3.2 transport in animals Flashcards
what are the 3 reasons for the need for transport systems
size
surface area to volume ratio
metabollic activity
why does size influence the need for a transport system
the innermost cells in an organism are further away increasing diffusion distance.
the diffusion rate is reduced and is too slow to supply oxygen and nutrients to the respiring tissues
The outer layer of cells also uses up the supplies so less reaches the cells deep inside the body
How does the surface area to volume ration influence the need for a transport system
small animals have a high SA:V meaning for each gram of body tissue they have sufficient surface area through which exchange can occur
how does metabolic activity influence the need for an exchange system?
releasing energy from food during aerobic respiration requires oxygen so an active animal requires a good supply of oxygen and nutrients for energy especially animals that keep themselves warm
What are features of an efficient transport system
A fluid or medium to transport oxygen and waste in
a pump to create pressure that will push the fluid around
exchange surfaces that enable substances to enter and leave the blood
tubes or vessels to carry the blood by mass flow
two circuits
What is a single circulatory system?
E.G. fish
blood flows through the heart once for every circuit
What is a double circulatory system?
E.G. mammals
the system has two separate circuits where one carries deoxygenated blood to the lungs and one where oxygenated blood is carried to the tissues
heart - body - heart - lungs - heart
What are the advantages of a double circulatory system?
the heart can increase the blood pressure after it has passed through the lungs so blood is under higher pressure and flows quicker
allows greater flow of blood to the tissues
enables high metabolic activity
Why can’t pressure be too high in the pulmonary circulation?
may damage the delicate capillaries in the lungs
What is an open circulatory systems
where the blood isn’t held in the vessels and instead circulates in the body cavity so the tissues are bathed directly in the blood
What are the disadvantages of open circulatory systems?
blood pressure and flow is low
circulation of blood may be affected by body movements or lack of them
what is a closed circulatory system?
Where the blood is contained in vessels
What are the advantages of a closed circulatory system?
higher pressure do blood flows more rapidly
more rapid delivery of oxygen and nutrients
more rapid removal of CO2 and other waste
transport is independent of body movements
what are the blood vessels called
arteries
arterioles
capillaries
veins
venules
what is the structure of an artery
lumen
endothelium
elastic fibres
smooth muscle
collagen fibres
What is the function of the arteries?
arteries carry blood away from the heart
How are arteries adapted to their function
the blood is at high pressure so the artery wall must be thick in order to withstand that pressure
the lumen is also relatively small to maintain high pressure
the inner wall is folded to allow lumen to expand as blood flow increases
how are arterioles adapted to their function
they are small blood vessels that distribute blood from the artery to the capillary
arteriole walls contain a layer of smooth muscle which contracts and constricts the diameter of the arteriole increasing resistance to the flow of blood reducing its rate
constriction of the arteriole can also be used to divert the flow of blood to regions of the body which require more oxygen
what is the structure of capillaries?
they have very thin walls and are one cell thick and consist of one layer of flattened endothelial cells
they have leaky walls
how does the structure of capillaries relate to their function
their thinner lumen causes red blood cells to be squeezed against its walls reducing diffusion distance
they are one cell thick so this reduces diffusion distance further
What is the function of venules?
they consist of thin layers of muscle and elastic tissue and blood flows from the capillaries to the venules
What is the structure of veins
veins have a relatively large lumen and thin layers of smooth muscle and collagen and elastic tissue
lumen
endothelium
elastic fibres
smooth muscle
collagen fibres
they contain valves
How is the structure of the veins related to their function
veins carry blood back to the heart at a relatively low pressure so the walls do not need to be thick
the layers of elastic fibres, smooth muscle and collagen fibres do not need to be thick as they don’t need to stretch and recoil and aren’t actively constricted to reduce blood flow
veins also contain valves to prevent the backflow of blood
the thin walls can be flattened by the action of the surrounding skeletal muscles and applies pressure to the blood.
define hydrostatic pressure
pressure that a fluid exerts when pushing against the sides of a vessel or container.
Define oncotic pressure
the pressure created by the osmotic effects of the solutes
what is tissue fluid
the fluid surrounding cells and tissues
what is tissue fluid composed of
similar to blood plasma but doesn’t contain most of the cells found in blood plasma or plasma proteins
so it contains many dissolved substances such as oxygen carbon dioxide minerals amino acids glucose etc.
