circulation and ventilation Flashcards
1
Q
challenges
A
- deliver O2 to cells within body
- diffusion of O2 in a solute is slow but it is the only way O2 can cross a membrane
2
Q
solutions
A
- no circulatory system, body plan where the most metabolically active cells are in direct contact with the environment (some aquatic invertebrates), diffusion is still very slow
- evolution of a circulatory system, most animals cannot rely on diffusion alone (evolution of multicellularity and large body size)
3
Q
limitations to no specific circulatory system or respiratory organs
A
- low metabolic rate
- restricted size (for large SA:V)
- boundary layer
- cellular organisation (most metabolically active cells must be on periphery, O2 then diffuses down to the less active cells not exposed to the environment)
4
Q
functions of a circulatory system
A
- deliver O2 to cells/organs
- remove CO2
- transport other solutes/nutrients
- transport heat
- enable movement
- provide immune response
5
Q
main requirements of a circulatory system
A
- circulatory fluid
- interconnecting tubes
- pump-contractile mechanism
6
Q
open circulatory system
A
- found in arthropods and most molluscs
- heart with vessels that are open ended
- haemolymph is distributes out of vessels and into spaces between tissues called sinuses and lacunae
- number of hearts depend on animals metabolic requirements/size
- 1 main large heart, possibly smaller auxillary hearts
- movement (internal muscle contraction) assists with the flow of haemolymph
7
Q
open circulatory systems, the heart
A
- in pericardial sinus, suspended by suspensory ligaments
1. heart contracts, haemolymph is driven into the arteries and out into the sinuses and lacunae
2. ostia close
3. during relaxation the ligaments expand the heart back to its original volume
4. ostia open bringing in haemolymph from the pericardial sinus
8
Q
advantages of an open circulatory system
A
- lower hydrostatic pressure means reduced energy cost
- spiders use this hydrostatic pressure to extend their legs (no extensor muscles)
9
Q
closed circulatory systems
A
- found in annelids, cephalopods, vertebrates
- fluid is contained within a network of vessels, systemic capillary bed
- heart(s) contracts, blood is driven into large then small vessels through tissues/organs
10
Q
advantages of a closed circulatory system
A
- increased hydrostatic pressure
- can regulate distribution of blood, useful for thermoregulation and other responses
11
Q
cephalopods (octopus and squid)
A
- molluscs with a closed circulatory system as they are active and intelligent, so have a high energy demand
- 1 systemic main heart, 2 branchial auxillary hearts
- allows for re-pressurisation of blood prior to entering the gills and allows for fast blood flow rates
1. systemic heaer pumps blood around systemic capillaries
2. deoxygenated blood is repressurised by branchial hearts and passes through gills back into the systemic heart
12
Q
closed circulatory system in vertebrates, the cardiovascular system
A
- heart, 2-4 chambered
- arteries take blood from the heart to organs
- arterioles within organs pass blood into the capillaries
- capillaries are where gaseous exchanges occurs
- capillaries converge into venules
- venules carry blood into the veins
- veins carry the blood to the heart
13
Q
cardiovascular system, teleosts, rays and sharks
A
- 2 chambered heart, 1 atrium, 1 ventricle
- accessory structures sinus venosus and conus arteriosus
- single circulatory system, blood passes through heart once per circulation of the body
- sinus venosus = where SA node is found (pacemaker), collects blood before it enters the atrium
- conus arteriosus = blood passes through before gills, evens out pressure so there is no significant fluctuations in blood pressure (gills aren’t damaged)
14
Q
teleosts, rays and sharks, problems with single circulatory system
A
- blood is cooled down by gills before it enters capillaries in muscles
- muscles work best when warm
15
Q
adaptation of bill fishes, some sharks, predatory fish such as tuna, regional endothermy
A
- need to move fast, have optimum muscle usage
- blood from gills run very close to periphery of animal and then into core
- arterioles run alongside warm venous blood running out of muscles
- heat exchange system to warm up oxygenated blood before it reaches the muscles
- regional endothermy, ectotherms but 37C internal temperature
- also have heater organs for eyes and brain
16
Q
double circulatory system
A
- found in amphibians, reptiles, birds, mammals
- blood passes through heart twice
- pulmonary circuit, blood
from the right - systemic circuit, blood
