Bio18 Ch8 Muscle Physiology Spr13 - Muscle Comprises largest group of tissues in body 3 types of muscle Cardiac muscle Chapter 8 Muscle Physiology Found

Bio18 Ch8 Muscle Physiology Spr13 - Muscle Comprises...

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Chapter 8 Muscle Physiology Muscle Comprises largest group of tissues in body 3 types of muscle Cardiac muscle Found only in the heart Smooth muscle Appears throughout the body systems as components of hollow organs and tubes Skeletal muscle Make up muscular system, attached to bones Classified in 2 different ways Striated or unstriated Voluntary or involuntary Categorization of Muscle Cardiac Muscle Found only in heart Striated Cells are connected by gap junctions and desmosomes at intercalated disks Fibers are joined in branching network Innervated by autonomic nervous system
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Smooth Muscle Found in walls of hollow organs, tubes No striations Filaments do not form myofibrils Not arranged in sarcomere pattern as found in skeletal muscle Spindle-shaped cells, single nucleus Cells usually arranged in sheets within muscle 2 major types Multiunit smooth muscle Single-unit smooth muscle Multiunit Smooth Muscle Neurogenic (stimulated by neural input)Consists of discrete units that function independently of one another Found in walls of large blood vessels large airways to lungs Ciliary body muscle (adjusts lens for near/far vision) Iris of eye (adjusts pupil size) Base of hair follicles Single-unit Smooth Muscle AKA visceral smooth muscle Self-excitable(does not require nervous stimulation) Fibers become excited and contract as single unit Cells electrically linked by gap junctions Can also be described as a functional syncytium Contraction is slow and energy-efficient Well suited for forming walls of distensible, hollow organs Muscle Function Controlled muscle contraction allows: Purposeful movement of the body or body parts Manipulation of external objects Propulsion of contents through various hollow internal organs, emptying to external environment Structure of Skeletal Muscle Muscle consists a number of muscle fibers lying parallel to one another and held together by connective tissue Single skeletal muscle cell is called a muscle fiber Muscle fibers are multinucleate, large, and cylindrical Fibers usually extend entire length of muscle
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