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BIOL 141 Lecture 5 notes

by: Camryn McCabe

BIOL 141 Lecture 5 notes Biol 141

Marketplace > Science > Biol 141 > BIOL 141 Lecture 5 notes
Camryn McCabe
Penn State
GPA 3.81

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notes on the muscle system
Janelle Malcos
Class Notes
Bio, Physiology, muscle system
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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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