Module 3.2 Transport in Animals Flashcards
3 main factors that influence the need for a transport system:
1) Size
2) Surface area to volume ratio
3) Level of metabolic activity
What happens to the diffusion pathway as the size of an organism increases?
The cells inside a large organism are further away from the surface - the diffusion pathway is increased. The diffusion rate is reduced, diffusion is too slow to supply the need. The outer layers use up the supplies so less reach the cells deep in the body.
Features of a good transport system:
1) Fluid (to carry the nutrients, oxygen and waste around the body)
2) A pump
3) Exchange surfaces
Extra good features:
1) Tubes or vessels
2) Two circuits
What happens in a single circulatory system?
The blood flows through the 💗 ONCE for each circuit of the body
Give an example of an organism that has a single circulatory system
Fish 🐠🐟🐡
What happens in a double circulatory system?
Blood flows through the 💗 TWICE for each circuit of the body
Do mammals have a single or double circulatory system?
Double
Name the 2 circuits in mammals
Pulmonary and systemic
Advantages of a double circulatory system?
Will deliver oxygen and nutrients quickly to the parts of the body that need it, the blood can flow more quickly by increasing the pressure of the 💗
In the single circulatory system of 🐟…
- The blood pressure drops as blood passes through the capillaries of the gill
- The blood has low pressure as it flows towards the body, and will be flowing fairly slowly
- Limited rate at which oxygen and nutrients can be delivered and wastes removed
In the double circulatory system of mammals…🚶🏽
- Blood pressure can’t be too high in pulmonary circuit otherwise it could damage the capillaries in the lungs
- The heart can increase the pressure of the blood so the blood flowing to the body can be under high pressure
- The systemic circuit can carry blood at a higher pressure than the pulmonary circuit
Why is it necessary that mammals have a good circulatory system?
Because they are active and need to maintain their body temperature. They require a lot of energy and need a good supply of oxygen and nutrients and they also need waste removed rapidly.
What does an open circulatory system mean?
Blood isn’t always in the blood vessels
Disadvantages of an open circulatory system:
- Low blood pressure
- Slow blood flow
- Circulation of the blood may be affected by body movements/ or lack thereof
Advantages of closed circulatory systems:
- Higher pressure
- Blood flows faster
- More rapid delivery of oxygen and nutrients
- More rapid removal of waste
What do all blood vessels have?
An inner layer of lining called Endothelium
Why is the wall of the left ventricle so much thicker than the wall of the right ventricle?
The left ventricle has to pump blood through the aorta then to the whole body via the systemic circuit and this is a great distance so a lot of pressure needs to be created.
The right ventricle only has to pump blood to the lungs which is a shorter distance so not as much pressure is required.
What would happen if your coronary artery became blocked?
The flow of blood would be restricted so less oxygen would get to the cardiac muscle, causing a heart attack.
Describe how blood flows around the heart and body
THE RIGHT HAND SIDE IS DEOXYGENATED:
Blood enters via the vena cava
It moves into the right atrium
It goes through the right atrioventricular valve
It moves into the right ventricle
It goes through the semilunar valve
Blood exits the heart via the pulmonary artery and goes to the lungs to be oxygenated
THE LEFT HAND SIDE IS OXYGENATED:
Blood enters via the pulmonary vein
It moves into the left atrium
It moves through the left atrioventricular valve
It moves into the left ventricle
It goes through the semilunar valve and goes to the body
External features of the heart
- Made out of cardiac muscle
- Most of the heart is made of 2 ventricles which have very thick muscular walls
- Above the ventricles are the atria, they have thinner walls
- The coronary arteries supply the cardiac muscle with oxygen for aerobic respiration
- The arteries carry blood away from the heart
- Veins carry blood into the heart
- The bottom of the heart is called the apex
All blood vessels are lined with endothelium to
Reduce friction
🌟Arteries
Take blood away from the heart at high pressure
Have a small lumen to maintain pressure
Have thick walls containing collagen to help withstand the high pressure
Have elastic tissue which stretches and recoils to maintain pressure
The smooth muscle contracts, constricting the airway and narrowing the lumen e.g. can redirect blood flow
🌟Veins
Take blood into the heart at low pressure
Large lumen = less friction
Thinner walls than arteries
Walls have thin layers of collagen, elastic tissue and smooth muscle
Valves = blood flows in one direction
🌟Capillaries
V small
Allow exchange of materials
Thin walls of flattened endothelial cells (squamous epithelial) to reduce the diffusion distance
Narrow lumen - squeezes RBCs up next to the wall to reduce diffusion distance further
Arterioles and venules
Help bridge the gap between blood vessels
Diastole😴
The atria and ventricles relax and recoil
Pressure in ventricles drops rapidly after ventricular systole
Ventricular pressure falls below atrial pressure
AV valves open
Blood flows from veins into atria
Blood flows through open AV valves into ventricles
Volume of blood in the atria and ventricles increases
Pressure in atria and ventricles slowly increases
Atrial systole
Both atria contract
Pressure in atria increases
Pressure in atria rises above that of the ventricles
Pressure increase causes blood to flow through open AV valves into ventricles
Volume of blood in ventricles increases
Ventricular systole
Ventricles contract from base upwards Pressure in ventricles greater than in atria AV valves close Atm SL valves also closed Pressure in ventricles exceeds that of the major arteries SL valves open Blood pumped out of heart Pressure drops in ventricles SL valves close
🌟Explain how the cardiac cycle is coordinated
Cardiac muscle is myogenic
The SAN is located at the top of the right atrium and acts as a pacemaker
SAN initiates wave of electrical excitation which spreads over the atrial wall causing atrial systole
AVN delays the wave of excitation by 0.1s to allow atrial systole to finish before ventricular systole begins
Wave of electrical excitation spreads down septum to the bundle of HIS and then to purkyne fibres
Ventricles contract from apex up. Blood pumped up to major arteries.
