Cardiac muscle (heart muscle) is involuntary striated muscle that is found in the walls and histological foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle.These three types of muscle all form in the process of myogenesis. The cells that constitute cardiac muscle, called cardiomyocytes or myocardiocytes, contain only three nuclei.nother histological difference between cardiac muscle and skeletal muscle is that the T-tubules in the cardiac muscle are bigger and wider and track laterally to the Z-discs. There are fewer T-tubules in comparison with skeletal muscle.
The four main economic variables (in macroeconomics) are 1. Real Gross Domestic Product (GDP) 2. The unemployment rate 3. The inflation rate 4. The interest rate-----5. Level of the stock market 6. Exchange rate
There are four primary types of economic systems in the world: traditional, command, market and mixed. Each economy has its strengths and weaknesses, its sub-economies and tendencies, and, of course, a troubled history.