Question

Need to know a and b

A. compare in detail, the components of cardiac muscle with that of smooth muscle.

B. why should many of these types of muscles be involuntary?

Answer 1

Cardiac Muscle -

It form the myocardium of the heart, shows striations but is involuntary . It is meant for automatic and rhythmic contractions.

Each musclefiber has a single rounded nucleus placed centrally.

each muscle fiber branches and anastomoses with the neighbouring fibers at intercalated discs.

Myocytes are about 80 mu m long and 15 mu m broad.

The sarcoplasm contains more number of mitochondria and less number of myofibrils and sarcopasmic reticulum, when compared to skeletal muscle.

The cardiac muscle cells are located in the walls of the heart, appear striated and they are under involuntary control.

smooth muscle fibers are located in walls of hollow visceral orgens,except the heart ,appear spindle -shaped, and are also under involuntary control.

Types of involuntary muscle in smooth mucles and cardiac muscles

The smooth muscles - each muscle fiber is an elongated spindle shaped cell with a single nucleus placed centrally.

The lenght of the smooth muscle is highly variable (15-500 MU M)

THEY often aggregate to form bundles and fascicles.

they are found in the wall of GI tract, respiratory tract , urogenital tract, blood vessels and a few muscles of the eye.

They are arranged circularly inside and longitudinally outside in the wall of the GI TRACT and urogenital tract etc.

They are made up of actin and myosin filaments.

There are two types of smooth muscles - multi- unit and unitary  

Multi -unit- nerve muscle establish direct contact with several myocytes muscles contract under nervous stimulus, eg- smooth muscles of iris large arteries .

unitary smooth muscle- They have their own rhythmic contractility that is independent of nerve supply . contraction of muscle is stmulated by startch .However the nerve supplying them can alter the rate of contraction eg -smooth muscles of the stomach , intestine , uterus and ureter.

Cardiac muscle have a type of involuntary muscle . These are discribe the above.