Transport in animals Flashcards
when organisms get bigger, why aren’t simple exchange processes enough to satisfy them
- as organisms get bigger, so do the distances between cells and outside of body
- metabolic demands
- SA:V ratio
- molecules
- waste products
- food
why isn’t diffusion possible when an organism gets too big
- to transport substances into the inner core of the body would be too slow
- organism wouldn’t survive
metabolic demands
- high
- multicellular organisms need lots of food and produce lots of waster products
- diffusion over long distance isn’t enough to supply needed quantities
SA:V ratio
- gets smaller as organisms get bigger
- diffusion distances get bigger
- amount of surface area available to absorb or remove substances get smaller
molecules
e.g hormones/enzymes may be made in one place but needed in another
waste products
- of metabolism
- need to be removed by cells
- transported to excretory organs
food
- digested in one organ system
- needed in every cell for respiration
what do circulatory systems generally carry
- oxygen
- carbon dioxide
- nutrients
- waste products
- hormones
common features of circulatory systems
- liquid transport medium which circulates around the system
- vessels that carry the transport medium
- pumping mechanism to move fluid around the system
mass transport
when substances are transported in a mass of fluid with a mechanism for moving the fluid around the body
open circulatory system
- few vessels to contain the transport medium
- transport medium is pumped straight from heart into body cavity of the animal
haemocoel
- open body cavity
- transport medium generally under low pressure
in an open circulatory system how does exchange take place
- transport medium comes into direct contact with tissues and cells
in an open circulatory system how does the transport medium return to the heart
- open ended vessel
examples of open circulatory systems
- invertebrate
- fish
- most insects
haemolymph
insect blood
what does haemolymph carry
- food
- nitrogenous waste products
- cells involved in defence against disease
disadvantage of an open circulatory system
- amount of haemolymph flowing to a particular tissue can’t be varied to meet changing demands
- steep diffusion gradients can’t be maintained for efficient diffusion
closed circulatory system
- blood is enclosed in blood vessels
- blood doesn’t come into direct contact with any cells of the body
how does the heart pump blood around the body in a closed circulatory system
- quickly
- under pressure
where does blood return in a closed circulatory system
directly to the heart
how do substances enter and leave the blood in a closed circulatory system
- by diffusion
- through walls of blood vessels
how can the amount of blood flowing to a particular tissue be adjusted in a closed circulatory system
- narrowing / widening of blood vessels
examples of where closed circulatory systems are found
- all vertebrate groups
- mammals
- phyla e.g fish and worms
single closed circulatory system
- blood flows through heart and is pumped out to travel all around the body before returning to the heart
- blood travels once through the heart for each complete circulation
in a single closed circulatory system how many sets of capillaries does blood flow through before returning to the heart
2
in the first set of capillaries in a singled closed, what does blood exchange
- carbon dioxide
- oxygen
in the second set of capillaries in a single closed where is blood exchanged
- between blood and cells
- in different organ systems
how does blood flow back to the heart in a single closed
- at lower pressure
- slowly
disadvantage - single closed
- slow flow back to heart
- limiting efficiency of exchange process
- activity levels of animals is low
why do fish (single closed) have quick exchange systems
- counter current exchange system
- body weight supported by water
- don’t maintain their own body temperature
- reducing their metabolic demands
why do birds and mammals need an efficient exchange system
- need to maintain their own body temperature
- active
- high metabolic demands
double circulatory system - advantages
- most efficient
double closed circulatory system
- involved 2 separate circulations around the heart for a complete circulation
in mammals explain the 2 different circulatory systems
- blood pumped from heart to lungs to collect O2/remove CO2
- returns to heart
- blood flows through heart and is pumped out to travel around body
- returns to heart again
how many times does blood travel through the heart in a double circulatory system for a complete circulation
twice
