In: Anatomy and Physiology
Compare and contrast cardiac and skeletal muscle in the following:
Cellular structure
Excitation-Contraction Coupling
Action potential of Skeletal Muscle cells and Cardiac Contractile muscle cells
Production of ATP
Role of Calcium
Mechanisms for increased strength/force of contraction
Cardiac muscle | Skeletal muscle | |
Cellular structure | striated with alternating dark or light bands, branched, uninucleated fibers occurs in heart walls , involuntary, gap junctions are present | striated with alternating dark or light bands and are unbranched, tubular, multinucleated fibers, seen attached to skeleton, voluntary. no gap junctions are present |
Excitation- Contraction Coupling | Myogenic initiation of contraction, contraction by sliding filament mechanism. present both troponin and tropomyosin. level of development of the sarcoplasmic reticulum is moderately developed. | Neurogenic initiation of contraction, contraction by sliding filament mechanism. present both troponin and tropomyosin.level of development of sarcoplasmic reticulum is well developed. |
Action potential of skeletal muscle cells and Cardiac contractile muscle cells | they have action potential with plateau, the duration is only 100-150milliseconds. their action potential is governed by the gap junctions and voltage difference between action potential generated cell and resting membrane potential. both ECF and SR are sources of cytosolic calcium | more duration for action potential than cardiac muscle. with the release of Ach , action potential is initiated, which further propagates across the membrane surface and to T tubules. SR is the only source of cytosolic calcium. |
Production of ATP | can produce ATP by utilizing the lactic acid produced in skeletal muscle. also, they contain a large number of mitochondria, enabling aerobic respiration, thus can produce a large quantity of ATP. | ATP is produced from the TCA cycle, oxidative phosphorylation, and glycolysis |
Role of Ca2+ | physically reposition the troponin-tropomyosin complex thus uncovers the actin cross-bridge binding sites | physically reposition the troponin- tropomyosin complex thus helping in covering the actin cross ridge binding sites. |
Mechanisms for increased strength/force of contraction | slow - speed of contraction. on binding the myosin head with ATP, helping it to pull actin filaments, thus helping in contraction. with any sympathetic stimulation, preload gets increases with increasing the force of contraction. | fast or slow depending on the type of fiber- the speed of contraction. mostly they have high contractile speed. as fast twitches are using anaerobic metabolism, they require only less amount of myoglobin, they also have more phosphorylase enzyme, and because of larger diameter they twitch fastly. |