Transport in Animals

Pregunta	Respuesta
List 4 reasons why transport systems in animals are needed	1) High metabolic demands - needs a faster way of transporting substances than diffusion 2) Small surface area to volume ratio so surface for substances to diffuse in and out of the body is relatively small 3) Molecules like enzymes are made in one part of the body but are needed in another 4) Waste products need to be transported from cells to excretory organs
What do most circulatory systems have in common?	Liquid transport medium, vessels to carry transport medium, pumping mechanism to transport the fluid.
What is a mass transport system?	When substances are transported in a mass of fluid with a mechanism for moving the fluid around the body.
What is an open circulatory system?	Where the transport medium is pumped straight from the heart into the body cavity of an animal. There are few vessels to carry the transport medium. The transport medium comes directly into contact with cells and tissue and circulates at a low pressure.
What is the haemocoel?	The open body cavity of animals with an open circulatory system
What is haemolymph?	Insect blood
What does haemolymph transport?	Food and nitrogenous waste products
Describe the basic structure of an open circulatory system in an insect	The body cavity is split by a membrane and the heart extends along the length of the thorax and the abdomen. The haemolymph circulates and comes into direct contact with tissues and cells before returning to the heart through open ended vessels.
What is a closed circulatory system?	One where the blood is enclosed in blood vessels and does not come directly into contact with cells. A heart pumps the blood under a high pressure around the body and it returns directly to the heart.
What is a single closed circulatory system?	Blood flows through the heart and is pumped all around the body in one cycle.
What happens in the two sets of capillaries that blood passes through in a single closed circulatory system?	In the first, oxygen and carbon dioxide are exchanged. In the second, other substances are transferred .
Why are the activity levels of animals with a single closed circulatory system relatively low?	Blood pressure drops considerably as blood travels a long distance before reaching the heart again, which limits the efficiency of the exchange processes
How are fish able to have high activity levels with only a single closed circulatory system?	They have a countercurrent gaseous exchange mechanism in their gills which allows them to take a lot of oxygen from the water. Their body weight is supported by the water and they do not maintain their own body temperature. This reduces the metabolic demands of the fish.
What is a double closed circulatory system?	Two separate circulations around the body pumped by the heart. Blood is pumped from the heart to the lungs and back, and in a separate circulation, blood is pumped from the heart to the rest of the body and back. Blood travels around the whole body with two pumps from the heart.
What is the structure and function of elastic fibres in blood vessels?	Made up of elastin so they can stretch and recoil to provide vessels with flexibility.
What is the function of smooth muscle in blood vessels?	They have the ability to contract and relax to change the size of the lumen
What is the function of collagen in blood vessels?	They provide structural support to maintain the shape of vessels.
What is the function of arteries?	They carry blood away from the heart to the tissues of the body.
State the 4 layers of tissue in an artery	endothelium, elastic layer, muscle layer, tough collagen outer layer
What is the function of endothelium in blood vessels?	It is smooth to allow blood to pass easily over it.
What is the function of the elastic layer in veins and arteries?	They stretch to withstand the force of the blood pumped through the vessels which allows them to take the larger blood volume. They recoil to even out the surges of blood to keep a continuous flow.
What is the function of the muscle layer in blood vessels?	They constrict or dilate to control the flow of blood into individual tissues.
What is the function of the collagen outer layer of blood vessels?	Maintain the amount the vessels can stretch
What are arterioles?	They link the arteries and capillaries.
What is the difference between arteries and arterioles?	Arterioles have less elastin and more smooth muscle in their walls, which allows the to vasoconstrict and vasodilate.
What are capillaries?	Microscopic blood vessels that link arterioles with venules and spread through all the tissues of the body.
What is the average diameter of a capillary?	7.5 - 8μm
How are capillaries adapted to their role?	Provide a large surface area for substances to diffuse across, smaller than arterioles so rate of blood flow falls, walls are a single endothelial cell thick so there is a short diffusion distance
Where do veins carry blood to?	The heart
Where do arteries carry blood to?	Cells
What is the main vein carrying blood from the body to the heart?	Vena Cava
Why do veins have valves?	To prevent backflow as pressure in them is very low
What are the walls of veins made out of?	Endothelium, elastic fibres, muscle, collagen
How are veins adapted to transport blood at a low pressure and against gravity?	Valves at intervals to prevent backflow, they run between large active muscles so when they contract the squeeze the veins to force the blood towards the heart, breathing acts as a pump as the movements cause pressure changes which moves the blood towards the heart.
What does blood plasma carry?	Glucose, amino acids, mineral ions, plasma proteins, red blood cells, white blood cells, platelets.
What is albumin?	A kind of plasma protein that maintains the osmotic potential of the blood
What is fibrinogen?	A kind of plasma protein used for blood clotting
What are globulins?	A kind of plasma protein involved in transport and the immune system
What are megakaryocytes?	Large cells found in the red bone marrow, they form platelets.
Define oncotic pressure	The tendency for water to move into the blood by osmosis
What is hydrostatic pressure?	The pressure created by water in an enclosed system
What are erythrocytes?	Red blood cells
Compare the hydrostatic and oncotic pressures at the arterial end of a capillary and describe what this does to the movement of water between it and the tissue fluid.	The hydrostatic pressure is higher than the oncotic attracting water in, which causes the net flow of water to move out of the capillary to balance out pressure.
What is tissue fluid?	It surrounds the cells and allows diffusion across it to and from the cells and blood. It has the same composition as plasma but without red blood cells and plasma proteins.