from the left - blood from right often has lower blood pressure to avoid damage to the lungs
17
Q
advantage of double circulatory system
A
- efficient and rapid delivery of blood flow to the organs/brain/muscles by pre-pressurising blood twice
18
Q
amphibians, cardiovascular system
A
- lower metabolic rate than other vertebrates
- 3 chambered heart
- 2 atria
- 1 ventricle but ridge between left and right ventricle, not complete segregation but effective at keeping oxygenated and deoxygenated blood separate
19
Q
amphibians, circulatory mechanism
A
- pulmocutaneous circuit, oxygen poor blood from right to lungs
- oxygen rich blood into systemic circuit
- CO2 diffused out the skin
- when submerged, blood flow to the lungs in shut down, cutaneous respiration
20
Q
reptiles, crocodilian cardiovascular system
A
- most reptiles have a 3 chambered heart with ventricular ridge like amphibians
- crocodilians have an almost complete septa dividing left and right ventricle
- Foramen of Panizza, a hole with a valve that connects the left and right aorta
21
Q
cardiac shunting, how crocodiles pump blood when they are holding their breath
A
- shuts down blood to lungs by increasing pressure in right ventricle, closing the pulmonary artery
- blood is shunted into the aortic arch, opening the foramen
- blood is pumped to the systemic capillary bed bypassing the pulmonary circuit (lungs)
22
Q
mammals and birds
A
- endotherms, require 10x more energy than ectotherms of the equivalent size (10x O2 demand, 10x waste)
- effective pump needed
- complete separation of ventricles, no mixing of oxygenated and deoxygenated blood
23
Q
4 chambered heart, cardiac cycle
A
- systole = contraction, heart pumps blood
- diastole, relaxation, chambers fill with blood
24
Q
cardiac output
A
= volume of blood pumped by the left ventricle (ml/min)
= heart rate (bpm) * stroke volume (mL/beat)
- average at rest ~70*70 = 5L/min
- a person’s blood does one complete circuit per minute at rest
25
Q
4 chambered heart, valves
A
- 4 valves made from very thin connective tissue
- maintain unidirectional flow
- pressure from one side opens valve, pressure from the other closes it
- atrioventricular valves between the atria and ventricles
- semilunar valves in the pulmonary trunk and aorta
- heart murmur = leaky valve
26
Q
AV and SA node
A
- cells of the heart are myogenic/autorhythmic
- SA node in top of right atrium is the pacemaker
- AV node in the bottom of the right atrium transports depolarisation down the septum into the ventricles using AV bundle branches and Purkinje fibres, branches out into myocardial tissue at the bottom of the ventricle
- allows rapid spread of depolarisation and almost simultaneous contraction
27
Q
the heart beat
A
- depolarisation begins at the SA node and spreads outward through the atrial muscle
- its spread to the AV node is delayed by 0.1 seconds, allowing the contraction and the emptying of the atria before the contraction of the ventricles
- once the AV node is depolarised it spreads rapidly into the ventricles, the atria start to repolarise
- nearly simultaneous depolarisation of all the cells in the ventricles allow for forceful contraction
28
Q
electrocardiogram (ECG)
A
- PQRST trace tracks electrical signals
- P = atrial depolarisation
- QRS complex = depolarisation of ventricles, atrial repolarisation
- T = ventricular repolarisation
29
Q
blood vessels structure
A
- capillaries, one red blood cell thick, very thin walls, short, slow flow to facilitate gas exchange (500x slower than the aorta)
- arteries, thick elastic walls to maintain high blood pressure (blood pressure then decreases from capillaries to veins)
- veins are 0.3x thickness of arteries, contain valves to assist blood flow
30
Q
blood pigments
A
- haemoglobin, contains iron
- haemocyanin, structurally similar to haemoglobin but contains copper, seen in molluscs and arthropods free floating in haemolymph
- haemerythrin, rare, seen in sipunculids, priapulids and brachiopods
- chlorocruorins, very rare, seen in few select marine annelids
31
Q
function of blood pigments
A
- main function is to increase carrying capacity of oxygen in the blood
- removes CO2
- buffers blood (free CO2 is dissolved as carbonic acid lowering blood pH)
32
Q
erythrocytes
A
- bioconcave
- 7-8 micrometers diameter
- anucleate, no organelles
- contain essential enzymes
- made in the bone marrow, at the ends of long bones and the shaft of flat bones
- ~120 day lifespan, broken down in the liver (formation of bile salts)
33
Q
erythrocytes, obtaining ATP
A
- no mitochondria but its essential enzymes need ATP to function
- anaerobic metabolism using Embden Meyerhof pathway to convert glucose into ATP
