exchange and transport Flashcards
what do living organisms need to keep them alive?
oxygen, water, glucose, amino acids, minerals
what do living organism need to get rid of?
carbon dioxide urea, creatinine
factors that affect the need for exchange systems
size of organism/ SA:Vol ratio/ diffusion distance
metabolic rate
endotherm/exotherm
unicellular vs multicellular organisms
unicellular e.g. amoeba has lower metabolic rate (lower demand for O2 and glucose), simple diffusion takes place across its plasma membrane e.g. O2: this is sufficient bc of short diffusion distance, so it can rely on simple diffusion alone and doesn’t need a specialised exchange surface
multicellular e.g. dolphin has small SA:Vol ratio and large diffusion distance, higher metabolic rate (very active), so have higher O2 demand and are endotherms so maintain body temp. therefore they have a specialised exchange surface (alveoli in lungs)
as an organism gets bigger, what means it needs a specialised exchange surface/ transport system?
as an organism gets bigger, it becomes more difficult for it to exchange substances across its outer surface, so it therefore needs a transport system which allows them to survive
as size of organism increases, what happens to its SA:vol ratio?
SA:Vol decreases
why do small organisms not require a specialised exchange surface or transport system?
e.g. unicellular amoeba
large enough SA:Vol for exchange to take place over their surface
all the cytoplasm is very close to the environment in which they live and so diffusion will supply oxygen etc
circumference of circle equation
2π r
area of circle equation
π r^2
surface area of cuboid equation
2(bh+bl+hl)
volume of cuboid equation
hbl
features of an efficient exchange surface??
large surface area
thin
good blood supply/ventilation
moist
permeable
why does an efficient exchange surface have a large surface area?
maximum number of molecules can diffuse per unit time
why is an efficient exchange surface thin?
reduced diffusion distance so faster rate of diffusion
why does an efficient exchange surface have good blood supply and/or ventilation?
maintains steep concentration gradient
why is an efficient exchange surface moist?
enables gases to dissolve
protects cells from drying out
why is an efficient exchange surface permeable?
gases can diffuse through cell membrane
what makes alveoli an efficient exchange surface?
large SA so max. no. of CO2 and O2 molecules can diffuse per unit time
alveolar walls are 1 cell thick (squamous epithelium cells= thin) so reduced diffusion distance
good blood supply, maintaining steep conc. gradients of O2 from alveoli into capillaries and CO2 from capillaries to alveoli (partial pressure gradient)
have moist lining (lung surfactant), enabling case to dissolve in it and then diffuse
permeable walls so gases can diffuse through.
property of water within alveoli
water has high surface tension bc the H2O molecules on the surface are pulled together by strong H bonds
what is pulmonary surfactant?
a mixture of lipids and proteins which is secreted into the alveolar space by epithelial type II cells
pulmonary surfactant function?
lowers the surface tension at the air/liquid interface within the alveoli of the lungs
this stops the walls of the alveoli sticking together and collapsing as we exhale
what happens when someone has respiratory distress syndrome?
no surfactant produced so high surface tension
alveoli stick together
cannot take breath
e.g. in newborn babies
what does pO2 stand for?
partial pressure of oxygen
what is partial pressure of oxygen?
concentration of O2 in a mixture of gases related to the pressure it contributes
summarise the exchange of O2 and CO2 that takes place as the blood flows past an alveolus in mammalian lung
blood in pulmonary capillaries has lower pO2 and higher pCO2 than alveolar air
gases move across respiratory membranes down pressure gradients
O2 enters blood
CO2 diffuses from pulmonary capillaries into alveolar air and is eliminated during expiration
where does the newly oxygenated blood from pulmonary capillaries go?
it is gathered into pulmonary vein, transported back to heart and then enters systematic circulation via aorta.
how much oxygen diffuses into the blood per minute at rest?
250cm3
why is blood only 95% saturated with oxygen when it leaves the pulmonary capillaries?
some air inhaled does not take part in gas exchange e.g. in trachea, bronchi, nose (dead space)
some of the blood in the lungs doesn’t go through any alveolar capillaries e.g. bronchial circulation from aorta returns via pulmonary vein
pO2 in:
inspired air
alveolar air
blood entering pulmonary capillary
blood leaving pulmonary capillary
160
104
40
104
pCO2 in:
inspired air
alveolar air
blood entering pulmonary capillary
blood leaving pulmonary capillary
0.3
40
45
40
nasal cavity conditions and why
good blood supply to warm air
humid environment so airways don’t dry out
pleural fluid functions
decreases friction to protect delicate lungs
transmits pressure gradients
ciliated epithelium function
trachea & bronchi= lined with ciliated epithelium
goblet cells secrete mucus which traps dust/pathogens
cilia beat in a synchronised pattern to waft the mucus to the pharynx where it can be coughed up/ swallowed
prevent disease
are inspiration and expiration passive or active?
inspiration= active
expiration=passive
mechanisms of breathing: inspiration
external intercostals contract
ribs move up and out
diaphragm contracts, moves down & becomes flatter
thorax volume increases and pressure decreases
air drawn in (bc ATM exceeds lung pressure)
internal intercostals relax
elastic fibres stretch
mechanisms of breathing: expiration
external intercostals relax
ribs move down and in
diaphragm relaxes, moves up, becomes dome-shaped
thorax volume decreases so pressure increases
air expelled (lung pressure exceeds ATM)
internal intercostals contract
elastic fibres recoil
mechanisms of breathing: expiration
external intercostals relax
ribs move down and in
diaphragm relaxes, moves up, becomes dome-shaped
thorax volume decreases so pressure increases
air expelled (lung pressure exceeds ATM)
internal intercostals relax
elastic fibres recoil ( to expel air)
what is breathing controlled by?
involuntary control (autonomic nervous system) carried out by breathing/respiratory centre in the medulla oblongata
how does breathing rate increase (in terms of control)
chemoreceptors bind to sensory neurone
travels to breathing centre in brain
to motor neurone
to muscles involved in breathing, which increase rate and depth of breathing
why is forced expiration an active process?
internal intercostals contract pulling the ribs down hard and abdominal muscles contract forcing the diaphragm up to force air out of the lungs more forcefully
requires energy from respiration
where is cartilage present in the lungs?
trachea as ‘C’ shaped rings
bronchus: arranged in plates
in some larger bronchioles
NOT alveolus: would prevent it stretching
cartilage function in lungs
SUPPORT
strong so prevents collapse of trachea, bronchi & bronchioles
flexible so trachea & bronchi can bend & extend
“c” shaped rings allow oesophagus to expand behind trachea
where are goblet cells present in the lungs?
trachea
bronchi
goblet cells function
CLEANING
secrete mucus, which contains glycoproteins (traps dust and pathogens)
where are ciliated cells present in the lungs?
trachea
bronchi
bronchioles
ciliated cells function
CLEANING
cells with hair-like projections which beat to waft mucus up the airway
require energy as ATP
where is smooth muscle found in the lungs?
trachea
bronchi
bronchioles
NOT alveolus bc they must maintain short diffusion distance
where is smooth muscle found in the lungs?
