Muscles: Types, Groups, Anatomy, Functions, Composition, Development

Muscles are specialized tissues responsible for movement and support in the human body. They work by contracting and relaxing, enabling various actions like walking, lifting, and even maintaining posture. In this article, muscles, types of muscles, muscle structure, muscle function, and common muscle disorders and diseases are discussed. Muscles are a topic of the chapter Locomotion And Movement in Biology.

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This Story also Contains

1. What are Muscles?
2. Types of Muscles
3. Muscle Structure
4. Muscle Function
5. Common Muscle Disorders and Diseases

What are Muscles?

Muscles are specialised tissues in the human body whose major function is to move by their ability to contract. They are essential for a wide range of operations or activities that occur or take place within the body, such as maintaining posture, providing means and enabling locomotion, and assisting in critical functions like breathing and digestion. They contribute to overall health by way of supporting the skeletal system, protecting the internal organs, and offering help in metabolic processes.

Muscles take part in movement but play a crucial role in the overall health of the body. Regular muscle activity improves cardiovascular health, supports metabolic functions, and aids in maintaining a healthy weight. Other than daily movements, muscle strength is also vital for daily acts and the prevention of injuries of any type.

Types of Muscles

The types of muscles in the human body are broadly divided into three categories: skeletal, cardiac, and smooth muscles.

Skeletal Muscles

• They are striated in appearance.

• Multinucleated fibers

• Voluntary control

• Fixed to bones by tendons

• Extensively in limbs and torso

• Cause movement due to contraction and relaxation abilities

• Examples: Biceps brachii (arm), Quadriceps femoris (thigh)

Cardiac Muscles

• Striated with intercalated discs

• One nucleus per cell

• Involuntary

• In the Walls of the heart (myocardium)

• Pump blood throughout the body

• Contraction occurs continually in a rhythmic manner.

Smooth Muscles

• Not striated

• One nucleus per cell

• Autonomic nervous control

• In the Walls of hollow organs (e.g., intestine, blood vessels)

• Move substances along the body

• Examples: Muscles in the digestive tract, blood vessel walls.

Also Read:

• MCQ Practice for Muscles
• Locomotion and Movement
• Human Skeletal System
• Joints

Muscle Structure

Muscle structure is complex, comprising different parts that interact to produce contraction and movement.

Muscle Fibers

• Elongated, cylindrical cells

• Several nuclei peripherally located

Sarcomere: The Functional Unit

• Repeating units of myofibrils

• Units responsible for muscle contraction

Myofibrils, Actin and Myosin Filaments

• Myofibrils: Contractile threads within muscle fibers

• Actin (thin) and myosin (thick) filaments: proteins involved in contraction.

Connective Tissue Components

• Endomysium: surrounds individual muscle fibres

• Perimysium: encases bundles of fibres (fascicles)

• Epimysium: encloses the entire muscle

Tendons and their Role in Muscle Attachment:

• Connect muscles to bones

• Transmit force from muscle contraction to the skeleton.

Muscle Function

The mechanism of muscle function centres on the process of contraction and how muscles contract.

Sliding Filament Theory:

• Actin and myosin filaments slide past each other

• Shortens the sarcomere, producing contraction.

Role of ATP and Calcium Ions:

• ATP provides energy for contraction

• Calcium ions control the interaction of actin and myosin.

Neuromuscular Junction and Action Potential:

• Synapse between a motor neuron and muscle fibre.

• Action potential leads to muscle contraction.

Isotonic and Isometric Contractions:

• Isotonic: length of the muscle changes (e.g. lifting a weight)

• Isometric: muscle does not change in length (e.g. holding a position)

Concentric and Eccentric Contractions:

• Concentric: Muscle shortens when contracting

• Eccentric: Muscle lengthens when contracting

Common Muscle Disorders and Diseases

Several disorders and diseases can compromise muscle and thus function and quality of life.

Muscular Dystrophy

• Duchenne muscular dystrophy: Progressive muscle weakness

• Becker muscular dystrophy: Similar but milder

Genetic Basis and Treatment Options:

• Genetic mutations that alter muscle proteins.

• Treatment is symptomatic and aims to retard the progression.

Myasthenia Gravis

• Muscle weakness, fatigue

• Autoimmune disorder at the neuromuscular junction.

Treatment and Management:

• Medications aimed at improving nerve-muscle communication.

• Immunosuppressive therapies.

Muscle Cramps and Strains

• It is caused by dehydration, overuse, and electrolyte imbalance.

• This can be prevented by regular stretching and proper hydration.

Treatment and First Aid:

• Rest, application of ice, compression, elevation (RICE)

• Gentle stretch and rehydrate

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