34
Q
oxygen dissociation curves
A
- saturation of haemoglobin with oxygen increases with partial pressure of oxygen
- sigmoid shaped curve
- 4Hb subunits, 4O2 molecules bind, first molecule is difficult to bind then changes conformational shape to make it easier for next 3 molecules to bind
- at high partial pressures, Hb binds to O2, oxyhaemoglobin
- at low partial pressures O2 is offloaded
- can shift to left with an increase in affinity or to the right if affinity decreases
35
Q
partial pressures at tissues
A
- lungs, 100mmHg, 98% saturation
- tissues at rest, 40mmHG, 68% saturation, 30% offloaded
- can drop to 2ommHg with exercise, 75% offloaded
36
Q
factors that decrease the affinity of haemoglobin to oxygen
A
- increase in temperature
- increase in CO2
- decrease in pH
- increase in DPG
Affinity decreases with exercise (capillary beds run through working muscle, increasing temperature, CO2 and decreasing pH), so more oxygen is offloaded at capillaries
37
Q
DPG
A
- diphosphoglycerate
- compound erythrocytes create to alter the affinity of Hb to oxygen
38
Q
relationship of CO2 and Hb
A
- CO2 diffuses into the blood
- 5-10% stays as dissolved CO2 in plasma (some forms carbonic acid then dissociates)
- 80% into erythrocytes resulting in O2 offloading
- 5-10% binds to Hb to form carbaminohaemoglobin (HbCO2)
39
Q
chloride shift
A
- occurs at systemic capillary beds when CO2 diffuses in
- bicarbonate in the erythrocyte exchanges for chloride ion in plasma
- increases carrying capacity of the blood for CO2
- buffers change in pH
- acts to destabilise binding of O2 to Hb (allosteric modulator)
- opposite occurs at lungs (Haldane effect)
39
Q
how does CO2 initiate the offloading of O2 from erythrocytes
A
- enters erythrocytes and reacts with water to form bicarbonate and hydrogen ion
- hydrogen ion influences Hb binding to O2
- enzyme carbonic anhydrase
- CO2 + H2O = HCO3- + H+
- H+ + HBO2 = HHb + O2
40
Q
Bohr effect
A
- phenomenon whereby affinity of Hb to bind to O2 is influenced by pH/CO2
- more CO2 = lower pH = lower affinity = more O2 delivered to tissues
41
Q
the oxygen cascade
A
- gradient of partial pressure of O2 determines the rate of supply
- decreases from ambient air to alveolar gas, arterial blood, capillary blood, mitochondria
- mitochondria has a baseline oxygen demand that must be met
- in order to speed up rate of diffusion, the ppO2 in the capillary beds must be kept high to maintain a large concentration rate
42
Q
smoking and the oxygen cascade
A
- smoking reduces the amount of O2 into arterial blood
- smaller ppO2 difference at capillaries means less efficient gas transfer
43
Q
problems aquatic organisms face extracting O2 from water
A
- content of O2 is lower (lower solubility of O2 in water than air)
- denser than air (x800)
- more viscous (x35)
= slower rates of diffusion in water, more ATP needed (less efficient), must move 1L water to extract 1ml O2 (25ml in air)
44
Q
solubility of gas in water depends on
A
- the gas ( CO2 is more soluble in water than O2)
- the presence of solutes (sea water holds less O2 than freshwater due to its dissolved ions)
- pressure of the gas
- temperature of the water
45
Q
organisms that do not have a specific circulatory system or respiratory organs
A
- mainly invertebrates
- notable vertebrates include amphibians (eliminate CO2 through skin, take up O2 through skin in water) and blennies (use integument to respire when in rockpools at low tide)
46
Q
limitations of having no specific circulatory system/ respiratory organs
A
- low metabolic rate
- small (SA:V)
- boundary layer
- cellular organisation (metabolically active cells in direct contact with environment)
47
Q
boundary layer
A
- all animals/ surfaces are subject to the boundary layer effect but the boundary layer is thicker in water
- small layer of non-moving water around the animal where viscous forces dominate (sticky)
- speed of flow of water increases with distance from the surface
- limits O2 and nutrient delivery to the surface of the animal
48
Q
boundary layer solutions
A
- small so large surface area
- low metabolic rate
- motile, generates turbulence to disrupt laminar flow
- cells with high metabolic demand at surface
49
Q
juvenile fish
A
- underdeveloped gills
- rely on diffusion through integument
50
Q
oxygen requirements of animals with a high metabolic rate
A
- convective gas transport needed
- specific respiratory structures, large surface area, very thin, often associated blood/haemolymph supply
50
Q
starfish
A
- no circulatory system
- papillae = extensions of surface specialised for gas transport to increase surface area, specialised respiratory structures
