The functional units that can make a muscle shorten are:
a) Z lines
b) Myofibrils
c) Sarcomeres
d) Cross-bridges
Answer (2)
The functional units that allow a muscle to shorten are called sarcomeres. They consist of myofilaments and are organized in myofibrils. Therefore, the correct answer is c) Sarcomeres.
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The functional units that can make a muscle shorten are called Sarcomeres.
To understand this, let's break down the structure of muscles:
Muscle Structure : Muscles are composed of bundles of muscle fibers, which are in turn made up of smaller units called myofibrils.
Myofibrils : These are long, thread-like structures that run parallel along the length of the muscle fiber. Each myofibril contains repeating units called sarcomeres.
Sarcomeres : A sarcomere is the basic unit of a muscle's structure and function. It is the segment between two Z lines (the borders of a sarcomere) in a myofibril. Sarcomeres contain the contractile proteins actin and myosin.
How Muscles Shorten : When a muscle contracts, the sarcomeres shorten. This happens because the myosin heads, also known as cross-bridges, bind to actin filaments and pull them toward the center of the sarcomere. This action is powered by ATP and results in the shortening of the entire muscle fiber, which is what makes the muscle contract.
Importance of Sarcomeres : They are essential as they are the fundamental units that allow muscles to contract. Without them, muscle contraction would not occur, underscoring their role as the functional units responsible for muscle shortening.
Based on this information, the correct answer is: c) Sarcomeres .