trachea
bronchi
bronchioles
NOT alveolus bc they must maintain short diffusion distance
smooth muscle function
contracts to constrict airway (e.g. if harmful substance in air)
relaxes to dilate airways to increase airflow to alveoli
where are elastic fibres found in the lungs?
trachea
bronchi
bronchioles
alveoli
elastic fibres fucntion
IN BRONCHIOLES: stretch when SM contract to constrict airway
recoil when SM relaxes to dilate airway
IN ALVEOLI: stretch to allow alveoli to expand (prevents bursting)
recoil to expel air
where is squamous epithelium found in the lungs?
only alveoli
squamous epithelium function
EXCHANGE
thin, flattened cells to give short diffusion distance for increased rate of gas exchange
small blood vessels in lungs function?
supplies cells with oxygen, especially ciliated epithelium bc beating requires energy
what is this?
a spirometer
why does the subject of a spirometer wear a nose clip?
to prevent breathing in & out of nose
what does the chamber in the spirometer contain?
why?
medical-grade oxygen so it floats on the surface of the tank
O2 will get used up over time so lid will fall
purpose of soda lime in a spirometer?
absorbs carbon dioxide
what does the rotating drum in a spirometer produce?
a kymograph
how does a spirometer work?
breathe out into tank (upper half will rise)
breathe in from tank (upper half will fall)
tracemarker is attached to the mobile upper half connected to kymograph which record change in oxygen
how to measure tidal volume from a spirometer volume vs time graph?
how to measure oxygen consumption
peak to trough
draw tangent from first to final peak and make triangle
why does the total volume in the tank decline in a spirometer?
subject uses up O2 from the tank due to gas exchange in alveolus
soda lime absorbs any CO2 expired
why does exhaled air contain some/less O2?
contains less O2 than inhaled
some inhaled air doesn’t reach alveolus
so we breathe this O2 out
what does inhalation mix fresh air with?
inhalation mixes fresh air with stale air= residual volume left in lungs from previous breath
what is this?
a spirometer trace
a health campaigner claims that giving up cigarettes improves lung function. evaluate this claim
FOR:
FEV1 is around 2L lower for COPD patients, which could suggest lung function is better in non-smokers
COPD patients volume plateaus at lower quantity
AGAINST:
no info about control variables e.g. age, gender which may affect FEV: invalid practical
COPD may be caused by other factors/ not told COPD patient is a smoker. may be due to work hazard e.g. breathing toxic chemicals
sample size too small to be sure of this claim
no data from patients which have given up smoking so no evidence that FEV would increase
other respiratory conditions not taken into account
repeats, means, statistical tests
why do large, active organisms need a specialised exchange surface for gaseous exchange?
have small SA;Vol ratio
active organisms have a high demand for oxygen
diffusion distance is too great so diffusion takes too long
the lungs are surrounded by the diaphragm and intercostal muscles. how does this improve the efficiency of gaseous exchange
enables ventilation to supply O2 to alveoli & remain CO2
describe the features of the lungs that make them effective organs for gas exchange
many alveoli to give large SA
alveolar wall & capillary wall both 1 cell thick (so thin) so short diffusion distance
good blood supply/many capillaries maintains steep conc grad
contains elastic tissue to stretch & recoil to expel air
good ventilation maintains steep conc. grad. for O2
features of alveoli which make them suitable for gas exchange
large SA so more O2 can diffuse
thin/1 cell thick so short diffusion distance
elastic tissue recoils to expel ar
moist so gases can dissolve
why is it necessary for amoeba to divide once it reaches a certain volume
as amoeba grows, diffusion distance for O2 increases
central regions of amoeba are O2 deprived unless division reduces size
tidal volume definition
normal tidal volume
volume of air that flows in & out of the lungs with each breath during quiet breathing (usually measured at rest)
around 0.5dm3 (but only 0.35dm3 reaches alveoli)
vital capacity definition
normal vital capacity
maximum volume of air that can be moved by the lungs in one breath (strongest possible exhalation followed by strongest possible inhalation)
2.5-5dm3
inspiratory reserve volume definition
maximum volume of air that can be inspired in excess of the tidal volume
expiratory reserve volume definition
maximum volume of air that can be expired in excess of the tidal volume
residual volume definition
normal residual volume
volume of air left in the lungs after maximum forced expiration
1.5dm3
total lung capacity defintion
total volume of air in lungs after maximum inhalation (total volume of air that lungs can hold)
how to calculate oxygen consumption
gradient of graph (change in y over change in x)
per second (multiply x60 to get per minute)
how to calculate tidal volume
take the mean average of >3 readings from peak to trough of breaths
how to calculate breathing rate
count the number of full breaths in 1 minute
what does a steeper gradient on a O2 used vs time graph mean?
when may this happen?
higher O2 demand due to higher breathing rate and deeper breaths e.g. during exercise
what is pulmonary ventilation rate and how do you calculate it?
total air breathed per minute
tidal volume x breathing rate
how can athletic training affect the condition of the lungs?
more efficient: improved network of pulmonary capillaries so more oxygen taken up
slightly increased lung volume
increased alveoli size
increased strength in muscles so can breathe in more air for a longer time period
faster breathing rate so more oxygen per second
higher tidal volume
do all fish need to swim constantly in order to breathe?
no
do fish have lungs as well as gills
NO
except lungfish
do fish get their oxygen and food at the same time via mouthfuls of water?
yes
do whales and dolphins have lungs?
yes
what problems do fish have regarding gas exchange?
fish have small SA;Vol ratio bc they are multicellular and fairly large therefore diffusion via skin would take too long bc distance is too great
water=1% O2, air=21% O2. in warmer water, solubility of O2 decreases so fish need specialised exchange surface
multicellular and active so fairly high metabolic rate (but they are ectotherms so cannot increase metabolic rate to maintain temp: demand for O2 slightly lower than endothermic organisms of the same size)
water is 100x thicker and 1000x denser than air, so requires more energy to cross gas exchange surfaces. (water only flows over gills in one direction)
O2 diffuses 8000x faster in air compared to in water
how many pairs of gills do fish have?
3-5 pairs
what are the gills covered by?
a bony plate called the operculum
what are gill rakers made of
gill rakers function
bone or cartilage to prevent food particles reaching gill filaments and obstructing gas exchange
distance between 2 lamellae?
