INTRODUCTION Muscle tissue is one of the four primary tissue types consisting elongated muscle cells that are highly specialized for carrying out certain responsibilities.
Muscles are responsible for movement of different parts of the body; posture; respiration; production of body heat; communication; constriction of organs and vessels and contraction of heart.
General properties of muscles:
Contractility is the ability of muscle to shorten forcefully although its shorten forcefully, it lengthens passively.
Excitability is the capacity of muscle to respond to a stimulus. Often the stimulus is from the nerves that we consciously control.
Extensibility means a muscle can be stretched beyond its normal resting length and still contract.
Elasticity
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They form sheets, bundles and sheaths around other tissues.
The sarcoplasmic reticulum is poorly developed in the smooth muscle and caveolae may function as a T tubule system.
Smooth muscle is innervated by the autonomic nervous system, its involuntary and its more variable in function than other muscle types.
Phasic smooth muscles are those that are undergoing periodic contraction and relaxation. Continuously contracted muscles are called tonic smooth muscle. (human physiology)
There are two types of smooth muscles:
Visceral smooth muscle fibers which contract slowly, connected by the gap junctions meaning that they behave as a single unit and can be auto-rhythmic.
Multiunit smooth muscle fibers contract rapidly in respond to the stimulation by neurons and function independently.
Smooth muscle can contract auto-rhythmically as a result of elongation or when simulated by autonomic nervous system or hormone.
Increase of calcium ions which is released from sarcoplasmic reticulum or enters from extracellular fluid; the next step is for the calcium ions bind to the calmodulin this forms calcium-calmodulin complex which activates an enzyme. This enzyme th