In: Anatomy and Physiology
Compare and contrast cardiac and skeletal muscle in terms of electrical stimulus and action potentials (excitation-contraction coupling), role of calcium, energy use and production, and ways to develop increased force of contraction. How does the vulnerability of the myocardium relate to the fact that heart disease is the leading cause of death?
Cardiac muscle | skeletal muscle | |
Stimulation |
SA or AV node Autonomic innervation |
NM junctions Via voluntary motor innervation |
Action potential | 220-400 ms | 2-4 ms |
Structural fibere | Large branching with single nuclei near | Long tube shaped with multinucleated cells |
T tubule | at Z line | at A-I juntion |
Sarcoplasmic reticulum | less abundant with cistern at one terminal end | more abundant with two terminal cistern |
Role of Ca2+ | Increases contractility by binding to troponin c and hence expose the actin binding site | Increases contractility by binding to troponin c and exposing binding site on actin |
Energy utilisation and production |
aerobic metabolism glucose, fatty cids, ketone bodies To lesser extend amino acid |
Creatinie phosphate, anerobic glycolysis ( lactic acid), areeobic glycolytic pathway |
Increased force | Hypertrophy, by Increasing cell size | Hypertrophy by Increasing cell size and number. |
Heart requires oxygen supply for genration of energy and metabolism. Hence, even if small decrese in oxygen supply by decreses blood supply/obstruction to blood flow will lead to Ischemia and hence Heart myocardium is vulnerable to hypoxia and is leading cause of death.