Muscle ICS PDF

Muscle ICS Objectives Types, functions, and characteristics of Muscle Histological Organization Connective Tissue Components Muscle Organization Understand Contractile units of Muscle Function of Muscles Movement Posture Heat Skeletal Muscle Cardiac Muscle Smooth Muscle O...

Muscle ICS Objectives Types, functions, and characteristics of Muscle Histological Organization Connective Tissue Components Muscle Organization Understand Contractile units of Muscle Function of Muscles Movement Posture Heat Skeletal Muscle Cardiac Muscle Smooth Muscle Organization of a Skeletal Muscle Epimysium – dense CT surrounding a group of fascicles Perimysium – thicker CT surrounding a group of fibers to form a fascicle Endomysium – delicate layer of reticular fibers surrounding individual muscle fibers Connective Tissue Components Primary Proteins Sliding Filament Theory Triad System Triad Neuromuscular Junction Motor Endplates of Skeletal Muscle Accessory proteins Accessory proteins maintain precise alignment of thin and thick filaments. Titin forms an elastic lattice that anchors thick filaments in the Z lines and help prevent excessive stretching of the sarcomere. α-Actinin bundles thin filaments into parallel arrays and anchors them at the Z line. Nebulin helps α-actinin anchor thin filaments to Z lines and is thought to regulate the length of thin filaments during muscle development. Tropomodulin maintains and regulates the length of the sarcomeric actin filament. Desmin forms a lattice that surrounds the sarcomere at the level of the Z lines, attaching them to one another and to the plasma membrane, thus forming stabilizing cross-links between neighboring myofibrils. Myomesin holds thick filaments in register at the M line C protein forms several distinct transverse stripes on either side of the M line Dystrophin is responsible for linking (as anchors) the internal cytoskeletal system of individual myofibers and provide support to structural proteins within the extracellular matrix. Duchenne muscular dystrophy (DMD) Myasthenia Gravis Cardiac vs. Skeletal Muscle Three types of cell junction make up an intercalated disc: fascia adherens, desmosomes and gap junctions. Fascia adherens are anchoring sites for actin and connect to the closest sarcomere. Desmosomes stop separation during contraction by binding filaments, joining the cells together. Desmosomes are also known as macula adherens. Gap junctions allow action potentials to spread between cardiac cells by permitting the passage of ions between cells, producing depolarization of the heart muscle. Myocardial Infarction A localized injury to cardiac muscle tissue that results in the death of cells is repaired by replacement with fibrous connective tissue. Consequently, cardiac function is lost at the site of injury. This pattern of injury and repair is seen in nonfatal myocardial infarction (MI). Specific markers in the blood confirm MI. These markers are the structural subunits TnI and TnT of the cardiac troponin complex. They are usually released into the bloodstream within 3 to 12 hours after an MI and remains elevated for up to 2 weeks. Actin and Myosin are randomly arranged. Smooth Muscle Chronic Asthma Respiratory airways are hypersensitive and hyperresponsive to a variety of stimuli. Clinical findings include airflow obstruction caused by smooth muscle constriction around airways, airway mucosal edema, intraluminal mucus accumulation, inflammatory cell infiltration in the submucosa, and basement membrane thickening. Pathologic findings include thickening of smooth muscle layer (hypertrophy and hyperplasia).  Terms to know: Autoimmune disease: A condition in which an individual’s immune system mistakes the individual’s own tissue for a foreign invader and attacks the tissue, as in myasthenia gravis or multiple sclerosis. Caveolae: Small, cup-shaped indentations in the sarcolemma of smooth muscle cells; may be involved in the uptake of calcium during contraction. Dystrophin: A large, rod-shaped protein that plays a critical role in connecting the molecular contractile mechanism of skeletal muscle to the surrounding extracellular matrix so that the force of the actin-myosin contraction can be transferred to other structures to do useful work. The lack of dystrophin is a key feature of some types of muscular dystrophies. Fibrosis: Abnormal formation of connective tissue, including fibroblasts and connective tissue fibers, to replace normal tissues in response to tissue damage caused by disease or injury. Synaptic cleft: The small space between a presynaptic axon terminal and the postsynaptic membrane of a muscle cell or a neuron upon which the axon forms a synapse. Varicosity: A local swelling in a tube-like structure such as an axon.