Definition of Voluntary muscles 

• Voluntary muscles are those that are movable by your own freewill of a person . They are usually connected to the skeleton system.
• The muscles are connected to bones via the use of tendons. They are responsible for all types of vertebrates’ motions.
• The voluntary muscles make up around 40 percent of the total body weight and typically are long and situated close to the bones.
• The muscles of the voluntary are known as striated because they comprise long thin, multinucleated muscle fibers . They are crossed by an alternating pattern of white and red lines of white and red which create the appearance of striated.
• Every muscle cell has a nucleus, in which the nucleus is located on the outside inside the cell.
• Muscle fibers covered by a specific cell membrane known as myolemma or the sarcolemma.
• The sarcolemma, or sarcolemma, is the voluntary muscles and connects the muscle fibers with each other as well as connective tissues.
• In addition, the muscle fibers are composed of contractile units, Sarcomeres that shrink, which causes the muscles to relax and contract. The sarcomeres have myosin and actin proteins that together cause the contraction of muscles by sliding against one another.
• Each muscle fiber is connected to one another via connective tissue. They communicate with each other via blood vessels and nerves.
• The control of these muscles is controlled by a portion that is part of the peripheral nervous system known as”somatic nerve system.
• The system of the somatic nerve is comprised of efferent and afferent nerves that transmit messages to the central nervous system, and they relay messages from CNS towards the voluntary muscles to trigger their contraction.
• They aren’t myogenic and require an external signal from the nerve for contraction.
• Voluntary muscles need a substantial amount of energy to perform their relaxation and contraction. Therefore, they have numerous mitochondria that can meet energy demands.
• Voluntary muscles show rapid relaxation and contraction when compared to involuntary muscles. However, they tire quickly and require frequent intervals of rest.
• They are vital as they play a role to move organs and the movement of the body.
• A few examples of voluntary muscles are triceps, biceps, the diaphragm and quadriceps muscles and pectoral muscles, abdominals and hamstrings.

Examples of voluntary muscles

Diaphragm

The diaphragm is the primary respiratory muscle which aids the breathing process by reducing and increasing the size of the wall in the chest. This is the shape of a dome skeletal muscles that is located underneath the lungs as well as the heart. It divides the abdominal region and the chest. The diaphragm muscle is a voluntary one which controls by the phrenic nerve that connects the neck to the diaphragm. There are numerous openings in the diaphragm to allow for the movement of certain structures such as the esophageal opening to the vagus nerve, the aortic opening for the aorta along with the opening that serves the inferior vena cava.

Apart from respiratory functions the diaphragm can also be involved in non-respiratory functions. The diaphragm is responsible for increasing abdominal pressure, which aids in the elimination of vomit, urine and the feces. It also exerts an esophageal pressure in order to stop acid reflux. The spasmodic diaphragm movement produces the distinctive sound that is that is referred to as hiccupping.

Biceps

Bicep muscles are those that have two heads or two points of origin. The two for humans are the Bicep femoris and bicep brachii. The bicep brachii muscle is the muscle that is located on the front on the arm’s upper part. Its tendons link this muscle to the protrusion in the inner part of to the head of radius. It is one of the two bones in the forearm. The biceps brachii bends forearm towards the upper arm, and is therefore used for pulling and lifting movements.

Its size, the size and shape of the bicep brachii’s size is believed to be a sign of the strength of your body. The bicep is an example of a muscle that are located behind the thighs. It is located in the rear of the isthmus as well as the behind the femur. It is linked to the fibula’s head and the tibia. It plays a role in the movements of the thighs as well as it is involved in flexing the leg in the knee.

Definition of Involuntary muscles 

• Involuntary muscle are those muscles which aren’t operated by the will of the user or by conscious and are typically connected to organs that show constant and frequent contractions and relaxation.
• Involuntary muscles are also referred to as smooth muscles, or non-striated muscles because there aren’t any streaks when examined under a microscope.
• They are mainly located along the internal organs’ walls such as the stomach, the urinary bladder, the intestine and blood capillaries.
• The muscle cells that make up smooth muscles are thin, long and spindle-shaped. They have the nucleus located in the middle.
• The myolemma, also known as sarcolemma, is found as an outer membrane on muscle fibers which functions to connect the muscles to one another. The sarcolemma in this case is smaller and has a lower concentration.
• One of the most common examples of muscles that are involuntary includes the heart muscle that is different both in function and structure from other muscles that are involuntary.
• The muscle of the cardiac is made up of heart muscle cells known as cardiomyocytes, which are joined with intercalated discs. The muscle cells are surrounded by collagen fibers as well as other substances that constitute an extracellular matrix.
• The cardiac muscle’s contraction differs from the contraction of smooth and skeletal muscles. Action potentials are created inside the muscle by electrical stimulation.
• This can trigger releases of calcium ions from cells into the sarcoplasm-reticulum. The rise of calcium ions causes the myofilaments to slide past each other, causing excitation-contraction.
• Myogenic muscle in the Cardiac Muscle is in which nerve impulses are created within the muscles.
• Most of the cells in the muscle fibers of the muscles that are involuntary work as one unit in which the contraction and relaxation take place together.
• The muscles that are involuntary can be controlled through the autonome nervous system of the peripheral nerve system.
• The motor nerves of the autonomous nervous system consist of a type of neurotransmitter-filled bulges termed varicosities.
• Because gap junctions connect muscles cells that are involuntary neurons, neuron signals are transferred between cells through neurotransmitters.
• Involuntary muscles are able to contract and relax. the involuntary muscles is slow and occurs in regular intervals.
• This means that the muscles do not get tired rapidly and they can continue to work.
• They also have a lower energy requirements as compared with voluntary muscles and, consequently, have less mitochondria.
• Involuntary muscles play a role in the movement of organs of the internal system, and assist in the movement of food and fluids through the digestive system.
• Examples of involuntary muscles include the cardiac muscles and smooth muscle that lines the digestive tracts, blood vessels and urogenital tracts, respiratory tract, etc.

