The muscular system is one of the most important organ systems! Without it, you wouldn’t be able to move your eye muscles to read this page or to lift heavy things. without the muscular system you couldn’t make the facial expressions that allow you to communicate with friends and family. Understanding of this important body system can help you develop better body literacy, or an understanding of your body, your internal organs, and how it all works together. Read on to learn some interesting facts about the muscular system.
Fun Facts About the Muscular System
- The largest muscle in the human body in your body is the gluteus maximus.
- The masseter, or the muscle in your jaw, is the strongest muscle based on its size.
- The smallest muscles in the human body are in your inner ear.
- The smallest muscle is the stapedius muscle, its purpose is to stabilize the smallest bone in the body, the stapes or strirrup bone of the middle ear.
- Your body contains over 600 muscles.
- Muscle makes up about 40% of your total body weight.
- Muscles typically work in pairs.
- Muscles can’t push, they can only pull.
- The hardest working muscle in your body is the heart. It’s working constantly at blood circulation!
- Most of the body heat that keeps you warm is generated by muscle movement. This keeps your body temperature at a steady 37 degrees Celsius.
Types of Muscles
- There are three different types of muscle tissue in your body: skeletal, cardiac, and smooth.
- Skeletal muscles connect to your bones and allow you to move.
- Skeletal muscle makes up almost 40% of your total body mass. Skeletal muscles are voluntary muscles, meaning you use these muscles with conscious control.
- Cardiac muscle is the muscle that makes up the heart. These are striated and involuntary muscle – meaning we don’t have to think about making these muscles move with our conscious mind. Imagine if you had to focus to keep your heart beating!
- Smooth muscles are found in your digestive system to keep food moving throughout your stomach and intestines, iris of the eye, and even in your blood vessels (circulatory system). does not have striations like cardiac and skeletal muscle, but it does have the ability to contract due to the presence of actin and myosin.
Functions of the Muscular System
The three main functions of muscles are:
- Contraction for skeletal movement
- Contraction for propulsion (moving forward)
- Contraction for pressure regulation (controls blood pressure)
How Muscles Work
- All muscles function by contracting and relaxing. A muscle fiber receives a nerve impulse and in turn releases proteins and chemicals that initiate either contraction or relaxation.
There are four types of muscle contractions:
- When muscle tension changes, but the length of the muscle stays the same, isometric contraction occurs. One example of this is when you use your abdominal muscles to do a plank.
- Alternatively, exercises such as running, swimming, squats, and pushups (where the muscle is contracting under a constant load) are known as isotonic contraction. In this type of contraction, the length of the muscle does change and the tension is constant.
- Isotonic and isometric contractions are opposites
- Eccentric contractions focus on the lengthening phase of a muscle movement. For example, the lowering phase of a bicep curl is the eccentric portion. This type of contraction generates the most force.
- A concentric contraction is the shortening phase of a movement. This occurs when you stand up from a squatting position or lift an object off the ground. Force is still being generated, the muscle fibers are just actively shortening instead.
- Eccentric and concentric contractions are opposite as well
- The Sliding Filament Theory is an explanation of how muscles contract and relax.
The Sliding Filament Theory:
- A nerve impulse travels to the muscle and releases a chemical called acetylcholine which causes depolarization. Depolarization allows calcium ions to be released from the sarcoplasmic reticulum.
- The calcium binds to troponin which allows tropomyosin to move from its active site on actin.
- The myosin filaments now attach to actin forming a cross bridge. The myosin heads use something called a “power stroke” to pull the thin filaments.
- ATP, or energy, allows myosin to pull actin (thin) filaments inwards causing a muscle contraction.
- Once ATP and calcium are depleted, the nerve impulse stops and actin returns to its resting position. The muscle is now relaxed and lengthened.
Types of Neuromuscular Disorders
Neuromuscular disorders affect the nerves that control voluntary muscles and the nerves that communicate sensory information back to the brain. Nerve cells (neurons) send and receive messages to and from the body to help control these muscles. When the neurons become unhealthy or die, communication between the nervous system and muscles breaks down. As a result, muscles weaken and waste away (atrophy).
Muscular dystrophy is a group of diseases that cause progressive weakness and loss of muscle mass. In muscular dystrophy, abnormal genes (mutations) interfere with the production of proteins needed to form healthy muscle.
Myasthenia gravis (MG) is a disorder in which antibodies destroy the communication between nerves and muscle, resulting in weakness of the skeletal muscles. Myasthenia gravis affects the voluntary muscles of the body, especially those that control the eyes, mouth, throat and limbs.
Cerebral palsy (CP) is a group of disorders that affect a person’s ability to move and maintain balance and posture. CP is the most common motor disability in childhood. Cerebral means having to do with the brain. Palsy means weakness or problems with using the muscles.
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