Muscular System

Muscular System: The muscular system is composed of specialized cells called muscle fibres. Their predominant function is contractibility. Muscles attached to bones or internal organs and blood vessels are responsible for movement. Nearly all movement in the body is the result of muscle contraction. Exceptions to this are the action of cilia, the flagellum on sperm cells, and the amoeboid movement of some white blood cells.

Muscles allow a person to move, speak, and chew. They control heartbeat, breathing, and digestion. Other seemingly unrelated functions, including temperature regulation and vision, also rely on the muscular system. The three types of muscles are Skeletal muscle, Cardiac muscle and Smooth muscle. In this article, we find out more about the muscular system and how it controls the body.

What are Muscles?

Muscles are specialised tissue responsible for the movement of different body parts. They are soft tissues, and muscle cells are also known as myocytes. The muscles contain unique proteins called actin and myosin that help in the contraction and relaxation of muscles.

Types of Muscles

Based on location in the human body, there are three types of muscles.

• Striated or Skeletal Muscles
• Non-Striated or Smooth Muscles
• Cardiac Muscles

Skeletal Muscle

This type of muscle creates movement in the body. There are more than 600 skeletal muscles, and they make up about 40 per cent of a person’s body weight. When the nervous system signals the muscle to contract, groups of muscles work together to move the skeleton. These signals and movements are nearly involuntary, yet they do require conscious effort. However, humans do not need to concentrate on individual muscles when moving.

Cardiac Muscle

The cardiac muscle is an involuntary muscle. This type makes up the walls of the heart and creates the steady, rhythmic pulsing that pumps blood through the body from signals from the brain. This muscle type also creates the electrical impulses that produce the heart’s contractions, but hormones and stimuli from the nervous system can also affect these impulses. This can happen with an increase in the heart rate increases especially when you are scared.

Smooth Muscle

Smooth muscle makes up the walls of hollow organs, respiratory passageways, and blood vessels. Its wave-like movements propel things through the bodily system, such as food through your stomach or urine through your bladder. Like a cardiac muscle, smooth muscle is involuntary and contracts in response to stimuli and nerve impulses.

Types of Muscles Based on Muscle Action

Muscles are of three types based on location:

1. Voluntary Muscles: The muscles that can be controlled at our will are called voluntary muscles. They are attached to our bones and provide movement to the body parts. Therefore, they are also known as skeletal muscles.
2. Involuntary Muscles: The muscles that cannot be controlled at one’s will are called involuntary muscles. They are found in our internal organs like the oesophagus, stomach, intestines, etc.

Difference between Voluntary Muscles and Involuntary Muscles

Muscles in the Body

The human body has more than 630 muscles. The important muscles of the human body are mentioned below.

1. Masseter: This muscle is the strongest in the human body. This muscle is located near the lower jaw and helps in chewing food.
2. Diaphragm: It is present below the lungs; it is the dome-shaped muscle that is involved in respiration.
3. Intercostal muscle: This muscle is present between the ribs and helps in breathing by facilitating inhaling and exhaling.
4. Biceps brachii: It is in front of the upper arm between the shoulder and the elbow.
5. Triceps brachii: It is a large muscle that lies on the back of the upper arm. This muscle is mainly responsible for the extension of the elbow joint.

Functions of the Muscular System

The main functions of the muscular system are:

Mobility

The muscular system’s main function is to allow movement. When muscles contract, they contribute to the gross and fine movement.

Stability

Muscle tendons stretch over joints and contribute to joint stability. Muscle tendons in the knee joint and the shoulder joint are crucial in stabilisation.

Posture

Skeletal muscles help keep the body in the correct position when someone is sitting or standing. This is known as posture.

Circulation

Skeletal muscles help keep the body in the correct position when someone is sitting or standing. This is known as posture.

Respiration

Breathing involves the use of the diaphragm muscle. The diaphragm is a dome-shaped muscle located below the lungs. When the diaphragm contracts, it pushes downward, causing the chest cavity to get bigger. The lungs then fill with air. When the diaphragm muscle relaxes, it pushes air out of the lungs.

Digestion

Smooth muscles in the gastrointestinal or GI tract control digestion. The GI tract stretches from the mouth to the anus. Food moves through the digestive system with a wave-like motion called peristalsis. Muscles in the walls of the hollow organs contract and relax to cause this movement, which pushes food through the oesophagus into the stomach.

Urination

The urinary system comprises both smooth and skeletal muscles, including those in the bladder, kidneys, penis or vagina, prostate, ureters and urethra. The muscles and nerves must work together to hold and release urine from the bladder.

Childbirth

Smooth muscles in the uterus expand and contract during childbirth. These movements push the baby through the vagina. Also, the pelvic floor muscles help to guide the baby’s head down the birth canal.

Vision

Six skeletal muscles around the eye control its movements. These muscles work quickly and precisely, allowing the eye to maintain a stable image, scan the surrounding area, and track moving objects.

Organ Protection

Muscles in the torso protect the internal organs at the front, sides, and back of the body. The bones of the spine and the ribs provide further protection. Muscles also protect the bones and organs by absorbing shock and reducing friction in the joints.

Temperature Regulation

Maintaining normal body temperature is an important function of the muscular system. Almost 85 per cent of the heat a person generates in their body comes from contracting muscles.

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