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Biology 1.2.2
AS OCR biology - transport in animals
| Question | Answer |
|---|---|
| What is a single circulatory system and which type of species has one? | Blood flows around the body then back to the heart, one circuit, heart has 2 chambers, e.g. fish : heart -> arteries -> gills -> veins -> body tissues -> veins -> heart |
| What is a double circulatory system and what types of species have one? | Blood flows around 2 circuits, heart has 4 chambers e.g. mammals. Pulmonary circuit - blood flows from heart to lungs and back to heart. Systemic circuit - oxygenated blood flows around the body then back to the heart |
| What are the advantages of a double circulatory system? | Heart can keep blood flowing through lungs at low pressure to not damage delicate capillaries & alveoli. Heart can keep blood flowing through systemic circuit at a high pressure, moves quickly, fast supply of O2 and nutrients, fast removal of CO2 |
| What is an open circulatory system? | Blood doesn't always remain in the blood vessels, it can circulate the body cavity e.g. insects |
| How does the circulatory system work in insects? | Blood enters the long muscular tube that lies under the dorsal surface through ostia. Muscle pumps blood to head by peristalsis. Blood flows into body cavity (open system). Insects are small so blood doesn't travel far, O2 and CO2 aren't carried in blood |
| What is a closed circulatory system and why do certain species have it? | Blood always remains in blood vessels. Mammals and fish have one because blood can be pumped at a higher pressure, faster movement, faster supply of O2 and nutrients, faster removal of CO2 |
| What are the features of an effective circulatory system? | Pump (e.g. heart), a transport medium (e.g. blood), a method of keeping high pressure (e.g. arteries), an exchange surface (e.g. capillaries) |
| What is the complete circulatory system of a) fish b) humans? | a) closed and single circulatory system b) closed and double circulatory system |
| What is the function of arteries, veins and capillaries? | Arteries - carry high pressure blood away from heart. Veins - carry low pressure blood towards the heart. Capillaries allow teh exchange of materials bewteen the blood and the tissue cells via tissue fluid. |
| How are arteries adapted to their function? | Lumen relatively narrow for high pressure. Strong walls withstand high pressure - thick, collagen. Elastic tissue allows walls to expand and recoil as heart pumps, pulse. Recoil maintains high pressure when heart relaxes. cont |
| Continued | Smooth muscle can contract to constrict artery. Endothelium is smooth to reduce friction with flowing blood, folded and can unfold when the artery stretches. High pressure ensures blood reaches all extremities of the body |
| How are veins adapted to their function? | Large lumen low pressure. Thin walls, thin layers of collagen, muscle, elastic tissue. Valves stop backflow of blood. Thin walls mean contraction of surrounding skeletal muscle applies pressure -> blood in 1 direction. Smooth endothelium reduces friction |
| How are capillaries adapted to their function? | Wall 1 cell thick, squamous epitheliia, short diffusion pathway. Narrow lumen same size as red blood cell squeezes red blood cells forcing them to give up O2 and reducing diffusion pathway to cells. Smooth endothelium reduces friction with flowing blood |
| What is the heart? | A muscular pump that creates pressure to propel blood around the body |
| What are the major veins and arteries connected to the heart? | Vena cava - deoxygenated blood from body to right atrium. Pulmonary artery- deoxygenated blood from right ventricle to lungs. Pulmonary vein -oxygenated blood from lungs to left atrium. Aorta- oxygenated blood left ventricle to rest of body |
| What is the septum? | The muscular wall separating the 2 sides of the heart |
| What are valves, examples, and how are they held open? | Valves are flaps of tissue that prevent the backflow of blood. Atrioventricular valves between atria and ventricles, bicuspid left, tricuspid right. Semilunar valves between arteries and ventricles. Tendinous chords stop valves turning inside out |
| Why do atria have thin walls? | They don't need to generate much pressure as the blood is only travelling to the ventricles which are near by |
| Why is the left ventricle thick? | 2 to 3 times thicker than the right. It controls the systemic circuit so needs to create enough pressure to pump blood a long distance and overcome friction |
| Why is the right ventricle thinner? | It controls the pulmonary circuit, so blood pressure is low as the lungs aren't far away. High blood pressure would damage delicate capillaries and alveoli in the lungs, especially since capillaries are in close contact with alveolus walls |
| What are the types and properties of cardiac muscle? | Striped muscle is strong but tires easily. Smooth muscle is flexible and doesn't tire. |
| Describe the external structure of the heart | The heart is surrounded by a double membrane called the pericardium. Coronary arteries and veins lie over grooves that indicate where the inner walls are. Coronary arteries bring oxygenated blood to the heart - blockage = angina, heart failure/attack |
| What is the cardiac cycle + steps? | The sequence of events involved in 1 heartbeat - diastole, atrial systole, ventricular systole |
| What occurs during diastole? | Atria & ventricles relax. Semilunar valves close because pressure in arteries is > ventricles. Internal volume increases because blood enters atria from veins. Atrioventricular valves open because pressure in atria is > ventricles. Blood enters ventricles |
| What occurs during atrial systole? | The atria contract, creating pressure to push blood into the ventricles. The atrioventricular valves then close, because blood fills the valve flaps |
| What occurs during ventricular systole? | 4 valves are closed. ventricle walls conrtact from apex upwards, blood pressure increases, blood rises. Semilunar valves open because pressure in ventricles > major arteries. Blood leaves heart through aorta/ pulmonary artery. Ventricle walls recoil |
| Explain the sound of the heart beat | The first sound (lub) is caused by the atrioventricular valves closing when the ventricle walls start to contract. The second sound (dup) is caused by the semilunar valves closing when the ventricle walls relax |
| How is cardiac muscle very different to other muscle in the body? | It is myogenic so contracts and relaxes without hormonal or nervous stimulation. |
| Which contracts at a higher frequency - atria or ventricles? | Atria! |
| Describe the movement of electrical signals through the heart | SAN is muscle tissue in right atrium that generates waves of electrical excitation at regular intervals that initiate contraction, pacemaker, contracts causing atrial systole P wave.between atria + ventricles is a layer of non-conducting tissue, AVN... |
| Continued | is the only way through. AVN delays signal to so atria finish contracting. AVN transmits impulse to bundle of His, which transmits it to the Purkyne tissue, which conduct impulse down inter-ventricular septum to apex. Purkyne fibres transmits impulse.... |
| Continued | up the ventricle walls so ventricular systole occurs upwards (QRS wave). Ventricle walls relax, T wave |
| What are electrocardiograms? | Monitor electrical activity of the heart: sensors attached to the skin detect waves of electrical excitation made by the heart, convert it into a trace |
| What is 1) arrhythmia, 2) tachcardia and 3) bradycardia 4) heart block? | 1) heart beats irregularly. 2) heart rate is fast e.g. stress, exercise. 3) long intervals between each heart beat. 4) damage to Purkyne fibres disrupt movement of electrical signals through the heart. |
| What is 1) fibrillation, 2) abnormal ventricular hypertrophy and 3) myocardial infarction and what do they look like on a ECG trace? | 1) contractions of heart chambers is unsynchronised, jumpy trace. 2) increase in muscle thickness of ventricle, deep S wave. 3) heart attack, elevated S and T section |
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