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Human Phys
Circulatory and Heart pt.1
| Question | Answer |
|---|---|
| Why do we need circulatory systems? pt.1 | - Cell survival requires necessary nutrients, waste and gas exchange - As cells get larger their surface area to volume ratio decreases - Therefore, as cells get larger, they cannot survive on diffusion alone |
| pt.2 | - cells stay small and evolve multicellularity to cope with increasing gene sizes allowing further functions - Evolution engineered a way by selecting multicellular organisms with increased surface areas to volume ratios to allow for exchange |
| Open vs Closed circulatory systems | Open: haemolymph pumped around by heart in vessels then released to tissues for exchange Closed: blood pumped round in vessels, but doesn't leave, but exchange happens through vessel endothelium cells |
| What does the human circulatory system need? | - a heart that pumps and is responsive to hypoxia - contractile cells that respond effectively - pumps the correct haemodynamics (blood flow) - deoxygenated and oxygenated blood flows correctly in 2 way system |
| Human heart | - two closed circuits (pulmonary and systemic) - 4 chambers - right and left seperated |
| Human heart development | The atriums and the right and left ventricles are derived from different embryonic lineages |
| Pulmonary and systemic systems | - pulmonary: high pressure, low flow - systemic: low pressure, high flow Hypoxia reaction: - pulmonary: vasodilation - systemic: vasoconstriction Differences due to environmental conditioning and development |
| Vascular systems | - consists of: arterioles and arteries, veins and venules, and capillaries |
| Arteries | Higher pressure Thicker walled More elastic No valves |
| Veins | Lower pressure Thinner walled Less elastic Valves present |
| EC barrier | - barrier of endothelial cells - breakdown can allow disease |
| Pulmonary hypertension | - rare life-threatening disorder of the lungs characterised by abnormally elevated pulmonary pressure and right heart failure that if untreated leads to premature death - hypertension treatment based on vasodilators/constrictors |
| Cardiac muscles (cardiomyocytes) | - connected by 3 main structures at the sarcolemma that provide mechanical links 1) fascia adherens 2) desmosomes 3) gap junctions - facilitates conduction of the cardiac impulse |
| Electrical conduction system of the heart | Cardiac excitation - depolarisation: Na+ ions in - repolarisation: K+ ions out |
| Cardiac excitation sequence (seen on an echocardiogram) | - atrial: SA node generates impulse, AV node delays impulse - ventricular: ventriular depolarisation begins at apex, atrial repolarisation occurs - ventricular depolarisation complete, then repolarisation occurs |
| Ventricular Myocyte AP | - fast response action potentials due to rapid depolarisation - specific changes in the permeability of the cardiomyocyte membrane to different ions determine the AP shape and duration |
| Sinoatrial (SA) node | - primary pacemaker - no true resting potential |
| EC coupling in cardiac muscle | - depolarisation of membrane - opening of plasma membrane, flow of Ca2+ into cytosol, bind to receptors on ER surface - increased cytosolic Ca2+ concentration leads to contraction |
Created by:
reub8n
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