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Bio — 6.2
circulatory system
| Question | Answer |
|---|---|
| Concept of Circulation | - 17th century English physician, William Harvey - arteries and veins were part of single connected blood network - arteries pumped blood from heart (to lungs and body tissues) - veins returned blood to heart (from lungs and body tissues) |
| Atria | - act as reservoirs - blood returning to heart is collected via veins (and passed on to ventricles) |
| Ventricles | - act as pumps - expelling blood from heart at high pressure via arteries |
| Systemic Circulation | left side of heart pumps oxygenated blood around body |
| Pulmonary Circulation | right side of heart pumps deoxygenated blood to lungs |
| Function of Arteries | convey blood at high pressure from heart ventricles to tissues of body and lungs to tissues of body and lungs |
| Structure of Arteries | - narrow lumen to maintain high blood pressure (~80-120mmHg) - thick wall containing outer layer of collagen to prevent artery from rupturing under high pressure - arterial wall has inner layer of muscle and elastic fibers to maintain pulse flow |
| Flow of Blood in Arteries | - expelled from heart upon ventricular contraction - flows through arteries in repeated surges called pulses - blood flows at high pressure and muscle and elastic fibers assist in maintaining pressure between pumps |
| Muscle Fibers in Arteries | - form rigid arterial wall that is capable of withstanding high blood pressure without rupturing - can contract to narrow lumen, which increases pressure between pumps and helps to maintain blood pressure throughout the cardiac cycle |
| Elastic Fibers in Arteries | - allow arterial wall to stretch and expand upon flow of pulse through lumen - pressure exerted on arterial wall is returned to blood when artery returns to its normal size (elastic recoil) - helps push blood forward through artery and maintain pressure |
| Function of Capillaries | - arteries split into arterioles which split into capillaries, decreasing arterial pressure as total vessel volume increases - branching of arteries into capillaries ensures blood is moving slowly and all cells near blood supply |
| Function of Capillaries — Material Exchange | after material exchange has occurred, capillaries will pool into venules which will in turn collate into larger veins |
| Structure of Capillaries | - very small diameter (~5 micrometers) which allows passage single red blood cell at a time - capillary wall is made of single layer of cells to min diffusion distance for permeable materials |
| Structure of Capillaries — Permeability | - surrounded by basement membrane which is permeable to necessary materials - may contain pores to further aid in transport of materials between tissue fluid and blood |
| Capillaries — Continuous | capillary wall may be continuous with endothelial cells held together by tight junctions to limit permeability of large molecules |
| Capillaries — Fenestrated | in tissues specialized for absorption (e.g. intestines, kidneys), capillary wall may be fenestrated (contains pores) |
| Capillaries — Sinusoidal | some capillaries are sinusoidal and have open spaced between cells and be permeable to large molecules and cells (e.g. in liver) |
| Flow of Blood in Capillaries | - flows through capillaries very slowly and at low pressure to allow for maximal material exchange - high blood pressure in arteries is dissapated by extensive branching of vessels and narrowing of lumen |
| Function of Veins | collect blood from tissues and convey it at low pressure to atria of heart |
| Structure of Veins | - very wide lumen to max blood flow for more effective return - thin wall with less muscle and elastic fibers as blood is flowing at very low pressure (~5-10 mmHg) - bc pressure is low, valves prevent backflow |
| Flow of Blood in Veins | - very low pressure in veins can make difficult for blood to move against downward gravity - contain numerous one-way valves in order to maintain circulation of blood by preventing backflow |
| Flow of Blood in Veins — Periodic Contractions | - when skeletal muscles contract, they squeeze vein and cause blood to flow from site of compression - veins typically run parallel to arteries and similar effect can be caused by rhythmic arterial bulge created by pulse |
| Heart Structure — Chambers | - two atria: smaller chambers near top of heart that collect blood from body and lungs (reservoirs) - two ventricles: larger chambers near bottom of heart that pump blood to body and lungs (pumps) |
| Heart Structure — Heart Valves | - atrioventricular valves (between atria and ventricles): bicuspid valve on left side; tricuspid valve on right side - semilunar valves (between ventricles and arteries): aortic valve on left side; pulmonary valve on right side |