How is tissue fluid formed (summary)
as blood plasma leaks from the capillaries it carries all the dissolved substances into the tissue fluid
How would you describe the movement of blood plasma from the capillaries
mass movement rather than diffusion
How does tissue fluid form? (detailed )
at the arterial end of a capillary the blood is at a relatively high hydrostatic pressure and this pressure tends to push the blood fluid out of the capillary walls
the fluid that leaves the blood consists of plasma with dissolved nutrients and oxygen and the cells that are too large to be pushed through the gaps such as erythrocytes tend to remain in the blood
The tissue fluid surrounds the body cells so exchange of gases and nutrients can occur across the plasma membranes
oxygen and other nutrients enter the cells and carbon dioxide and other waste products leave the cells
How does tissue fluid return to the blood?
the blood pressure at the venous end of the capillary is much lower allowing some of the tissue fluid to return to the capillary carrying co2 and other waste products
where does some tissue fluid go if not the blood
some tissue fluid is directed to the lymph system which drains the excess tissue fluid out of the tissues and returns it to the blood system in the subclavian vein in the chest
what influences the movement of fluids in the capillaries
hydrostatic pressure of the blood tends to push fluids out of the blood and into the tissues
the hydrostatic pressure of the tissue fluid tends to push fluid into the capillaries
the oncotic pressure of the blood tends to pull water back into the blood so it has a negative figure (venule end)
the oncotic pressure of the fluid tends to pull water into the tissue fluid
give a simple description of the heart
the heart is a muscular pump with two sides
the right side pumps deoxygenated blood to the lungs to be oxygenated
the left side pumps oxygenated blood to the rest of the body
What are some external features of the heart?
it is made of cardiac muscles and has a coronary artery that provides it with oxygenated blood
describe the flow of blood through vessels of the heart
deoxygenated blood flows from the vena cava to the right atrium and oxygenated blood flows through the pulmonary vein to the left atrium
from the atria blood flows through the atrio-ventricular valves to the ventricles and these valves have tendinous cords attached to them to prevent them from turning inside out when the ventricles contract
the septum separates the ventricles from one another
oxygenated blood flows through the aorta from the left ventricle to the rest of the body and deoxygenated blood flows through the pulmonary artery from the right ventricle to the lungs and through the semi-lunar valves
describe the structure of the chambers in the heart
Atria - the walls of the atria are rather thin because these chambers do not need to create a large amount of pressure
describe the structure of the chambers in the heart
Atria - the walls of the atria are rather thin because these chambers do not need to create a large amount of pressure
right ventricle - the wall of the right ventricle are thicker than those of the atria as it pumps deoxygenated blood to the lungs, the alveoli are very delicate and can be damaged by high pressure
left ventricle - the walls of the left ventricle are thicker than that of the right as the blood needs to be pumped to the rest of the body and needs sufficient pressure to overcome the resistance of systemic circulation
What is the definition of the cardiac cycle?
The events that occur in one heartbeat
What occurs during atrial systole
both right and left atria contract and a small increase in pressure occurs helping to push blood into the ventricles
What occurs during ventricular systole
both left and right ventricles contract at their base so blood is pushed up towards the arteries
What occurs during diastole
The muscular walls of all four chambers relax and elastic recoil allows the chambers to expand creating a decrease in pressure and allowing blood to flow in from the veins
Describe the action of the atrio-ventricular valves during systole
blood in the atria pushes the atrio-ventricular valves open and the valves remain open while the atria contract but close when the atria begin to relax and this closure is caused by the swirling action of blood in the ventricles
higher blood pressure behind valve causes it to open but a higher pressure in front causes it to close and low pressure behind cannot open the valve
Describe the action of the semi-lunar valves during systole
before ventricular contraction the pressure in the major arteries is higher than that of the ventricles so they remain closed
ventricular systole raises the blood pressure in the ventricles very quickly and once the pressure is above that of the major arteries they open
during diastole when pressure in the ventricles drops below that of the major arteries the semi-lunar valves close so blood doesn’t flow back into the ventricles
describe the pressure in blood vessels
the further the blood flows along the arteries the more pressure drops and fluctuations become less obvious
