The nervous system and human muscles forming by the tissues are called the nervous tissue and the muscular tissue respectively. Those are grouped as excitable tissues as the nerve cell or a muscle cell can be excited by various stimuli to produce an impulse which is transmitted along the cell membrane. The muscles cell has an additional contractile mechanism which is activated by the impulse. As the human muscles are meant for contraction and relaxation, their cells are elongated and thread-like.for this reason the muscles are also called muscle fibres.
By virtue of contraction and relaxation the human muscles help in various functions, those are as follows:
a) Locomotion: It means the movement of the body as a whole from one place to another.
b) Moving: It means the movement of a particular part of the body in respect to the body itself.
c) Body postures maintain.
d) Maintain of vital functions, which means breathing, pumping action of heart, intake of food, movement of visceral organs, production of voice and speech and so on.
e) Thermoregulation: It means the production of heat to maintain the body temperature.
Different type of human muscles: -
The human muscles are generally classified into three types; those are the skeletal, the smooth and the cardiac type. Now let us have some discussion:
i) Skeletal Muscles: These types of human muscles are so named because they are mostly attached to bones of the body and are involved with skeletal movements. In Histological manner, these muscles display a strained appearance due to presence of transverse striations and so these are also called striated muscles. They are known as voluntary muscles also since these muscles are under voluntary control. However, some striated voluntary muscles are exceptional in that sense that they do not remain attached to the skeleton. Such types of non-skeletal striated voluntary muscles are found in tongue, upper end of the oesophagus, penis, anal sphincter, external urethral sphincter etc.
ii) Smooth muscles: On the basis of their histological structure, these human muscles are called smooth muscles or plain muscles or non-striated muscles because they lack of cross striations. As they have no voluntary control, they are also called involuntary muscles. These type of human muscles are mostly located in the wall of hollow visceral organs, such as , alimentary cannel, gall bladder, urinary bladder, uterus, respiratory tract, spleen, etc. For this cause they are often called visceral muscles. In the wall of blood vessels, interior of eye and dermis of skin such type of striated involuntary muscles are also present.
iii) Cardiac muscles: - The human muscles of the heart are called the cardiac muscle. The muscle present in the heart is not same as other visceral muscle though the heart is a visceral organ in the human body. For this reason the cardiac muscle are placed in a separate group. It exhibits the feature of both skeletal muscles and the smooth muscles partly. According to its structure, it shows cross striations like the skeletal muscles, but functionally, it is involuntary like the smooth muscles. For this manifestation the cardiac muscle is referred to as human muscles of striated-involuntary types of muscle.