how many capillary networks are used in a double circulatory system
1
rate at which blood is pumped - double circulatory
- quickly
- high pressure
give main components of blood vessels
- collagen
- elastic fibers
- smooth muscle
what are elastic fibers made of
elastin
elastic fibres
- stretch and recoil
- provides vessel walls with flexibility
smooth muscle
- contracts or relaxes
- changes size of lumen
collagen
- gives structural support
- maintains shape and volume of the vessel
arteries
- carry blood away from the heart
- generally carry oxygenated blood
which artery doesn’t carry oxygenated blood
- pulmonary artery
- umbilical artery (during pregnancy)
what pressure is the blood at the arteries at
higher pressure
what do artery walls contain
- smooth muscle
- elastic fibers
- collagen
elastic fibers aid arteries -
- enable them to withstand force of blood pumped out of the heart
- can stretch to withstand larger blood volume
- in between contractions can recoil and return to original length
why is it useful that artery walls recoil and return to original length in between heart contractions
- to even out surges of blood pumped from heart
- ensures continuous flow
how does a smooth endothelium lining of the artery help
- when heart contracts allows blood do flow over it smoothly
arterioles
link arteries and capillaries
arteriole features
- more smooth muscle less elastic fibers
- as they have little surge
arterioles function
- controls flow of blood to individual organs
- by vasoconstriction or vasodilation
how do arterioles vasoconstrict
- when smooth muscle contracts
how do arterioles vasodilate
- when smooth muscle relaxes
aneurysm
- a bulge or weakness in a blood vessel
what are the most common places for aneurysms
- brain arteries
- aorta
what can increase risks from aneurysms
high blood pressure
capillaries
-microscopic blood vessels which link arterioles to venules
- form an extensive network all throughout the body
capillary lumen -
- small
- so red blood cells have to travel in single file
capillary function
exchange substances through capillary walls between blood and tissue cells
where do many substances pass out of capillary walls into fluid surrounding cells
- the large gaps between endothelial cells which make up capillary walls
how are capillaries adapted
- large sa for diffusion
- total cross sectional area is always greater than arterioles supplying them so rate of blood falls
- single endothelial cell thick = short diffusion distance
why is it good that the rate of blood flow falls in capillaries
- gives them more time for exchange of materials by diffusion
veins
-carry blood away from body cells towards the heart
- generally deoxygenated
which vein doesn’t carry deoxygenated blood
- pulmonary vein
- umbilical vein
flow of deoxygenated blood from capillaries to heart pathway :
- venules
- large veins
- inferior and superior vena cava
venules
small veins
how much of your blood volume is in veins
60%
blood pressure in veins
lower
medium sized veins have valves - why
prevent back flow of blood
why do veins have a large lumen
so blood flows easily
venules function
link capillaries with veins
venule features
- thin walls
- little smooth muscle
how is the body adapted to allow blood to return to the heart from the lungs when it is being pumped back against gravity and at low pressure
- veins have 1 way valves
- bigger veins run between active muscles in the body
- breathing movements of chest act as a pump
1 way valves helping blood pump back to the heart
- flaps on inner lining of vein
- when open blood can pass through
- if blood flows backwards valves close preventing back flow
big veins running between active muscles - aiding blood pumping back to heart
- when muscles contract they squeeze veins
- forces blood to heart
breathing movements aiding blood being pumped back to heart -
- causes pressure changes
- squeezing action move blood in the veins of abdomen and chest towards heart
main transport medium in circulatory system
blood
what does blood mainly consist of
plasma - 55%
what does plasma carry
- dissolved glucose
- amino acids
- mineral ions
- hormones
- plasma proteins (e.g albumin)
- red blood cells
- white blood cells
- platelets
albumin
responsible for maintaining osmotic potential of blood
red blood cells
carry oxygen around body
platelets
fragments of larger cells involved in clotting
what is the main component of plasma
water
what does the blood transport
- O2 and CO2 to and from respiring cells
- digested food from small intestine
- nitrogenous waste products to excretory organs
- hormones
- food molecules from storage to cells which need them
