BSC216 week of 1/25
BSC216 week of 1/25 216
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This 14 page Class Notes was uploaded by Alexandra on Thursday January 28, 2016. The Class Notes belongs to 216 at University of Alabama - Tuscaloosa taught by Jason Pienaar in Winter 2016. Since its upload, it has received 46 views. For similar materials see Human Anatomy and Physiology II Lecture in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 01/28/16
cardiovascular system: Heart 01/28/2016 ▯ Heart’s position ▯ Thoracic cavity o In mediastinum (slightly left) o Posterior to the sternum o Rests on diaphragm Cone shaped Base o Points to right shoulder Apex o Points to left hip ▯ Surface anatomy of heart chambers Atria o Receive blood from veins o Produce atrial natriuretic peptide Ventricles o Pump blood into arteries Sulcus o Right atrioventricular sulcus Separates atrium from ventricle o Posterior interventricular sulcus In between ventricle o Left atrioventricular sulcus Separates atrium from ventricle o Anterior interventricular sulcus In between ventricles ▯ Double pump Pulmonary pump (right) o Deoxygenated blood pumped to lungs by right ventricle o Gas exchange occurs between alveoli and pulmonary capillaries o Oxygenated blood returned to left atrium Systemic pump (left) o Oxygenated blood pumped to body by left ventricle o Gas exchange occurs between capillaries and tissues o Deoxygenated blood returned to right atrium ▯ Layers of pericardium Fibrous pericardium o fused to diaphragm serous pericardium o lubricates o double layer parietal pericardium o outer layer of serous membrane visceral pericardium (epicardium) o inner layer of serous membrane pericardial cavity all part of pericardium o visceral pericardium is also part of heart membrane myocardium endocardium heart wall ▯ Coronary circulation Myocardium is too thick for complete O2 and nutrient diffusion from inner blood Collection of vessels (coronary circulation) supplies outer layers of heart o Coronary arteries Deliver oxygenated blood to coronary capillary beds Aorta Right coronary artery Marginal artery Posterior interventricular artery Left coronary artery Anterior interventricular artery Circumflex artery o Coronary veins Drains deoxygenated blood Coronary sinus Small cardiac vein Middle cardiac vein Great cardiac vein ▯ Major arteries (away from heart) and veins (to the heart) Each heart chamber has a great vessel associated with it Aorta o Receives oxygenated blood from left ventricle Superior vena cava o Drains systemic circuit above diaphragm o Empties into right atrium Inferior vena cava o Drains systemic circuit below diaphragm o Empties into right atrium Pulmonary trunk o Receives deoxygenated blood from right ventricle o Sends blood to lungs from right ventricle Pulmonary veins (x4) o Carries oxygenated blood from lungs o Blood from lungs left atrium ▯ Chambers and valves Each heart chamber has a valve associated with it Semilunar valves o Pulmonary valve Pulmonary trunk into right ventricle Prevents backflow into right ventricle o Aortic valve Aorta into left ventricle Prevents backflow into left ventricle Atrioventricular valves o Tricuspid valve Between right atrium and right ventricle It has 3 cusps Prevents backflow into right atrium o Mitral (bicuspid) valve Between left atrium and left ventricle It has 2 cusps Prevents backflow into left atrium ▯ Atrium structures Auricles o Associate with atriums o Expand to provide more space for blood o Pectinate muscles Allow right atrium to expand if needed Fossa ovalis o Bypasses right ventricle in fetal heart o Because lungs don’t work in fetus yet ▯ Ventricle structure Right ventricle o Not as muscular bc low pressure pulmonary circuit Left ventricle o Very muscular bc high pressure systemic circuit Trabeculae carnae o Prevent suction when ventricle collapses o That would be extra work Chordae tendineae, papillary muscles o “heart strings” o Ensure valves only open one way ▯ Cardiac skeleton Framework of o Collagenous fibers o Elastic fibers Concentrated in o Heart chamber walls o Fibrous rings around valves o Sheets of tissue that interconnect rings Functions o Structural support (especially around openings of great vessels) o Anchors cardiocytes, giving platform to pull against o Electrical insulation between atria and ventricles ▯ Flow of blood ▯ ▯ ▯ muscle histology skeletal o long, cylindrical cells o multi-nucleated o obvious striations cardiac o branching cells o uni- or bi-nucleated o obvious striations o intercalated discs smooth o fusiform cells o uni-nucleated o no striations Cardiac vs. Skeletal muscle o Identical in both Sarcolemma Myofibril Skeletal Extensive sarcoplasmic reticulum Small T tubules Normal sized mitochondria Cardiac Underdeveloped sarcoplasmic reticulum Massive T tubules (calcium) Large sized mitochondria Sarcomere I band A band o Quantity/size varies Sarcoplasmic reticulum T tubule Nucleus o Unique to cardiocytes Cardiac muscle cells Intercalated discs Interdigitating folds Desmosomes Gap junction Nuclei surrounded by glycogen ▯ Cardiomyocyte Pacemaker cells vs. Contractile cells Heart beats rhythmically o Average of 75 bpm o Vertebrate heart beats are Myogenic Muscle contraction signal originates WITHIN heart muscle cells Autorhythmic Doesn’t depend on nervous system for rhythm Pacemakers = 1% of cardiomyocytes o SA (sinoatrial) node= main pacemaker group o AV (atrioventricular) node= 2 ndmain pacemaker group o Purkinje fiber system= 3 main pacemaker group o Rhythmically and spontaneously generate action potentials o Lack voltage-gated sodium ion channels in sarcolemma o Contains non-specific cation channels in sarcolemma ▯ Contractile cardiac muscle action potential Rapid depolarization o Na+ flows into cell Initial repolarization o K+ flows out of cell o Only a few K+ channels open Plateau phase o Select K+ channels still open o Ca 2+flows into cell through time gate closing Ca 2+ channels Repolarization phase o More K+ channels open until all open ▯ Cardiac pacemaker cell action potential Slow initial depolarization phase o Open slowly, whatever cation outside flows in slowly Full depolarization phase o Ca2+ voltage gated, open a bit faster than first (slow) channel o Crossed threshold Repolarization phase o Time gated closing of Ca2+ channels o Select few K+ channels open Minimum potential phase o More voltage gated K+ channels open continuous, rhythmic action potential ▯ Cardiac conduction system Cardiac skeleton provides electrical insulation SA node generates an action potential that spreads through the right atrium via gap junction o Faster than normal spread bc higher conc of gap junctions o Atrial conducing fibers Same as cardiomyocytes, just more gap junctions AV node delay due to low number of gap junctions and insulating cardiac skeleton o Time delay allows atria to fill with blood o AV bundle = “bundle of His” Purkinje fiber system rapidly spreads the action potential to the contractile cells of the ventricles ▯ ECG/EKG waveforms ECG (electrocardiogram) measures summed action potentials of contractile cardiocytes You are measuring the contractile cell’s action potential P wave o Measures contractile cells in right atrium o Atrial depolarization, initiated by the SA node, causes the P wave With atrial depolarization complete, the impulse is delayed at the AV node QRS complex o Ventricular depolarization begins at apex, causing the QRS complex o Atrial repolarization occurs Ventricular depolarization is complete T wave o Ventricular repolarization begins at apex, causing the T wave Ventricular repolarization is complete ▯ ▯ ▯
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