Transport in animals

Frage	Antworten
why is a transport system needed in multicellular animals?	1. If the animal is too big, then oxygen and nutrients would be used up before reaching the inner layer of cells. 2. An active animal will need a larger amount of oxygen and nutrients than a less active animal. 3. surface area:volume ratio; The surface-area-to-volume ratio of a large animal is relatively small. Larger animals do not have a large enough surface area to supply all of the oxygen and nutrients that they need.
Define Single Circulatory system	A circulation in which the blood flows through the heart once during each circulation of the body e.g. fish
Define Double Circulatory System.	A circulation in which the blood flows through the heart twice during each complete circulation of the body e.g. mammals
Define Open Circulatory System	The blood is not always in vessels e.g. insects
Define Closed circulatory system,	The blood is always in vessels e.g. fish
What is the external structure of the heart?	The largest parts of the heart are the ventricles. Above the ventricles is the atria which are much smaller. The coronary arteries lie over the surface of the heart and carry oxygenated blood to the heart muscle. At the top of the heart are the veins that carry blood to the heart, and arteries that carry blood away from the heard.
What is the internal structure of the heart?	Divided into four chambers. The two upper chambers are atria which receive blood from the major veins (deoxygenated blood from the body flows into right atrium from the vena cava, and oxygenated blood flows from the lungs into the left atrium). The two lower chambers are the ventricles. They are separated from each other by the septum and from the atria by the atrioventricular valves which prevent the blood from flowing the wrong way. These are attached to tendinous cords which prevent the valves from turning inside out.
What is the difference between the walls in the chambers of the heart?	1. The walls of the atria are very thin. They do not need to create much pressure are they are only pushing the blood into the ventricles 2. The walls of the right ventricle are thicker than the atria as only need to pump blood to the lungs. 3. The walls of the left ventricle are thicker than the right as the blood is pumped around the entire body and so needs to be under high pressure.
Describe the cardiac cycle of the heart.	1. When both the atria and the ventricles are relaxed, blood flows into the atria from the major veins. 2. The blood flows through the atrioventricular valves into the ventricles 3. The atria contract simultaneously, pushing blood into the ventricles 4. Blood fills the atrioventricular valve, causing them to snap shut and preventing the blood from flowing back into the ventricles 5. When the pressure in the arteries is higher than the pressure in the ventricles, the semilunar valves shut 6. The walls of the ventricles contract, starting from the bottom 7. When the pressure in the ventricles is higher than the pressure in the arteries, the semilunar valves is pushed open and blood is pushed out of the heart. The contraction only lasts for a short time 8. The ventricles relax 9. When the pressure in the ventricles drops to below that of the atria, the atrioventricular valves open again 10. When the pressure in the ventricles drops to below that of the arteries, the semilunar vavles shut again
Why is the excitation delayed at the septum?	To allow for the atria to finish contracting and for the blood to flow into the ventricles.
Why does the purkyne tissue do?	conducts cardiac action potentials
What does the SAN do?	starts the waves of depolarisation in the heart
What does the AVN do?	Passes in the wave of depolarisation from the ventricles.
What the process of excitation in the heart?	1. The SAN initiates a wave of excitation at regular intervals in the right atrium. 2. Wave of excitation travels over the walls of both atria. This causes the muscle cells to contract. 3. At the base of the atria is a disc of tissue that cannot conduct the electrical impulse, so the only route through to the ventricles is via the AVN, which is at the top of the septum. 4. The excitation is delayed here, the wave then passes away from the AVN down specialised conduction tissue known as Purkyne tissue. 5. At the base of the septum, the wave of excitation spreads out over the walls of the ventricles. 6. The excitation spreads upwards from the apex, the muscles contract, pushing blood up to the major arteries at the top of the heart
What is the function of the arteries?	Carry blood at high pressure away from the heart and around the body.
What is the structure of the arteries?	1. Relatively small lumen 2. Thick wall 3. Wall contains elastic tissue that allows the wall to stretch and then recoil. 4. Contains smooth muscle 6. Endothelium is folded and can unfold when the artery stretches.
What is the function of the veins?	Carry blood at low pressure to the heart
What is the structure of the vein?	1. Lumen is large. 2. Thinner layers of collagen, smooth muscle and elastic tissue. 3. Contain valves to prevent blood flowing in the wrong direction.
How is the blood pumped back to the heart in the veins as there is not pressure?	The surrounding skeletal muscles apply pressure to the vessels which forces it the blood to move along in the direction dictated by the valves.
What is the structure of the capillaries?	1. Walls are one cell thick. 2. lumen is the same diameter as a red blood cell (about 7μm).
how is tissue fluid formed from plasma?	At the arterial end of a capillary, blood is under high pressure due to contractions of the heart. Pushes the blood fluid out of the capillaries. through the tiny holes. This fluid consists of plasma with dissolved nutrients and oxygen.
what is the role of haemoglobin?	To carry oxygen around the body in the red blood cells.
What are the properties of haemoglobin that makes it able to carry oxygen?	Haemoglobin consists of four subunits. Each subunit consists of a polypeptide and a haem group. The haem group contains one iron ion. The iron ion has an affinity for the oxygen. A molecule of haemoglobin can hold four molecules of oxygen.
What is the oxygen disassociation curve?	The S shaped curve produced when haemoglobin takes up oxygen.
what happens during the formation of the dissociation curve?	At a low oxygen tension the haemoglobin does not readily take up oxygen. When the oxygen tension rises, the diffusion gradient rises. Once one molecule of oxygen has associated with a haem group, the shape of the haemoglobin molecule slightly changes, making it easier for the second the third molecules of associate. But, once the haemoglobin molecule contains three oxygen molecules, it is difficult for the forth to associate with the last haem group. It is difficult to achieve 100% saturation. A consequence of this is that the curve levels off again, meaning that the graph is S-shaped.
what percentage of oxygen can be carried in the blood?	20%
How is carbon dioxide carried in the blood?	5% dissolves in the plasma 10% combines with haemoglobin to form carbaminohaemoglobin 85% is transported as hydrogencarbonate ions
How does the carbonic acid form in the blood?	It enters the red blood cells and combines with water to form carbonic acid, which is catalysed by carbonic anhydrase.
What is the equation for the formation of carbonic acid?	CO2 + H2O → H2CO3
What happens when the carbonic acid dissociates?	It form Hydrogen ions and Hydrogencarbonate ions H2CO3→ H+ + HCO3-
How is the cell charge kept constant?	by the chloride shift
What is the chloride shift?	the movement of chloride ions into the cell
What does the haemoglobin act as?	A buffer
Why does the haemoglobin act as a buffer?	Hydrogen ions could cause the contents of the cell to become very acidic.
How does the haemoglobin act as buffer?	They oxyhaemoglobin dissociates, and the hydrogen ions are taken up by the haemoglobin to form haemoglobonic acid.
What is the Bohr effect?	It is the effect when there is more cardon dioixide which lowers the pH.
What happens to the curve when the Bohr shift occurs?	The oxyhaemoglobin dissociation curve shifts down and to the right.
what is the difference in the affinity between the adult and fetal haemoglobin?	Fetal haemoglobin has a higher affinity for oxygen than the adult haemoglobin.
Why does the fetal haemoglobin have a higher affinity?	The fetal haemoglobin must be able to ‘pick up’ oxygen from the haemoglobin from its mother.
Where is the dissociation curve of the fetal haemoglobin in comparison with the adult haemoglobin?	The fetal haemoglobin is to the left of the curve for adult haemoglobin.

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	Erstellt von megan.radcliffe16 vor fast 10 Jahre