On an ECG trace, what do the points P,QRS and T show?
P= atrial systole
QRS complex= ventricular systole
T= diastole
🌟The blood contains …
Erythrocytes (RBCs) Leucocytes (type of WBC) Platelets Plasma CO2 Salts C6H12O6 Urea Amino acids Hormones Proteins
Tissue fluid bathes the cells of tissues to transport
Oxygen and glucose etc to cells and to take carbon dioxide and other wastes back to the blood
🌟Tissue fluid contains…
Neutrophils Some glucose Some amino acids Some oxygen Quite a lot of carbon dioxide
🌟Lymph contains…
Neutrophils Lymphocytes Lots of fats Little glucose Few amino acids Little oxygen Lots of carbon dioxide
Blood pressure in vessels
Pressure decreases as you get further from the heart
Pressure fluctuates in the arteries - ventricular systole inc. pressure, diastole decreases it
Elastic tissue stretches and recoils- maintains high pressure in arteries
Pressure drops in arterioles and capillaries
As you get further from the heart, there is more friction so the pressure drops
No fluctuations in pressure in capillaries- no elastic tissue
Low pressure in capillaries prevents bursting
Low pressure in veins
Haemoglobin
Found in erythrocytes Transports O2 as oxyhaemoglobin Made up of 4 units/ polypeptide chains 2 alpha units 2 beta units Each has a prosthetic haem group Each haem group contains 1 Fe 2+ ion Affinity for oxygen Each can attract and hold 1 oxygen molecule A haemoglobin can hold 4 molecules of oxygen (8 atoms)
🌟Explaining the formation of hydrogencarbonate ions
CO2 diffuses into RBCs
CO2 reacts with H2O (catalysed by carbonic anhydrase) to form carbonic acid
Carbonic acid dissociates to form H+ ions and hydrogen carbonate ions
Hydrogen carbonate ions diffuse out and into plasma
Chloride ions diffuse in to maintain charge (chloride shift)
Hydrogen ions associate with haemoglobin to produce haemoglobinic acid
Oxyhaemoglobin dissociates (under influence of hydrogen ions) to form haemoglobin and oxygen
Oxygen released into plasma before being used by respiring cells
Explaining a Bohr effect graph
At higher partial pressures of CO2, more CO2 reacts with H2O so more carbonic acid is made. More carbonic acid will then dissociate so more H+ ions associate with haemoglobin causing more O2 to be released. Higher partial pressures of carbon dioxide cause lower oxyhaemoglobin saturation.
How is CO2 transported?
5% dissolved in plasma
10% combined with haemoglobin to form carbaminohaemoglobin
85% transported in the form of hydrogencarbonate ions
Chloride shift
Hydrogencarbonate ions have left the RBCs so CL- ions move in to balance charges
To stop the RBCs becoming v acidic, H+ ions combine with haemoglobin in RBCs to form haemoglobinic acid. Haemoglobin acts as a buffer
🌟Why is it essential that a fetus has a different type of haemoglobin than that of the mother?
The fetus gains oxygen from the mother across the placenta. The partial pressure of oxygen in the placenta is low (2-4kPa). This means that the mother’s oxyhaemoglobin dissociates and the maternal haemoglobin releases oxygen. The foetus has a higher affinity for oxygen. This maintains a diffusion gradient towards the foetus.
