Module 3 Section 2: Transportation in Animals Flashcards
Why do larger organisms need transport systems
They have a low surface area to volume ratio so it’s harder to supply all the cells with everything they need
Higher metabolic rate
Larger organisms move around more so their muscles are respiring quickly so they need rapid supply of glucose and oxygen
What does a circulatory system do in a mammal
It uses blood to carry glucose and oxygen around the body
Also carries hormones and antibodies (to fight disease) and waste (like CO2)
What happens in a single circulatory system
The blood only passes through the heart once for each complete circuit of the body
What happens in a double circulatory system
The blood passes through the heart twice for each complete circuit of the body
What happens in a fish’s circulatory system
In fish, the heart pumps blood to the gills (to pick up oxygen) and then on through the rest of the body (to deliver the oxygen) in a single circuit
What does a mammalian heart look like and how does it work
The heat is divided down the middle, so it acts like two hearts joined together
The right side of the heat pumps blood to the lungs ( picks up oxygen )
From the lungs it travels to the left side of the heart which pumps it to the rest of the body
When blood returns of the heart, it enters the right side again
What are the two systems of the circulatory system
Like two linked loops
One sends blood to the lungs - the pulmonary system
The other sends blood to the rest of the body - systemic system
What is an advantage of the mammalian double circulatory system
It can give the blood an extra push between the lungs and the rest of the body
This makes the blood travel faster, so oxygen is delivered to the tissues more quickly
What happens in a closed circulatory system
The heart pumps blood into arteries.
These branch out into millions of capillaries
Substances like oxygen and glucose diffuse from the blood in capillaries into the body cells, but the blood stays inside the blood vessels as it circulates
Veins take the blood back to the heart
What happens in an open circulatory system
The heart is segmented
It contracts in a wave, starting from the back, pumping blood into a single main artery
That artery opens up into the body cavity
The blood flows around the insect’s organs, gradually making its way back into the heart segments through a series of valves
What does an insect’s circulatory system provide it with
Supplies the insect’s cells with nutrients
Transports substances such as hormones around the body
Doesn’t supply the insect’s cells with oxygen - this is done by a system of tubes called the tracheal system
Structure and function of arteries
Carry blood from the heart to the rest of the body
All arteries carry oxygenated blood except pulmonary arteries, which take deoxygenated blood to the lungs
Wall are thick and muscular
Contain smooth muscle which can contract and relax to control blood pressure and provides strength to withstand high pressure
Have elastic tissue to stretch and recoil as the heart beats and allows it to withstand the surging of the blood which helps maintain high pressure
Inner lining ( endothelium ) is folded, allowing artery to expand - also allows it to maintain high pressure
What can arteries branch into and what is their structure
Arteries can branch into arterioles, which are much smaller than arteries
Have a layer of smooth muscle
Less elastic tissue
Smooth muscle allows them to expand or contract - to control amount of blood flowing to tissues
What can arterioles branch into and what is their function
Branch into capillaries
Smallest of the blood vessels
Substances like glucose and oxygen are exchanged between cells and capillaries, so they’re adapted for efficient diffusion
e.g. their walls are only one cell thick
What do capillaries connect to
Connect to venules
Have very thin wall that can contain some muscle cells
Venules join together to form veins
Structure and function of veins
Take blood back to heart under low pressure as there is no surge from the heart
All veins carry deoxygenated blood ( oxygen has been used up by body cells ), except for the pulmonary veins which carry oxygenated blood to the heart from the lungs
Wider lumen than equivalent arteries
Very little elastic or muscle tissue
Contain valves to stop the blood flowing backwards
Blood flow though the veins is helped by contraction of body muscles surrounding them
Contain more collagen than arteries to provide strength as they carry large volumes of blood
What is tissue fluid