51
Q
cocurrent gas exchange
A
- medium travelling in same direction as blood
- exchange stops when it reaches equilibrium so only ~50% exchange, not very efficient
52
Q
countercurrent gas exchange
A
- medium and blood flow in opposite directions
- maintains concentration gradient, ~75% exchange
- most efficient, seen in majority of aquatic organisms
53
Q
crosscurrent gas exchange
A
- blood broken up into streams and travels alongside medium for a short length
- efficient but not as efficient as countercurrent (~65% exchange)
- seen in birds (doesn’t need to be as efficient as air is easier to transport)
54
Q
tidal gas exchange
A
- seen in mammals, exchange between lung sacs and blood
- not very efficient ~60% exchange but air is easier to transport than water
55
Q
aquatic vs terrestrial respiratory structures
A
- gills (branchial), typically aquatic and outside body
- lungs (pulmonary), typically terrestrial and inside body
56
Q
external vs internal gills
A
- external gills, ventilation not required but vulnerable to damage and requires structural support
- internal gills, ventilation required to generate flow of water through gill e.g. Molluscs, gills in mantle cavity, protected
57
Q
gills, passive vs active ventilation
A
- passive ventilation typically occurs in freshwater (more fast moving environment), energy not expended but external gills (vulnerable to damage, required external support) e.g. gill tufts on mayflies/stoneflies
- active ventilation, pump water over gills or flap gills (unusual, energy expensive and gills are delicate), usually mechanism that creates unidirectional flow of water over gills, reliable, controllable, more effective, energy and muscles/cilia required
58
Q
different types of gills
A
- tuft gills, raise area of integument, primitive, not usually associated with blood/haemolymph supply
- filament gills, usually associated with blood/haemolymph supply e.g. nudibranchs
- book gills e.g. Limulus (horeshoe crabs), unusual, actively flaps gills
- lamellar gills, crustaceans and fish
59
Q
lamellar gills, crustacea
A
- hidden in cephalothorax, set of gills at top of each pair of legs (birameous appendages) under carapace in branchial chamber
- beating of scaphognaithite (specialised antennae at anterior within branchial chamber) reduces pressure, drawing water in at posterior
- creates unidirectional flow of water into branchial chamber from posterior to anterior
60
Q
lamellar gills, intertidal and terrestrial crustacea
A
- gills have more support
- stops gills from collapsing when branchial chamber empties allowing respiration via air
61
Q
lamellar gills, fish
A
- gill filaments supported by gill arch (often 3-4 gill arches each side)
- v-shaoed arrangement, 2 lines of overlapping filaments per arch
- secondary lamellae arise from filaments
- highly vascularised
- countercurrent blood flow
- buccal-opercular pumping mechanism (water flows through mouth, buccal cavity, gills, opercular cavity, operculum)
62
Q
fish, buccal-opercular pumping
A
- mouth opens, buccal cavity floor lowers reducing pressure, water flows into buccal cavity
- mouth closes, raising buccal cavity floor increasing pressure, water forced from buccal cavity over gills and into opercular cavity
- opercular cavity compresses, operculum opens, water flows out
63
Q
fast swimming predatory fish, RAM ventilation
A
- stops using buccal-opercular pumping when fish reaches certain swimming speed (species-specific)
- instead opens mouth while swimming to allow water to flow over gills
- opening and closing mouth would generate turbulence, slowing them down
(different to plankton feeding fish)
64
Q
terrestrial respiratory organs
A
- lamellar gills (terrestrial crustaceans)
- trachea (insects)
- lungs
65
Q
tracheal system, insects
A
- system of air filled tubes
- delivers O2 directly to tissues in gaseous form, very efficient delivery (flying is energetically expensive, circulatory system involving fluid too slow)
- often regulated by spiracles
- terminate right next to mitochondria (very short diffusion distance dissolved in fluid)
- trachea branch into tracheoles
- air sacs often present, enlargements of tracheal system
66
Q
tracheal system, cell activity and osmolarity
A
- active muscle cells are mobilising sugars, increasing the osmolarity of the cytoplasm
- water is drawn from the tips of tracheoles into the cell, delivering dissolved oxygen
- in inactive cells, the tracheoles are filled with fluid, fluid accumulates as the osmolarity inside the cell is lower
67
Q
insects, types of ventilation
A
- conspicuous ventilation, involving flexing and contraction of the abdomen
