PSIO 201 5th Edition Lecture 23Outline of Last Lecture Muscle PerformanceOutline of Current Lecture I. Cardiac MuscleII. Smooth MuscleCurrent LectureAll types on muscle create tension – two common themes1. 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 courseB) 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
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