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Skeletal Muscle
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The cell membrane of the muscle fiber is the sarcolemma and has the ionic properties characteristic of excitable cells, manifested as a resting membrane voltage of about –90 mV and the ability to generate and propagate a muscle action potential. The sarcolemma is coated on the outside by a basement membrane formed largely of glycoproteins, and each muscle fiber is surrounded by a delicate layer of connective tissue, the endomysium (Figure 9.1). Groups of about 10 to more than 100 muscle fibers are bundled together into fascicles, the number of muscle fibers in a fascicle being larger in muscles that produce greater force, with less fineness of control. Fascicles are surrounded, in turn, by another layer of connective tissue, the perimysium. The whole muscle is ensheathed by a dense layer of irregular connective tissue, the epimysium.
Applications of Biomaterials in Soft Tissue Replacement
Published in Yaser Dahman, Biomaterials Science and Technology, 2019
Muscle tissue functions by transforming chemical energy into mechanical energy. It can be differentiated into three types: skeletal, smooth, and cardiac (Marieb, 2006). Skeletal muscle tissues have long, striated, and multinucleate cells. They attach to bones and help in the movement and stabilization of the skeleton. Each muscle consists of many muscle fascicles (bundle of cells), and each fascicle consists of many muscle fibers (cell). Each muscle fiber consists of many myofibrils, which consist of the functional unit of the muscle (actin and myosin). Smooth muscle tissue consists of short, spindle-shaped, non-striated cells. Smooth muscle is involuntary, and can be found in the organs of the visceral region of the body such as stomach and intestines where they allow these organs to contract and expand. Cardiac muscle tissue consists of short, striated, branched cells. Cardiac muscle is only found in the heart and is responsible for the circulation of blood (Marieb, 2006).
Muscle Physiology and Electromyography
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
Figure 2 shows the gross structure of a muscle. The muscle belly is composed of a large number of fasciculi, bundles of individual muscle fibers held together by a connective tissue sheath (perimysium). A softer connective tissue, endomysium, fills the spaces between the muscle fibers. The fasciculi are enclosed in the epimysium, a tougher connective tissue sheath, which is continuous with the perimysium of the individual fasciculi internally and with adjacent structures externally. At the ends of the muscle, the epimysium is extended into the tendon or aponeurosis.
Mechanism of peripheral nerve modulation and recent applications
Published in International Journal of Optomechatronics, 2021
Heejae Shin, Minseok Kang, Sanghoon Lee
The main structure of the PNS is a nerve that has an enclosed structure like a cable bundle in which neurons are gathered, playing the role of the passage for the electrochemical signals. As shown in Figure 1(a), a neuron consists of a cell body with the nucleus, a dendrite that receives nerve signals, generating an action potential when the signals exceed the threshold, and an axon that transmits the generated signals to an axon terminal to transfer the signal to another neuron. In some cases, this axon is covered with a myelin sheath, making the speed transmission is significantly faster compared to the unmyelinated neurons, which are covered with connective tissue called the endoneurium. In addition, the axon terminal forms a synapse with adjacent neurons, in which the electrical signal transmitted through the axon is converted into a chemical signal by releasing a molecule called a neurotransmitter that is a chemical messenger inhibiting or activating the neuron by influencing the receptor on the targeted neuron or organ. The aggregate of these nerve fibers is called a fascicle, and this fascicle is surrounded by connective tissue called the perineurium. Inside the fascicle, afferent fibers that send afferent (sensory) signals to the CNS and efferent fibers that send efferent (motor) signals from the CNS could be both located in a fascicle or a nerve which is called a mixed nerve fiber. The group of fascicles is called a nerve. A nerve is surrounded by epineurium, and it also consists of blood vessels that provide nutrients for the whole structure. (Figure 1(b)).[10]