Compare the hydrostatic and oncotic pressures at the venous end of a capillary and describe what this does to the movement of water between it and the tissue fluid.	The hydrostatic pressure in the blood is lower than the oncotic pressure, so the net flow of water is into the capillary.
Where does 10% of the tissue fluid that leaves the blood vessels go to?	Into lymph vessels
Why are erythrocytes biconcave shaped?	To increase their surface area and to allow them to pass easily through capillaries.
Why do red blood cells have a short life?	They have no nucleus to make room for more haemoglobin
How many oxygen molecules can bind to one haemoglobin molecule?	4
What is positive cooperativity?	When haemoglobin changes shape when oxygen binds to it to make it easier for the next oxygen molecule to bind.
How is a steep oxygen concentration gradient maintained between air in alveoli and red blood cells?	Oxygen binds to haemoglobin so free oxygen concentration stays low, which means the steep concentration gradient is maintained until the erythrocyte is saturated with oxygen
Describe the change in saturation of haemoglobin with oxygen as partial pressure of oxygen increases	At a low pO2, few haem groups are bound to oxygen, so haemoglobin does not carry much oxygen. At higher pO2, more haem groups are bound to oxygen, making it easier for more oxygen to be picked up. The haemoglobin becomes saturated at very high p02.
Describe the change in saturation of haemoglobin with oxygen as partial pressure of carbon dioxide increases	As pCO2 increases, haemoglobin gives up oxygen more easily. This is known as the bohr effect.
Why is the bohr effect important?	Active tissues, with a high pCO2, receive more oxygen. Also, in the lungs, where the proportion of carbon dioxide in the air is relatively low, oxygen binds to the haemoglobin molecules readily.
How does fetal haemoglobin differ from adult haemoglobin and what effect does this have?	Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin, so as partial pressure of oxygen increases, it removes oxygen from the maternal blood. If the partial pressures were the same no oxygen would be transferred to the fetal blood.
What are the three ways carbon dioxide is transported form tissues to lungs?	5% dissolved in blood plasma 10-20% combines with the amino groups in the polypeptide chains of haemoglobin to form carbaminohaemoglobin. 75-85% is converted into hydrogen carbonate ions in the cytoplasm of red blood cells.
What happens to most of the CO2 in red blood cells?	It reacts with water to form carbonic acid, and then the carbonic acid dissociates to form hydrogen carbonate ions and hydrogen ions.
What enzyme catalyses the reaction between carbon dioxide and water in the cytoplasm of red blood cells?	Carbonic anhydrase
What is the chloride shift?	When hydrogen carbonate ions move out of erythrocytes into the plasma down the concentration gradient and chloride ions move into the cell as a result to maintain the electrical balance of the cell.
Why is important for carbon dioxide to be converted into hydrogen carbonate ions in red blood cells?	To maintain a steep carbon dioxide concentration gradient between respiring cells and red blood cells.
What happens to carbonic acid in red blood cells when the blood reaches lung tissue?	Carbonic anhydrase catalyses the breaking down of carbonic acid into carbon dioxide and water. The carbon dioxide diffuses out of the blood into the lungs.
What happens to hydrogen carbonate ions when the blood carrying them reaches lung tissue?	They diffuse back into red blood cells and react with hydrogen ions to form carbonic acid. This is broken down by carbonic anhydrase to form carbon dioxide which diffuses into the lungs. Chloride ions diffuse out of the red blood cells back into the plasma down an electrochemical gradient.
How are H+ ions removed from erythrocytes?	Haemoglobin acts as a buffer by accepting free hydrogen ions to form haemoglobinic acid. This prevents changes in the pH as ions move in and out of the cell.
Describe the process of deoxygenated blood being pumped across the heart.	The blood enters the right atrium from the vena cava. Pressure builds in the atrium until the atrio-ventricular valve (the tricuspid valve) opens to let blood flow into the right ventricle. The atrium contracts to force all the blood into the right ventricle. The ventricle contracts, closing the tricuspid valve to prevent backflow. The blood is pumped through the semilunar valves and into the pulmonary artery and towards the lungs.
What do the tendinous chords in the heart do?	Prevent valves from being turned inside out
Describe how oxygenated blood is pumped through the heart.	Oxygenated blood from the lungs enters the left atrium from the pulmonary vein. As pressure in the atrium builds the bicuspid valve opens, filling the left ventricle with blood. The atrium contracts, then the ventricle contracts and pumps the blood through semilunar valves into the aorta towards the rest of the body.
What is the inner dividing wall of the heart?	The septum
What occurs during diastole?	The heart relaxes. The atria and ventricles fill with blood.
What occurs during systole?	The atria contract, followed by the ventricles.
What does cardiac muscle being myogenic mean?	It has its own intrinsic rhythm, so the body doesn't have to use up resources to maintain the basic heart beat
Describe the nerve impulse process in the heart	The sino-atrial node causes the atria to contract. The signal is picked up by the atrio-ventricular node, which causes a slight delay do allow the atria to finish contracting. It then stimulates the bundle of His, a bundle of conducting tissue made up of purkyne fibres, which pass through the septum. At the apex the purkyne fibres spread out through the walls of the ventricles. The impulse passes through the fibres, causing the ventricles to contract from the apex upwards. This allows more efficient emptying of the ventricles.
What is tachycardia?	When the heart beats too fast
What is bradycardia?	When the heart beats too slow
What is an ectopic heartbeat?	One that is out of the normal rhythm of the heart
What is atrial fibrillation?	When the atria contract very fast, causing blood to not pump effectively
What is arrhythmia?	Abnormal rhythm of the heart

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