50 micrometres
what prevents lamellae from collapsing?
water
what must happen for fish to get water to flow over their gills?
the pressure in the buccal cavity must be greater than the flow in the opercular cavity
how does the structure of gills relate to their function?
lots of filaments and lamellae so large SA so increased rate of diffusion of O2/CO2
filaments and lamellae have thin walls so short diffusion distance between blood and water to increase rate of diffusion of O2/CO2
filament tips overlap to increase resistance to flow of water, giving time for diffusion of gases
good blood supply via capillary network in the lamellae maintains steep conc grads
countercurrent flow (water flows in opposite direction to blood in lamellae), maintains the conc grad across full length of gill
describe and explain the countercurrent system in fish
counter current means water and blood flow in opposite directions
this ensures concentration of O2 in the water is always higher than in the blood so con grad is maintained across the full length of the gill
more oxygen will diffuse into the blood
describe mechanism of inspiration in a fish
mouth open and operculum closed
floor of buccal cavity lowers (muscles involved so active) so volume increases so pressure decreases
water flows in via the mouth down a pressure gradient
sides of opercular cavity start to bulge outwards (muscles involved so active), so volume of cavity increases and pressure decreases
mouth closes and buccal cavity rises, decreasing volume and increasing pressure
pressure higher in BC than OC is water is forced to flow over the gills down a pressure gradient
describe mechanism of expiration of a fish
sides of opercular cavity move inwards
operculum/opercular valve opens
water is expelled
use of mechanism of fish ventilation
water only flows in 1 direction over the gills and out
general insects facts ab gas exchange
tough exoskeleton so no exchange via skin
fairly large SA:vol ratio. fairly small organisms
active and multicellular so have certain O2 demands
short diffusion distance so rely on simple diffusion via tracheal system
circulatory system is separate from their gas exchange system
no blood pigments
what are spiracles
microscopic parts of an insect which can be opened and closed
parts of an insect
head
thorax
abdomen
wings
spiracles
tracheae adaptions in insects
held open by chitin
enables O2 and CO2 to diffuse down the tracheae
tracheoles adaptations
lots of them increases SA for diffusion
0.1 micrometre thin walls for short diffusion distance
tracheole fluid at ends of tracheoles. O2 dissolves into this and diffuses through it
ends of tracheoles are within muscle tissue so short diff. distance
how do insects maintain rates of diffusion when they are active?
muscle respire anaerobically and produce lactic acid, decreasing water potential so tracheole fluid is drawn into muscles by osmosis
this draws more air in and exposes more surface air of walls for more diffusion
increases rate of diffusion
open vs closed spiracles
OPEN: hairs are sensory and also trap humid air so decrease water potential to decrease water loss
CLOSED: less gas diffusion/ventilation and less water loss (air sacs along tracheae to store O2 when spiracles are closed)
ADAPTATIONS OF INSECTS FOR EFFICIENT GAS EXCHANGE
size of spiracles can be changed to draw air in or out
larger insects may use abdominal muscles (ATP needed) to cause pressure changes to draw air into tracheae system
during flight, wing movement can cause change in thorax shape to draw more air in
insects= small size so short diff. distance so simple diff. is sufficient
O2 diffuses slowly through tracheal fluid but during activity, muscles resp. anaerobically to release lactic acid, decreasing water potential is fluid moves into muscles by osmosis, increasing rate of diffusion
air sacs can store O2 to be used when spiracles are closed
some insects have external gills
lots of tracheoles increases SA
tracheole ends in muscles for short diffusion distance
tracheae held open by chitin enables O2 to get to exchange surface
why will we never see giant insects?
larger insects would have higher O2 demand, small SA:vol and larger diff distance so simple diffusion not sufficient for supply to tissues/cells
large surface area adaptation in insects, fish and humans
INSECTS: many tracheoles
FISH: many lamellae and filaments
HUMANS: many alveoli
maintaining conc gradients in insects, fish, humans
INSECTS:ventilation of abdomen by pumping air in. air sacs. open/close spiracles
FISH: counter-current flow, buccal pumping
HUMANS: blood flow past alveoli. ventilation brings more O2 and removes CO2
short distances for gas exchange in insects, fish, humans
INSECTS:ends of tracheoles penetrate muscle tissue. walls are 0.1 micrometer thin
FISH:filaments and lamellae have thin walls. capillaries inside filaments
HUMANS: squamous epithelium makes up alveoli and capillary walls. one cell thick
good blood supply adaptations in insects, fish, humans
INSECTS: n/a
FISH: rich blood supply, capillary network, gill filaments
HUMANS: capillary network surrounds alveoli
factors that affect the need for a transport system?
size
SA:vol
level of activity
body temperature
how does size affect the need for a transport system?
small animals do not need a transport system bc all cells r surrounded by/nr. env.
simple diffusion alone supplies enough O2/nutrients to meet demand
several layers of cells, internal distances= too great for diffusion to be effective & O2/nutrients= used up by outside layers
how does SA:vol affect the need for a transport system?
small animals have large SA:vol but large animals usually have small SA:vol
insufficient O2/nutrients supplied to internal cells bc distance too great so diffusion takes too long
can be solved by changing shape e.g. flatworms=v. thin and have large SA:vol
how does level of activity affect the need for a transport system?
active animals need more energy and therefore a faster rate of respiration
C6H12O6+6O2->6CO2+6H2O+ energy
how does body temperature affect the need for a transport system?
endotherms (warm blooded animals) e.g. birds/mammals maintain their body temp at a constant level often higher than surrounding temps so have higher energy demand so increased rate of resp
ectotherms (cold blooded) e.g. fish/reptiles/amphibians rely on heat from environment to increase body temp so have lower energy demand
what do large. multicellular organism need a transport system for?
transport nutrients (minerals, O2, glucose, amino acids, fatty acids, glycerol)
transport waste e.g. CO2, urea
SOME transport hormones and anitbodies
why do small simple organisms not require a transport system?
examples
large SA:vol & short diffusion distance so rely on simple diffusion
low energy demands
e.g. amoeba, sponges jellyfish
why do large multicellular organism require a transport system?
examples
large, active so high metabolic rate so higher demand for O2, glucose and removal of waste
small SA:vol and large diffusion distance too great to meet demand for nutrients
basic components of a circulatory system?
circulating fluid
pumping device
blood vessels
valves
input form an exchange surface
circuits
basic components of a circulatory system: circulating fluid
often called the blood w/ respiratory pigment Hb
often used to carry oxygen, glucose, hormones, urea, CO2
what respiratory pigment do insects have?
haemolymph
basic components of a circulatory system: pumping device
e.g. heart
creates pressure difference which forces blood flow
basic components of a circulatory system: blood vessels
blood is at least partially contained in tubes to carry it towards tissues and back to the heart
basic components of a circulatory system: valves
allow blood flow in correct direction
prevent back flow (particularly important where blood is at low pressure)
basic components of a circulatory system: input from exchange surface
enables oxygen and glucose to enter the blood capillaries and waste to be removed
basic components of a circulatory system: circuits
sometimes one circuit e.g. fish
sometimes there are 2 circuits: one to pick up O2 and one to deliver it e.g. in humans
closed circulatory systems w/ example
in closed circulatory system, blood is fully enclosed within blood vessels at all times so high pressure and rapid flow can be maintained, giving greater control over distribution
valves also maintain flow in 1 direction
EG fish, mammals, amphibians, birds
open circulatory systems w/ example
heart pumps haemolymph through short vessels into a large cavity called a haemocoel
the haemolymph directly bathes tissues, enabling diffusion
fluid is not enclosed within blood vessels so it moves slowly and at low pressure in the cavity (due to the movement of the organism)
inefficient bc little control over direction of circulation
when heart relaxes, haemolymph is sucked back via pores called Ostia
EG insects, molluscs
how to carry out dissection of an insect?
