Chapter9 - Chapter 9 1 Overview of Muscle Tissues...

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Chapter 9 1 Overview of Muscle Tissues Myofilaments : actin and myosin are contractile proteins. Actin filaments are constantly breaking down and re-forming Muscle fibers are cells of smooth and skeletal muscle Cardiac muscle is not considered to have muscle fiber Myo or mys are prefixes that mean muscle Sarco prefix means flesh Sarcolemma is the plasma membrane of muscle fibers Sarcoplasm is the muscle fibers cytoplasm A) Types of Muscle Tissue 1) Skeletal muscle tissue: are organs that attach to and cover bony skeleton Is attached to the skeleton and its fibers are the longest muscle cells Cells are striated (have stripes) Is voluntarily (conscious control) Contractions are rapid Are responsible for all locomotion and manipulation Enable you to respond quickly to changes in the external environment—for example, by jumping out of the way of a runaway car, directing your eyeballs, and smiling or frowning. 40% of body mass Most responsible for generating heat 2) Cardiac muscle tissue: bodies blood pump forms the bulk of the heart walls cells are striated Is controlled involuntarily . The hearts pacemaker cells (neural controls) allow the heart to speed up when running. Cardiac muscle has pacemaker cells which depolarize (fire) at a set rate (autorhythmicity) which can be increased or decreased by the nervous system. Contractions are at a steady rate 3) Smooth muscle tissue Located chiefly in the walls of hollow visceral organs such as stomach, urinary bladder, and respiratory passages. Is controlled involuntarily . Its fibers are nonstriated . Its role is to force fluids and other substances through internal body channels Contractions are slow and sustained Smooth muscle in blood vessels help maintain blood pressure
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Chapter 9 2 B) Functional Characteristics of Muscle Tissue 1) Excitability or responsiveness/irritability Is the muscle fibers ability to receive and respond to a stimulus (any change in our body or outside our body). The stimulus is usually a chemical—for example, a neurotransmitter released by a nerve cell, or a local change in pH. The response is generation of an electrical impulse that passes along the sarcolemma (plasma membrane) of the muscle cell and causes the cell to contract. 2) Contractility Is the muscle fibers ability to shorten forcibly when adequately stimulated. 3) Extensibility Is the ability to be stretched or extended Muscle fibers shorten when contracting, but they can be stretched, even beyond their resting length, when relaxed. 4) Elasticity Is the ability of a muscle fiber to recoil and resume its resting length after being stretched. C)
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Chapter9 - Chapter 9 1 Overview of Muscle Tissues...

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