The fluid that surrounds cells in tissues
Made from substances that leave the blood plasma e.g. oxygen, water and nutrients
Why doesn’t tissue fluid contain red blood cells or big proteins
These are too large to be pushed out through the capillary walls
What is the function of tissue fluid
Cells take in oxygen and nutrients from the tissue fluid and release metabolic waste into it
Process of pressure filtration
At the arterial end of the capillary bed, the hydrostatic pressure inside the capillaries is greater than the oncotic pressure in the tissue fluid
This forces the fluid out of the capillaries and into the spaces around the cells, forming tissue fluid
As the fluid leaves, the hydrostatic pressure reduces in the capillaries - so the hydrostatic pressure is much lower than the oncotic pressure at the venule end of the capillaries
At the venule end of the capillary bed, the hydrostatic pressure in the capillaries is lower than the oncotic pressure in the tissue fluid
This is due to the fluid loss from the capillaries (oncotic pressure stays the same)
This means some water re-enters the capillaries from the tissue fluid at the venule end by osmosis
What is oncotic pressure caused by
Generated by plasma proteins present in the capillaries which lower the water potential
The plasma protein albumin has an osmotic effect and give blood in the capillaries a relatively high solute potential (and so a lower water potential) compared with the surrounding fluid
This means that water has a tendency to move into the blood in the capillaries from the surrounding fluid by osmosis
What is the purpose of the lymphatic system
Fluid that has not re-entered the capillaries at the venule end of the capillary bed
This extra fluid eventually gets returned to the blood through the lymphatic system
This is a drainage system made up of lymph vessels
What are the smallest lymph vessels
Lymph capillaries
Process of drainage into the lymphatic system
Excess fluid drains into the lymph capillaries (blind-ended tubes) and then the lymph vessels
Now called lymph
Valves in the lymph vessels stop the lymph going backwards
Lymph gradually moves towards the main lymph vessels in the thorax by the squeezing of body muscles
This is where it’s returned to the blood, near the heart (flows into veins near collar bone)
(Orange arrows tissue fluid)
Structure of the blood
Red blood cells
White blood cells
Platelets
Proteins
Water
Dissolved solutes
Structure of tissue fluid
Very few white blood cells
Very few proteins
Water
Dissolved solutes
Structure of lymph
White blood cells
Only proteins are antibodies
Water
Dissolved solutes
Contains fatty acids (absorbed through villi of small intestine)
Comments of red blood cells
Can also be called erythrocytes
Red blood cells are too big to get through capillary walls into tissues fluid
Comments on white blood cells
Can also be called leucocytes
Most white blood cells are in the lymph system
They only enter tissue fluid when there’s an infection
Comments on platelets
Only present in tissue fluid if the capillaries are damaged
Comments on proteins in the blood
Most plasma proteins are too big to get through capillary walls
Where is water potential lowest in the animal transport fluids
Tissue fluid and lymph have a higher water potential than blood
Comments on dissolved solutes
Solute (e.g. salt) can move freely between blood, tissue fluid and lymph
How do tissue fluid, blood and lymph all relate to one another
Blood forms tissue fluid
Tissue fluid forms lymph
Function of the right and left side of the heart
Right side of the heart pumps deoxygenated blood to the lungs (pulmonary system)
Left side of the heart pumps oxygenated blood to the rest of the body (systemic system)
What are the two valves in the heart
The atrioventricular valves link the atria to the ventricles
Semi-lunar valves link ventricles to the pulmonary artery and aorta
Both stop blood flowing the wrong way
How do the valves in the heart work
Only open one way, whether they’re open or closed depends on the relative pressure of the heart chambers
If there’s higher pressure behind a valve, it’s forced open
If pressure is higher in front of the valve, it’s forced shut
What is the cardiac cycle
Ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating round the body
The volumes of the atria and ventricles change as they contract and relax, altering the pressure in each chamber
This causes valves to open and close, which directs the blood flow through the heart
What is atrial systole
Ventricles relax, atria contract
Atria contract which decreases volume and increases pressure
