TRANSPORT IN ANIMALS Flashcards
Mammals double circulatory system
The heart is divided down the middle
Right side pumps blood to the lungs
The left side pumps the blood to the rest of the body
Advantage of double circulatory system- heart can give an extra push between the lungs and the rest of the body, making the blood travel faster and quicker
Open circulatory system
Blood isn’t closed in vessels
Invertebrates
Blood flows freely in the body cavity
Heart is segmented it contracts in a wave starting from the back and pumping blood into a single main artery
The artery opens up into the body cavity
The blood flows around the insects organs, gradually making its way back into the heart segments through a series of valves
Closed circulatory system
Enclosed in vessels
The heart pumps blood into arteries, these branch out into millions of capillaries
Substances like oxygen and glucose diffuse from the blood in the capillaries into the body cells, but the blood stays inside the blood vessels as it circulated
Veins take the blood back to the heart
Arteries
Walls are thick and muscular
Contain elastic tissue
Inner lining is folded
Arterioles
Smooth muscle
Less elastic tissue
Capillaries
Walls are one cell thick
Venues
Thin walls containing some muscle cells
Veins
Wider lumen
Little elastic and muscle tissue
Valves
Tissue fluid and pressure filtration
Fluid that surrounds cells in tissues
Cells take in oxygen and nutrients from the tissue fluid and release metabolic waste into it
PRESSURE FILTRATION
At the start of the capillary bed, nearest the arteries, the hydrostatic pressure inside the capillaries is greater than in the tissue fluid which causes the difference in hydrostatic pressure to force fluid out the capillaries into the spaces around cells forming tissue fluid
As the fluid leaves the hydrostatic pressure reduces in the capillaries so the hydrostatic pressure is much lower at the end of the capillaries bed nearest the venules
There is another type of pressure here called osmotic pressure which is generated by plasma proteins present in the capillaries which lower the water potential
At the venule end of the capillary bed the water potential in the capillaries is lower than the water potential in the tissue fluid due to fluid loss from the capillaries and high oncotic pressure this means that some water renters the capillaries from the tissue fluid at the venule end by osmosis
The extra tissue fluid gets returned to the blood by the lymphatic system
The cardiac cycle
Ventricles are relaxed and the atria contact which decreases their volume and increases the pressure
This pushes blood into the ventricles through the atrioventricular valves
There is a slight increase in ventricular pressure and volume as the ventricles receive ejected blood from the contracting atria
The atria relax and the ventricles contract increasing their pressure
The pressure becomes higher in the ventricles than atria which forces the atrioventricular valves to shut and prevent backflow
The high pressure in the ventricles opens the semilunar valves where blood is forced out into the pulmonary artery and aorta
The ventricles and atria relax, the high pressure in the pulmonary artery and aorta causes the semilunar valves to close to prevent backflow
The atria film with blood due to the higher pressure in the vena cava and pulmonary vein
As the ventricles relax the pressure falls below the pressure in the atria which causes the atrioventricular valves to open and blood flows passively into the ventricles from the atria
The atria contract and the whole process begins again
Cardia muscle regular beating
Cardiac muscle is myogenic
SAN sets the rhythm through 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 activity from being passed directly from the atria to the ventricles, instead the waves of electrical activity are transferred from the SAN to the AVN
The AVN is responsible for passing waves of electrical activity to the bundle of His there is a slight delay before the AVN reacts to make sure that the ventricles contract after the atria have emptied
The bundle of His is a group of muscle fibres responsible for conducting the waves of electrical activity to the finer muscle fibres int he right and left ventricle walls called the Purkyne tissue
The Purkyne tissue carries the waves of electrical activity into the muscular walls of the right and left ventricles causing them to contract simultaneously from the bottom up
Electrocardiograph
P= depolarisation of atria QRS= depolarisation of the ventricles T= depolarisation of the ventricles
Oxyhaemoglobin
Haemoglobin is a large protein with a quaternary structure made of 4 polypeptide chains
Each chain has a haem group which contains iron
Haemoglobin has a high affinity for oxygen
Reversible reaction
Haemoglobin saturation
Partial pressure of oxygen is a measure of oxygen concentration
Haemoglobin affinity for oxygen varies depending on the partial pressure of oxygen
Oxygen loads onto haemoglobin to form oxyhemoglobin where there is a low pO2
Oxygen enters the blood capillaries at the alveoli in the lungs
Alveoli have a high pO2 so oxygen loads onto haemoglobin to form oxyhemoglobin
Oxygen unloading
Haemoglobin gives up its oxygen more readily at a higher partial pressure of carbon dioxide
When cells respire they produce CO2 which raises the pCO2 and increases the rate of oxygen unloading
Most CO2 from respiring tissues diffuses into red blood cells where it reacts with water to form carbonic acid catalysed by the enzyme carbonic anhydride
The carbonic acid dissociates to five hydrogen ions and hydrogencarbonate ions
The increase in H+ causes oxyhaemoglobin to unload its oxygen so that haemoglobin can take up H+ ions which forms the compound haemoglobonic acid
The HCO3- ions diffuse out the red blood cells and are transported in the blood plasma
To compensate for the loss of HCO3- from the red blood cells, chloride ions diffuse into the red blood cells which is called chloride shift and it prevents any change in pH that could affect the cells
When the blood reaches the lungs the low pO2 causes some of the HCO3- and H+ ions to recombine into CO2
CO2 then diffuses into the alveoli and is breathed out
