mass transport in animals Flashcards
cardiovascular system
delivers O2 and removes CO2
- unicellular organisms - diffuse (become large SA:V)
- in insects - O2 - straight to respiring tissue (mass flow and diffusion)
- in fish, humans - mass flow of air to lungs, diffusion of O2 into blood, mass flow of blood, diffusion of O2 into tissues
cardiovascular system / circulatory system transports / supplied
- useful molecules to cells and removes waste molecules from cells via blood supply
the blood
plasma - liquid part of blood
water + dissolved substances
glucose + ions + hormones, lactic acid
Co2 Urea
Proteins eg antibodies and clotting proteins
cells - RBC, WBC, thrombocytes
lipids
idea of the circulatory system
double circulation
- pulmonary circulation:
heart -> lungs -> heart
- systematic circulation
heart -> entire body -> heart
- oxygenated and deoxygenated blood never mix (high conc grad for diffusion)
structure of the cardiovascular system
jugular vein - head and arms - cartid artery
superior vena cava
pulmonary artery - lungs - pulmonary vein
inferior vena cava - heart - aorta
hepatic vein - liver digestive tract - hepatic artery
hepatic portal vein
renal vein - kidney - renal artery
iliac vein - trunk and legs - iliac artery
structure of the heart
superior and inferior vena cava bring deoxygenated blood from systemic circulation into the right atrium
pulmonary artery carries deoxygenated blood to the lungs - has semi-lunar valve (pulmonic values)
pulmonary vein brings oxygenated blood from the lungs into left atrium
aorta carries oxygenated blood to the body - has semi-lunar value (aortic valve)
upper chambers - atria, atrium
longer chambers - ventricles
atrio-ventricular values to regulate opening between atria and ventricles - connected to the heart muscle by chorae tendinae
left ventricle has thicker muscle walls to generate higher pressure for systemic circulation
mechanism of valves
when pressure in A greater than B the value will open
when pressure in B greater than A the value will close
ie valves respond to changes in pressure
the cause of the change in pressure is the contraction / relaxation of the cardiac muscle
cardiac cycle - general
the left side and right side of the heart work in synchronously ie do the same thing at the same time
contraction - systole
relaxation - diastole
cardiac cycle consists of atria contracting, then relaxing, followed by ventricles contracting, then relaxing
cardiac cycle - stages
atrial systole - atria contract, atrioventricular valves open, semilunar values close, ventricles are relaxed
early ventricular systole - atria relax, ventricles contract, atrioventricular valves forced closed, semilunar values still closed
late ventricular systole - atria relax, ventricles contract, atrioventricular valves remain closed, semilunar vales forced open
early ventricular diastole - atria and ventricles relax, atrioventricular and semilunar valves closed, atria begin to passively fill with blood
late ventricular diastole - atria and ventricles relax, atria passively fills with blood as atrioventricular vales open, semilunar vales close
graphs for heart
atrial systole - high pressure in aorta, left ventricle middle pressure, left atrium low pressure
ventricular systole - left ventricle and aorta pressure increase - around same, left atrium pressure low - lub
ventricular diastole - all pressure decreases
one note
similarities between the right and left sides
timing is the same - valves open and close at the same time
volume of blood pumped into aorta from left ventricle and pulmonary artery from right ventricle are identical
differences between right and left sides of heart
pressure in aorta greater than pressure in pulmonary artery because left ventricle has more muscle so generates more contractile force
cardiac calculations
stroke volume (volume in 1 beat) is the aortic pressure change from when semilunar valves open to the peak
heart rate (number of beats per minute) = 60 / time of one heart beat
cardiac output (volume pumped per minute) = stroke volume x heart rate
blood vessels
aorta - arteries - arterioles - networks of capillaries - venules - veins - vena cava
arteries and arterioles
Flow of blood in the arteries and arterioles is affected / influenced by the heart:
1. Generates high pressure (due to the ventricular systole).
2. Fluctuations in pressure (due to alternate systole and diastole of the ventricle).
To deal with the high pressure and the fluctuations in pressure, the artery has:
1. Thicker muscle wall: NOT used for contraction. Resists the high pressure without bursting.
2. Thicker layer of elastic tissue: allows stretching of the artery to accommodate / in response to the high pressure and then recoil to the original position (Elastic recoil).
slight dip then drop in aortic pressure due to elastic stretch and recoil - felt as a pulse
arterioles
arteries branch into narrower blood vessels called arterioles which transport blood into capillaries
Arterioles can contract and partially cut off blood flow to specific organs
Eg. During exercise blood flow to the stomach and intestine is reduced which allows for more blood to reach the muscles
Unlike arteries, arterioles have a lower proportion of elastic fibres and a large number of muscle cells
The presence of muscle cells allows them to contract and close their lumen to stop blood flow
capillaries
The wall of the capillary is one cell thick - short diffusion distance to exchange materials with tissues.
Exchange from the blood to the tissue: Glucose, aa, O2, ions, hormones, eg. insulin delivered to liver and muscle.
Exchange from the tissue to the blood: CO2, urea, ions, lactic acid, hormones, eg. insulin secreted from the pancreas.
