1.2- S5: Transport in animals

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What is transport?
The movement of oxygen, nutrients, hormones, waste and heat around the body.
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Why do multicellular organisms need transport systems?
Large organisms have lower surface area to volume ratios and nutrients cannot reach deeper layers of cells by diffusion. Multicellular organisms are active so they require nutrients faster for respiration.
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What are features of a good transport system?
A fluid medium to carry dissolved nutrients around the body. A pump to increase the pressure and allow the nutrients to reach cells faster. Exchange surfaces.
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Describe and explain the features of a single circulatory system.
Blood passes through the heart once on each circuit. Fish: Heart pumps to gills which pick up oxygen then to the rest of the body to deliver oxygen.
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Why are there limitations to single circulatory systems?
The blood pressure is reduced in the gills so blood does not flow as quickly to the rest of the body, limiting the rate of respiration.
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Describe and explain the features of a double circulatory system.
Blood passes through the heart twice in each circuit. Mammals: (right side) pulmonary circulation/system carries blood to the lungs to pick up oxygen. (left side) The systemic circulation/system carries oxygen to the rest of the body.
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What are advantages to a double circulatory system?
Systemic circulation carries blood at a higher pressure due to the pumping action of the heart so blood can travel faster and oxygen is delivered to tissues more quickly for respiration.
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What is a closed circulatory system?
Vertebrates- blood enclosed inside blood vessels. Tissue fluid bathes cells and tissues. Substances diffuse from capillaries into body cells but blood always stays inside vessels. The heart can pump at a higher pressure so exchange is faster.
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What is an open circulatory system?
Invertebrates- blood isn't always enclosed within vessels. Flows in body cavity- cells bathed in blood. Heart is segmented (blood enters through ostia,) contracting in a wave, pumping blood into a single main artery.Artery opens up into body cavity.
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What is the function and structure of arteries?
Carry blood away from heart. The lumen is small- maintains high pressure. The folded endothelium allows it to expand and cope with higher pressure. Their walls have elastic fibres which stretch and recoil when heart pumps.Collagen provides strength.
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What is the function and structure of capillaries?
Smallest blood vessels. Substances like oxygen and glucose are exchanged between cells and capillaries so they're adapted for efficient diffusion by having one squamous cell thick walls. Narrow lumen the diameter of RBC shortens diffusion distance.
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What is the function and structure of veins?
Take blood to heart under low pressure. Wider than arteries. Little elastic fibres as they are not actively constricted. Blood flow helped by contraction of skeletal muscle around vein and valves preventing backflow. Large lumen aids flow of blood.
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What is tissue fluid made up from?
Plasma mediium with dissolved oxygen, carbon dioxide, salts, glucose, fatty acids, amino acids, hormones and plasma proteins. Cells include erythrocytes, leucocytes, and fragements called platelets.
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Explain how tissue fluid is formed from the blood .
Arteriole end of the capillary bed, higher hydrostatic pressure from contraction of heart muscle. Fluid forced out of capillaries into spaces around cells, forming tissue fluid. Pressure in capillaries is lower at venous end.
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How does fluid re-enter the capillaries at the venous end of the capillary bed?
The water potential of tissue fluid is less negative than the water potential in the blood. Therefore fluid enters capillary by osmosis. Also there is some hydrostatic pressure in the tissue fluid.
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How does tissue fluid drain into lymph vessels?
Excess tissue fluid passes into lymph vessels through lymph capillaries. Valves in the lymph vessels prevents the backflow of lymph. Lymph moves towards main lymph vessels in the thorax where it is returned to the blood near the heart.
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What are the main differences between blood, tissue fluid and lymph?
RBC only in blood. Few WBC in tissue fluid (only during infection.) Platelets only in blood. Proteins mainly in blood, too large for capillary walls. More glucose in blood. Lymph has more fats.
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What form of blood does the left and right side of the heart pump?
double pump. Left hand side: oxygenated blood to body. Right hand side: deoxygenated blood to the lungs.
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What are the coronary arties?
They are surroung the heart muscle, providing oxygenated blood to the heart muscle , and restricted blood flow to this muscle could result in angina or myocardial infarction.
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What is the purpose of valves in the heart and how do they work?