This pushes the blood into the ventricles through the atrioventricular valves
There’s a slight increase in ventricular pressure and volume as the ventricles receive the ejected blood from the contracting atria
What is ventricular systole
Ventricles contract, atria relax
Contracting ventricles decreases their volume and increases their pressure
Pressure becomes higher in the ventricles than atria
Forces atrioventricular valves to shut to prevent back flow
The high pressure in the ventricles opens the semi-lunar valves - blood is forced out into the pulmonary artery and aorta
What is diastole
Ventricles relax and atria relax
The higher pressure in the pulmonary artery and aorta causes the semi-lunar valves to close, preventing back flow
The atria fill with blood (increasing their pressure) due to the higher pressure in the vena cava and pulmonary vein
As the the ventricles continue to relax, their pressure falls below the pressure in the atria
This causes the atrioventricular valves to open and blood flows passively (without being pushed by atrial contraction) into the ventricles from the atria
The atria contract and the whole process repeats
Cardiac cycle order
Atrial systole, ventricular systole, diastole
How to calculate cardiac output
Volume of blood pumped by the heart per minute ( measured in cm3 min-1)
Cardiac output = heart rate x stroke volume
What is special about the cardiac muscle
It is myogenic - it can contract and relax without receiving signals from nerves
This pattern of contraction controls the regular heart beat
What is the SAN
The sino-atrial node (SAN) is in the wall of the right atrium
This sets the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls
How does the SAN start the cardiac cycle
SAN sends out regular waves of electrical excitation to the atrial walls
This causes the right and left atria to contract at the same time
A band of non-conducting collagen tissue prevents the waves of electrical excitation from being passed directly from the atria to the ventricles
What happens when the waves from the SAN reach the band of non-conducting collagen
The waves of electrical activity are transferred to the atrioventricular node (AVN)
This passes the waves on to the bundle of His
There’s a slight delay before the AVN reacts to make sure the ventricles contract after the atria have emptied
The bundle of His (group of muscle fibres) conduct the waves of electrical excitation to the muscle fibres in the right and left ventricle walls, called the purkyne tissue
The Purkyne tissue carries the waves of electrical excitation into the muscular walls of the right and left ventricles, causing them to contract simultaneously from the bottom up
How do doctors check someone’s heart function
Electrocardiograph - a machine that record the electrical activity of the heart
How do electrocardiograph measure heart activity
The heart muscle depolarises (loses electrical charge) when it contracts, and repolarises (regains charge) when it relaxes
An electrocardiograph records these changes in electrical charge using electrodes placed on the chest
What is the trace that is produced by an electrocardiograph called
An electrocardiogram (ECG)
What does one full heart beat on an ECG look like
One full heart beat has:
A P wave: curved spike at the start
A QRS complex: sharp drop to the Q and then a sharp spike to R and another sharp drop to S
A T wave: curved spike larger than the P wave
What is the P wave caused by on an ECG
Caused by the contraction (depolarisation) of the atria (atrial systole)
What does the QRS complex refer to on an ECG
Caused by the contraction (depolarisation) of the ventricles (ventricular systole)
What does the T wave represent on an ECG
Due to the relaxation (repolarisation) of the ventricles
What does the height of each wave indicate on an ECG
Indicates how much electrical charge is passing through the heart
A bigger waves means more electrical charge, so (for P and R waves) a bigger wave means a stronger contraction
How is tachycardia shown on an ECG
This is when the heart beat is too fast and there is less pause between each cycle
This may be ok during exercise, but at rest it means that blood isn’t being pumped efficiently
How is bradycardia shown on an ECG
When the cardiac cycle is occurring too slowly
How are ectopic heart beats shown on an ECG
This is where there is an extra heartbeat
Can be caused by the atria or ventricles contracting too early
Occasional ectopic heartbeats in a healthy person will not cause a problem
(Early contraction of atria in diagram)
