Lecture 10 Notes PDF
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Summary
These lecture notes cover various aspects of cardiac and circulatory systems, including different types of pumps, invertebrate hearts such as crab hearts, and vertebrate cardiac muscle types. The document also discusses the myogenic mechanism, cardiac action potential, and the electrical connections between cardiac muscle cells.
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Lecture 10: 27 Jan. Hearts/Cardiac Muscle Readings: 561, 339-339, 329-330, 672-675, 694-697, Box 25.1 1 1 Types of Circulatory Pumps a) specialized muscular chamber valves ensure 1-wa...
Lecture 10: 27 Jan. Hearts/Cardiac Muscle Readings: 561, 339-339, 329-330, 672-675, 694-697, Box 25.1 1 1 Types of Circulatory Pumps a) specialized muscular chamber valves ensure 1-way flow most adult hearts b) contractile elements not strictly part of circ. system facilitate venous return to heart c) peristaltic contractions some inverts., embryonic verts. 2 2 Invertebrate Hearts e.g. many arthropods neurogenic: definition? posterior cardiac ganglion nerves; spontaneous rhythmic depolarization anterior axons innervate cardiac muscle 25.5 19.6 3 3 Crab Heart heart suspended in pericardial sinus by ligaments hemolymph coming from gills, pools in sinus hemolymph enters heart through ostia sucked in (“-ve pressure” relative to sinus) as heart relaxes: “diastole” heart contraction closes 1-way ostia valves blood forced out through arteries ligaments stretch, store elastic energy after contraction, ligaments recoil, expanding heart and opening ostia 4 4 Crab Heart heart suspended in pericardial sinus by ligaments hemolymph coming from gills, pools in sinus hemolymph enters heart through ostia sucked in (“-ve pressure” relative to sinus) as heart relaxes: “diastole” heart contraction closes 1-way ostia valves blood forced out through arteries ligaments stretch, store elastic energy after contraction, ligaments recoil, expanding heart and opening ostia 5 5 Crab Heart 25.23 6 6 Vertebrate Cardiac Muscle 13.2 7 7 Vertebrate Cardiac Cell Types pacemaker cells muscle but non-contractile membrane potential changes cyclically: found in sinus venosus (e.g. fish), SA node (mammals) contractile cells e.g. atria, ventricles also can transmit AP transmitting (conducting) cells non-contractile muscle; transmit AP bundle of His, AV node, Purkinje fibers timing, coordination of contractions 8 8 Vertebrate Cardiac Muscle myogenic: define? consequence? video contrast with neurogenic skeletal muscle: 20.2 9 9 Myogenic Mechanism esp. pacemaker cells membrane potential changes cyclically “Funny” all cardiac muscle cells do this, but pacemaker cells do it fastest “pacemaker potential” “Funny” channel nonselective for monovalent cations; e.g.? Na+ influx > K+ efflux; consequence? 12.23, sort of 10 10 Cardiac Action Potential how does it get to threshold? 1. initial AP depolarization: voltage-gated Na+channel 2. voltage-gated Na+channel inactivated 3. voltage-gated Ca++ channel (L-type) open, plateau phase; extended depolarization 4. Ca++ channel close, K+ open repolarization consequences? 11 11 12.23 12 12 Skeletal Muscle Ca2+ Refractory Period External Stimulations 13 13 Cardiac Muscle Tetanus? what would happen in cardiac muscle if you stimulated it again during plateau phase? 14 14 Cardiac Muscle Cells Electrically Connected gap junctions concentrated at intercalated discs between cells transmits deplorization to connected cells consequences for contraction? video 15 15 Different Cells, Different Potentials 16 16