cut open exoskeleton of insect
stain tracheoles with methylene blue
explain why bone is described as a tissue and gills are described as organs?
bone performs one/few functions
tissue has one/few types of cells
gills contain blood/bone/epithelial/connective tissue
precautions taken when using a spirometer?
use nose clip
use medical grade oxygen
ensure no medical problems e.g. asthma
disinfect mouth piece
compare mechanism of normal expiration with forced expiration of the lungs
external intercostals relax, diaphragm relaxes, elastic recoil
passive
internal intercostals contract-> ribs pulled down
abdominals contract to force diaphragm up
active
describe how to use a spirometer to measure the tidal volume of a person
nose clip
patient breathes in and out
resting/quiet breathing
switch on chart recorder and calculate volume on chart
what type of circulation is more efficient?
why?
closed
open: blood loses pressure in body cavity, cannot regulate direction of blood flow
why are open circulatory systems sufficient for insects?
they are small
they have a separate system for oxygen transport
advantages of closed circulatory system
higher pressure
rapid flow maintained
greater control of distribution
compare open vs closed circulatory system:
OPEN= few blood vessels. CLOSED=blood is enclosed within blood vessels
OPEN= lower blood pressure
OPEN e.g. locust, transport system is haemolymph. CLOSED= blood containing haemoglobin
OPEN insect, haemolymph carries waste nitrogenous products, defence cells, food. CLOSED fish= carries CO2 and O2 too
CLOSED= more efficient; supply&elimination is faster
OPEN has haemocoel. absent in CLOSED
OPEN: blood in direct contact with tissues&cells.CLOSED: exchange via diffusion through blood vessel walls
CLOSED=exchange in capillaries. none in OPEN
BOTH have heart to pump transport medium around
describe single circulation with an example?
blood passes to the heart only once during complete circulation of the body
fish
disadvantage of single circulatory system
pressure drops in gill
why is a single circulatory system sufficient for fish?
they gain support from the water
they are ectotherms so have lower energy needs and less demand for oxygen and glucose
describe double circulation with examples
blood passes through the heart twice during complete circulation of the body
pulmonary and systemic circuit
birds, mammals, amphibians
advantages of double circulation
blood pressure is maintained as blood is re-pressurised by heart
different pressures can be achieved in pulmonary and systemic circuit, preventing damage to lungs
can meet higher metabolic demands
what happens in heart of amphibians?
ventricle mixing of oxygenated and deoxygenated blood
less oxygen to the body
why is frog system less effective at supplying body with oxygen?
blood will not be fully oxygenated
lower pressure
may still be carrying oxygen
complete vs partial double circulation
PARTIAL=only 3 chambers, ventricles not separated and oxy/deoxy blood not fully separated
BOTH= double bc blood passes 2x through heart for each complete circulation. both have pulmonary and systemic systems
compare mammals/birds, amphibians and turtles circulatory systems
MAMMALS: oxy & deoxy blood do not mix. DO in other 2
MAMMALS have 4 chambered heart w/ 2 atria and 2 ventricles. TURTLES/AMPHIB have 3 chambered heart w/ 2 atria and one ventricle (partially separated ventricle in turtles)
ALL 3 are doubel circulatory systems where blood passes through heart twice in 1 full circulation
ALL 3 are closed systems w/ blood vessels
ALL 3 have a heart to pump blood
ALL are effective but MAMMALS are most efficient at delivering fully oxy blood to body
TURTLES/AMPHIB are ectotherms. MAMMALS are endotherms so have higher metabolic rate/higher O2 demand bc they must maintain body temp
TURTLE/AMPHIB have less O2 available to body cells but AMPHIB system is sufficient bc they cna absorb O2 through skin. TURTLE heart has folds and grooves ventricular chamber, so partially separated and less oxy/deoxy mix
compare single and double circulation
single=1 circuit. double=2 circuits: pulmonary and systemic
single=BP low when it reaches body tissues bc already gone through 1 set of capillaries.double= faster bc comes back to heart before pumped to systemic tissues
single: heart is a single pump. double: heart is double pump
single=less efficient than double
single=successful in fish bc ectotherms and don’t support own weight BUT animals need double bc higher metabolic needs/rate
single: BP limited by delicate nature of gills but double: control BP in lungs so high in systemic and low in delicate pulmonary
animals w/double=more active bc blood reaches respiring tissues faster due to higher pressure
in 1 complete cycle, blood in double passes through heart2x but only 1x in single
both have heart to pump. single=2 chambers. double=3 or 4
size of heart?
12cm long
structure of heart?
4 chambers
2 thin-walled atria and 2 thicker walled ventricles
heart is formed of mainly cardiac muscle-the myocardium
heart also has inner epithelial lining, the endocardium and an outer covering, the pericardium
what do the AV/SL valves do & how
prevent back flow of blood
valve tendons and papillary muscles prevent the valves turning inside out
what is the cardiac cycle?
a sequence of events which makes up one heartbeat
the chambers of the heart contract in a certain sequence so that they pump the blood efficiently
how long is each cardiac cycle?
about 0.8 seconds
what are the stages of the cardiac cycle?
cardiac diastole
atrial systole
ventricular systole
briefly, what is diastole?
resting period
atria and ventricles are relaxed
describe what happens during diastole
blood under low pressure enters atria from pulmonary vein and vena cava
atria fill w/ blood and become distended
initially bi/tricuspid valves shut, but as atria fills w/ blood, pressure in atria increases and eventually exceeds that of the ventricles, causing the AV valves to open.
some blood flows into the relaxed ventricles
semilunar valves shut as pressure in aorta/PA is larger than in the ventricles
briefly what is happening in atrial systole
`atria contracting
describe atrial systole
atria contract simultaneously, pressure in atria rises, more blood flows into ventricles
contraction of atrial walls seals of vena cava and PVs, preventing back flow of blood into veins as pressure in atria increases
why do atria have thinner walls than ventricles?
they only need to create enough pressure to pump the blood a short distance into the ventricles
briefly what is happening in ventricular systole
atria relax
ventricles contract
describe ventricular systole
atria walls relax
ventricles contract and the pressure increases and soon exceeds the pressure in the aorta and PA so semilunar valves are forced open
Pressure in ventricles higher than in atria so AV valves close (LUB sound) and back flow is prevented
blood expelled from ventricles through aorta and PAs
what happens after ventricular systole?
ventricular and atrial diastole
high pressure develops in both arteries and this forces blood back towards ventricles so semilunar valves close (DUB sound), preventing back flow
atria then start filling again
what is the function of the pericardial fluid?
prevents friction when the heart beats
what percentage of the heart’s muscle mass is cardiac muscle?
what is this specialised for?
