Cardiovascular System.docx

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Department
Biological Sciences Program
Course
BSCI 201
Professor
Justicia Opoku
Semester
Spring

Description
Cardiovascular System The cardiovascular System The function of the cardiovascular system is to delivery oxygen and nutrients and to remove carbon dioxide and other waste products Transport of substances such as: Oxygen & nutrients to cells Wastes from cells to liver and Kidneys Hormones, immune cells, clotting proteins to specific target cells Aclosed system of the heart and blood vessels The heart pumps blood Blood vessels allow blood to circulate to all parts of the body Blood is used for delivery Overview of the cardiovascular System The Heart Located in the thoracic cavity Diaphragm separates abdominal cavity form thoracic cavity Size of first Weights approximately 250-350 grams Valves present for unidirectional blood flow Valves prevent backflow Four chambers: 2 atria and 2 ventricles Blood Vessels Blood Muscle generates more force so the heart needs to generate more force to pump the blood through the whole body. Left side also has more musculature. Properties of Cardiac Muscle Intercalated Disks Gap Junction: so heart contracts as a unit Electricity can pass through these sells and creates one uniform contraction Desmosomes: resist Stress Specialized junctions that hold cells together. Aerobic muscle No cell division after infancy – growth by hypertrophy You can’t replace Heart cells. Heart grows through mass (hypertrophy) 99% contractile cells 1% autorhythmic cells Creates a rhythm to beat on it’s own Heart is set to beat at 100 bpm but nervous system and endocrine system adjust the bpm based on what is appropriate for their metabolic needs The heart’s Covering: The pericardium Pericardium is a double-walled membranous sac surrounding heart Serous fluid fills the space between the layers of pericardium Lubricates heart decreasing friction Prevents blisters because of the covering Covering keeps the heart moist. Pericarditis = inflammation of pericardium The Heart: 4 Chambers Right and Left side act as separate pumps Septa: Separates chambers Interventricular Septum Separates the two ventricles Interatrial septum Separates the two atria Four chambers Atria are receiving chambers RightAtrium LeftAtrium Ventricles are discharging chambers Right Ventricle Left Ventricle The Heart: Valves Allow blood to flow in only one direction to prevent backflow Four Valves Atrioventricular (AV) valves are between atria and ventricles Bicuspid (mitral) valves (left side of heart) 2 flaps: named after a pop’s hat Tricuspid Valve (right side of the heart) 3 Flaps Semilunar valves are between ventricle and artery Pulmonary semilunar valve Aortic Semilunar Valve Aorta The Heart: Valves AV valves Anchored in place by chordae tendinae (“Heart strings”) Gives the heart it’s unique shape. It’s shape helps blood leave the heart. Open during heart relaxation and closed during ventricular contract Semilunar Valves Closed during heart relaxation but open during ventricular contraction When one set it open, the other set is closed. This is known as complimentary Valves These valves operate opposite of one another to force a one-way path of blood through the heart. Valves and Unidirectional Blood Flow Pressure within chambers of heart vary with heartbeat cycle Pressure differences drives blood flow: high pressure to low Pressure Movement of blood pushes the valves open Normal direction of flow Veins to atria Atria to ventricles Ventricles to arteries Valves prevent backward flow of blood All valves open passively based on pressure gradient The farther you get from the heart, the lower the blood pressure. Highest BP is in the heart Blood Vessels: Heart  arteries  arterioles  capillaries  venules  Veins (Then starts again) Arteries are relatively large, branching vessels that conduct blood away from the heart Arterioles are small branching vessels with high resistance Branching of Arteries Capillaries are site of exchange between blood and tissue Capillaries: only site of gas Exchange Venules are small converging vessels Veins are relatively large converging vessels that conduct blood to the heart By the time we’re in the veins, there is no blood pressure. Movement (skeletal muscle pump) moves the blood from the veins back to the heart Doesn’t matter when people are sleeping because they are horizontal and the subtle movements People with paralysis: They have problems, They need to go to PT so that they can move the blood flow. Closed System Pressure drives blood Flow Series flow through the Cardiovascular System Parallel Flow within the systemic or Pulmonary Circuit Pulmonary Circuit Supplied by right Heart Blood vessels from heart to lungs and lungs to heart Systemic Circuit has higher pressure from the heart because the entire body needs blood and so the heart has to get it there. Supplied by left heart Blood vessels from heart to systemic tissues and tissues to heart Not all arties carry oxygenated Blood Arteries LeadAWAY from the heart PulmonaryArteries are deoxygenated. Left Ventricle  aorta  system circuit  venae cavae  right atrium  right ventricle  