The basic and the most important functional property of all the three types of muscles is excitability, i.e., the ability to respond to stimulation and become active.
Striated muscles are, however, more excitable as compared to other muscles. These respond to different stimuli such as mechanical, thermal, chemical or electrical and in the living body nerves are responsible for bringing about the stimulation.
Once a part of the muscle fibre is stimulated by a stimulus of adequate strength, it is conducted within no time to all its other parts.
This property is called as conductibility. Conduction is much faster in striated muscles as compared to other types of muscles.
In cold blooded animals like the frog the rate of conduction is 3—4 meters per second, while in warm blooded animals it is 6—12 meters per second.
All the three types of muscles possess the property of contraction and relaxation and these two actions together constitute the twitch’.
Muscles can be stimulated by mechanical, thermal, chemical or electrical stimuli. Nerves are responsible for bringing about the stimuli in the body.
When a muscle is contracted it shortens and becomes thicker but its total volume barely changes. Contraction is stronger as well as faster in striated muscles as compared to other types of muscles.
All the muscles in the body at a given time are never found in a perfectly relaxed state.
Although showing no outward signs of activity, they are in a state of mild contraction which causes them to resist being stretched. This activity of muscle is known as muscle tonus.
5. Tensility and elasticity:
All the muscles possess the property of tensility, i.e., the ability to stretch (to a limited extent).
When the cause producing the stretching of the muscle disappears, the muscle resumes its former state (relax), this property is called elasticity.
6. Threshold or liminal, sub liminal and supra-liminal stimuli:
All the muscles contract only when they receive the stimulation of a certain strengh. The lowest limit of stimulus capable to bring contraction in muscles is called the threshold or liminal stimulus.
A stimulus weaker than the threshold (which fails to bring contraction of the muscles) is called sub-liminal stimulus and the stimulus which is stronger than the threshold is called supra-liminal stimulus.
7. Refractory period:
After stimulation there is a brief period during which the muscle does not remain in a excitable state, this period is called refractory period or the period of relaxation of muscles.
8. The period of latent excitation and contraction of muscles:
The period between the application of the stimulus and beginning of the muscular contraction is called the period of latent excitation or the latent period.
The period during which muscle remains in a contraction state is called the period of contraction (shortening) of the muscle.