Abstract
Muscle is a soft tissue, having a special ability for contraction. The contraction of the muscle fibers creates force and that causes movement of body as well as visceral organs.
Three types of muscles, namely skeletal, cardiac, and smooth muscles, are present in the body. The skeletal muscle is voluntary, while the cardiac muscle and smooth muscle are involuntary. Muscle fibers have some special properties, i.e., excitability, contractility, extensibility, and elasticity. The skeletal muscle fibers have a long cylindrical structure with many nuclei located in the periphery. The active contractile unit of muscle is known as sarcomere. Each myofibril contains several types of protein cells, called myofilaments. During contraction, action potential propagates through the sarcolemma and travels down the T-tubules causing the sarcoplasmic reticulum to release Ca2+ ions to the sarcoplasm. The myosin head then attaches to the binding site of the G-actin molecule, and the formation of crossbridges occurs. The following power stroke occurs, which forces and leads to the shortening of muscle fiber. Muscle relaxation occurs when the release of the neurotransmitter stops at the neuromuscular junction. In smooth muscle, cells are small and have one central nucleus. No neuromuscular junctions exist; instead, varicosities transmit the nerve impulse to cells. Contraction and relaxation are slower than the skeletal muscle, and less energy is required for contraction. Cardiac muscle cells are small and branched and have a single nucleus. An intercalated disc is present at the junction between two cells. Gap junction located at the intercalated disc spreads action potential from one cell to another.D. Banerjee (X) ∙ P. K. Das ∙ J. Mukherjee
Department of Veterinary Physiology, West Bengal University of
Animal & Fishery Sciences, Kolkata, West Bengal, India
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023
P.
K. Das et al. (eds.), Textbook of Veterinary Physiology, https://doi.org/10.1007/978-981-19-9410-4_10Graphical Abstract
Description of the graphic: (1) Skeletal muscle fibers have a long cylindrical structure with many nuclei located in the periphery. The active contractile unit of muscle is known as sarcomere. Each myofibril contains several types of protein cells, called myofilaments. (2) In smooth muscle, cells are small and have one central nucleus. Two types of smooth muscles are single-unit smooth muscle and multiunit smooth muscle. (3) Cardiac muscle cells are small and branched and have a single nucleus. An intercalated disc is present at the junction between two cells. Gap junction located at the intercalated disc spreads action potential from one cell to another. (4) During contraction of skeletal muscle, action potential propagates through the sarcolemma and travels down the T-tubules causing the sarcoplasmic reticulum to release Ca2+ ions to the sarcoplasm. The myosin head then attaches to the binding site of the G-actin molecule, and the formation of crossbridges occurs
Keywords
Skeletal muscle ∙ Cardiac muscle ∙ Smooth muscle ∙ Muscle contraction ∙ Muscle fibers ∙ Crossbridge
Learning Objectives
• Functions, properties, and types of muscle tissues
• Microscopic structure of a skeletal muscle
• Major phases of skeletal muscle contraction and relaxation and their neural control
• Sources of energy for skeletal muscle contraction, mechanism of muscle fatigue, and rigor mortis
• Structure and contraction mechanisms of smooth and cardiac muscle
• Different muscular disorders of domestic animals
10.1