Unit 3.2- Transport in animals Flashcards
What are features of an EFFECTIVE transport system?
- Fluid or medium to carry nutrients
- A pump to create pressure
- Exchange surfaces
What are features of an EFFICIENT transport system?
- Tubes or vessels to carry the blood by mass flow
- Two circuits
What animals have a double circulatory system?
Mammals
What are the advantages of a double circulatory system?
- Delivers oxygen and nutrients more quickly
- The blood can flow more quickly by increasing pressure to the heart
What are the disadvantages of a single circulatory system?
The rate at which oxygen and nutrients are delivered to the tissues and waste products are removed is limited
What is the blood pressure like in the circulatory system of a fish?
- Drops as the blood passes through the capillaries in the gills
- Low pressure and speed as it flows towards the body
Why are fish not as metabolically active as mammals?
They do not need to maintain body temperature so do not need as much energy. The single circuit is sufficient for their needs
Why do mammals need a double pump system?
They need more energy so they can maintain their body temperature.
Arterioles definition:
Small blood vessels that distribute blood from an artery to the capillaries
Venules definition:
Small blood vessels that collect blood from capillaries an lead into the veins
What are the disadvantages of an open circulatory system?
- Blood pressure and speed of flow is low
- Circulation of blood may be affected by body movements
What are the advantages of a closed circularity system?
- Higher pressure so the blood flows more quickly
- More rapid delivery of oxygen and nutrients
- More rapid removal of carbon dioxide and other wastes
- Transport is independent of body movement
What layer do all types of blood vessels have?
Inner layer of lining made of a single layer of cells called endothelium. This is particularly smooth to reduce friction with the blood
What layers do capillaries have?
- Endothelium
- Lumen
What layers do arteries and veins have?
- Collagen fibres
- Smooth muscle
- Elastic fibres
- Endothelium
- Lumen
What are the features of arteries?
- Small lumen to maintain high blood pressure
- Folded inner wall in order to allow the lumen to expand as the blood flow increases
What are features of arterioles?
- Contain a layer of smooth muscle which can contract to constrict the diameter to reduce blood flow
- This can be used to divert the flow of blood to regions of the body that are demanding more oxygen
What are features of capillaries?
-Very thin walls to allow the exchange of nutrients and waste products
- lumen about the diameter of an erythrocyte (7um)
-This squeezes the erythrocytes against the walls to reduce diffusion distance
-Also reduces rate if flow
Walls consist of flattened epithelial cells to reduce diffusion distance
-Leaky walls
What are features of veins?
- Large lumen to ease flow of blood
- Thin walls as they do not need to constrict the lumen
- Valves because of low pressure
- Walls are thin so can be flattened by skeletal muscles which applies pressure to the blood
Hydrostatic pressure definition:
The pressure that a fluid exerts when pushing against the sides of a vessel
Lymph definition:
The fluid held in the lymphatic system, which is a system of tubes that returns excess tissue fluid to the blood system
Oncotic pressure definition:
The pressure created by the fluid outside the blood vessels pushing against them
How is tissue fluid different to blood plasma?
It does not contain most of the cells found in blood and does not contain plasma proteins
What kind of movement is the flow of blood plasma into tissue fluid? (diffusion, active transport etc)
Mass movement
How is blood pushed out of the capillaries at the arterial end of the capillary bed?
The blood is at a relatively high hydrostatic pressure which PUSHES the blood out
Through what processes does the exchange of substances into and out of cells take place?
- Diffusion
- Facilitated diffusion
- Active transport
How are waste products able to return to the blood?
The blood pressure is much lower at the venule end of the capillary
What happens to the tissue fluid that does not return to the blood?
It enters the lymphatic system
Why does some tissue fluid go into the lymphatic system?
It drains the excess tissue fluid out of the tissues and returns it to the blood system in the subclavion vein in the chest
What makes up the lymphatic in the lymphatic system?
Similar composition to tissue fluid but contains more lymphocytes as these are produced in lymph nodes
Lymph nodes definition:
Swellings found at intervals along the lymphatic system. They have an important play in the immune response
What kind of hydrostatic pressures do blood plasma, tissue fluid and lymph have?