Define bradycardia
a slow heart rhythm
define an ectopic heartbeat
an extra beat or an early beat of the ventricles
Define an electrocardiogram
trace that records the electrical activity of the heart
Define fibrillation
uncoordinated contraction of the atria and ventricles
define myogenic muscle
muscle that can initiate its own contraction
define purkyne tissue
specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum to the ventricles
describe the sino-atrial node
small patch of tissues that send waves of excitation at regular intervals to initiate contractions
Define tachycardia
a rapid heart rhythm
How do the contractions at the atria and ventricles differ
the atrial muscles tend to contract at a higher frequency
How is the contraction of the heart initiated
the SAN initiates a wave of excitation at regular intervals
Describe the contraction of the atria
wave of excitation spreads over the walls of the atria and travels along the membranes of the muscle tissue causing the cardiac muscles to contract
Why does the heart contain collagen which can’t conduct electricity
Makes sure there is a delay in contractions of the ventricles and atria by ensuring that the SAN excitation wave doesn’t pass to the ventricles and cause them to contract
describe the contraction of the ventricles
After a short delay the wave of excitation is carried away from the AVN and down conducting tissue called PURKYNE tissue
this runs down the interventricular septum and at the base of the septum the wave of excitation spreads out and upwards the walls of the ventricles
describe the pqrst waves in an electrocardiogram
p - excitation of the atria
qrs - ventricular stimulation
t- diastole
Describe the association of oxygen with haemoglobin
association of oxygen and haemoglobin occurs at areas of high pO of oxygen such as the lungs and dissociates at areas with a low pO of oxygen such as respiring tissues
What affects the ability of haemoglobin to associate with oxygen
the concentration of oxygen in the surrounding tissue
describe how haemoglobin associates with oxygen
haemoglobin doesn’t readily associate with oxygen because the haem groups are in the centre of the haemoglobin molecule making it difficult to reach
once an oxygen molecule associates with the haem group it causes a conformational change allowing more oxygen to enter the molecule easier
how does foetal haemoglobin differ to that of adults
foetal haemoglobin must be able to associate with oxygen in an environment where oxygen tension is low enough to make adult haemoglobin release oxygen
define chloride shift
movement of chloride ions into the erythrocytes to balance the charge as hydrogencarbonate ions leave the blood cell
Describe the formation of hydrogencarbonate ion
carbon dioxide diffuses into the blood plasma and then the red blood cells where it combines with water to create carbonic acid catalysed by CARBONIC ANHYDRASE
which the dissociates to release H+ ions and HCO3- ions
describe what occurs after carbonic acid dissociates in the red blood cells
HCO3- ions diffuse out of the red blood cells into the blood plasma the charge inside the red blood cells is maintained by a chloride shift
Build up of the H+ ions causes the contents of the red blood cell to become more acidic and to prevent this they are taken out of the solution by associating with haemoglobin to produce haemoglobonic acid
What is the effect of increasing carbon dioxide concentration
causes oxyhaemoglobin to dissociate more due to the decreased oxygen tension
What is the bohr effect
co2 enters the red blood cell to form carbonic acid and dissociates to release H+ ions
these H+ ions affect the pH of the cytoplasm and can affect the tertiary structure of haemoglobin reducing its affinity for oxygen and making it release the oxygen
What is the bohr shift
downwards shift in the haemoglobin dissociation curve
how do you calculate cardiac output
stroke volume * heart rate
what does tachycardia imply
the heart isn’t pumping blood efficiently
what does bradycardia imply
electrical activity issue, not passing on from SAN correctly
describe the bohr effect in terms of the graph
at the same oxygen tension the percentage saturation is lower because more oxygen dissociates
how do we know that when the first oxygen binds the quaternary shape of haemoglobin is altered
small increase in concentration, but very steep concentration
How does size affect haemoglobin
smaller animals have a higher SA:V so they lose heat rapidly and have a higher metabolic rate and need it to have a lower oxygen affinity
how does your environment affect haemoglobin
low oxygen environments need haemoglobin to have a higher oxygen affinity - left shift
How does activity level affect haemoglobin
need to be able to quickly dissociate oxygen to ensure that when there is more respiration occurring more O2 will be released to maintain a high metabolic rate so a low affinity is needed
What occurs at low pCO2
(lungs) causes some of the HCO3- ions to associate with H+ ions and CO2 diffuses into the alveoli
Why do H+ ions cause oxygen dissociation
as the H+ ions bind to the haemoglobin instead to form haemoglobonic acid
