BIO 251 1st Edition Lecture 14 Outline of Last Lecture I. Skeletal, smooth, cardiacII. Structure of smooth muscle III. Molecular basis of smooth muscle contractionIV. Multiunit vs. single unit smooth muscle V. Multiunit VI. Single unit VII. Smooth muscle mechanics VIII. Modification of contractile strength IX. Cardiac muscle X. Top hat questionsXI. Diseasea. Muscle dystrophy i. Duchenne Outline of Current Lecture I. Introduction to circulatory system a. Function b. 3 components c. 2 separate loopsThese 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.II. Structure of heart a. Location b. Heart as dual pumpc. One way blood flowIII. Myocardium a. Structure b. Interconnections IV. Electrical & contractile activity of heart cells a. 2 types myocardial cells b. Autorhythmic cell APc. Contractile cell APd. Molecular basis V. Electrical activity of entire heart a. Autorhythmic regions of heartb. Spread of AP in heartc. ElectrocardiogramsCurrent Lecture-Introduction to circulatory systemoOverall function-Gets nutrients & oxygen from all cells in body-Removes wastes from all cells in body -Blood is transport medium which -Gets blood to pass by all cells in bodyoCirculatory system consists of 3 components-Heart-Acts as pump for blood -Blood vessels -Passageway for blood -Blood-Transport mediumoCirculatory system has 2 separate loops (13.2)-Pulmonary -Blood mvmt between heart & lungs-Systemic -Blood mvmt between heart & all other body parts-Structure of heart (CD Anatomy Review 3, 4, 5, 7)oLocation in body (13.5)-Size of clenched fist, located in chest cavity, midway between sternum and backbone -Broad base at top of heart, tapers to an apex at bottom -Top lies to right of sternum, apex is left to sternum oHeart as a dual pump (13.2)-Divided into 2 halves separated by muscle separated by muscle wall -Each half functions as separate pump-Right side-Receives blood from systemic circulation and pumps it to pulmonary circulation to get blood oxygenated -Left side-Receives blood from pulmonary circulation & pumps it to systemic circulation so rest of body gets freshly oxygenated blood -Each half divided into 2 chambers-Atrium-Upper chamber-Receives blood returning to heart and transfers to lowerchamber-Ventricle -Lower chamber-Pumps blood out of heart -Veins -Blood vessels that return blood to heart -Venae cavae-Brings blood from systemic circulation to heart-Pulmonary veins -Bring blood from lungs to heart-Arteries-Blood vessels that carry blood away from the heart-Aorta-Carries blood from heart to systemic circulation -Pulmonary artery -Carries blood from heart to lungs-Blood flow in circulatory systems -Pulmonary -All blood flows through lungs-Systemic -Blood divided up among different body systems-EX: one drop of blood visits only one body tissue/trip, not all tissues/trip)-Both sides of heart simultaneously pump equal amounts of blood-Pulmonary circulation is low pressure, low resistance -Systemic circulation is high pressure, high resistance -Left side heart performs more work, and much thicker oOne-way blood flow in heart-Blood flow in heart is 1 fixed direction -Requires valves to prevent backflow -4 one way valves (13.7 & 13.8)-Open & close passively b/c pressure differences -Forward pressure gradient open valves -Backward pressure gradient closes valves-2 Atrioventricular (AV) valves-One on each side of heart between atrium & ventricle -1 aortic valve-Junction of left ventricle & aorta -1 pulmonary valve -Junction of right ventricle & pulmonary artery -No valves between atria & veins -Backflow not problem b/c atrial pressure not higher than venous pressure & entry sites of vein into atria are compressed during atrial contraction-Cardiac Muscle: Myocardium oStructure -Cardiac muscle fibers interlaced & arranged spirally around circumference of heart -During ventricular contraction, diameter of chambers reduced & apex pulled upwards; wrings blood out of chambersoInterconnections of cardiac muscle cells (13.9)-Adjacent cells joined end to end -Intercalated discs (joining point) composed of-Gap junctions -Allow AP to pass from cell to cell -None between atrial & ventricular cells -No Aps can be passed directly between atria & ventricles -Desmosomes -Good at holding cells together under mechanical stress-Electrical & contractile activity of heart cells (CD: cardiac AP 5-17)o2 types of myocardial cells-99% contractile cells-Mechanical work of pumping -1% autorhythmic cells -Specialized for initiating & conducting ApsoAutorhythmic cell AP (13.12)-Initial phase of slow Depolarization caused by decrease in passive outward leak of K+ -As K+ channels close at end of previous repolarization phase and an increase in Na+ leaking into cell through "funny" channels -Inside cell slowly becomes more positive & drifts toward thresholdoContractile cell AP (13.13)-AP in contractile cells are different than autorhythmic cells -When AP reaches contractile cardiac cell via gap junction, Na+ channels open wide & Na+ rushes into cell -Results in Depolarization of membrane -Na+ channels then close around +30 mv-Depolarization of membrane causes opening of slow Ca++ channels and Ca++ moves slowly inside cell -Depolarization cause most K+ channels to inactivate -These 2 mechanisms work together to create plateau phase of AP-Repolarization eventually occurs as Ca++ channels close, K+ channels open & K+ moves out of celloMolecular basis of contractile cell contraction (13.14)-AP moves across cell membrane, Ca++ enters cell from ECF -AP moves does T tubule and causes release of Ca++ from SR-All this Ca++ entering contributes to plateau phase & prolonged contraction of cardiac muscle -3 times longer than skeletal muscle contraction -Ca++ binds to troponin & troponmyosin moves away from binding sites on actin, allowing cross bridge cycling -Ca++ eventually removed by active transport & muscle relaxes-Long refractory period of cardiac AP & muscle contraction prevents tetanus of cardiac muscle -Tetanus of cardiac muscle would cause death!-Electrical activity of entire heart (CD: intrinsic conduction system 3-6)oAutorhythmic regions of heart (13.10)-Sinoatrial node (SA node) -Located in right atrial