How is fibrillation shown on an ECG
This is a really irregular heartbeat
The atria or ventricles completely lose their rhythm and stop contracting properly
Can result in anything from chest pain and fainting to lack of pulse and death
Arterial end of the capillaries compared to venule end of the capillaries
Arterial end:
Hydrostatic pressure (created by the heart contracting) is greater than the oncotic pressure
Water leaves the capillaries through small gaps in the capillary wall (fenestrations)
Tissue fluid circulates around the cells and exchange takes place
Venous end:
Oncotic pressure is greater than hydrostatic pressure
Fluid moves back into the capillaries carrying waste products
How do lymph vessels help fight disease
Lymph vessels contain lymph nodes
Lymphocytes build up in the lymph node when necessary and produce antibodies which are passed into the blood
Lymph nodes also intercept bacteria and other debris from the lymph, which are ingested by phagocytes in the nodes
How are erythrocytes adapted for transporting oxygen
Biconcave to gives them a larger surface area which allows for maximum diffusion of gases
This shape also allows them to pass through narrow capillaries
Contains haemoglobin: red pigment (globular protein) that combines with oxygen
No organelles so there’s more space for haemoglobin and so more oxygen
Large SA:V so oxygen is always close to the surface
Structure of haemoglobin
Large protein with a quaternary structure (made up of more than 1 polypeptide chain)
Each chain has a haem group which contains iron
How does haemoglobin carry out its function
Haemoglobin has a high affinity for oxygen - each molecule can carry 4 oxygen molecules
Oxygen joins to the iron in haemoglobin to form oxyhaemoglobin
This is a reversible reaction:
Hb + 4O2 ⇌ HbO8
As oxygen binds to haemoglobin, it is taken out of solution
This maintains a steep concentration gradient in terms of dissolved oxygen
What is the partial pressure of oxygen
Partial pressure of oxygen (pO2) is a measure of oxygen concentration
The greater the concentration of dissolved oxygen in cells, the higher the partial pressure
Can also be called oxygen tension
What is the partial pressure of CO2
A measure of the concentration of CO2 in a cell
How does haemoglobin’s affinity for oxygen change
Varies depending on the partial pressure of oxygen
Oxygen loads onto haemoglobin to form oxyhaemoglobin where there’s a high pO2
Oxyhaemoglobin unloads it’s oxygen where there’s a lower pO2
How is oxygen loaded onto haemoglobin from the lungs
Oxygen enters blood capillaries at the alveoli in the lungs
Alveoli have a high pO2 so oxygen loads onto haemoglobin to form oxyhaemoglobin
As soon as one oxygen molecule binds, the haemoglobin changes shape making it easier for other oxygens to bind, this is positive cooperativity/ cooperative binding
Because the oxygen is bound the haemoglobin, the free oxygen concentration in the erythrocytes stays low
So a steep diffusion gradient is maintained until all of the haemoglobin is saturated with oxygen
How is oxygen unloaded from the haemoglobin to the tissues
When cells respire, they use up oxygen, this lowers the pO2
The concentration of oxygen in the cytoplasm of body cells is lower than in the erythrocytes.
Oxygen moves out of the erythrocytes down a concentration gradient
Once the first oxygen molecule is released by the haemoglobin, the molecule again changes shape and it becomes easier to remove the remaining oxygen molecules
What does an oxygen dissociation curve show
Shows how saturated the haemoglobin is with oxygen at any given partial pressure
Why does the shape of the dissociation curve change
Graph is S shaped because when the haemoglobin combines with the first O2 molecule, it’s shape alters in a way that makes it easier for other molecules to join too
As the Hb starts to become saturated, it gets harder for oxygen to bind
This means the curve steepens in the middle where it’s easy for oxygen molecules to join, and shallow bits at each end where it’s harder
When the graph is steep, a small change in pO2 causes a big change in the amount of oxygen carried by Hb
What happens on the dissociation curve when pO2 is high
E.g. in the lungs
Haemoglobin has a high affinity for oxygen
Meaning it will readily combine with oxygen
This means it has a high saturation of oxygen
What happens on the dissociation curve when pO2 is low
E.g. in respiring tissues
Haemoglobin has a low affinity for oxygen
Meaning it releases oxygen rather than combines with it
Which is why it has a low saturation of oxygen