- platelets to damaged areas
- cells and antibodies needed for immunity
what are other functions of the blood
- maintain body temperature
- acts as a buffer to minimize pH changes
what can substances dissolved in plasma with the exception of large plasma proteins and rbcs pass through
fenestrations in capillary walls
what do plasma proteins give the blood in capillary walls
- high solute potential
- low water potential
compared to surrounding fluid
as blood in capillaries have a high solute concentration and low water potential with surrounding flood what tends to happen
- water from surrounding fluid moves into blood via osmosis
oncotic pressure
tendency of water to move into blood by osmosis
hydrostatic pressure
- pressure from the surge of blood that occurs every time the heart contracts
where is the hydrostatic pressure high
- at arterial end of capillary (blood flows from arterioles into capillaries )
- this forces fluid out of the capillaries at high pressure (4.6kpa)
due to the high hydrostatic pressure at the arterial end of capillaries, what happens
- fluid is squeezed out of capillaries
- due to hydrostatic pressure being higher than oncotic pressure
where does the fluid that leaves the capillaries due to high hydrostatic pressure at the arterial end go
- the spaces between cells and fluid
- known as tissue fluid
composition of tissue fluid
- same as plasma
- without plasma proteins and rbcs
what happens as the blood moves through the capillaries towards the venous system
-balance of forces change
- hydrostatic pressure falls
- oncotic pressure stays the same
average oncotic pressure
-3.3 kpa
hydrostatic pressure - arterial end
4.6 kpa
hydrostatic pressure venule end
2.3 kpa
why does the hydrostatic pressure fall at the venule end of the capillary
- fluid has moved out
- pulse is completely lost
what happens to the capillaries at the venule end as hydrostatic pressure has fallen
- water moves back into them via osmosis as oncotic pressure is greater
- around 90% of tissue fluid is back in blood vessels
what happens to the tissue fluid which doesn’t return to capillaries
- around 10% that leaves blood vessels drains into a system of lymph capillaries
- it is now known as lymph
lymph composition
similar to plasma -
- less oxygen
- fewer nutrients
- has fatty acids
how has fatty acids entered lymph
from villi from small intestine
lymph capillaries join to form larger vessels
how is lymph transported through these
by squeezing of body muscles
what prevents back flow of lymph
one way valves
what are found along lymph vessels
lymph nodes
what builds up in lymph nodes
lymphocytes
why do lymphocytes build up in lymph nodes
- to produce antibodies
- these are passed into blood
another role of lymph nodes
- intercept bacteria and debris from lymph
- these are ingested by phagocytes
what are large lymph nodes a sign of
the body fighting off an invading pathogen
where are lymph nodes found
neck
armpits
groin
stomach
erythrocytes adaptations
- bioncave shape
- no nuclei
- haemoglobin
rbcs- no nuclei
- maximizes amount of haemoglobin that fits into cells
rbcs no nuclei - disadvantage
- limits their life to only around 120 days
rbcs haemoglobin
red pigment which carries oxygen
rbcs - bioncave shape
- larger surface area
- simple disc structure so there’s more availability for gases to exchange / space
- helps pass through narrow capillaries
haemoglobin - structure
- large globular conjugated protein
- 4 peptide chains
- each has an iron haem prosthetic group
how many oxygen molecules can each haemoglobin bind to
4
when oxygen binds to haemoglobin what is formed
oxyhaemoglobin
why can oxygen easily bind to rbcs in the lungs
- o2 levels in rbcs are low here
- steep conc gradient
what happens when 1 o2 molecule binds with haemoglobin
- the haemoglobin changes shape
- making it easier for the next oxygen molecules to bind
- known as positive cooperativity
the oxygen concentration of the rbc stays low in the lungs until what
all haemoglobin is saturated with oxygen
what happens when blood reaches tissues in terms of 02 concentration
- concentration of o2 is much lower in body cells than rbcs
- o2 moves out of rbcs down conc gradient
once the first o2 molecule is removed from haemoglobin at the body cells what happens
- haemoglobin changes shape
- making it easier to remove remaining o2 molecules
oxygen disassociation curve
shows how blood carries and releases oxygen
in an oxygen disassociation curve what is the %saturation of haemoglobin in the blood plotted against
partial pressure of oxygen
why does the curve level out when all oxygen has bound to hemoglobin