- autoventilation, flexions in the body from flying assists with ventilation
- microscopic ventilation, muscles surrounding tracheoles constrict, assisting with air flow
67
Q
ventilation in amphibians
A
- gills as tadpoles, lungs as adults
- cutaneous respiration as adults and tadpoles, typically only voiding CO2 when not hibernating in water
- lungs are simple convoluted sacs
- ventilated by buccopharyngeal pumping
68
Q
amphibians, buccopharyngeal pumping
A
- nostrils/nares open, buccal cavity floor lowers, reducing pressure, air flows into the buccal cavity
- nostrils close, glottis opens, buccal cavity floor raises, increasing pressure, air flows into lungs
- lungs empty by elastic recoil, nostrils open and air is pushed back out
69
Q
ventilation in reptiles
A
- varying complexity, massive variability within the taxon
- unicameral, simple single chambered lung not always perfused with blood, snakes and lizards
- multicameral, complex multiple chambers with bronchi, monitor lizards and crocodiles
- evolution of suction method of ventilation involving contraction of intercostal, abdominal and thoracic muscles
70
Q
2 main mechanisms of ventilation in reptiles
A
- snakes, use ribs to ventilate lungs, muscles contract exhale, elastic recoil for inhale
- crocodiles, abdominal muscles contract for exhale, diaphragm contracts for inhale
71
Q
ventilation in aquatic reptiles
A
- use integument
- e.g. yellow-bellied sea snake, use lungs and integument (23%) for O2 uptake, 100% CO2 offload using integument
72
Q
ventilation in mammals
A
- complex lungs with alveoli
- operates via suction involving diaphragm and internal and external intercostal muscles
- gaseous exchange occurs within alveoli, very thin membranes
- tidal breathing, lungs never fully empty
- cells within alveoli secrete fluids to facilitate diffusion over a membrane
73
Q
alveoli, pulmonary surfactants
A
- water secreted within alveoli has high surface tension, ‘sticky’, would cause alveoli to collapse
- glandular cells line alveoli and secrete pulmonary surfactants, phospholipids
- reduces surface tension, helps keep all alveoli the same size, facilitates uniform inflation and stops alveoli from overstretching
74
Q
lungs, inhalation and exhalation mechanism
A
- inhalation, contraction of diaphragm, contraction of external and anterior internal intercostal muscles, drop in air pressure and expansion of lung volume
- exhalation, relaxation of all muscles, increase in air pressure and reduction of lung volume
75
Q
ventilation system in birds
A
- palaeopulmonal system, unique to birds
- system of air sacs and lungs/parabronchi
- gaseous exchange occurs in parabronchi, don’t change shape
- ventilation via bellows action
- anterior/cranial sacs are cervical, interclavicular, anteriorthoracic
- posterior/caudal sacs are posterior thoracic and abdominal
- it takes 2 cycles for air to pass through system and out, unidirectional
- crosscurrent flow of blood
76
Q
ventilation mechanism in birds
A
- contraction of internal intercostal and thoracic muscles increases volume in air sacs
- contraction of external intercostal and abdominal muscles decrease volume in air sacs
1. air sacs expand, air flows from mouth through mesobronchus to posterior air sacs
2. air sacs contract, air is pushed through parabronchi
3. air sacs expand, air is drawn from parabronchi into anterior air sacs
4. air sacs contract, air is pushed out bird from anterior air sacs
77
Q
general adaptations of high-altitude flying birds
A
- heightened hypoxia tolerance
- larger lungs
- higher tolerance to low CO2 levels, allows more O2 uptake
- greater lung volume, thinner surface area
- pulmonary vasculature doesn’t constrict under hypoxia
- larger hearts and greater maximal stroke volume
- cerebral blood flow not inhibited by hypocapnia (increase in CO2 levels)
- neurones have higher tolerance to low levels of O2
78
Q
adaptations specific to bar-headed goose (Anser indicus)
A
- greater ventilation rates
- breathe deeper and at reduced frequency
- larger lungs
- greater proportion of oxidative flight muscles (lower diffusion distance)
- haemoglobin has a higher affinity to O2, greater sensitivity to temperature
- capillary density in heart is greater
- capillary exchange length is longer
79
Q
bar-headed goose, Anser indicus
A
- migrate over the Himalayas in one day
- ascend 4,000-6,000m in 7-8 hours
- change in altitude would leave mammals comatose, low O2 (also less lift, harder to fly)
- remain within 340m of the ground
- avoid periods of strong winds (less control)
- selects paths with smallest altitude change
- doesn’t glide, energetically expensive journey
