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Muscle Tissue
Lecture Unit 1
Question | Answer |
---|---|
Properties of muscle tissue | EXCITABILITY: Responds to stimuli from neurons. CONTRACTILITY: Is able to shorten. Flex muscles, shorter & fatter. ELASTICITY: Can recoil after contraction. EXTENSIBILITY: Capable of stretching during flexion of antagonistic muscles. |
Functions of muscle tissue | MOVEMENT-works with skeletal system. MAINTENANCE OF POSTURE. TEMPERATURE REGULATION. STORAGE & MOVEMENT OF MATERIALS. SUPPORT ABDOMINAL ORGANS. JOINT STABILIZATION-muscle tone. |
Three Types of muscle tissue | Cardiac-only in heart, Smooth-all organs, blood vessels, Skeletal-attached to skeleton. |
Characteristics of cardiac muscle | In myocardium. Fibers Y shaped/branched. Uninucleated (small percentage are binucleated). Striated-striped dark and light proteins. Involuntary. Intercalcated discs-junction point between heart cells. Auto-rhythmic-contracts 100b/m w/o nervous system. |
Characteristics of smooth muscle | In walls of visceral organs. Fusiform shape (wide middle and tapered at each end). Uninucleate. No striations. Involuntary. Fatigue resistant. |
Characteristics of skeletal muscle | Made of cylindrical muscle cells (myofibers). Fiber-like (long and cylindrical) Multinucleate-from fused myoblasts. Striated. Voluntary. Contains myoglobin-O2 binding pigment. Innervated-neuromuscular junctions. Vascular. |
Myoblasts fuse to form a: | Skeletal muscle fiber. Myoblasts become multi-nucleated. |
Connective tissue wrappings | Endomysium, Perimysium, Epimysium, Deep Fascia, All four are continuous with the tendon. Help produce movement. |
Endomysium | Surrounds each muscle fiber. Areolar and reticular fibers. |
Perimysium | Surrounds groups of muscle fibers (fascicles). Dense irregular CT. |
Epimysium | Surrounds whole muscle (group of fascicles). Dense irregular CT. |
Deep fascia | Surrounds muscle groups. Dense irregular CT. Superficial. |
Muscle attachments | Tendons, Origin, Insertion. |
Tendons | Attach muscle to bones, skin, cartilage. Aponeruosis is a flat tendon (ex. galea aponeruotica). |
Origin | Less movable attachment of muscle. |
Insertion | More movable attachment of muscle. |
Microscopic Anatomy | Sarcolemma, Sarcoplasm, Transverse tubules or T-tubules, Sarcoplasmic reticulum. |
Sarcolemma | Cell membrane |
Sarcoplasm | Cytoplasm |
Transverse tubules or T-tubules | Invaginations of sarcolemma. Conduct impulses to deepest regions of cell |
Sarcoplasmic reticulum | Elaborate smooth ER. Surrounds each myofibril. Stores calcium. Contains terminal cisternae-site of calcium release. Right next to T. tubules. |
Order of muscle organization. Largest to smallest | 1. Muscle 2. Facicle 3. Myofiber 4. Myofibrils 5. Myofilaments |
Myofibrils | Found inside of muscle fibers. Shorten during muscle contraction. Long row of repeating segments-sarcomeres. Composed of myofilaments. Organelle. |
Myofilaments | Composed of thin and thick filaments. Thin filaments: actin, troponin, and tropomyosin. Thick filaments: Myosin. Be able to label all 4. Troponin/Tropomyosin complex=TTC-referred to together. Molecule. |
Sarcomeres | Functional unit of the skeletal muscle fiber. Responsible for striated appearance of muscle. Defined from z disc (or line) to z disc. |
Sliding Filament Theory (Steps 1-3) | 1. Nerve impulse causes sarcoplasmic reticulum to release Ca from terminal cisternae. 2. Ca binds to troponin. 3. Troponin-Tropomyosin complex (TTC) slides off of binding sites on actin. |
Sliding Filament Theory (Steps 4-6) | 4. Myosin heads (thick filaments) attach to actin (thin fil). 5. Heads swivel inward, pulling the actin toward center of sarcomere. 6. Myosin heads release; process repeated. (Actin-myosin binding powered by ATP & triggered by Ca2+). |
Rigor Mortis | Death is not an event but a process. Tissues continue to live after the brain, heart, and lungs fail. A few hrs after death, ATP runs out: Myosin cant detach from actin. Calcium cant be taken up by SR. Leads to continual muscle contration. |
After Rigor Morits | After 15-24 hours the myofibrils begin to deteriorate allowing muscles to relax. Random twitching can occur. Cells live until they run out of oxygen and glucose. Muscle cells live for 1-2 days. Skin/hair can live for a couple of weeks. |
Tetanus | Caused by the bacterium Clostridium tetani. Excessive muscle contraction. Stuck contracted, over contracted. |
Botulism | Caused by the bacterium Clostridium botulinum. Muscular paralysis. Under contration. Botox approved by FDA in 2002. Lessen appearance of wrinkles by paralyzing muscles. Effects last for 120 days. |
Terminal cisternae | dead-end sacs of the sarcoplasmic reticulum that border T-tubules, calcium is stored here |