Muscular System

Muscular System - Muscular System Assigned Readings:...

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Muscular System Assigned Readings: Chapter 9 (all of it pp. 247-283) Lecture Outline I.Overview of Muscle Tissues A. Types of Muscle Tissue 1. Skeletal muscle 2. Cardiac muscle 3. Smooth muscle B. Functional Characteristics of Muscle Tissue 1. Excitability 2. Contractility 3. Extensibility 4. Elasticity C. Muscle Functions 1. Produce movement 2. Maintaining posture 3. Stabilize joints 4. Generate heat II. Skeletal Muscle A. Gross Anatomy of Skeletal Muscle 1. Nerve and blood supply – cappilaries and nerve cells wrap around, nerves and neurons are making contact with individual muscle cells 2. Connective tissue sheaths: endomysium, perimysium, epimysium – fascicle is a grouping of several muscle cells, and these groups make up a muscle body. Epimysium is the outermost connective
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tissue and surrounds muscle body and contributes to tendon, Perimysium surrounds the fascicle, endomysium is on the inside between individual muscle cells. All 3 of these connective tissues span the entire length of the muscle and extend to contribute to the tendon 3. Attachments span joints; origin and insertion – each muscle body has an origin and insertion, origin is where it originates and insertion is where it terminates, usually origin is the more stable and proximal (closer to body) – Direct attachments, indirect attachments (tendons) B. Microscopic Anatomy of a Skeletal Muscle Fiber Dark band is A band, Light band is I band, and alternate, Sarcolemma is cell membrane, Nuclei lie on outside of cell so not to get in the way of fibers, lots of mitochondria in muscle cells 1. Muscle “fibers” 2. Myofibrils – contractile organelle which spans the entire length of the cell, hundreds of these in a muscle cell and do the actual work 3. Myofilaments – make up myofibrils, make the stripes a. Thick filaments - composed myosin - b. Thin filaments - composed of strands of actin Tropomyosin and troponin are regulatory proteins – are also in the thin actin filaments and can start and regulate contractions o Sarcomere is one contractile unit of muscle that repeats, change their length when they contract (sliding filament theory) actin and myosin overlap one another and myosin produces movement by grabbing actin and pulling actin toward the center M- line which makes the Z-disks move close to one-another o Z- disk holds actin so that they face one another with myosin in between held by the M-line o Myosin binding sites found on actin, any given myosin head is in close proximity to the binding sites on actin
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o Troponin and Tropomyosin regulate the availability of the binding sites of actin, if tropomyosin is present, myosin cannot bind to actin. Troponin acts as the intermediate between tropomyosin and actin, when troponin receives a signal to contract, it moves and takes tropomyosin with it o Calcium is intracellular signal that tells troponin to start to contract
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This note was uploaded on 03/24/2009 for the course BIOL 252 taught by Professor Johnson during the Spring '07 term at UNC.

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Muscular System - Muscular System Assigned Readings:...

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