hemoglobin is saturated and can’t take any more o2 up
at high partial pressure of oxygen what is the oxygen haemoglobin saturation like
rbcs are rapidly loaded with oxygen
in a drop of oxygen pressure levels what happens to haemoglobin saturation in the graph
oxygen is released from hemoglobin and diffuses into cells
what helps oxygen disassociate with haemoglobin at respiring cells
low pH in tissues compared to lungs
bohr effect
- as partial pressure of carbon dioxide rises
- haemoglobin gives up oxygen more readily
what happens due to the bohr effect in lungs
- in active tissues with higher partial pressure of co2
- haemoglobin gives up o2
more readily
what happens due to the bohr effect in lungs
- proportion of carbon dioxide is lower
- oxygen binds to haemoglobin molecules readily
when a fetus is dependent on a mother supplying it oxygenated blood in the womb, how does it work
- oxygenated blood from mother runs close to deoxygenated fetal blood
- as fetal blood has a higher affinity for oxygen than adult haemoglobin at each point along the curve
- removing oxygen from maternal blood as they move past each other
how is carbon dioxide transported from tissues to lungs
- plasma (5%)
- combined with amino acid groups in polypeptide chains of haemoglobin
- converted to hydrogen carbonate ions in cytoplasm of rbcs
what is formed when carbon dioxide combine with the amino acid chains of haemoglobin
carbaminohaemoglobin
when co2 reacts with h2o what is formed
carbonic acid
when carbonic acid disassociates what forms
hydrogen ions
hydrogen carbonate ions
what form is most of the carbon dioxide in when it diffuses into blood from cells when it is traveling to the lungs in
hydrogen carbonate ions
what enzyme catalyses the reaction between co2 and h2o to form carbonic acid in blood cell cytoplasm
carbonic anhydrase
how do the negatively charged hydrogen carbonate ions move out of the rbcs into plasma
diffusion down a concentration gradient
chloride shift
negatively charged chloride ions move into rbcs maintaining electrical balance
of cell
how to rbcs maintain a steep concentration gradient for co2
to diffuse from respiring tissues into rbcs
removing co2 and converting it into hydrogen carbonate ions
what happens when the blood reaches the lung tissue where there’s a low conc of co2
carbonic anhydrase catalyses reverse reaction breaking down carbonic acid into co2 and water
what happen when hydrogen carbonate ions diffuse back into rbcs
-they react with h+ ions to form more carbonic acid
- when this is broken down by carbonic anhydrase it releases free co2
- diffused out of blood into lungs
how to chloride ions diffuse out of rbcs into plasma
down electrochemical gradient
how does haemoglobin assist with exchange of Co2
- acts as a buffer
- prevents changes in pH by accepting H+ ions in a reversible reaction
- forms haemoglobinic acid
where does deoxygenated flow into the heart
- right side
where does the right side of the heart pump blood to
the lungs
where is oxygenated blood found in the heart
left side
where does oxygenated blood in the heart get pumped to
rest of the body
what is the heart made of
cardiac muscle
cardiac muscle
- contracts and relaxed at a regular rhythm
- doesn’t get fatigue or require rest
what supplies the cardiac muscle with oxygenated blood
- coronary artieries
why does the cardiac muscle need oxygenated blood
to keep it contracting and relaxing all the time
what membrane is the heart surrounded by
inelastic pericardial membranes
inelastic pericardial membranes
help prevent heart ever over distending with blood
pathway of blood of heart - start with deoxygenated blood
- enters vena cava
- right atrium
- right ventricle
- av valve (tricuspid)
- right ventricle m
- semi lunar valve
- pulmonary artery
- lungs
- pulmonary vein
- left atrium
- av valve (bicuspid)
- left ventricle
- semi lunar valve
- aorta
- body
where does deoxygenated blood from the upper half of the body flow into the heart through
superior vena cava
where does deoxygenated blood from the lower half of the body flow into the heart through
- inferior vena cava
atria features
- thin muscular walls
when blood pressure increases in the atria what happens
av valves open to allow blood to flow into ventricle
when the ventricle contracts what closes
valves to prevent back flow back to atria
tendinous cords role
makes sure valves don’t turn inside out due to pressure increase when ventricle contracts
when the right ventricle contracts, where does the deoxygenated blood go
- through the semilunar valves
- into the pulmonary artery
semi lunar valves
prevents backflow of blood
