Transport in animals Flashcards
Circulatory system in a fish
The heart pumps blood to the gills and then on through the rest of the body in a single circuit
Circulatory system in mammals
The heart is divided down the middle:
- The right side of the heart pumps blood to the lungs
- From the lungs it travels to the left side of the heart, which pumps it to the rest of the body
- When blood returns to the heart it enters the right side again
Systemic system
System in mammals where blood is sent to the rest of the body
Pulmonary system
System in mammals where blood is sent to the lungs
Advantage of the double circulatory system
The heart can give blood an extra push between the lungs and the rest of the body so the blood travels faster, so oxygen is delivered to the tissues more quickly.
What is a closed circulatory system
The blood is enclosed inside blood vessels
What is an open circulatory system
Blood isn’t enclosed in blood vessels all the time and flows freely through the body cavity
How does the close circulatory system work
1) The heart pumps blood into arteries which branch into millions of capillaries
2) 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 circulates.
3) Veins take blood back to the heart.
How does the open circulatory system work
1) The heart is segmented. It contract in a wave, starting from the back, pumping the blood into a single main artery
2) That artery opens up into the body cavity
3) 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 open circulatory system supply an insect with
With nutrients and transports things like hormones around the body. It doesn’t supply the insect’s cells with oxygen though - this is done by a system of tubes called the tracheal system
What are the five types of blood vessels
Arteries, arterioles, capillaries, venules and veins
What do arteries do
Carry oxygenated (except pulmonary arteries) blood from the heart to body
Properties of arteries
- Thick muscular walls
- Elastic tissue to stretch and recoil as the heart beats, maintaining high pressure
- Inner lining (endothelium) is folded so the artery can expand helping to maintain the high pressure
What are arterioles
What arteries branch into which are much smaller
Properties of arterioles
- Has a layer of smooth muscle but less elastic tissue, this allows them to expand or contract controlling blood flow
What are capillaries
What arterioles branch into and are the smallest blood vessels and substances such as oxygen and glucose are exchanged between cells and capillaries, so adapted for efficient diffusion. Such as one cell thick walls.
What are venules
Capillaries connect to these and have thin walls that contain some muscle cells.
What are veins
Take deoxygenated (except pulmonary veins) blood back to the heart under low pressure
Properties of veins
- Wide lumen
- Little elastic tissue
- Contain valves
What is tissue fluid
The fluid that surrounds cells in tissues made from substances that leave the blood plasma such as oxygen, water and nutrients.
Does tissue fluid contain RBC or big proteins
No. They are too large to be pushed out of the capillary walls
What activity happens between cells and tissue fluid
Cells take in oxygen and nutrients from the tissue fluid, and release metabolic waste into it
What is a capillary bed
The network of capillaries in an area of tissue
How does substances move out of the capillaries into the tissue fluid
By pressure filtration
Process of pressure filtration
1) AT the start of the capillary be, nearest the arteries the hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid. This difference forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid.
2) As fluid leaves, the hydrostatic pressure reduces in the capillaries so is much lower at the end of the capillary bed that’s nearest to the venules
3) At the venule end of the capillary bed, the water potential in the capillaries is lower than the WP in the tissue fluid due to fluid loss from the capillaries and the high oncotic pressure. Therefore, some water re-enters the capillaries from the tissue fluid at the venule end by osmosis.
What is oncotic pressure
The pressure exerted by the proteins in the blood plasma which lower the water potential.
Where does excess tissue fluid drain to
Lymph vessels through a drainage system called the lymphatic system
Stages of lymphatic system
1) Excess tissue fluid passes into the lymph vessels once inside it’s called lymph. Valves in the lymph vessels stop the lymph going backwards.
2) Lymph gradually moves towards the main lymph vessels in the thorax. Here it’s returned to the blood, near the heart.
What can be found in tissue fluid
Water, dissolved solutes, very few WBC, very few proteins
What can be found in lymph
WBC, Water, dissolved solutes and antibodies
What is the rules of pressure for a valve
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.
Which side of the hearts walls are thicker
Left
What happens during the first stage of cardiac cycle - atria contraction and ventricles relax
The ventricles are relaxed. The atria contract, which decreases their volume and increases their pressure. This pushes the blood into the ventricles through the AV valves. There is a slight increase in ventricular pressure and volume as the ventricles receive the ejected blood from the contraction atria.
What happens during the second stage of cardiac cycle - atria relax and ventricles contract
The atria relax and ventricles contract leading to a decrease in volume and increase in pressure. The pressure becomes higher in the ventricles than the atria, which forces the AV valves shut to prevent backflow. The high pressure in the ventricles opens the semi-lunar valves. Blood is forced into the pulmonary artery and aorta
What happens during the third stage of cardiac cycle - atria relax and ventricles relax
The ventricles and atria both 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 due to the higher pressure in the atria. This causes the AV valves to open and blood flows passively into the ventricles from the atria. The atria contract and the whole process begins again.
Cardiac output is
Volume of blood pumped by the heart per minute (Q= HR x SV)
What can the heart muscle be described as
Myogenic - can contract and relax without receiving signals from nerves controlling the regular heartbeat.