prevent backflow of blood as they only open one way. If there is higher pressure behind the valve, it is forced open. Movement of blood causes valve pockets to fill, shutting valves. Tendinous cords attach valves to ventricles- stop valves inverting
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How do the walls of chambers in the heart vary?
The left ventricle is thicker and more muscular than right ventricle- contract powerfully pump blood to body+ overcome resistance of systemic circulation. Right side to lungs- nearby. Ventricles thicker than atria as they push blood out of heart.
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What is the cardiac cycle?
The sequence of events in one heartbeat.
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What is the role of the septum?
It separates the ventricles to ensure oxygenated and deoxygenated blood are separate.
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Explain what happens during diastole.
Atria relax and ventricle walls recoil and relax, decreasing pressure by increasing volume. Higher pressures in main arteries= SL valves close. Blood flows into atria and open AV valves into ventricles due to low pressure in ventricles. DUB SOUND
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Explains what happens in atrial systole.
The atria fill, decreasing volume- increase pressure helps to push blood into ventricles. The ventricle walls stretch to fill with blood. Atria contract to decrease their volume further and force remaining blood out.
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Explains what happens in ventricular systole.
Atria relax after contracting. Ventricles are at a higher pressure than the atria so valves pockets are full and AV valves shut to prevent backflow. Semi-lunar valves are forced open, blood leaves via main arteries. LUB SOUND.
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What do the terms 'myogenic' and 'fibrillation' mean?
mŷs- muscle ancient greek. Muscles can contract without receiving signals from nerves. Fibrillation- inefficient pumping.
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Explain the regular beating of the heart due to muscle excitation.
SAN initiates wave of excitation.Spread over both walls of atria- contract simultaneously atrial systole. Waves of excitation from SAN to AVN at the inter-ventricular septum. Waves passed onto Purkyne tissue. apex of ventricles- simultaneous contract
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Why is there non conducting fibres at the base of atria?
Collagen (non-conducting tissue) at base of atria ensures excitation not directly spread to ventricle walls
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Describe the stages on an electrocardiograph from ECGs.
The P wave is caused by depolarisation and atrial systole. QRS is caused by ventricular systole and depolarisation. The T wave is caused by repolarisation of the ventricles (diastole.)
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Explain how oxygen is transported in the body.
erythrocytes in the form of oxyhaemoglobin. Hb- large globular protein with a quaternary structure (4 polypeptide chains.) Each chain has a haem group containing [Fe]2+ making it red. High affinity for oxygen (4 molecules.) OXYHAEMOGLOBIN.
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What is partial pressure of oxygen?
The measure of concentration of oxygen and oxygen tension.
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How does affinity for oxygen vary?
When the pO2 is higher (lungs) Hb has a higher affinity for oxygen. When pO2 is lower, Hb has a lower affinity for oxygen.
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Explain the shape of an oxygen dissociation curve.
S shape: Haem groups attracting oxygen are in centre of Hb molecule- difficult to associate. pO2 rises- eventually associates. Haemoglobin conformational change. Easier for 2nd and 3rd O2 to join. 4th difficulty joining- 100% saturation unlikely.
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Explain why mammilian fetal haemoglobin has a higher affinity for oxygen
When mother's blood reaches the placenta, the oxygen saturation decreases due to respiration of mother. Fetus must have a higher affinity for oxygen (combine under lower pO2.) fetal curve to the left of adult haemoglobin curve.
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Explain the Bohr effect.
CO2 from respiring tissues converted into carbonic acid by carbonic anhydrase. Carbonic acid dissociates->H+ ions and HCO3- ions. HCO3 ions diffuse into plasma, Cl- ions diffuse into RBC. H+ ions form haemoglobinic acid.ions recombine-> CO2 in lung
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What is the effect of CO2 on O2 release?
More hydrogen ions produced in RBCs make oxyhaemoglobin release more oxygen. At any pO2, more O2 released due to CO2.
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Why do multicellular organisms need transport systems?

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Large organisms have lower surface area to volume ratios and nutrients cannot reach deeper layers of cells by diffusion. Multicellular organisms are active so they require nutrients faster for respiration.

Card 3

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What are features of a good transport system?

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Card 4

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Describe and explain the features of a single circulatory system.

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Card 5

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Why are there limitations to single circulatory systems?

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