50%
rhythmic contraction
what are individual muscle cells called?
myocytes
brief description of group of myocytes
branched
join together by a series of intercalated discs forming a dense network
how are pacemaker cells connected to surrounding muscle fibres?
via intercalated discs
what do pacemaker cells do?
co-ordinate the heartbeat and allow excitation to spread from cell to cell quickly
do cardiac muscle cells have a long or short refactory period?
what is this?
long
when they are completely unable to contract
long refactory period in cardiac muscle cells function
ensures that each contraction is separated by a resting period
allows the heart to refill with blood before the next contraction
prevents oxygen debt so cardiac muscles down fatigue
how are cardiac muscle cells’ high oxygen demands met?
numerous capillaries
oxygenated blood in aorta flows into coronary artery, into capillaries which supply the muscle cells with oxygen (by diffusion out of capillaries)
where does deoxygenated blood from the cardiac muscle go?
into cardiac veins
then drains into coronary sinus
empties into right atrium
what happens if embryonic heart cells are separated into a Petri dish and kept alive?
what does this tell us about the origin of a heart beat?
each is capable of generating its own electrical impulse followed by a contraction
its not a nerve impulse, but an inherent property of cardiac muscle cells (myogenic)
what does cardiac muscle do if a heart is surgically removes?
continues to contract rhythmically
why do myocytes have many mitochondria?
to prevent fatigue
intercalated discs function
enable synchronised contraction
gap junctions so allow quick ion movement between cells
how many nuclei do myocytes have?
multiple
heart rate definition
the number of times the heart beats in 1 minute
stroke volume definition
the amount of blood pumped by each ventricle with each heartbeat
average stroke volume
70ml per beat in an adult at rest
cardiac output definition
the volume of blood ejected from the left or right ventricle into the aorta or pulmonary artery per minute
cardiac output equation
heart rate x stroke volume
cardiac output units
ml/minute
factors affecting heart rate
autonomic innervation
hormones
fitness levels
age
factors affecting stroke volume
heart size
fitness levels
gender
contractility
duration of contraction
preload (EDV)
afterload (resistance)
what is auscultation?
listening to a patient’s heart sounds
valved disorders trigger abnormal heart sounds/murmurs
these can be heard with a stethoscope
what is stenosis?
when heart valves become rigid
the loss of flexibility of the valve interferes with normal function and may cause the heart to work harder to propel blood through the valve, which actually weakens the heart
why does cardiac output increase when somebody exercises?
increased oxygen/glucose demand due to muscle cells respiring when muscles contract
increased heart rate to pump more blood to meet demand
exercise increases venous blood return to the heart, causing increased heart rate
volume of blood in heart increases, resulting in extra stretching of left ventricular wall, meaning a stronger contraction and stroke volume increases
effect of training on cardiac output?
increased cardiac output of trained person without increasing heart rate
increased ventricular wall stretching and stronger contractions causes the muscle in the left ventricle wall to increase in thickness
therefore at rest, stroke volume is higher in a trained athlete than untrained, so it takes less bpm to deliver same cardiac output
explain change in aortic pressure during heart cycle
rises during ventricular systole as blood is forced into aorta
then gradually falls, but never below around 12kPa, because of the elasticity of its wall, which creates a recoil action: essential if blood is to be constantly delivered to the tissues
recoil provides temporary rise in pressure at the start of diastole
explain change in atrial pressure during heart cycle
always relatively low bc the thin walls of the atrium cannot create much force
it is at its highest when the atria are contracting (atrial systole), but drops when the bicuspid valve closes and its walls relax
the atria then fill with blood, which leads to a gradual build-up of pressure until a slight drop when the bicuspid valve opens and some blood moves into the ventricles
explain change in ventricular pressure during heart cycle
low at first, but gradually increases as ventricles fill with blood during atrial systole
bicuspid valves close and pressure increases dramatically as the thick muscular walls of ventricle contract
as pressure rises above that of the aorta, blood is forced into the aorta past the semi-lunar valves
pressure decreases as ventricles empty and walls relax at the start of diastole
explain change in ventricular volume during heart cycle
almost the mirror image of ventricular pressure, but w/ a short time delay
volume increases during atrial systole, as ventricles fill with blood, and then drops suddenly as blood is forced out into the aorta when ventricular pressure exceeds aortic pressure
volume increases again as the ventricles fill with blood during diastole
what is an ECG
a record of the wave of electrical activity caused by atrial systole (P), ventricular systole (QRS), and the start of ventricular diastole (T)
what is angina?
a condition in which plaques build up and reduce the blood flow to the cardiac muscle through the coronary artery.
it results in pain during exercise
what is a myocardial infarction
heart attack
takes place when atherosclerosis leads too formation of a clot that blocks the coronary artery entirely, depriving the heart muscle of oxygen so it dies
can stop the heart functioning
what is the cardiac cycle controlled by?
a small patch of specialised myogenic muscle tissue in the walls of the right atrium: PACEMAKERS
what does myogenic mean
initiate their own contraction
what are the 2 nodes in the heart?
sinoatrial node (SAN)
atrioventricular node (AVN)
affects of nerves and hormones on HR and how
- accelerator/sympathetic nerve acts on the SAN to increase HR
- vagus nerve acts on the SAN to lower HR
- adrenalin and noradrenalin act on the SAN to increase HR
endocrine and nervous system can change the frequency of the heart beats (waves of excitation from SAN)
what is the SAN and what does it do?
acts as a pacemaker (sets rate of heart)
SAN= specialised group of cardiac fibres (cells) which initiate a wave of excitation which spreads across the walls of the atria, causing depolarisation and therefore co-ordinated simultaneous contraction
what happens when the wave of excitation reaches the AVN? what is the AVN?
AVN= a second group of specialised cells near the base of the right atrium
AVN delays the conduction by about 0.13 seconds
AVN provides route for transmission of the wave of excitation from the atria to the ventricles
what is the AVN continuous with?
what is this?
bundle of His
modified cardiac fibres running down the inter ventricular septum; they fan out over the wall of the ventricles forming a network of fibres called Purkyne fibres
what happens when wave of excitation reached bundle of His
wave of excitation conducted by Purkyne fibres to the apex of the ventricles and then radiates upwards through the walls of the ventricles, causing depolarisation and therefore the cells contract from the apex up, forcing blood up and out of the heart
what is the non-conductive tissue
between atria and ventricles
atrioventricular septum
advantages of co-ordinating the heartbeat?
- ensures cells in the atria contract at same frequency & in synchrony
2.ensures ventricular systole is delayed before both ventricles contract in synchrony so that we have maximum pumping effect
how does an ECG work?
a pair of surface electrodes are placed directly on the heart, and record a repeating pattern of potential changes.
as impulses spread from the atria to the ventricles, the voltage measured between the 2 electrodes varies
this provides a ‘picture of electrical activity of the heart
how come an ECG works on humans?
the body is a good conductor of electricity
thereof the potential differences generated by the heart are conducted to the body surface where they can be recorded by the surface electrodes placed on the skin
what is the P wave?
electrical activity during atrial systole depolarisation
what is the QRS wave?
electrical activity during ventricular systole depolarisation
atria also repolarise during this period, but the event is hidden by the greater depolarisation in the ventricles
what is the T wave?
ventricular repolarisation (recovery of ventricular wall)
what is the Q-T interval?
contraction time (ventricles contraction)
what is the T-P interval?
filling time: ventricles relaxed and filling with blood
when the SAN sends out its wave of excitation, why does this not go all the way down into the ventricles?
what would happen if the atria and ventricles all contracted at the same time?
