Difference between Voluntary and Involuntary Muscles

In humans, nearly half of the whole body weight is due to the muscles. Our body contains more than 650 different types of muscles which can be of three different types based on their structure and movement: Skeletal muscles, smooth muscles and cardiac muscles. These three types of muscles are further divided into two main categories of muscles on the basis of their control mechanisms: voluntary and involuntary. Let us see how voluntary muscles differ from involuntary muscles!

Voluntary Muscles:

Voluntary muscles are the muscles that are under conscious control and can be controlled at will or we can choose when to use them. They are also known as skeletal muscles as they are attached to the bones.

Voluntary muscles are responsible for the movement of body parts and the locomotion. They are made up of muscle fibers which are multinucleated cells with nuclei located towards the periphery of the cells. The cell membrane of a muscle fiber is known as sarcolemma. The muscle fibers are arranged together in a bundle to form the muscle. The strength of voluntary muscles can be increased by exercising regularly.

Involuntary Muscles:

Involuntary muscles, which are also known as smooth muscles, are the muscles in the human body that act without conscious control or cannot be controlled at will. They are mainly controlled by the autonomic nervous system in the body. So, involuntary muscles include all the muscles whose activity is not affected by voluntary nerve activity.

The involuntary muscles are spindle-shaped and contain a single, centrally located nucleus. They are visceral so mostly found in the walls of hollow organs such as the stomach, intestine, urinary bladder, uterus, etc. They are responsible for the movement of food in the alimentary canal, contraction of the uterus during labor or childbirth and controlling the internal diameter of the blood vessels. Cardiac muscles are also involuntary muscles; they maintain the blood circulation throughout the body by maintaining the heartbeat.

Based on the above information, some of the key differences between voluntary and involuntary muscles are as follows:

Voluntary Muscles	Involuntary Muscles
They are the muscles that can be controlled at will or are under the conscious control.	They are the muscles that cannot be controlled at will or act without conscious control.
They are also known as skeletal muscles.	They are also known as smooth muscles.
They are found attached to the bones in the body.	They are found in the walls of hollow or internal organs like the alimentary canal, uterus etc.
They help us move our body parts at our will and are responsible for locomotion of the body.	They allow internal movements of the organs such as movement of food in the alimentary canal, contraction of the uterus during childbirth etc.
They exhibit fast contractions.	They exhibit slow contractions.
They are controlled by the somatic nervous system.	They are controlled by the autonomic nervous system.
They require more energy.	They have a low energy requirement.
They are long and cylindrical in shape.	They small and spindle-shaped.
Their cells are multinucleated and nuclei are located towards the periphery of the cell.	Their cells are uninucleated and nuclei are located at the center of the cell.
They get fatigue and need rest at intervals.	They do not fatigue and work continuously.