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When a muscle is stretched, primary type Ia sensory fibers of the muscle spindle respond to both changes in muscle length and velocity and transmit this activity to the spinal cord in the form of changes in the rate of action potentials. Likewise, secondary type II sensory fibers respond to muscle length changes (but with a smaller velocity ...
The protein complex composed of actin and myosin, contractile proteins, is sometimes referred to as actomyosin.In striated skeletal and cardiac muscle, the actin and myosin filaments each have a specific and constant length in the order of a few micrometers, far less than the length of the elongated muscle cell (up to several centimeters in some skeletal muscle cells). [5]
A muscle spindle, with γ motor and Ia sensory fibers. A type Ia sensory fiber, or a primary afferent fiber, is a type of afferent nerve fiber. [1] It is the sensory fiber of a stretch receptor called the muscle spindle found in muscles, which constantly monitors the rate at which a muscle stretch changes.
The overlap of actin and myosin gives rise to the length-tension curve, which shows how sarcomere force output decreases if the muscle is stretched so that fewer cross-bridges can form or compressed until actin filaments interfere with each other. Length of the actin and myosin filaments (taken together as sarcomere length) affects force and ...
The stretch reflex (myotatic reflex), or more accurately "muscle stretch reflex", is a muscle contraction in response to stretching a muscle. The function of the reflex is generally thought to be maintaining the muscle at a constant length but the response is often coordinated across multiple muscles and even joints. [ 1 ]
The Frank-Starling mechanism occurs as the result of the length-tension relationship observed in striated muscle, including for example skeletal muscles, arthropod muscle [4] and cardiac (heart) muscle. [5] [6] [7] As striated muscle is stretched, active tension is created by altering the overlap of thick and thin filaments. The greatest ...
The thin filaments are placed between 2 myosin filaments and contain only the actin filaments of neighboring sarcomeres. Bisecting the I band and serving as an anchoring point for the two adjacent actin filaments is the Z disc. During muscle contraction, the I band will shorten, while an A band will maintain its width. [2]
Each muscle fiber contains sarcolemma, sarcoplasm, and sarcoplasmic reticulum. The functional unit of a muscle fiber is called a sarcomere. [2] Each muscle cell contains myofibrils composed of actin and myosin myofilaments repeated as a sarcomere. [3] Many nuclei are present in each muscle cell placed at regular intervals beneath the sarcolemma.