due to non-conductive tissue between the atria and ventricles (atrioventricular septum) through which the impulse cannot conduct
ventricles and atria would contract at the same time/ventricular systole wouldn’t be delayed, so wouldn’t be filled with blood, meaning they do not have the maximum pumping effect, so there is a lack of blood flow to the lungs and body
step by step heart conduction
SAN (at top of RA) generates electrical activity
wave of excitation passes over both atria, causing cardiac muscle cells to contract. atrial systole initiated
atrioventricular septum prevents conduction of impulse to ventricles
AVN (at top of septum)= only route for impulse to take. its delayed in the node, giving time for atria to finish systole
impulse carried down Purkyne tissue down to base of interventricular septum, spreads out over walls of ventricles and upwards, causing muscle to contract, pushing blood out of arteries at top of heart
what is bradycardia?
slow herat rate
resting heart rate less than 60bpm
bradycardia
ECG trace
causes?
symptoms
pattern of electrical activity is normal but slow
could indicate good aerobic fitness (elite athlete), drug use (tranquillisers, beta blockers; overdose of non-prescription or prescription)
causes may need investigation due to risk of blood clots
fatigue, dizziness, low blood pressure
what is tachycardia?
rapid heart rate
reskin heart rate greater than 100bpm
tachycardia
causes
symptoms
treatment
exercise, excitement, stress, drugs (e.g. caffeine, nicotine, amphetamine)
sometimes HR is so high that little blood is actually pumped bc filling time is so short, leading to a lower CO
symptoms include palpitations, shortness of breath and fainting
treatment may involve relaxation therapy, beta blockers
what is atrial fibrillation?
abnormal rhythm of the heart
heartbeat is irregular as has lost its rhythm
atria contracting more frequently than ventricles
no clear P wave
atrial fibrillation
symptoms
describe
causes?
risks
rapid impulses generated by atria (so contract fast-fibrillate)
heart doesn’t pump blood effectively, as heartbeat is unco-ordinated
waves are initiated by atrial cells so disorganised
could be caused by scar tissue from a previous heart attack
risk of blood clots and strokes
what is ventricular fibrillation?
electrical impulses firing from multiple points in ventricles
rhythm of heartbeat is lost
no clear P,QRS or T waves
unco-ordinated contraction, so there is fluttering and little blood is pumped
IRREGULAR
(usually contraction of cardiac muscles is coordinated)
solution for ventricular fibrillation?
cause of ventricular fibrillation
defibrillation: heart is shocked so stops, when it restarts, it may do so with a normal rhythm
caused by lack of O2 to heart e.g. due to CHD, causes blood clot so blood flow is prevented
what is an ectopic heartbeat?
heart bets too early follows by a longer-than-normal gap until next heartbeat
extra heart beats that are out of normal rhythm
how often do people have ectopic heartbeats?
usually 1 per day
what does a large PR interval suggest?
indicates slow conduction between atria and ventricles
could be slow conduction by AVN/ in delay at AVN or slow atrial conduction
what part of the heart is enlarged in a person with pulmonary hypertension, giving a large P wave
right atrium
right side of heart has to work harder to pump blood through the pulmonary arteries
what are the 5 types of blood vessel?
artery
arteriole
capillary
venule
vein
artery diameter
up to 3cm (aorta)
arteriole diameter
less than 100 um
capillary diameter
average 8um
venule diameter
20-30um
vein diameter
up to 2.5 cm (inferior vena cava)
artery components
tunica adventitia
tunica media (v thick)
tunica intima
lumen
artery wall thickness and why
thick
maintain and withstand high pressure
what is tunica adventitia in arteries made from
collagen (fibrous protein), provides strength to withstand high pressure
elastic fibres (made from fibrous protein elastin), stretch to prevent bursting and recoil to propel blood and even out surges in blood pressure
what is tunica media in arteries made from?
elastic lamellae (made from fibrous protein elastin) which stretch to prevent bursting and recoil to propel blood and even out surges in blood pressure
muscle (smooth muscle), maintains blood pressure
what is tunica intima in arteries made from?
endothelium (impermeable), smooth lining to decrease friction so increase blood flow, folded or corrugated so can expand when artery stretches
connective tissue
artery lumen size and why
narrow
small relative to diameter of artery
smaller comparable to veins
maintains blood pressure
what makes up a capillary
endothelial cells
basement membrane
pores in capillary wall
pinocytic vesicles
basement membrane in a capillary wall description
filter
prevents proteins and erythrocytes leaking out
endothelial cells in capillary wall description
1 cell thick
decreases diffusion distant for oxygen
pores in capillary wall description
fenestrations allow tissue fluid formation
what makes up an arteriole
tunica adventitia
tunica media
tunica intima
lumen
arteriole tunica media makeup compared to arteries
less elastic tissue
more smooth muscle
bc lower pressure
what is the diameter of an arteriole controlled by?
muscle layer
what is a venule made from?
tunica adventitia
tunica media (may be absent)
tunica intima
lumen
venule lumen diameter control?
not precisely controlled
what makes up a vein
tunica adventitia
tunica media
tunica intima
lumen
valves to prevent backflow of blood
tunica adventitia in veins description
thick layer of collagen and elastic fibres
provides strength
tunica media in veins description
poorly developed
less smooth muscle and elastic fibres in the wall
tunica intima veins description
endothelium with little connective tissue
sometimes indistinct from tunica media under a microscope
vein lumen diameter and why
large (larger comparable to arteries)
can accommodate large volumes of blood
eases blood flow back to heart because a smaller percentage of blood is in contact with the walls so there is less resistance to flow
vein wall thickness and why
thinner wall
doesn’t need to withstand a high blood pressure
blood flow is what speeds during systole and diastole?
why?
blood is expelled from the heart only when it contracts, therefore bloodflow through the arteries is intermittent
rapid during systole
slow during diastole
blood flow in capillaries? why?
flowing evenly
due to elastic recoil of the artery walls
what is a pulse?
expansion of the artery as ventricular systole forces waves of blood in, a pulse is felt especially in arteries close to the skin surface
where is blood flowing the fastest?
in arteries
where is blood flowing the slowest?
capillaries
what is the velocity of blood flow inversely proportional to?
cross sectional area of the blood vessel
why does blood flow slowly through the capillaries?
there is adequate time for the exchange of materials between the capillaries and the adjacent tissues
how is blood flow in capillaries increased?
localised increases in metabolites e.g. CO2 and H+ and a decrease in O2 cause vasodilation, increasing blood flow to the capillary bed
how is blood flow in capillaries reduced?
there are pre-capillary sphincter muscles (smooth muscles)
when these contract they cause construction, which either prevents or reduces the flow of blood to a capillary network
blood can then bypass the capillary bed
what is another name for a bypass vessel?
shunt vessel
how is blood flow in veins maintained?
