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Striated muscles are the muscles that are under the control of our brain. Therefore, these muscles are also called voluntary muscles. They are made up of muscle fibres called myofibrils.
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Key Terms: Striated Muscles, Skeletal Muscles, Cardiac Muscles, Muscles
Key Highlights
- The four complex proteins- Actin, Myosin, Tropomyosin, and Troponin together constitute myofibrils.
- The two types of striated muscles are skeletal and cardiac muscles.
- Blood is pumped throughout the body through the cardiac muscle contractions.
- The voluntary movements of the body, including breathing and eye blinking, are controlled by skeletal muscles.
- Stretchability and contractility are the two defining characteristics of skeletal muscles.
What are Striated Muscles?
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Striated muscles have alternating bands of bright and dark muscle that give them a striped appearance. These muscles serve the function of maintaining body alignment and posture.
- The basic structural and functional unit of striated muscles are called sarcomeres which are made up of two protein filaments: Actin and Myosin.
- The cytoplasm of the striated muscle is enclosed by a plasma membrane known as the sarcolemma, which surrounds the muscle fibre.
Striated Muscles
Functions of Striated Muscles
It serves three primary functions
- Locomotion and Body Movements- These are controlled by the skeletal muscles.
- Pumping Blood throughout the Body- It is regulated by cardiac muscle.
- Heat Generation- Heat is produced by the contractions of striated muscles. Temperature regulation is supported by this action in the body.
What are the Types of Striated Muscles?
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The two types of muscle that fall under the category of striated muscle are:
Skeletal muscle
It is a type of muscle that is responsible for maintaining body posture and regulating body temperature.
- They are the muscles that are connected to our bones, allowing us to participate in various tasks.
- The skeletal muscle fibres, blood vessels, nerve fibres, and connective tissue are the essential parts of these muscles.
- The epimysium that envelops these muscles maintains their structural integrity even during muscular contractions.
Cardiac Muscle
The cardiac muscle is a specialised striated muscle that is present in the heart of the human.
- They are involuntary striated muscles that control the contraction and relaxation movements of the heart by pumping blood to it.
- Cardiac muscle is composed of two distinct layers: Endocardium (Inner layer), and Epicardium (Outer layer).
How do Striated Muscles Work?
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The overall working of striated muscles depends on the contraction and relaxation of muscles which usually contract at the same time. When they contract at various intervals, they are referred to as parallel muscles.
- Actin and myosin, two long protein strands that twist around one another in a helical pattern, are the building blocks of muscle, and these strands are known as myofibrils.
- These two proteins work in tandem to generate a contraction force that pushes the muscle cell's fibres.
- Calcium induces the troponin complex to shift position on actin filaments, exposing myosin-binding sites in striated muscle.
- Myosin, which is attached to ADP and inorganic phosphate (Pi), may then form cross-bridges with actin, and the release of ADP and Pi causes contraction in the muscle.
Problems Related to Improper Functioning of Striated Muscles
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The overall process of muscle contraction and relaxation will be disrupted in the absence of proper functioning of striated muscles. This may cause various muscle-related problems in the body such as:
- Pain
- Jerking of Muscles
- Breathing Problems
- Difficulty in Muscular Movements
Sample Questions
Ques. What is a motor unit? (2 marks)
Ans. The basic structural components of skeletal muscle are called motor units. They send signals from the brain to other parts of the body, causing muscle contraction.
Ques. What is a tropomyosin? (2 marks)
Ans. The striated muscles contract by using various types of protein filaments, one of which is tropomyosin. Its primary purpose is to prevent the muscles from contracting at inappropriate times. To accomplish this function, it prevents actin and myosin filaments from coming in contact with each other.
Ques. What do you understand about aponeurosis? (2 marks)
Ans. Aponeuroses are thin sheaths of connective tissue that assist in filling the space between our muscles and bones. Tendons and aponeuroses are very similar. They provide stability and strength to our body by supporting our muscles.
Ques. Are myofibrils a component of myocytes? (2 marks)
Ans. Myofibrils are the most prevalent organelle in myocytes, making up between 50 and 60 per cent of the cytoplasm. Sarcomeres are discrete, continuing units made up of overlapping layers of thin and thick myofilaments that collectively form myofibrils.
Ques. What are I- Bands? (2 marks)
Ans. The area of a striated muscle sarcomere containing thin filaments is known as the I band. When examined under a light or electron microscope, this region seems to be the lightest. Only the thin filaments are present in the I band.
Ques. What are non-striated muscles? (2 marks)
Ans. Smooth muscles that lack striations are called non-striated muscles.
- They are present in various internal organs, including the bladder, intestines, and stomach.
- These muscles are also called involuntary muscles.
Ques. What are the defining features of striated muscles? (3 marks)
Ans. The defining features of striated muscles are:
- These are voluntary muscles located in the hands, feet, pharynx, and other parts of the body that can be controlled by willpower.
- Since they display alternating bands of light or dark, or striations, when examined under a microscope, these muscles are also referred to as striped muscles.
Ques. What is a tendon and a ligament? (2 marks)
Ans. Tendons join muscle to bone, while ligaments join bone to bone. A limited degree of stretching is possible for both ligaments and tendons. An injury may result from them stretching beyond their limits
Ques. What are the differences between striated and smooth muscles? (3 marks)
Ans. The differences between striated and smooth muscles are as follows:
| Striated Muscle | Smooth Muscle |
|---|---|
| Muscles with striation are called striated muscles. | No striation |
| They are voluntary muscles. | They are involuntary. |
| Multinucleated | Uninucleated |
Ques. What are microfilaments? (2 marks)
Ans. Two entangled strands of the globular protein actin make up microfilaments. These are also called actin filaments. They are essential for the movement, division, and contraction of cells, including muscles.
Ques. What are the important functions of striated muscles? (2 marks)
Ans. The important functions of striated muscles are:
- Maintaining body posture and position,
- Storing nutrition,
- Controlling movement,
- Regulating body temperature, and
- Stabilising joints
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