Question

Which of the following is incorrect about skeletal muscles? (a) Striped appearance under microscope hence called striated muscle. (b) They are voluntary muscles. (c) Primarily involved in locomotory actions and changes the body postures. (d) They are Involuntary muscles.

Short answer

The incorrect statement about skeletal muscles is (d). They are not involuntary muscles, instead, they are voluntary muscles.

Step-by-step solution

Evaluate Option (a)

Skeletal muscles do indeed have a striped appearance under a microscope because of their alternating light and dark bands, giving them the name 'striated muscle'. Therefore, this statement is correct about skeletal muscles.

Evaluate Option (b)

Skeletal muscles are under conscious control, meaning they can be voluntarily controlled. Hence, the statement 'They are voluntary muscles' is also correct.

Evaluate Option (c)

Skeletal muscles are primarily involved in locomotory actions and changing the body's postures. This is an accurate description of one of their primary functions, making this statement also correct.

Evaluate Option (d)

The claim 'They are involuntary muscles' is the incorrect statement. Skeletal muscles are voluntary, not involuntary. They are under conscious control and can be intentionally contracted or relaxed.

Key concepts

Striated Muscle Structure

Striated muscles, also known as skeletal muscles, are characterized by their distinctive striped appearance when observed under a microscope. This pattern arises from the arrangement of two types of protein filaments within the muscle fibers: actin and myosin. These filaments are organized into repetitive units called sarcomeres, which are the basic functional units of muscle contraction.

Within the sarcomeres, the overlapping of thick myosin and thin actin filaments creates light and dark bands known as I bands and A bands, respectively. The Z line, running through the I band, marks the boundary between adjacent sarcomeres. When a muscle contracts, these sarcomeres shorten as the actin and myosin filaments slide past one another, a process powered by ATP. The intricate organization of these proteins is essential for muscles to function properly and account for the striated appearance responsible for the muscle's name.

Voluntary vs Involuntary Muscles

Muscles can be broadly categorized into two groups: voluntary and involuntary. Voluntary muscles, such as skeletal muscles, are under conscious control, which means an individual can decide when to move them. These are the muscles you use when lifting objects, walking, or smiling.

On the other hand, involuntary muscles are not under conscious control and are primarily responsible for essential body functions that are not consciously directed, such as the beating of the heart or the movement of food through the digestive system. These include smooth muscles found in organs and the myocardium making up the heart muscle. The correct understanding of these two types of muscles is crucial, given that each plays vital roles in daily survival and activities.

Locomotory Actions of Muscles

Locomotory actions of muscles are movements that enable the body to travel from one place to another or to change posture. Primarily, skeletal muscles are responsible for these movements. They attach to the skeletal system via tendons and, upon contraction, they exert force on the bones, thereby generating movement. Such actions include walking, running, jumping, and swimming.

Coordination between muscles and the nervous system is essential for locomotion; signals from the brain are sent to the muscles to initiate movement. Muscle groups often work in pairs, with one muscle contracting while the opposing muscle relaxes, a process known as antagonism, exemplified by the biceps and triceps during arm movements.

Muscular System Functions

The muscular system serves several critical functions beyond locomotion. It is essential for maintaining posture and stabilizing joints, ensuring that the body remains upright and can carry out precise movements. Additionally, muscles play a significant role in thermoregulation; muscle contractions generate heat as a by-product, helping to maintain the body's temperature.

Muscles also protect internal organs by acting as a cushion against external impacts. Furthermore, certain muscles are involved in processes such as respiration, with the diaphragm and intercostal muscles contributing to the expansion and contraction of the thoracic cavity during breathing. Understanding these functions highlights the importance of the muscular system in overall health and physical well-being.