How does affinity for oxygen change for adult and fetal haemoglobin
Fetal haemoglobin has a higher affinity for oxygen (better at absorbing oxygen than its mother’s blood) at the same partial pressure of oxygen
This means at a given partial pressure of oxygen, fetal Hb is more saturated than adult Hb
How does the fetus get oxygen in the womb
The fetus gets oxygen from the mother’s blood across the placenta where they run close to eachother
By the time the mother’s blood has reached the placenta, the oxygen saturation has decreased (some has been used up by the body)
For the fetus to get enough oxygen to survive, it’s haemoglobin must have a higher affinity for oxygen (so it takes up enough)
If it’s haemoglobin had the same affinity for oxygen as adult haemoglobin, it’s blood wouldn’t be saturated enough
How does carbon dioxide concentration affect oxygen unloading
Haemoglobin gives up its oxygen more readily at high partial pressures of CO2
Means cells can get more oxygen during activity
When cells respire they produce carbon dioxide, which raises pCO2, increasing the rate of oxygen unloading
This is because of how CO2 affects blood pH
What happens to CO2 as it’s transported from the respiring tissues to the lungs
Most of the CO2 from respiring tissues diffuses into red blood cells
It reacts with water to form carbonic acid, catalyses by the enzyme carbonic anhydrase
The rest of the CO2, around 10%, binds directly to haemoglobin and is carried to the lungs
The carbonic acid dissociates to give H+ ions and hydrogencarbonate (HCO3-) ions
This increase in H+ ions causes oxyhaemoglobin to unload its oxygen so that haemoglobin can can take up the H+ ions
This forms a compound called haemoglobinic acid (this stops the hydrogen ions from increasing the cell’s activity)
The HCO3- ions diffuse out of the red blood cells and are transported in the blood plasma
To compensate the loss of HCO3- ions from the red blood cells, chloride ions diffuse into the red blood cells
This is called the chloride shift and it maintains the balance of electrical charge between the red blood cells and the plasma
When the blood reaches the lungs, the low pCO2 causes some of the HCO3- and H+ ions to recombine into CO2 (and water)
The CO2 then diffuses into the alveoli and it breathed out
Where do chloride ions go after free CO2 diffuses into the lungs
Diffuse out of the red blood cells back into the plasma down an electrochemical gradient
What happens to CO2 when it reaches the lungs, before it diffuses out
Lung tissue has low conc of CO2
Carbonic anhydrase catalyses the reverse reaction to break down carbonic acid into carbon dioxide and water
HCO3- ions diffuse back into erythrocytes and react with H+ ions to form more carbonic acid
When this is broken down by carbonic anhydrase it releases free carbon dioxide
This diffuses out of the blood into the lungs
Equation for carbon dioxide turning into carbonic acid and what is dissociates to form
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
How does the size of the red blood cell make it adapted to substance exchange in the capillaries
Red blood cells are approx 7μm
This makes it almost the same size as the capillary lumen (about 7 - 10μm)
This creates a shorter diffusion pathway for substance exchange
Red blood cells also go along capillaries in single file so there’s more time for gas exchange
How do substances move out of the capillaries and into the tissue fluid
In a capillary bed (network of capillaries in an area of tissue), substances move out of the capillaries, into the tissue fluid, by pressure filtration
How does oxygen transfer from the maternal blood to the fetal blood
Oxygen diffuses from the maternal haemoglobin to the fetal haemoglobin in the placenta
Oxygen dissociates from the maternal Hb and binds to the fetal Hb
Why is it necessary for fetal Hb to switch to adult Hb when the offspring matures
Adult metabolic demands are higher to Hb must be switched so Hb more readily unloads oxygen to respiring tissues
Necessary for reproduction because if the offspring becomes a mother then they need to have Hb with a lower affinity to supply fetus with oxygen
What is insect blood called
Hemolymph
What are the fibres called that the wave of electrical excitation travels through after reaching the apex of the heart (watch spelling)
Purkyne fibres
How is oncotic pressure caused
Large plasma proteins cannot pass through capillary wall
Imbalance of large plasma proteins between blood and tissue fluid results in oncotic pressure
Labelled heart closed
Where to cut to dissect heart
Labelled heart open
