BIOL 460 1st Edition Lecture 23 Outline of Last Lecture I Blood Clotting a Platelets b Hemostasis c Platelet release reaction d Formation of clot Outline of Current Lecture I Dissolution of Clots II Anticoagulants III Cardiac output IV Stroke Volume Effects a Frank Starling Law V Venous Return Current Lecture Blood Clotting Continued 1 Dissolution of Clots a Prekallikrein XII kallikrein b Plasminogen kallikrein thrombin or tissue plasminogen activator Plasmin enzyme that digests fibrin c Same steps that form clot also aid in dissolution of clot thrombin XII d TPA used to dissolve clots in stroke and myocardial infarctions produced by endothelial cells e Also use streptokinase produced by streptococcus to dissolve fibrin 2 Anticoagulants a Aspirin inhibits COX 1 inhibits platelet release reaction b Coumarin warfarin inhibits activation of vitamin K no Ca2 binding to clotting factors c Heparin inhibits thrombin what blood storing glassware is coated with d Citrate binds Ca2 making it unavailable e EDTA binds Ca2 making it unavailable Cardiac Output 1 CO SV HR 2 Average CO 75ml beat 70 beats min 5500 ml min These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 3 Anything that affects HR chronotropic effect a Can be or b Determined by cardiac center in medulla i Influenced by higher brain centers and baroreceptors measure BP ii Baroreceptors are located in carotid sinus and aortic arch iii Drop in BP causes a reflex increase in HR c HR affected by balance of sympathetic and parasympathetic innervation d Sympathetic Effect i B1 receptors ii Adenylate cyclase cAMP 2nd messenger system iii Steepens slope of pacemaker potential by directly opening more HCN channels cAMP iv Epinephrine cAMP HCN channels open e Parasympathetic Effect i Decreases slope of pacemaker potential ii Muscarinic receptors open K channels in cells of SA node iii Depolarizes more slowly 4 What affects stroke volume a End diastolic volume i Amount of blood in ventricle ii Preload workload imposed on heart before it contracts iii SV proportional to EDV b Total Peripheral resistance i Fluid moves through tube and experiences friction with walls of tube ii Greater diameter decreases resistance iii Higher peripheral resistance increases arterial pressure which means the heart must produce a higher pressure to reach ejection phase iv PR is actually friction v Sometimes called afterload workload after contraction vi Peripheral resistance increases stroke volume decreases vii SV EDV PR c Contractility of Myocardium i How forcefully ventricles contract at any given moment ii Affected by norepinephrine and epinephrine iii Said to be positive inotropic ino sinew effect iv Heart contracts more forcefully via sympathetic post ganglionic neurons increasing Ca2 in sarcoplasm d Frank Starling Law of the Heart Otto Frank and Ernest Starling i The more the heart is stretched the more forcefully it contracts ii Length tension relationship like skeletal muscle iii Increases distance that the thin filaments slide past thick filaments iv Can t stretch so far that heart can t contract 1 Pericardial sac prevents 2 Bands of tissue in ventricles moderator bands between walls of tissue and interventricular septum e Heart can adapt to changes in peripheral resistance increase in PR counteracted f Can adapt to changing end diastolic volumes g Intrinsic feature results in R ventricle and L ventricle always pumping same amount of blood i Heart attack affects this ii RV lungs LV stopped b c of damage iii Blood backs up in pulmonary circuit iv Increases pulmonary resistance v Increases pressure in pulmonary artery vi R ventricle contracts more forcefully causing an increase in blood pressure which causes pulmonary hypertension vii This forces fluids out into lungs causing pulmonary congestion can drown in own fluids Venous Return 1 Essentially systemic circuit 2 Affects end diastolic volume which effects stroke volume 3 2 things affect venous return VR a Venous pressure increase in pressure increases return b Total blood volume controlled by kidneys 4 Veins are thinner with less muscular walls 5 Stretch in response to an increase in venous pressure have high compliance 6 Capacitance Vessels store blood 2 3 of blood is in systemic veins at any given time 7 Arteries have much less compliance resistance vessels 8 Average venous pressure is 2mmHg 9 Average artery pressure is 90 100mmHg 10 Big drop in BP due to friction mostly in arterioles which have a small lumen 11 What affects venous return a Change in pressure in veins i Venules 10mmHg ii Superior and inferior vena cavae 0mmHg iii P 10mmHg
View Full Document