pumping action of the heart
contractions of skeletal muscle during normal movements squeezes on the thin walled veins
this increases the pressure of the blood inside
valves ensure that this pressure directs blood back to the heart. veins run close to/within muscles/
inspiratory movements reduces pressure in the thorax, helping to create a pressure gradient to draw blood towards the heart which is in the thorax. expiratory pressure changes means pressure increases in veins outside the heart, speeding blood flow in to the heart
describe and explain how the structure of the arteries and veins links to their functions: ARTERIES
ARTERY function= transport blood away from the heart under high pressure
thick walls with collagen= strength to withstand high pressure
lots of elastic fibres can stretch and recoil= convert pulses to smooth flow
smooth muscle can contract= constricts the lumen to maintain blood pressure and flow
folded epithelium= prevents damage as the artery wall stretched in due to systolic pressure
describe and explain how the structure of the arteries and veins links to their functions: VEINS
VEIN function= transport blood back to the hart under low pressure
thinner walls, much less smooth muscle and elastic tissue= flow may be increased due to skeletal muscle contraction which squeezes on veins
larger lumen= less resistance to flow and smaller % of blood in contact with walls
has valves, helps to prevent back flow as blood is under low pressure
components of blood?
erythrocytes
plasma
platelets
leukocytes
what are leukocytes
phagocytes
neutrophils
lymphocytes (T and B)
what are platelets
fragments of dead cells
involved in blood clotting
what’s plasma made up of?
it is a straw-coloured liquid
90% water
plasma proteins
carries cells, nutrients (to where they are required) and waste
carries ions (HCO3-, Na+,Cl-), hormones. urea, CO2, heat (thermoreg.), antibodies (glycoproteins), glucose, amino acids, lipid proteins (e.g. cholesterol)
plasma proteins examples
albumen carries steroid hormones
fibrinogen involved in blood clotting
erythrocytes lifespan and why
3 months
due to damage
survive on anaerobic respiration
where are erythrocytes broken down?
in the liver
used to make bile
hydrostatic pressure definition
positive or negative
blood pressure inside the capillaries/arteries cause by fluid pushing against the sides of the vessel
heart=pump (cause)
POSITIVE
oncotic pressure definition
positive or negative
the net pressure that drives reabsorption: the movement of a fluid from the tissue fluid back into the capillaries.
due to the presence of plasma proteins (solute decreasing water potential) in the blood and the absence of these in the tissue fluid
negative
what is the net filtration pressure (NFP)
represents the interaction of the HP and OP, driving fluid out of the capillary
it is equal to the difference between the HP and the OP
negative when net reabsorption into capillaries is occurring
positive when net filtration out of capillaries is occurring
what percentage of tissue fluid drains into lymphatic vessels?
10%
why does some excess tissue fluid drain into lymphatic vessels?
prevents buildup/accumulation
drain goes back into blood supply
tissue fluid function
exchange between cells and tissue fluid takes apace
bathes cells, providing them with glucose and amino acids
cells release waste products and tF carries these away
describe tissue fluid formation
TF formation occurs at arterial end of capillary bed
there is a high HP at this end
net HP>net OP
fluid is forced out via fenestrations
water glucose and solutes to tissue cells
this is pressure filtration
red blood cells and large plasma proteins remain in the blood vessels as they cannot pass through the basement membrane
describe tissue fluid reabsorption
TF reabsorption occurs at venous end of capillary bed
net HP<net OP
OP has not changed between arterial end and venous end as plasma proteins remain in blood
HP in venous end has reduced because fluid was lost from the blood
fluid and waste products/ solutes e.g. salt are reabsorbed by osmosis
about 10% of the fluid drains into lymphatic vessels and can eventually join back with normal circulation 8
suggest why it is important that capillary walls are impermeable to albumen, the most abundant plasma protein
must stay in blood where it raises solute concentration, keeping OP high
draw water in with tissue fluid
if it diffused out, OP decreases so more water accumulates -> oedema
what is oedema
swelling in a tissue caused by accumulation of tissue fluid
net filtration pressure is higher/ oncotic pressure is lower in capillary
reasons for oedema
heart disease causes high BP, raising HP, so higher NFP, so more fluid accumulates
Kwashiorkor’s= lack of protein in diet= less plasma proteins in capillary= lower OP in capillary= higher NFP = more fluid accumulates/forms and less reabsorbed due to lower OP
kidney disease= lose proteins in urine = as above
what is the lymphatic system?
how is it arranged?
a system of vessels that drain excess fluid away from the tissues
blind ending lymphatic capillaries are found draining all the tissues
the end of the lymph capillaries have tiny valves which allow fluid to flow in but not out
the blind ending lymph capillaries join to form larger lymphatic vessels, which join up with the circulatory system at the subclavian vein in the neck
lymph composition
lymph is a colourless/pale yellow fluid similar to tissue fluid (minus the proteins)
composition depends on the tissue:
in liver it contains proteins as they are made by the liver
in small intestine more lipids as these are absorbed here via villi of ileum
what causes the movement of the lymph
skeletal muscle contraction
respiratory pump
hydrostatic pressure
valves
smooth muscle in lymphatic vessels
functions of the lymph
returns 10% of tissue fluid back to the blood
returns plasma proteins to blood (made by liver)
lacteals allow FA and glycerol to enter blood
help to prevent pathogens entering circulation
name 2 blood components that move out of the capillaries
water form plasma
neutrophils
name 2 components of the blood that do not move out through the capillary walls
large plasma proteins
erythrocytes
name 4 transported substances that would move out of the blood into the tissues
glucose
amino acids
salts/hormones
mineral ions
how is hydrostatic pressure generated
pumping action of the heart
state a major component of plasma that contributes to the osmotic pressure (solute potential)
plasma proteins
explain the importance of lymphatic drainage
returns 10% of tissue fluid back to blood via lymph
helps to prevent pathogens entering circulation
returns plasma proteins to the blood
more fluid is lost than reabsorbed by capillaries
prevents oedema/swelling/fluid retention
constituents of blood
plasma
RBC
WBC
platelets
constituents of tissue fluid
like plasma but without large proteins
WBC may squeeze out into TF
constituents of lymph
like tissue fluid but with more fat, WBC and antibodies
explanation of differences in constituents of blood, TF and lymph
most proteins are too large to cross capillary wall
WBC can squeeze through pores in capillary walls
formation of blood
stem cells in bone marrow
formation of tissue fluid
filtration pressure across capillary wall
formation of lymph
excess tissue fluid drains into the lymph
where is blood found
heart
blood vessels
where is tissue fluid found
bathing cells
where is lymph found
in lymph vessels and passes through the lymph nodes
function of blood
transport of substances and defence against disease
function of tissue fluid
transport over short distances and exchange of material within cells
function of lymph
returns excess fluid to the blood via the subclavian vein
defence
pressure of blood
high
pressure of tissue fluid
low
pressure of lymph
low
partial pressure of gases definition
pressure exerted by a gas in a mixture of gases
is directly related to the concentration of that gas in the mixture
normal atmospheric pressure
760mm Hg (sum of all major gases in the air)
% of oxygen in the air
21% or 20.95%
partial pressure of oxygen in air
21% of 760
160mm Hg
why is pO2 high in the pulmonary vein and systemic arteries?