🌟Why is it essential that fetal haemoglobin changes into adult haemoglobin after birth?
Foetal haemoglobin wouldn’t release oxygen readily enough (affinity too high)
Pregnant mothers would need a difference between the affinity of their haemoglobin and that of their foetus for oxygen
What brings about a drop in pressure between the arterioles and the venules?
It is further from the heart
The resistance slows blood flow down, reducing the pressure
There is an increased cross sectional area
Describe how production of CO2 during respiration leads to a higher concentration of hydrogen ions in the blood
CO2 reacts with H20 (catalysed by carbonic anhydrase)
Produces carbonic acid
Carbonic acid dissociates
H+ ions released
Describe how haemoglobin acts to reduce the conc. of H+ ions in the blood
Haemoglobin binds with H+ ions, taking them out of solution, to form haemoglobinic acid
Why wouldn’t a person with a fibrillating heart survive for long?
Pumping would be inefficient as the contractions of the atria and ventricles would be uncoordinated
Cells would be deprived of oxygen
Less blood would get to the body
Three differences (at least) between tissue fluid and blood
TISSUE FLUID: No RBCs No plasma proteins Some WBCs Low pressure Not in vessels No platelets
BLOOD: RBCs Plasma proteins Lots of WBCs High pressure Contained in vessels Platelets
🌟How is tissue fluid formed and drained?
At the arteriole end, the hydrostatic pressure (caused by heart action) is greater than the osmotic pressure. Between the cells of the capillary walls there are many small gaps. The hydrostatic pressure is greater than the osmotic pressure. Fluid is forced out of the capillaries carrying with it dissolved substances e.g. oxygen, glucose and neutrophils - this is tissue fluid.
At the venule end, the osmotic pressure is greater than the hydrostatic pressure. The presence of plasma proteins lowers the water potential in the blood. Fluid returns to the capillary, carrying with it dissolved waste e.g. CO2
RBCs, plasma proteins and some WBCs are too large to get out of the capillary pores.
Lymph fluid can enter the lymph vessels via valves.
What would happen is tissue fluid drainage in the body was inefficient?
A build up of fluid would occur causing swelling (oedema)
🌟Why is it important that the steepest part of the Bohr effect graph is between the pO2 of 2-5kPa?
At low pO2, oxygen dissociates from haemoglobin
This happens in respiring tissues
The steep part represents the pO2 in the tissues
Respiring tissues need lots of O2 for aerobic respiration
A small drop in partial pressure gives a large drop in saturation which releases a lot of oxygen
Why does inc. the pCO2 ensure greater delivery of O2 to muscle tissue?
More carbonic acid is made
More H+ ions released from its dissociation
More H+ ions means more haemoglobinic acid formed
Oxygen is released when oxyhaemoglobin dissociates
🌟Formation of lymph
Not all tissue fluid returns back to the capillaries
Pores allow fluid to leave the tissue fluid and enter lymph vessels
It will remove proteins (made by cells) out of the tissue fluid
It will remove neutrophils from tissue fluid
Low in O2 and C6H12O6 (used by cells)
Higher in CO2 and waste (made by cells)
A lot of fat (absorbed by intestines)
Contains lymphocytes (WBCs produced in lymph nodes) which engulf and digest bacteria in the lymph fluid (part of the immune system)
🌟Explaining the shape of the oxygen dissociation curve
At low pO2 - low saturation of haemoglobin with oxygen:
-haem group at centre (makes it difficult to associate)
As pO2 inc. - faster inc. in saturation:
- higher conc. of O2, steeper gradient for diffusion of O2 into haemoglobin
- once one O2 has associated –> conformational change in the shape of haemoglobin (makes it easier for O2 to diffuse in and associate)
At high pO2 - saturation is high but levels off (unlikely to ever reach 100%):
-when 3 O2 associated, difficult for 4th molecule to diffuse in and associate to reach 100% even at highest pO2
🌟The Bohr effect (releasing more oxygen e.g. during exercise)
- In low pO2 e.g. in respiring cells, oxyhaemoglobin dissociates and releases oxygen
- when CO2 is present (respiring tissues), there is more carbonic acid to dissociate and form more H+ ions
- H+ ions displace oxygen molecules on haemoglobin and form haemoglobinic acid
- more oxygen is released in the presence of CO2 - the Bohr effect
- the Bohr effect results in oxygen being more readily released when more CO2 is produced from respiration - releasing more CO2 will mean they need more O2 for aerobic respiration