Pulmonary artery  Pulmonary Circuit  pulmonary veins  left atrium  left ventricle Oxygenation of blood Exchange between blood and tissue takes place on capillaries Pulmonary Capillaries Blood entering lungs = deoxygenated blood Oxygen diffuses from tissue to blood Blood leaving lungs = oxygenated blood Systemic Capillaries Blood entering tissues = oxygenated blood Oxygen diffuses from blood to tissue Blood leaving tissues = deoxygenated blood Only site of gas exchange is capillaries Thin walls for diffusion of gases Gases: Oxygen and CO2 Pulmonary Circuit: Oxygen comes in and CO2 leaves the blood stream Systemic Circuit Oxygen goes out of the blood and CO2 leaves the blood stream Why do we need Oxygen Oxygen Phosphorylation: MakesATP so we can use this energy Certain cells needs moreATP Coronary Circulation Intrinsic conduction system (nodal system): heart muscle cells contract, without nerves impulses, in a regular continuous way. Blood in the heart chambers does not nourish the myocardium The heart has its own nourishing circulatory system consisting of Coronary arteries branch from the aorta to supply the hear muscle with oxygenated blood Cardiac veins drain the myocardium of blood Coronary sinus, a large vein on the posterior of the heart, receives blood from cardiac veins Blood empties into the right atrium via the corony sinus Bypass surgery. Done through stents where they uses vessels from other places to completely bypass the current vessel. Usually the current vessel has plaque or cholesterol buildup which is why it needs bypas Multiple stents is named after the number of stents. Quadruple bypass (4 stents) After about 4 they may have to use veins instead of the arteries Also hard to find arteries at that point which aren’t clogged Differences between blood vessels Wall of theArteries are the thickest Arteries are under the highest pressure. Strong muscular vessels. This allows them to resist the force that the heart generates Lumens of veins are larger Larger veins have valves to prevent backflow Skeletal muscle squeezes blood in veins toward the heart Walls of capillaries are only one cell layer thick to allow for exchange between blood and tissue Blood Vessels; MicroscopicAnatomy Three Layers (Tunics) Tunica Intima: endothelium Tunica Media Smooth muscle Controlled by sympathetic nervous system Radius can be altered may be used to control blood flow to individual capillary beds Used to regulate mean arterial pressure. Tunica externa is mostly fibrous connective tissue Arteries Rapid Transport Pathway, large diameter – little resistance Walls contain elastic fibrous tissues, under high pressure Smooth muscle regulates radius MajorArteries Aorta: Leaves left ventricle PulmonaryArteries: Leave right ventricle Capillaries Site of exchange between blood and tissue Substances exchanged due to concentration gradients Oxygen and nutrients leave blood. Carbon Dioxide and other wastes leave the cells They are ready to leave the cell Walls are 1 cell layer, small diffusion barrier 10-40 billion per body, total surface area 600 m^2 Most cells within 1 mm of a capillary Cartilage: not a very good blood supply. Eyes:Aren’t as vascularized Have direct gas exchange for one’s skin Exchange of nutrients through eyelids to the eyes. Can’t have blood vessels covering eye because then we couldn’t see Pores between endothelial cells, protein free plasma moves through pores Did allow leukocytes to but also allow proteins to as well. Capillary Exchange: Mechanisms Direct diffusion across plasma membranes Endocytosis or exocytosis Some capillaries have gaps (intercellular clefts), plasma membrane not joined by tight junctions Fenestrations (pores of some capillaries) Fluid Movements at capillary beds Blood pressures forces fluid and solutes out of capillaries Osmotic pressure draws fluid into capillaries Blood Pressure is higher than osmotic pressure at the arterial end of the capillary bed Blood pressure is lower than osmotic pressure at the venous end of the capillary bed. Chronic Hypotension Blood vessels push out too much blood and not the same amount coming back in Results in edema because of this Push out more fluid than how much that comes in. Parallel line for Osmotic Pressure Precapillary Sphincters Rings of smooth muscle that surround capillaries on the arteriole end Contract/relax in response to local factors only Contraction  constrict capillary  decrease blood flow Relaxation  increases blood flow Metabolites (waste products) cause relaxation If one is metabolically active, a lot of waste is created. CO2 will open the sphincters (relaxation of the sphincters) Capillary Beds Capillary beds consist of two types of vessels Vascular shunt – vessel directly connecting an arterioles to venules If there is backflow, the capillaries will not get blood and the blood will just run through shunts Blood just needs to get back to the veins so it uses the shunt in order to get blood back to veins. True capillaries – exchange vessels Oxygen and nutrients cross to cells Carbon dioxide and metabolic waste products cross into blood Factors affecting filtration and absorption across capillaries Kidney disease increase blood volume and