higher conc. of O2 because O2 has been inhaled and associated with haemoglobin
pO2 in atmosphere, alveolar air, pulmonary veins and pulmonary arteries in mm Hg
atmosphere=160
alveolar air= 104
PV= 104
PA= 40
what does the oxygen dissociation curve look like
slow increase
steep increase
levels out
why is there a slow increase at the start of the oxygen dissociation curve?
haem groups are found in the middle of the haemoglobin, so it is difficult for the firs oxygen to associate
why is there a steep increase in the middle of the oxygen dissociation curve?
once the first oxygen molecule associates there is a slight change in the shape of the haemoglobin- this makes it easier for more oxygen to diffuse in and associate with Hb
CONFORMATIONAL CHANGE
why does the oxygen dissociation curve level out at the end?
once the haemoglobin contains 3 oxygen molecules it becomes harder for the 4th to associate: despite the partial pressure being high it is difficult to get 100% saturation
relationship between partial pressure of oxygen and affinity w/ haemoglobin
when pO2 is low e.f in respiring tissues 2kPa, Hb has a low affinity for O2 so it unloads O2 and so it has a low saturation of O2 around 20%
where pO2 is high e.g. in lungs 12kPa, Hb has a high affinity for O2, so it has a high saturation of 95% and is loading O2
why is oxygen dissociation curve ‘s’ shaped/sigmoid
as one molecule of O2 binds to haemoglobin, the affinity of oxygen increases due to conformational change in the shape of Hb
difference between foetal and adult Hb oxygen dissociation curve graphs?
why?
foetal Hb curve is shifted to the left
at each point along the curve, foetal haemoglobin has a higher affinity for oxygen so therefore a higher oxygen saturation
this means that it can always load oxygen from the maternal haemoglobin in the placenta through the villi
e.g. at low pO2, adult Hb has lower % sat of oxygen so has unloaded O2 but foetal Hb has higher % sat so has loaded O2
difference between the myoglobin and haemoglobin oxygen dissociation curves?
why?
myoglobin curve is shifted to the left
myoglobin has a very high affinity for O2: this means that it will only dissociate & unload oxygen when oxygen levels are very low
in normally respiring tissues myoglobin still has a high saturation with oxygen
e.g. at low pO2, myoglobin has a high % sat, so will load O2. when pO2 is les than 1kPa, will unload
what is myoglobin important for?
important for habitats where oxygen concentrations are low e.g. high altitudes and deep water of lake/ocean
in which ways is CO2 transported away form respiring tissues?
about 5% dissolves directly in the blood plasma
about 85% is transported in the form of hydrogen carbonate ions in the blood plasma
a further 10% is combined directly with haemoglobin to form carbaminohaemoglobin
where doesCO2 bind to Hb
binds to amino acid residue on the globin portions(in polypeptide chain) (not competitively with O2)
what is carboxyhaemoglobin
dangerous?
carbon monoxide binds to Hb competitively against O2
irreversible, prevents O2 transport
higher affinity than O2
what is haemoglobinic acid?
uses?
HHb
H+ ions bind to Hb so Hb is a buffer and mops up H+, limiting a decrease in blood pH
when H+ bind to Hb, they change the shape of Hb (conformational), which reduces Hb affinity for O2 and makes it unload O2 more readily, so there is more dissociation of O2 from oxyhaemoglobin at respiring tissues where H+ conc is high
step by step how CO2 affects blood pH and how this leads to oxygen unloading
- CO2 diffuses into RBC down pCO2 gradient
- CO2 reacts with H2O, catalysed by carbonic anhydrase, to form carbonic acid
- acid dissociates into H+ and HCO3- ion
- HCO3- diffuses into blood plasma
- Cl- diffuse into RBC to maintain electrical balance= chloride shift
- H+ bind to Hb, forming haemoglobinic acid, which reduces its affinity for O2, so O2 unloads
- O2 dissociates to from oxyhaemoglobin
8.O2 diffuses out of RBC to respiring cells
what does carbonic anhydrase enzyme require to catalyse reaction?
requires cofactor (prosthetic group)
Zn2+ ion
where does the reverse of the CO2 oxygen unloading process happens?
in the lungs
what is the Bohr effect
the presence of carbon dioxide helps the release of oxygen from haemoglobin.
what is the Bohr shift
how can this be seen?
when more carbon dioxide is present the curve for oxygen dissociation shifts to the right
compare the oxygen dissociation curves where there is less carbon dioxide present and when there is more carbon dioxide in the blood
Bohr shift graph conclusions
the higher the pCO2, the more readily Hb unloads O2 to cells
this allows more O2 to be given to cells which have a high activity e.g. respiring tissues with low pO2 and high pCO2
e.g. at a certain pO2, the Hb % sat is lower when there is more w/ CO2 present in the blood. therefore if more CO2 present, Hb has a reduced affinity for O2
as pCO2 increases, the O2 dissociation curve shifts right
when is a haemoglobin said to be saturated and partially saturated?
partially saturated= when 1 to 3 ham sites re occupied
saturated=when all 4 hame sites are occupied
what does a haemoglobin saturation of 100% mean?
every harm group in all of the erythrocytes of the body is bound to oxygen
what is general haemoglobin saturation in a healthy individual with normal Hb levels?
95 to 99 %
example of a tissue with low metabolic rate
adipose
(body fat)
difference between foetal Hb and maternal Hb
both have 4 subunits
2 of the subunits of foetal Hb have a different structure that causes foetal Hb to have a greater affinity for O2 than adult Hb
partial pressure of oxygen in placenta, foetal blood and maternal blood?
lower in placenta than in maternal arteries
not large difference between foetal and maternal
what does a lower, more acidic pH promote?
therefore what does a higher, more basic pH inhibit?
oxygen dissociation from haemoglobin
effect of more CO2 in blood on pH?
more molecules need to be converted do more H+ ions, lowering blood pH
blood pH may become more acidic when certain byproducts of cell metabolism e.g. lactic acid, carbonic acid and CO2 are released into the bloodstream
tone of Hb when not transporting O2?
therefore what is the colour of deoxy blood?
bluish-purple
dark maroon
what is acclimatisation?
effect of low pO2 on blood
the process of adjustment that the respiratory system makes due to chronic exposure to high altitude
over a period of time, the body adjusts to accommodate the lower partial pressure of oxygen
the low pO2 at high altitudes results in a lower oxygen saturation level of Hb in the blood
in turn, the tissue levels of oxygen are also lower
effect of low oxygen saturation levels on kidneys and thereforre the blood?
kidneys are stimulated to produce the hormone erythropoietin (EPO), which stimulates the production of erythrocytes, resulting in a greater number of circulating erythrocytes in an individual at a high altitude over a longer period
with more RBCs, there is more Hb to help transport the available O2
even though there is low saturation of each Hb molecule,, there will be more Hb present, so more O2 in blood
adaptation of some animals at high altitude?
some have evolved Hb that has a higher affinity for oxygen than normal adult Hb in humans
this means their Hb is able to associate with oxygen more readily at lower partial pressures
where can a pulse be felt
arteries
sphincter muscles are typically found in the walls of which vessels?
arterioles
why does diastole follow systole?
cardiac muscle takes a short time to repolarise after being stimulated
