form a fibrous plaque called atheroma
- plaque blocks lumen of artery restricting blood flow and increasing blood pressure
46
what are the two diseases that can affect the arteries?
aneurysm and thrombosis
47
aneurysm
- atheroma damage and weaken arteries also narrowing them and increasing blood pressure
- when blood travels through weakened artery at high pressure it may push the inner layers of the artery through outer elastic layer to form a balloon like swelling-
- may burst causing haemorrhage
48
thrombosis
- atheroma ruptures the endothelium of artery
- damages the artery wall leaving rough surface
- platelets and fibrin accumulate at site of damage and form blood clot- thrombosis
- can cause complete blockage of arteries or it can become dislodged and block a blood vessel somewhere else in body
- debris from rupture can cause another blood clot further down artery
49
myocardial infraction
- if a coronary artery becomes completely blocked an area of the heart will be totally cut off from its blood supply receiving no oxygen causing a heart attack
- can cause damage and death to heart muscles
- symptoms may be pain in chest and upper body shortness of breath and sweating
- if large area, complete heart failure can occur
50
factors increasing CVD- high blood cholesterol and poor diet
- one of the main constituents of the fatty deposits that form atheroma
- atheroma can lead to increased blood pressure and blood clots
- could block flow of blood to coronary arteries, leading to myocardial infraction
- a diet high in saturation fats is associated with high blood cholesterol levels
- a diet high in salt also increases the risks as it increases blood pressure
51
factors increasing CVD- cigarette smoking
- nicotine increases blood pressure
- carbon monoxide combines with haemoglobin and reduces the amount of oxygen transported in blood also reduces amount of oxygen available to tissues- lack of O2 to heart muscles can lead to heart attack
- decreases amount of antioxidants in blood- important protecting cells against damage
- fewer antioxidants means cell damage in coronary arteries wall is more likely- leading to atheroma formation
52
factors increasing CVD- high blood pressure
- increases risk of damage to artery walls
- damaged walls have an increased risk of atheroma formation increasing blood pressure
- atheroma can cause blood clots to form
- leading to block flow of blood to heart muscles possibly resulting in myocardial infraction
- other factors with high blood pressure are being overweight, not exercising, excess alcohol consumption
53
potometer
- whilst underwater cut a shoot to prevent air from entering the xylem, cut it at a slant increase surface area available for water uptake
- potometer is removed from the water and all joints sealed with waterproof jelly
- an air bubble introduced into capillary tube
- as water is lost from the leaves by transpiration it is replaced by water in capillary tube
- distance bubble moves in a given time is used to calculate volume of water lost
- water from reservoir is used to move the bubble back to starting position so repeats can be taken
54
ringing experiments
- phloem vessels can be selectively removed by cutting a ring in a stem just deep enough to cut the phloem, but not xylem this is left for a period of time
- swelling seen above ring
- some tissues below ring begin to die whilst tissues above still grows
- phloem, not xylem, transports sucrose from sources to sinks
55
tracer experiments
- a plant id grown in lab and one leaf is exposed to carbon dioxide containing radioactive isotope 14C for period of time
- the 14C will accumulate in sugars produced by photosynthesis and can be traced as they move using autoradiography
- when placed in photographic film, the film becomes blackened at leaf and where phloem tissue is in stem
- autoradiographs of plants killed at different times show blackened section increasing from leaf to roots
- shows phloem alone transports sucrose and from the leaves to other plant organs
56
what are sources and sinks
source is where its made and sink is an area where it is used up
57
translocation 1
- active transport used to actively load the solutes from companions cells into sieve tubes of phloem at source
- this lower water potential inside sieve tubes, water enters tube by osmosis from xylem and companion cells
- creates high pressure inside sieve tubes at source end of phloem
58
translocation 2
at sink end, solutes are removed from phloem to be used up
- this increases water potential inside sieve tubes so water also leaves the tubes by osmosis
- this lowers pressure inside sieve tubes
59
translocation 3
- the result is pressure gradient from source end to sink end
- this gradient pushes solutes along the sieve tubes towards the sink
- when they reach sink the solutes will be used or stored
60
evidence for mass flow hypothesis
- pressure within sieve tubes shown by sap released when cut
- the conc of sucrose is higher in leaves than roots
- downwards flow in phloem occurs in daylight but ceases when leaves shaded or at night
- increases in sucrose levels in leaf are followed by similar increases in sucrose levels in phloem a little later
- metabolic poisons and/or lack of oxygen inhibits translocation sucrose in phloem
- companion cells possess many mitochondria and readily produce ATP
61
evidence against mass flow hypothesis
- function of sieve plates is unclear as they would seem to hinder mass flow (structural function preventing bursting under pressure)
- not all solutes move at same speed-they should do of movement is by mass flow
- sucrose is delivered at more or less the same rate to all regions rather than quicker to area of low sucrose conc
