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12 Cards in this Set
- Front
- Back
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Transport in mammals |
Closed circulation : blood is pumped from the heart to arteries, veins and capillaries. Blood passes the heart twice =double circulation (systemic and pulmonary) Delivery of oxygenated blood quickly to all regions of the body Blood reaches the tissues without being diluted by unoxygenated blood |
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Blood components |
Defends against disease, transports respiratory gases Plasma: 55% transports nutrients, waste, hormones, heat, dissolved proteins Red/erythrocytes : transports oxygen and CO2 White/leucocytes: Lymphocytes and phagocytes digest bacteria Platelets: result in clotting |
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Heart valves |
Atrioventricular valves: right side is tricuspid valve, the left side is bicuspid, under huge pressure and supported by tendons Semi lunar valves between ventricles and pulmonary artery (right) and aorta (left) |
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Heart |
Hollow organ, contained in tightly fitting membrane: pericardium Cardiac muscle consists of cylindrical columns of fibres , allowing for contraction in three dimensions, surrounded by plasma membrane: sarcolemma, connected by intercalated discs Myogenic origin |
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Coronary heart disease |
Atherosclerosis: Damage to artery walls as fat strands and fibrous tissue are deposited under the endothelium Raised blood pressure Lesion formation = plaques and thrombus are often formed as a result of exposed blood platelets |
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Consequences of coronary heart disease |
Embolus can cause blockage--> tissue deprived of oxygen from which it will die Problems in the coronary arteries can be fixed by heart by-pass operation (part of a blood vessel is taken from somewhere else so the blocked one can be passed) or coronary angioplasty (insert balloon or mesh into artery) |
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Heartbeat |
Beats 75 times/minute (0.8 s for each contraction) Systole: heart muscle contracts and diastole: the heart muscle relaxes Stroke volume is the volume of blood forced from the ventricles into the aorta and pulmonary arteries. Each surge stretches the artery walls, which is the pulse. |
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Control of the heartbeat
pacemaker: a very small bit of the muscle in the right atrium --> electric pulses spread through both artia--> atrial systole (delay before AVN stops both contractions from happening simultaneously) --> |
--> electric signal is picked up by the AVN, atrioventricular node at the base of the right atrium which is then passed by tiny conducting fibres called Purkeyne and fibres, collectively called bundles of his Bundles of his stimulates the ventricles from bottom up into contracting The heart has a relatively long rest period called refractory period (diastole) |
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Pacemaker |
Amount of blood from heart = cardiac output=stroke volume*pulse rate Regulated by Cardiovascular centre in the brain sends signals by two nerves: Sympathetic nerve which speeds up the rate of the heart + Vagus nerve which slows it down |
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Arteries |
Aorta-->artery-->arteriole-->capillary-->venule-->vein-->venacava thickest+ strongest walls, no valves Main arteries have elastic fibres to stretch for high pulse, and to recoil and push the blood forward Arterioles have smooth muscles to regulate the flow of blood from arteries into capillaries. |
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Capillaries |
tinytubes linking veins and arteries thin walls of one layer of endothelial cells to allow for exchange between blood and tissue no valves |
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Veins |
Carry blood back to heart Veinshave thin walls due to low pressure Venules consist of one endothelium cell layer and a few smooth muscles Veins have few elastic fibres because of low pressure, and have valves |