- Blood plasma: high
- Tissue fluid and lymph: low
What is oncotic pressure like in the blood plasma, tissue fluid and lymph?
- Blood plasma: more negative
- Tissue fluid and lymph: less negative
Does lymph contain fats?
Yes, especially near the digestive system
How does the hydrostatic pressures change along a capillary bed?
In the capillaries: High at the arterial end, low at the venule end
In the tissue fluid: Lower than on the capillaries, the same at both ends
How does the oncotic pressure change throughout a capillary bed?
The same for the whole stretch, bit more negative in the capillaries and less negative in the tissue fluid
How does oncotic pressure move substances in the blood?
- The oncotic pressure of the blood PULLS water into the blood
- The oncotic pressure of the tissue fluid PULLS water into the tissue fluid
Cardiac muscle definition:
Specialised muscle found in the walls of the heart chambers
What do semi-lunar valves do?
Stop blood re-entering the heart from the arteries
Why are the walls of the atria very thin?
The chambers do not need to create much pressure because they only have to push the blood into the ventricles
What is the thickness of the wall of the right atria like?
Thicker than the atria so that blood can be pumped to the lungs, but not too thick because the alveoli in the lungs are every delicate and could be damaged by high blood pressure
What is the thickness of the walls in the left ventricle like?
Two or three times thicker than in the right ventricle. The blood needs sufficient pressure to overcome the resistance of the systematic circulation
What is the bicuspid valve?
Left atrio-ventricular valve
What is the tricuspid valve?
Right atrio-ventricular valve
Why has the lefy side of the heart got a bicuspid valve and the right got a tricuspid?
The bicuspid valve can withstand more pressure
What does an electrocardiogram (ECG) do?
Monitors the activity of the heart
How does an electrocardiogram monitor the activity of the heart?
- A number of sensors are attached to the skin
- Some of the electrical activity generated form the heart spreads through the tissues to the skin
- The sensors on the sink pick up the electrical excitation and convert it into a trace
What does the bit to the left of the spike of a heart trace show?
The excitation of the atria
What does the spike on a heart trace show?
The excitation of the ventricles
What does the bit to the right of the spike of a heart trace show?
Diastole
What is a normal rhythm heart trace called?
Sinus rhythm
What is a slow heart trace called?
Bradycardia
What is a fast heart trace called?
Tachycardia
What kind of heart trace is it where the bit before the spike is not clear (atrial more frequent than ventricles)?
Atrial fibrillation
What kind of heart trace is it where the patient often feels as if a beat has been skipped?
Ectopic heartbeat
Cardiac cycle definition:
Control and coordination of the heart
What are the three stages of the cardiac cycle?
- Atrial systole
- Ventricular systole
- Diastole
Bradycardia definition:
A slow heart rhythm
Ectopic heartbeat definition:
An extra beat or an early beat of the ventricles (feels as if a beat has been missed)
Fibrillation definition:
Uncoordinated contraction of the atria and the ventricles
Myogenic muscle definition:
Muscle that can initiate its own contraction
Purkyne tissue:
Consists of specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum to the ventricles
Sano-atrial node definition:
The heart’s pacemaker. Small patch of tissue that sends out waves of electrical excitation at regular intervals in order to initiate contractions
Trachycardia definition:
A rapid heart rhythm
Do the atria or venrticles contract at a higher rate?
Atria
How many times a minute does the SAN send out waves of electrical excitation?
55-80
How do the atria contract?
- Wave of excitation spreads over walls of both atria and travels along membranes of muscle tissue. As the wave passes, it causes the cardiac muscle to contract. (Atrial systole)
- Wave of excitation is then conducted through the AVN as the tissue at the base of the atria is unable to conduct the wave of excitation so it cannot travel directly to the ventricles.
- Travelling through the AVN creates a delay which allows time for the atria to finish contracting and for the blood to flow down into the ventricles before they contract
How do the ventricles contract?
