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Transcript
From body From Lungs Chordae tendinae To Lungs No valves as Enter Atria To Body via AORTA (Eckert, 12-4) Mammalian Heart 51 14-14, Vander 2001 Mammalian Heart 52 1 Non-Mammalian Heart Examples: Amphibians and Reptiles (except crocodilians) with 3 chambers (= one ventricle, two atria) - incomplete ventricular septum - BUT separate rich and poor blood - AND alter pressure in systemic and pulmonary - can alter flow to systemic or pulmonary circuit 53 Cardiovascular System Amphibians: only vertebrates where O2 poor blood to skin (as well as to lungs) adults with paired pulmocutaneous arteries divide into two branches 1. Pulmonary 2. Cutaneous (to flanks and dorsum) skin provides 20-90% O2 uptake 30-100% CO2 release 54 2 Cardiovascular System Gets rich FROG Heart Gets poor conus arteriosus w/ spiral valve trabeculae (create channels) role of Tb and HR Pough et al., 2001 Fig 6-8 55 Cardiovascular System Reptilian Heart (not crocs) RAA = right aortic arch LAA = left aortic arch PA = pulmonary artery (no conus arteriosus, no spiral valve) 2 systemic arches and one pulmonary artery from single ventricle BUT, single ventricle functions as THREE 3-chambered heart anatomically 5-chambered heart functionally Pough et al., 2001 Fig 6-9a Muscular Ridge RA = right atrium LA = left atrium 56 3 Reptilian Heart (not crocs) not “primitive” 3-chambered heart anatomically 5-chambered heart functionally IVC = intraventricular canal AVV = atrioventricular valve RAA = right aortic arch LAA = left aortic arch PA = pulmonary artery 7 3 11 2 2 7 4 5 6 5 2 Muscular Ridge Muscular Ridge CP = cavum pulmonale CV = cavum venosum CA = cavum arteriosum Pough et al., 2001 Fig 6-9 57 Reptilian and Amphibian Circulation Cardiac Shunts (in 3-chambered heart) 1. temperature regulation 2. breath holding (diving, turtle in shell, inflated lizards) 3. stabilize O2 content of blood when breathe intermittently R to L O2 poor to systemic via aortic arches (short delay between valves opening) L to R O2 rich to pulmonary artery (longer delay between valves opening) 58 4 Shunting Explain why and how blood shunting can be useful to an ectotherm. Under what conditions would a lizard utilize a right-to-left shunt? Under what conditions would a lizard utilize a left-to-right shunt? 59 Mammalian fetus: Ductus arteriosus (R -> L shunt, lung bypass) -pulmonary artery to systemic arch -when lung inflate resistance down (pulm) -when lose placental circ. resistance up (syst) -closes at birth Foramen ovale (interatrial shunt R -> L) -hole in wall between atria -closes at birth 60 5 Bird chick: Chorioallantois = network of vessels under shell surface Interatrial septum -R -> L shunt, lung bypass -closes after hatching 61 Electrical Activity in the Mammalian Heart LA RA RV Influenced by autonomic NS LV Vander 2001 62 6 Cardiac Cells electronically linked by Gap Junctions (except from atrial to ventricular cells…) Sherwood 1997 63 Atria then Ventricles (Electricity => Contractility) Vander 2001 64 7 Recall AP and refractory-period differences… (Eckert, 12-7) 65 Types of Cardiac Cells: A. Contractile B. Conducting ~ autorhythmic SA node AV node ~ fast-conducting Internodal Interatrial Bundle of His Purkinje Etc. Vander 2001 66 8 Types of Cardiac Cells: A. Contractile B. Conducting - 1 autorhythmic SA node AV node -1 fast-conducting Internodal Interatrial Bundle of His Purkinje Etc. Pacemakers: -Normally HR driven by SA node -Others are Latent pacemakers -Called Ectopic pacemaker when node other than SA driving HR 67 Sherwood 1997 68 9 Sherwood 1997 ~ SA node ~ latent rate Sherwood 1997 69 SA The Heart Rate Train AV other oops Sherwood 1997 70 10 9-11, Sherwood 1997 Which way would you alter channel permeabilities to speed or slow HR?? ~Transient Ca2+ channels K+, Na+ Autorhythmic Cardiac Muscle (e.g. SA node) 71 Sherwood 1997 Contractile Cardiac Muscle Ca2+ current maintains plateau Vander 2001 72 11 Cardiac Muscle (the other striated muscle) -Small muscle fiber cells with only one nucleus -Individual fibers are connected to neighbors electronically via gap junctions -Two types of fibers: 1. Contractile (similar to skeletal muscle) 2. Conducting (including pacemaker cells) Do not contract, but transmit electrical signal -Cardiac contraction myogenic (arises within heart) Can be influenced by autonomic nervous system (alpha, beta adrenoreceptors increase [Ca2+]) -Long-lasting AP with long plateau phase, and long refractory period - why? 73 Cardiac Muscle (the other striated muscle) -Intracellular calcium from SR and across plasma membrane (unlike in skeletal) -Dihydropyridine receptors in T-tubules are voltage-activated calcium channels -Ryanodine receptors then release more calcium from SR into the cytoplasm (calcium-induced calcium release) -During relaxation, Calcium pumped actively back into SR and out across plasma membrane 74 12 Heart Work Loops (Eckert, 12-13) 75 (Q,R,S masks atrial repolarization) 76 (Eckert, 12-8) 13 77 P Q, R, S T (Eckert, 12-8) 78 14 Wiggers Diagram 760 mmHg = 1 atm = 9.8 m blood Valves open/close where pressure curves cross 1:2 14-25, Vander 2001 Measuring Blood Pressure 160mmHg 120mmHg 79 100mmHg 80mmHg 120/80 Laminar vs. Turbulent Flow 80 15 Gravity and BP Knut Schmidt_Nielsen811997 Cardiac Output: CO = cardiac output (ml/min from 1 ventricle) SV = stroke volume (ml/beat from 1 ventricle) = EDV – ESV (end-diastolic – end-systolic volume) HR = heart rate (beats/min) CO = HR x SV MABP = CO x TPR MABP = DP + 1/3(SP-DP) - Heart can utilize different types of energy sources (unlike brain) 82 16 Cardiac Output 6x Exercise Oxygen Consumption X 20 Knut Schmidt-Nielsen 1997 83 Sherwood 1997 Atrial Kick Heart filled ~same with increased HR 84 17 Sherwood 1997 Frank-Starling Curve Systole = Ventricular Emptying Diastole = Ventricular Filling (rest) Vander 2001 85 Cardiac Output Control Sympathetic speeds heart rate and increases contractility 1. Norepinephrine binds to beta1 adrenergic receptors 2. Increases cAMP levels and phosphorylation 3. Activates cation channels (Na+) and increases HR 4. Epi and Norepi activate alpha and beta1 adrenoreceptors which increase contractility and rate of signal conduction across heart 86 18 How increase contractility? More Ca2+ Vander 2001 87 HR control Parasympathetic vs. Sympathetic (Eckert, 12-5) 88 19 HR control Parasympathetic slows heart rate -Innervate Atria (Vagus nerve = Xth cranial nerve) -Cholinergic (ACh) -Alter SA node pacemaker potential: K+ permeability Ca2+ permeability Parasympathetic innervation of AV node slows passage of signal between atria and ventricles 89 20