thus blood pressure Decrease in plasma proteins Frothy Urine is a sign of this because you may be urinating proteins Heart Disease  pulmonary edema Seen first because it is closer to the heart Pulmonary circuit is under lower pressure than the systemic circuit Liver Disease  Decrease in plasma proteins Veins Veins:Avolume reservoir Factor that influence central venous pressure and venous return Large diameter, but thin walls Valves allow unidirectional blood flow. Veins are a volume reservoir because of a high Compliance Compliance is a measure of how the pressure of a vessel will change with a change in volume Low compliance arteries: small increase in blood volume causers a large increase in pressure High Compliance (veins): large increase in blood volume required to produce large increase in pressure. Veins expand with little change in pressure and function as blood reservoir 60% total blood volume in system veins at rest, veins hold large volume with small pressure change due to high compliance Volume that Veins have is about 3.5 times larger than how much volume arteries can hold Compliance: How easy is it to stretch (measured through pressure) The skeletal muscle Pump Most arterial blood is pumped by the heart Veins use the milking action of muscles to help move blood One-way valve in peripheral veins Skeletal muscle contracts Squeezing on veins increased pressure ( blood actually goes both ways but valves prevent backflow so it turns into unidirectional muscle) Blood moves toward heart Blood cannot move backwards due to valves Skeletal muscle relaxes Blood flows into veins between muscles People need movement. The Heart: Conduction System Special tissue sets the pace Sinoatrial node = SAnode (“Pacemaker”), is in the right atrium Atrioventricular Node =AV node, is at the junction of the atria and ventricles Atrioventricular bundle =AV bundle (bundle of His), in in the interventricular septum Bundle branches are in the interventricular septum Purkinje fibers spread within the ventricle wall muscles. Auto-rhythmic Cells Atria contract as a unit and then ventricles contract as a unit Atrial Contraction precedes ventricle contraction Auto-rhythmicity is the ability to generate own rhythm. Autorhythmic cells that provide pathway to spread excitation through the heart Sinoatrial node is the pacemaker of the heart Excites Atria Blood into ventricles Then the message goes to the atrioventricular node Excites Ventricles Alot more electrical wires going through ventricles This makes sure the ventricles contract Waves of contraction through cardiac muscle The Heart: Special Tissue sets the pace Conduction System Sinoatrial node = SAnode (“Pacemaker”), is in the right atrium Excites the atrium and excites theAV node Action potential spread through theAV bundle in order to get through the tough cardiac muscle Atrioventricular node =AV node, is at the junction of the atria and ventricles Atrioventricular bundle =AV bundle (bundle of His), is in the interventricular septum Gap Junctions also allow electrical signals to spread. Bundle branches are in the interventricular septum Purkinje fibers spread within the ventricle wall muscles Control of heart beat by pacemakers Auto-rhythmic cells have pacemaker potentials Heart sets it’s own stimulus: Funny Channels. These channels let in sodium themselves. When sodium goes in, it open voltage gated channels. T-Type Channels These T-Type channels open and allow calcium in. Threshold:Action Potential: When the L=type calcium channels open Calcium moves in Spontaneous depolarization caused by closing K+ channels and opening of cation channels Channels that open: If channels: NA+ moves in, net depolarization, then Ca2+ T channels: Further depolarization until threshold Car+ L Channels cause the action potential The Resting Membrane Potential Resting potential is caused by the membrane’s ability to maintain a positive charge on its outer surface opposing a negative charge on its inner surface. Maintains a concentration gradient by having potassium inside the cells, and sodium outside the cells K+ leak channels allow potassium to leave the cell. It leaves down it’s concentration gradient and leaves behind negatively charged proteins. The inside of the cell becomes more and more negative. -70mV is equilibrium in cells Form this a concentration gradient is created because it is potential energy If sodium moves into the cell (selectively), electricity comes in. Calcium does the same thing, it enters the cell and also can create electricity as it comes into the cell Resting Potential = Potential Energy Action potential: Stimulus – activate and allow sodium to flow into the cell and create electricity Thinking about something causes it to activate.Acetylcholine receptors start the neurons in order to start the sodium channels that open up. Stimulus is thinking Threshold Potential Once you open and hit a particular potential, a create amount of sodium channels open and creates an action potential. Returns to RMP Known as Repolarization ElectricalActivity in pacemaker Cells Depolarize to threshold with funny channels and T Type Ca2+ Sodium chan
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