- Wave of excitation is carried from the AVN and down purkyne (conducting) tissue, down the interventricular septum
- At the base of the septum, the wave of excitation spreads out over the ventricles, causing the muscles to contract.
- This means that the ventricles contract from the base upwards, which forces the blood up to the major arteries at the top of the heart
What happens in atrial systole?
- Right and left atria contract together
- The muscles in the walls are thin so there is only a small increase in blood pressure
What happens in ventricular systole?
- Right and left ventricles pump together
- Contraction starts at the apex (base) of the heart so that blood is pushed towards the arteries
What happens in diastole?
- The muscular walls of all four chambers relax
- Elastic recoil causes the chambers to increase in volume, allowing the blood flow in from the veins
How do the atrio-ventricular valves work?
- After systole, the ventricular walls relax and recoil
- The pressure in the ventricles rapidly drops below that of the atria
- Blood in the atria opens the antrio-ventricular valves
- The pressure in the atria and ventricles increases slowly as they fill with blood
- The valves close when the atria begin to relax due to a swirling motion in the blood around the valves when the ventricle is full
- As the ventricles contract (systole), the pressure in them starts to rise above that of the atria, forcing blood upwards
- This movement fills the valve pockets and keeps them closed
What prevents valves from turning inside out?
Tendinous cords
How do semi-lunar valves work?
- Before Ventricular contraction, the pressure in the arties is higher than in the ventricles so the semi-lunar valves are closed
- Ventricular systole raises the blood pressure in the ventricles quickly to above that of the arteries, forcing the semi-lunar valves open
- The blood is forced up the arteries and when the ventricle walls have finished contracting the heart muscle relaxes (Diastole)
- Elastic tissue in the walls of the ventricles recoils, returning them to their original size and causing the pressure to drop quickly
- As it drops below that of the arteries, the blood starts to flow back towards the arteries
- The semi-lunar valves are pushed closed by the book collecting in the pockets of the valves which prevents the blood from returning to the ventricles
What causes the pulse we can feel?
The pressure wave created when the left semi-lunar valve closes
What does the elastic recoil of the walls of the aorta help to maintain?
Blood pressure
Why is it important to maintain the pressure the gradient between the aorta and the arterioles?
It keeps the blood flowing towards the tissues
Affinity definition:
A strong attraction
Dissociation definition:
Releasing oxygen from the oxyhaemoglobin
Fetal haemoglobin definition:
The year of haemoglobin usually found only in the foetus
What does haemoglobin become when it takes up oxygen?
Oxyhaemoglobin
Is the oxygen + haemoglobin reaction reversible?
Yes
How is does the diameter of capillaries increase rate of diffusion?
It is 8um, the same as an erythrocyte so only 1 can get through at a time
What % of an erythrocyte is made up of haemoglobin?
95%
What does haemoglobin consist of?
- Four polypeptide chains
- Each bonded to one haem group
- Each haem group and one ion (Fe2+) in it which can carry one oxygen molecule
- Therefore each haemoglobin molecule can carry four oxygen molecules
What kind of affinity for oxygen does a haem group have?
High
What is partial pressure?
Oxygen tension. It is the concentration of oxygen, measures in KPa
What is the saturation of haemoglobin measure in?
%, 100% is fully saturated
At what concentrations of oxygen does oxygen bind to and dissociate from haemoglobin?
- Binds to haemoglobin when oxygen is at a high concentration
- Dissociates from haemoglobin when oxygen is at a low concentration
What shape is the haemoglobin dissociation curve?
S
What happens to a hemoglobin molecule’s affinity after it picks up an oxygen molecule?
It increases
Why does haemoglobin not readily associate with oxygen molecules at a low oxygen tension? What happens as oxygen tension increases?
The haem groups are in the centre of the molecule. As oxygen tension rises, the diffusion gradient of oxygen increases so eventually an oxygen molecule will bind with a haem group. This causes a conformational change in the shadow of the haemoglobin molecule, which allows other oxygen molecules to associate with haem groups relativily easily
Why does the haemoglobin dissociation curve eventually plateaux?