But even though the capillary wall is one-cell thick, the distance is still not short enough to exchange “stuff” efficiently to eg. the centre of a muscle mass or organ - the network of capillaries may not be near enough.
This is why tissue fluid is formed. Water + “stuff” bathes the tissue (eg. muscle or gland) to increase efficiency of exchange.
formation of tissue fluid
Hydrostatic pressure = blood pressure. Pressure due to the liquid part / plasma of the blood.
Osmotic pressure = a measure of how concentrated the blood is (solute potential).
If HP > OP, then water is forced out down the pressure gradient.
If OP>HP, then water is drawn in by osmosis down the y gradient.
- At the arteriole end of the capillary, blood travels at a high pressure due to ventricular systole, ie high hydrostatic pressure.
- The osmotic pressure of blood is due to glucose, ions, and plasma proteins (eg. clotting proteins, antibodies). Because these are dissolved in a large volume of blood, osmotic pressure is relatively low.
- Since HP is higher than OP, water is forced out of the capillaries into the surrounding tissues along with small solutes such as glucose, ions, hormones etc. = forms the tissue fluid which bathes the muscle / gland tissue.
- Exchange of glucose, oxygen, CO2, urea etc occurs between the muscle and the tissue fluid - down the concentration gradient of all these molecules.
- However, large proteins remain in the capillary, dissolved in a small volume of water and all the blood cells.
- A small volume of water remains in the venule end of the capillary, ie, there is low HP.
- The same number of plasma proteins are now dissolved in a small volume of water, therefore osmotic pressure increases.
- Since OP is greater HP, water is drawn in at the venule end of the capillary.
- Other substances such as CO2, urea etc diffuse into the capillary down the concentration gradient.
- The remaining / excess tissue fluid gets absorbed into the lymph capillaries, which eventually join the blood at the thoracic duct.
Lymph is a slow-moving liquid consisting of excess tissue fluid and white blood cells and absorbed chylomicrons.
veins
Veins have blood flowing at low pressure because far away from the pumping action of the heart + fluid forced out as tissue fluid and reabsorbed into larger lumens. Valves are present in veins to prevent back-flow of blood, so the blood flows in one direction back to the heart.
Blood may also have to flow back to the heart against gravity.
Veins pass close to skeletal muscles. When these muscles contract, the veins are squeezed, causing the valves to open, and allow the blood to flow upwards.
When the muscle is relaxed, the valve closes, and prevents the blood from flowing backwards.
pressure
General trend: High pressure at the ventricle, which decreases further away from the heart.
Because:
1. Friction against the endothelial walls of the blood vessels.
2. Increase in cross-sectional area of the blood vessels.
In arteries and arterioles, there is fluctuation in pressure (PULSATILE FLOW).
After reabsorption of tissue fluid back into the capillaries, the flow is no longer pulsatile.
arteries vs veins
arteries
- transport blood away from heart
- usually carry oxygenated blood exp PA
- narrower lumens than veins
- have more muscle
- have more elastic tissue
- transport blood under low pressure
- do not have valves exp semi-lunar in aorta and PA
veins
- transport blood vessels towards the heart
- usually carry deoxygenated blood exp PV
- wider lumens than arteries
- less muscle
- less elastic tissue
- transport blood under lower pressure
- have halves to prevent backflow
arteries
blood travels at high pressure - ventricular systole
pulsatile blood flow due to fluctuation in pressure
thicker smooth muscle - resist high pressure
thicker elastic tissue - stretching of artery to respond to high pressure then recoil
haemoglobin
Hb is a globular protein.
Quaternary structure - there are more than 1 polypeptide - there are four polypeptides (2a and 2b).
each polypeptide is associated with a haeme group, with an Fe2+ in each haeme.
Present in RBC to carry oxygen around the body.
haemoglobin in other organisms
Some bacteria only do anaerobic respiration eg. denitrifying bacteria. (O2 is toxic to them.)
Some organisms, eg. yeast do both aerobic and anaerobic resp depending on the availability of oxygen.
Multicellular organisms - different parts of the body / different cells are adapted to do different proportions of aerobic and anaerobic resp at diff times. Eg. brain can only do aerobic resp. Muscles prefer to do aerobic but can do anaerobic (and can be trained to do efficient anaerobic resp). RBC only do anaerobic because they lack mitochondria.
Haemocyanin is used (instead of Hb) by some crustaceans and molluscs (living in cold conditions). Haemocyanin has Cu+ instead of Fe2+.
Insects have oxygen delivered straight to respiring tissue, no need to have a circulatory system or a specialised molecule.
stages of haemoglobin
air into lungs by ventilation / inhalation
oxygen moves from alveoli to capillary / RBC by diffusion
binds to haemoglobin in RBC
circulation to supply the oxygen to all parts of the body
dissociates from haemoglobin into tissue fluid and then into respiring cells
used in aerobic respiration
dissociation curve
Hb binds to oxygen to form oxyhaemoglobin.
This occurs through co-operative binding = when the first O2 molecule binds to one Fe2+ / haeme group, the tertiary / quaternary structure changes, exposes another haeme group, making it easier for the next O2 molecule to bind. Binding of the second makes it easier for the third, etc.