where does the pulmonary artery take the deoxygenated blood
- to the capillary beds at the lungs
where does oxygenated blood from the heart enter
- pulmonary vein
- leads into left atrium
as pressure in the left atrium builds, what valve opens between the atrium and ventricle
- bicuspid valve
- causing left ventricle to fill with blood
when both the left atrium and ventricle are filled with blood, what contracts
- the atrium
- forcing all the blood into the left ventricle
when the left ventricle contracts, which valve does the oxygenated blood travel through
- semi lunar valves
- into the aorta
where does oxygenated blood go after leaving the heart
to the rest of the body
as the ventricle contracts the tricuspid valve closes - why
prevents backflow
why is the left side of the heart thicker than the right
- has to produce sufficient force
- to overcome aorta and arterial systems of whole body
- has to move blood at low pressure to extremities of the body
where does the right side of the heart have to pump blood
- lungs
- short distance
- only needs to overcome resistance of pulmonary circulation
septum
- inner dividing wall of the heart
- prevents oxygenated and deoxygenated parts of the heart from mixing
cardiac cycle
events in a single heart beat
how long roughly is the cardiac cycle
0.8 seconds
diastole
relaxation phase of cardiac cycle
events of diastole
- atria and ventricles fill with blood
- increasing volume and pressure of blood in the heart
- pressure in arteries is low
systole
contraction phase of cardiac cycle
events of systole
- ventricles and atria contact
- massive increase in blood pressure
- forces blood out of the heart
- now pressure in heart is lower
- pressure in arteries is higher
how can heart beat sounds be heard
stethoscope
what are the sounds of the heart
blood pressure closing heart valves
what are sounds of a heartbeat described as
lub dub
lub sound
- blood forced against AV valves as ventricles contract
dub sound
semilunar valves close as ventricles relax
myogenic
cardiac muscle has its own intrinsic rhythm
beats at around 60 bpm
average resting hr - adult
70 bpm
how is the basic rhythm of our heart rate maintained
a wave of electrical exication
where does the wave of electrical exication begin
sa node
SA node
- a pacemaker causing atria to contract
- it initiates the heart beat
why doesn’t the SA node also cause the ventricles to contract
there’s a layer of non- conducting tissue preventing it passing straight to ventricles
what receives the electrical impulse from the SA node
AV node
the AV node imposes a slight delay before stimulating what
bundle of his
bundle of his
bundle of conducting tissue made up of purkyne fibres
where do the purkyne fibres penetrate through
septum between ventricles
what happens at the bundle of his
- it splits into 2 branches
- conducts a wave of exication to the apex
at the apex what happens to the purkeyne fibres
- the spread out through the walls of ventricles
- this spread of exication causes ventricular systole from the apex
why is it good for ventricular systole to start at the apex
more efficient at emptying ventricles
why does the AV node delay before stimulating the bundle of his
to ensure the atria and ventricles do not contract at the same time
electrocardiogram
measures spread of electrical exication
why are electrocardiograms useful
it helps to see what happens in the heart as it contracts
what does ECG actually measure
electrical differences in your skin which are caused by electrical activity
how are ECGs used
- electrodes are stuck to clean skin
- ## signal from each electrode is fed to the machine
ECG uses
diagnose heart problems
tachycardia
when heart beat is rapid, over 100 bpm
when is tachycardia normal
exercise
fever
fright
anger
tachycardia treatments
- medication
- surgery
bradycardia
when heart rate slows down to below 60 bpm
when is bradycardia normal
if you are very fit
heart beats more slowly and efficiently
how is severe bradycardia treated
artificial pacemaker so heart beats steadily
ectopic heart beat
extra heart beats out of normal rhythm
atrial fibrilation
- abnormal rhythm of the heart
- rapid electrical impulses are generated in atria
- but they don’t contract properly, some do not reach ventricles
- so heart does not pump blood effectively
example of atrial fibrilation
arrhythmia
how is a bird ECG different to a humans
- R waves move down not up
- birds have faster heart rates
how is oncotic pressure established
- plasma proteins are too big
- they can’t leave the capillary
- water potential in capillary becomes lower than tissue fluid
- so water moves by osmosis into the capillary
