PSIO 201 5th Edition Lecture 23 Outline of Last Lecture Muscle Performance Outline of Current Lecture I Cardiac Muscle II Smooth Muscle Current Lecture All types on muscle create tension two common themes 1 sliding filaments actin and myosin 2 Regulation of cytoplasmic Ca2 A Cardiac Muscle Pumps BLOOD involves contraction of a muscle around a confined volume increasing the pressure so the fluid can be pushed through system Structural features smaller cells less extensive T tubule and SR system Myofibrils organized into sarcomeres Extensive cell to cell interactions intercalated discs containing gap junctions and desmosomes Functional Issues the sliding filament model crossbridge cycling with thin filament regulatory proteins Functional Differences SR Ca2 is not sufficient to support contraction there is an obligatory need to extracellular Ca2 Functional Issues Contraction NOT initiated by an electrical signal from the nervous system NO MOTOR UNITS Nervous imput influences the rate and strength of contraction The single twitch of cardiac muscle has a very long time course B Smooth Muscle Function to control diameter of tissue tubues Many types of smooth muscle small single nucleus lacks a clearly organized structure NO SARCOMERES Still There are thick and thin filaments with a rudimentrary overlapping organization crossbridges can form Regulation of cytoplasmic Ca2 is still the key generation of tension in smooth muscle BUT it DOES NOT interact with regulatory proteins on the thin filaments to permit myosin head groups to bind
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