Similarly in the tissues, there is co-operative dissociation of oxygen.
This is an adaptation to increase the efficiency of oxygen transport.
If every Hb molecule is associated with 4 O2 molecules, there is 100% saturation (not actually achieved in the body).
S shaped
partial pressure is the pressure exerted by one gas in a mixture
O2 dissociates from the haemoglobin due to H+ / acidity
aerobic respiration produces carbonic acid
anaerobic - lactic
affinity
ie ability to be associated
the affinity of haemoglobin for oxygen varies with partial pressure of oxygen and partial pressure of carbon dioxide
it also varies with the 3str of the haemoglobin molecule eg different species
loading/association - high po2
unloading/dissociation - lower po2
Bohr shift
right shift due to increased pCO2
eg under conditions of exercise
increase in muscle contraction, more ATP needed
more aerobic respiration, more CO2 released increasing pCO2
dissociation curve shifts to the right
shifts in dissociation curve
- Animals with high metabolic rate have right-shifted curves for the reason above (ie, efficient dissociation).
- Animals with low metabolic rate have left-shifted curves (not much CO2 produced, so O2 remains associated with Hb). Example = foetal Hb.
- Species that live in low oxygen conditions, eg in water, at high altitudes, in marshy areas have left-shifted curves. This increases efficiency of absorbing oxygen (when oxygen is not much available).
sickle cell anaemia
baby Hb - 2 alpha polypeptides and 2 beta polypeptides
in some population - mutation in the beta gene which makes the beta polypeptides dysfunctional - sickle-shaped - inefficient O2 delivery
describe the structure of haemoglobin
globular, water soluble
consists of four polypeptide chains, each carrying a haem group
describe the role of haemoglobin
present in red blood cells
oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues
name three factors affecting oxygen-haemoglobin binding
partial pressure of oxygen
partial pressure of carbon dioxide
saturation of haemoglobin with oxygen
how does partial pressure of oxygen affect oxygen-haemoglobin binding
as partial pressure of oxygen increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin
when partial pressure is low, oxygen is released from haemoglobin
how does partial pressure of carbon dioxide affect oxygen-haemoglobin binding
as partial pressure of carbon dioxide increases, the conditions become acidic causing haemoglobin to change shape
the affinity of haemoglobin for oxygen therefore decreases, so oxygen is released from haemoglobin
bohr effect
how does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding
it is hard for the first oxygen molecule to bind
once it does, it changes the shape to make it easier for the second and third molecules to bind, known as positive cooperativity
it is then slightly harder for the fourth oxygen molecule to bind because low chance of finding a binding site
explain why oxygen binds to haemoglobin in the lungs
partial pressure of oxygen is high
low concentration of carbon dioxide in the lungs, so affinity is high
positive cooperativity
name three common features of an mammalian circulatory system
suitable medium for transport, water-based to allow substances to dissolve
means of moving the medium and maintaining pressure throughout the body, such as the heart
means of controlling flow so it remains unidirectional, such as valves
draw the heart
relate the structures of the chambers to their function
atria - thin-walls and elastic so they can stretch when filled with blood
ventricles - thick muscular walls pump blood under high pressure - the left ventricle is thicker than the right because it has to pump blood all the way around
relate the vessels to their functions
arteries have thick walls to handle high pressure without tearing and are muscular and elastic to control blood flow
veins have thin walls due to lower pressure therefore requiring vales to ensure blood doesnt flow backwards. have less muscular and elastic tissue as they dont have to control blood flow
why are two pumps needed instead of one
to maintain blood pressure around the whole body
when blood passes through the narrow capillaries of the lungs, the pressure drops sharply and therefore would not be flowing strongly enough to continue around the whole body
therefore it is returned to the heart to increase the pressure
describe what happens during cardiac diastole
the heart is relaxed
blood enters the atria
increasing the pressure and pushing open the atrioventricular valves
this allows blood to flow into the ventricles
pressure in the heart is lower than in the arteries so semilunar values remain closed
describe what happens during atrial systole
the atria contract, pushing any remaining blood into the ventricles
describe what happens during ventricular systole
the ventricles contract
the pressure increases, closing the atrioventricular valves to prevent backflow
and opening the semilunar valves
blood flows into the arteries
name the nodes involved in heart contraction
sinoatrial node - wall of right atrium
atrioventricular node - between two atria
what does myogenic mean
the heart’s contraction is initiated from within the muscle itself, rather than by nerve impulses
how is the structure of capillaries suited to their function
walls are only one cell thick - short diffusion pathway
very narrow - can permeate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues
numerous and highly branches, providing a large surface area
what is tissue fluid
a watery substance containing glucose, amino acids, oxygen and other nutrients
it supplies these to cells while also removing any waste materials
general structure
tough outer layer - resists pressure
- collagen has high tensile strength to help stop arteries over-expanding
smooth muscle layer - can contract and control the flow of blood
elastic layer - strength and recoil to maintain blood pressure
endothelium - smooth layer of cells lining the lumen