What is the SA node
Like a pacemaker setting the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls
What does the SA node cause
The right and left atria to contract at the same time
What does non-conducting collagen tissue prevent
The waves of electrical activity from being passed directly directly from the atria to the ventricles.
What is the bundle of His
Group of muscle fibres responsible for conducting the waves of electrical activity to the Purkyne tissue
What is the QRS complex of an ECG
The main peak of the heartbeat caused by the ventricular contraction
What is the AV node responsible for
Passing the waves of electrical activity on to the bundle of His. However it has a slight delay to make sure the ventricles contract after the atria have emptied.
How does an ECG work
The heart depolarises when it contracts and repolarises when it relaxes and is recorded by the machine using electrodes placed on the chest.
What are the Purkyne tissue
Finer muscle fibres in the right and left ventricle walls. It carries the electrical activity into the muscular walls to the right and left ventricles causing them to contract simultaneously, from bottom up.
What is the P wave in an ECG
Caused by the contraction of the atria
What is an electrocardiograph
It records the electrical activity of the heart.
What is the T wave of and ECG
The relaxation of the ventricles
What does the height of the ECG indicate
How much electrical charge is passing through the heart and therefore a stronger contraction.
What is tachycardia
The heartbeat is too fast around 120 beats per minute. Showing the heart is not pumping blood efficiently
What is bradycardia
Below 60 bmp at rest
What is an ectopic heartbeat
Extra 5th heartbeat caused by an earlier contraction of the atria than in the previous heartbeats. Or it can be caused by early contraction of the ventricles.
What is fibrillation
A really irregular heartbeat where the atria or ventricles completely lose their rhythm and stop contracting properly
Structure of haemoglobin
A large protein with a quaternary structure made up of four polypeptide chains. Each one having a haem group containing iron which makes haemoglobin red.
What is haemoglobin like when binding to oxygen
Haemoglobin has a high affinity for oxygen so each molecule can carry four oxygen molecules. In the lungs, oxygen joins iron in haemoglobin to form oxyhemoglobin.
What type of reaction is the creation of oxyhaemoglobin
A reversible reaction where oxygen leaves oxyhemoglobin near the body cells, it turns back to haemoglobin.
What does haemoglobin saturation depend on
Partial pressure of oxygen so oxygen concentration. The greater the concentration of dissolved oxygen in cells, the higher the partial pressure.
What are blood capillaries at the alveoli like
They have a high partial pressure of oxygen so oxygen loads onto haemoglobin to form oxyhaemoglobin.
What happens when cells respire
They use up oxygen lowering the Po2. RBC deliver oxyhaemoglobin to respiring tissues, where it unloads oxygen. The haemoglobin then returns to the lungs to pick up more oxygen
What does the oxygen dissociation curve show
How saturated the haemoglobin is with oxygen at any given partial pressure.
On the disassociation curve what does it mean if the PO2 is high
Haemoglobin has a high affinity for oxygen so it has a high saturation
On the disassociation curve what does it mean if the PO2 is low
Haemoglobin has a low affinity for oxygen so it releases oxygen rather than combining with it.
Why is the disassociation graph S-shaped
When haemoglobin combines with the first oxygen molecule, its shape alters in a way that makes it easier for other molecules to join
What happens as haemoglobin becomes more saturated
It gets harder for more oxygen molecules to join. The curve has a steep bit in the middle where it is easy for oxygen molecules to join, and shallow bits at each end where its harder. When the curve is steep, a small change in PO2 causes a big change in the amount of oxygen carried by the Hb
Does fetal haemoglobin have a higher or lower affinity of oxygen than adult haemoglobin
Higher. It is better at absorbing oxygen than its mother blood at the same partial pressure.
How does the fetus get oxygen
From its mother’s blood across the placenta. By the time the mother’s blood reaches the placenta, its oxygen saturation has decreased. For the fetus to get enough oxygen to survive its haemoglobin has to have a higher affinity for oxygen. If its haemoglobin had the same affinity for oxygen as adult haemoglobin its blood wouldn’t be saturated enough
How does haemoglobin give up oxygen at higher partial pressures of carbon dioxide
It gives it up more readily at higher partial pressures of carbon dioxide. When cells respire they produce carbon dioxide which raises the pCO2 increasing the rate of oxygen unloading.
What happens to most CO2 from respiring tissues
1) Diffuses into RBC where it reacts with water to form carbonic acid catalyzed by the enzyme carbonic anhydrase.
2) The carbonic acid dissociates to give hydrogen ions and hydrogen carbonate.
3) The increase in H+ ions causes oxyhaemoglobin to unload its oxygen so that haemoglobin can take up the H+ ions forming haemoglobin acid.
4) The HCO3- ions diffuse out of the RBC and are transported in the blood plasma. To compensate for the loss of HCO3- ions from the RBC, chloride ions diffuse into the RBC. Called the chloride shift
5) When the blood reaches the lungs the low CO2 causes some of the HCO3- and H+ ions to recombine into CO2 and water.
6) The CO2 then diffuses into the alveoli and is breathed out
