General characteristics of muscles are as follows:
1. Contractibility:
The muscle tissue has the ability to contract which is an active energy process. The contraction ability of the muscle depends on the number of motor units involved and the type of stimulus reaching the motor units.
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2. Extensibility:
The muscle tissue can be stretched or extended to a significant degree when load is applied.
3. Elasticity:
The removal of load causes the muscle to return to its original length. It is to be noted that the original length is not attained immediately following the removal of load. This is called the extension remainder.
4. Irritability (Excitability):
The muscle when stimulated exhibits excitability.
5. Tone (Tonus):
The muscles even in the normal conditions are in a state of slight tension referred as tone or tonus. It is the degree of resistance felt when the muscle is passively extended. This happens as a result of reflex action which depends on the complete reflex arc. The reflex arc comprises of the following components:
(a) Sense Organ in the Muscle
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(b) Sensory Nerve (Afferent Nerve)’
(c) Spinal Cord
(d) Motor Nerve (Efferent Nerve)
(e) Motor End Organ
6. Effect of Temperature:
The duration of muscular contraction increases with lower temperature and decreases with increasing temperature. At OOC the irritability in the muscle is lost and no contraction occurs.
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7. All or None Law
A muscle fibre when stimulated either contracts completely or not at all. A minimal stimulus causes a maximal response.
8. Fatigue:
The muscle gradually experiences a loss in excitation for some time, when contracted for a long duration. This stage is called fatigue. Thus, the efficiency of contraction declines when the muscle reaches the state of fatigue.
9. Heat Production:
The contraction of the muscles results in an increased heat production above the resting values. This increased heat production occurs in relation with the phases before contraction, tension rise during contraction, and the events associated with the recovery phase.
10. Electrical Changes:
The muscle gets excited when stimulated. This causes a disturbance in the electrical equilibrium at the point of stimulation, causing an action potential.