BIOL 141 Lecture 5 notes
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This 3 page Class Notes was uploaded by Camryn McCabe on Tuesday February 9, 2016. The Class Notes belongs to Biol 141 at a university taught by Janelle Malcos in Spring 2016. Since its upload, it has received 24 views.
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Date Created: 02/09/16
Lecture 5 notes Muscle System Muscle Properties o Excitability- respond to chemicals released from motor neurons o Conductivity- ability to propagate electrical signals over membrane o Contractility- ability to shorten and generate force o Extensibility- ability to be stretched without damaging tissue o Elasticity- ability to return to original shape after stretched Muscle Tissue o Skeletal o Voluntary o Striated o Multinucleate (multiple nuclei per cell) o Attached to bone, skin, fascia (connective tissue) o Cardiac o Involuntary o Streated o Mononucleate (one nucleus per cell) o Autorhythmic (cells can self-regulate contraction; ability to excite themselves) o Instead of really long (like skeletal), highly branched and connected to each other o Smooth o Involuntary o Non-striated o Mononucleate o Hair follicles, walls of hollow organs Muscle Fascicles Muscle cells Myofibrils Myofilaments Group ofGroup Filled Have 3 types fasciclesof w/long of proteins muscle bundles of (myofilament cells proteins s). (myofibril Organized into s) sarcomeres Sarcomere- “contractile unit” of muscles o Mitochondria are near the muscle proteins that use ATP during contraction Sarcolemma- muscle cell membrane o Has transverse tubules (T-tubules)- tube-like structures which penetrate the interior of the cell Filled with extracellular fluid Lecture 5 notes Muscle System Sarcoplasm- cytoplasm of a muscle cell o Inside sarcoplasm: Myofibrils- long bundles of proteins Myoglobin- stores oxygen for use Binds oxygen for storage Glycogen- polymer of sugar Sarcoplasmic reticulum (SR)- muscle cell ER o Terminal cisternae- sacs of the SR, closely associate w/T- tubulues T-tubules and SR are able to exchange ions o Storage area for calcium ions in the muscle cell Myofibrils- bundles of 3 types of myofilaments (proteins) o Thick filaments- myosin protein Consist of a polymer of myosin proteins Consists of 100s of myosin proteins Single myosin- shaped like a golf club Head is mobile to extend and flex (bend or extend) Myosin can bind and hydrolyze ATP Release of energy allows head to change shape (aka bend or extend), therefore generating force o Thin filaments- actin protein Consist of a polymer of actin WITH troponin and tropomyosin accessory proteins Each actin monomer has an active site that can bind to the head of a myosin protein (myosin-binding site) Myosin in actin bind to each other Tropomyosin blocks active site of myosin in relaxed muscles Troponin binds to and regulates tropomyosin When Ca is present, troponin moves tropomyosin off active sites of actin o Elastic filaments- titin protein Together they form the sarcomere o Sarcomere = “organization of proteins” Structure of Sarcomere o A Band- thick filament Dark in color Partially overlaps w/thin filaments Lecture 5 notes Muscle System Lighter in color at H Band H Band = only thick filament (myosin) Length of myosin o I Band- thin filament only (actin) Light in color o Z disc- edge of sarcomeres Zwischen German for between Middle of actin 1 Sarcomere = 1 Z disc to another Z disc o M line- middle of sarcomere Mittel German for middle o Both Z disc and M line contain accessory proteins for stabilization Pattern of dark and light are the striations o There is sliding between filaments helps facilitate a contraction Sarcomere Contraction o Sliding filament theory: During contraction, thin filaments are pulled along thick filaments toward M-line of the sarcomere H Band and I Band shrink in size A Band stays consistent Uses ATP For the muscle to contract as a whole, need contraction of all sarcomeres, in all myofibrils, in all muscle cells
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