Examples of involuntary muscles

Cardiac muscle

Cardiac muscle is a striated involuntary muscle which is located on the heart’s wall and is subject to contractions and relaxations frequently. This muscle made up of individual cells of the heart known as cardiomyocytes, which are joined with intercalated discs. The muscle cells are enclosed by collagen fibers as well as other substances that constitute an extracellular matrix.

The contraction of the cardiac muscle differs from the contraction of both smooth and skeletal muscles. Myogenic in nature and the nerve stimulation is generated in the muscles. An action potential created within muscles as a result by electrical stimuli. This triggers an expulsion of calcium-ion ions from cells into the sarcoplasmreticulum. The rise of calcium ions causes the myofilaments to slide past each other, causing excitation-contraction. Cardiac muscles are connected to sympathetic and vagal nerves which control the contractions of muscle fibers.

Smooth muscle

It is an involuntary, nonstriated muscle composed of single unit or unitary muscles and multiunit muscles. Smooth muscle forms the wall of various organs within the body, such as the urinary tract, intestinal tract tract, blood vessels and the like. The ciliary muscle in eyes is also smooth muscle . It dilates and regulates the iris, which alters the form of the lens.

Single unit smooth muscles comprise muscles in which the relaxation and contraction of the whole muscle take place as a unit. Multiunit muscles are able to contract and relax in separate units. These muscle fibres are enclosed by nerve fibers made up of vesicles referred to as varicosities, or boutons that transmit neurotransmitters.

Differences between Voluntary muscles and Involuntary muscles (Voluntary muscles vs Involuntary muscles)

Basis for Comparison	Muscles that are voluntary	Voluntary muscle
Definition	Voluntary muscles are muscles which can be moved with at the discretion of a person . They are usually related to the skeleton system.	Involuntary muscles are those that are not operated by the will of the user or by conscious and are typically associated with organs which exhibit constant and frequent contractions as well as relaxation.
Also called	Voluntary muscles can also be referred to as the striated muscles or skeletal muscle.	Involuntary muscles are also referred to as nonstriated muscles , or smooth muscles.
Found	Voluntary muscles can be found in bone structures by way of tendon.	Involuntary muscles line the internal organs’ walls such as the stomach, intestine the urinary bladder, blood capillaries.
Cell’s shape	The muscle cells that make up those muscles that are voluntary cylindrical, and not branched with the nucleus situated in the outer reaches of the cell.	The muscle cells of the muscles of involuntary are thin and long. They are also spindle-shaped with a centrally-located nucleus.
Cell type	The muscle cells are multinucleated , with many mitochondria.	Muscle cells tend to be not inucleated with less mitochondria.
Sarcolemma	Sarcolemma that surrounds the fibers of voluntary muscle is more dense.	Sarcolemma that surrounds the involuntary muscle fibers is less dense.
Sarcomeres	Sarcomeres are found in muscles fibers.	Sarcomeres do not exist in muscle fibers.
CDs that are intercalated	Intercalated discs do not exist in the voluntary muscles.	Certain involuntary muscles, such as the cardiac muscle comprise intercalated discs.
Control	Muscles that are voluntary can be controlled through willpower or even conscious.	Involuntary muscles are those muscles that are not controlled by will.
System of nerves	The nervous system controlling the somatic nerves controls all voluntary muscles.	Autonomic nerve system regulates muscles that are involuntary.
Neuro stimuli	The nerve impulse that is present in voluntary muscles is produced via our nervous system.	Myogenic muscles can be found in some involuntary muscles where the stimuli are generated in the muscle.
Contraction type	Voluntary muscles contract and relax quick and strong.	the contractions as well as relaxation that occur in involuntary muscles are slow and rhythmic.
Energy requirement	It is more energy that is needed to allow the contraction and relaxation in voluntary muscle.	A lesser amount of energy is required to relax and contract of muscles involuntary to relax.
Fatigue and all	Muscles that are voluntary get tired quickly and require frequent periods of relaxation.	Muscles that are voluntary do not get tired and are able to work for a long time.
Involved in	They are vital as they play an important role with the movements of organs and the movement of the body.	Involuntary muscles participate in the movement of internal organs. They also aid in the flow of food and fluids through the digestive system.
Examples	Examples of voluntary muscles are the muscles of the triceps and biceps. the diaphragm and quadriceps muscles pectoral muscles and abdominals, hamstrings.	Examples of involuntary muscles include the cardiac muscle as well as smooth muscle that line of the intestinal tracts and blood vessels respiratory tract, urogenital tracts and more.