| Heart Structure — Blood Vessels (Veins) | - vena cava (inferior and superior) feeds into right atrium and returns deoxygenated blood from body - pulmonary vein feeds into left atrium and returns oxygenated blood from lungs |
| Heart Structure — Blood Vessels (Arteries) | - pulmonary artery connects to right ventricle and sends deoxygenated blood to lungs - aorta extends from left ventricle and sends oxygenated blood around body |
| Coronary Arteries | set of blood vessels within heart to provide nutrients and get rid of waste |
| Contractions of Heart | - myogenic: signal for cardiac compression arises within heart tissue itself - signal for heart beat is initiated by heart muscle cells rather than from brain signals |
| Sinoatrial Node | specialized cluster of heart muscle cells which direct contraction of heart muscle tissue in wall of right atrium |
| Heart Beat — 1st Beat | - electric impulse with reach SA node and fire electric impulse that will spread evenly between both atriums --> atrial contraction (first beat) - electric impulse reaches AV node and moves electric impulse into bundle of His |
| Heart Beat — 2nd Beat | bundle of His will then send electric impulse into Purkinje fibers --> causing ventricular contraction (second beat) |
| Nerve Signalling | - pacemaker is under autonomic (involuntary) control from brain, specifically medulla oblongata (brain stem) - nerves connected to medulla regulate heart rate by either speeding it up or slowing it done |
| Sympathetic Nerve | releases neurotransmitter to increase heart rate |
| Parasympathetic Nerve | releases neurotransmitter acetylcholine to decrease heart rate |
| Hormone Control | - hormone adrenaline (epinephrine) is released from adrenal glands (located above kidneys) - adrenaline increases heart rate by activating same chemical pathways as noradrenaline |
| Cardiac Cycle | - describes series of events that take place in heart over duration of single heart beat - comprised of period fo contraction (systole) and relaxation (diastole) |
| Systole — Atrial Contractions (Atrial Systole) | - blood returning to heart flows into atria and ventricles as pressure in them is lower (due to low blood amount) - when ventricles are ~70% full, atria will contract, increasing pressure in atria and forcing blood into ventricles |
| Systole — Ventricular Contractions | - as ventricles contract, ventricular pressure exceeds atrial pressure and AV valves close to prevent back flow (1st heart sound) - with both sets of heart valves closed, pressure builds in contracting ventricles |
| Final step in Systole | when ventricular pressure exceeds blood pressure in aorta, aortic valve opens and blood is released into aorta |
| Diastole — Drop of Ventricular Pressure | - as blood exits ventricle and travels down aorta, ventricular pressure falls - when ventricular pressure drops below aortic pressure, aortic valve closes to prevent back flow (2nd heart sound) |
| Diastole — Final Steps | - when ventricular pressure drops below atrial pressure, AV valve opens and blood can flow form atria to ventricle - throughout cycle, aortic pressure remains quite high as muscle and elastic fibers in artery wall maintain blood pressure |
| Electrocardiography — P Wave | represents depolarization of atria in response to signalling from SA node |
| Electrocardiography — QRS Complex | represents depolarization of ventricle triggered by signals from AV node |
| Electrocardiography — T Wave | represents repolarization of ventricles and completion of standard heart beat |
| Systolic Pressure | higher value that represents pressure in vessel when heart is contracting (i.e. pulse flow) |
| Diastolic Pressure | lower value that represents pressure in vessel when heart is relaxing |
| Normal Blood Pressure | 120/80 mmHg |
| High Blood Pressure | 140/90 mmHg |
| Low Blood Pressure | 90/60 mmHg |
| Atherosclerosis | hardening and narrowing of arteries due to deposition of cholesterol |
| Atherosclerosis — Steps (Deposition and Pressure) | - fatty deposits develop in walls of arteries and reduce diameter of lumen - restricted blood flow increases pressure in artery --> damages arterial wall |
| atherosclerosis — Steps (Fibrous Tissue and Plaques) | - damaged region is repaired with fibrous tissue --> reduces elasticity of vessel wall - lesions can be formed called atherosclerotic plaques |
| Atherosclerosis — Final Step | if plaque ruptures --> tear is formed --> released plaque (thrombus) can block capillaries and restrict blood flow |
| Risk Factors of Coronary Heart Disease (CHS) | smoking, high blood pressure (damages elasticity of artery, causes tears which causes blocks in capillaries), high blood cholesterol levels, high blood sugar levels, obesity, genetic factors, age --> over time, elasticity of artery decreases |
Created by:
soguzman
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