When a high saturation of oxygen is reached, some molecules won’t be able to take in any more oxygen, so further rises in oxygen concentration won’t have much affect on the % saturation
What is the partial pressure of oxygen and saturation of haemoglobin like in the lungs?
High partial pressure so high saturation
What is the partial pressure of oxygen and saturation of haemoglobin like in metabolising tissues?
Oxygen partial pressure is much lower than in the lungs so the saturation of haemoglobin drops dramatically, relaxing oxygen into the tissues
How is foetal haemoglobin different to adult haemoglobin?
It has a much higher affinity for oxygen so its haemoglobin dissociation curve is to the left of adult haemoglobin
Why does foetal haemoglobin need a high affinity to oxygen than adult haemoglobin?
- In the placenta, the oxygen tension is low and the foetal haemoglobin will absorb oxygen from the surrounding tissue which reduces the oxygen tension even further
- This causes oxygen to diffuse from the mother’s blood to the placenta
- This reduces the oxygen tension in the mother’s blood, which causes the maternal haemoglobin to release more oxygen (dissociation)
- Therefore foetal hemoglobin must be able to associate with oxygen in an environment where oxygen tension is low enough to make adult haemoglobin release oxygen
Carbonic anhydrate definition:
The enzyme that catalyses the combination of carbon dioxide and water
Chloride shift definition:
The movement of chloride ions into the erythrocytes to balance the charge as hydrocarbonate ions leave the cell
Bohr effect definition:
The effect that extra carbon dioxide has on haemoglobin, explaining the release of more oxygen
Haemoglobinic avid definition:
The compound formed by the buffering action of haemoglobin as it combines with excess hydrogen ions
What are the three ways carbon dioxide is transported to the lungs?
- About 5% is dissolved directly in the plasma
- About 10% is combined directly with haemoglobin to form a compound called carbaminohaemoglobin
- About 85% is transported in the form of hydrogen carbonate ions
How are hydrogen carbonate ions formed (transport of carbon dioxide)
- Carbon dioxide in the blood plasma diffuses into the erythrocytes
- Here it combines with water to form a weak acid called carbonic acid
- This is catalysed by the enzyme carbonic anhydrase
- CO2 + H2O - > H2CO3
What does carbonic acid dissociate to release? (transportation of carbon dioxide)
- Hydrogen ions (H+) and hydrogen carbonate ions (HCO3-)
- H2CO3 - > HCO3- + H+
What do the hydrogen carbonate ions do after they have been produced? (transportation of carbon dioxide)
-Diffuse out of the erythrocyte into the blood plasma
How is the CHARGE inside the erythrocyte maintained after the H+ ions leave?
Chloride shift. This is the movement of chloride ions (Cl-) from the plasma into the erythrocytes
What can happen if the hydrogen ions build up in an erythrocyte?
- Could cause the contents of the erythrocyte to become very acidic
- To prevent this, they hydrogen ions are taken out of solution by associating with the haemoglobin to produce haemoglobinic acid (HHB)
- The haemoglobin is acting as a buffer (a compound that maintains constant PH)
What does oxyhaemoglobin at a low partial pressure dissociate to produce?
- Haemoglobin and oxygen
- (HbO8 - > Hb + 4O2)
Why is haemoglobin able to take up hydrogen ions in the despairing tissues?
- The partial pressure of oxygen in the despairing tissues is low so oxyhaemoglobin dissociates, releasing oxygen, freeing up space for hydrogen ions.
- This forms haemoglobinic acid (Hb + H+ - > HB)
What causes the change in PH of haemoglobin?
- Carbonic acid which dissociates to release hydrogen ions
- This can affect the tertiary structure, reducing its affinity for oxygen
- This causes oxygen to be released into the tissues
Why does haemoglobin release more oxygen when there is more carbon dioxide?
Carbon dioxide entering erythrocytes causes hydrogen ions to be released, changing the tertiary structure, decreasing the affinity for oxygen and causing oxygen to be released
