L16 NPB 101 - Lecture 16 •  SmartSite: – ...

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Unformatted text preview: Lecture 16 •  SmartSite: –  Lecture 16 Notes •  Review –  Sleep/Wake •  Announcements: –  None •  Muscle –  Skeletal muscle •  Reading (Recommended): –  Relevant por<ons of Chapter 8 1 REV: Hypothalamus & Sleep •  Hypothalamus important in many regulatory func<ons. •  EEG provides electrical informa<on related to cor<cal synap<c ac<vity. •  Sleep defini<on based on EEG paOerns (along with Eye and Muscle electrical paOerns). •  Sleep is an ac<ve process ac<vated by the VLPO •  Sleep Depriva<on alters our physiological capacity in many systems 2 –  Slow Wave Sleep (80%) –  Paradoxical (REM) Sleep (20%) –  90 minute cycles for a total of about 7.5 hours/night Muscle Physiology 3 Muscle •  Comprises largest group of <ssues in body •  Three types of muscle –  Produce force; different control mechanisms –  Similar contrac<le mechanisms; different morphologies –  Skeletal muscle (40 ­50% of body mass) –  Smooth muscle (5 ­10% of body mass) –  Cardiac muscle •  Make up muscular system  ­ voluntary •  Appears throughout the body systems as components of hollow organs and tubes – involuntary; ANS control •  Found only in the heart •  Classified in two different ways –  Striated or unstriated –  Voluntary or involuntary 4 Categoriza<on of Muscle Fig. 8 ­1; pg. 258 5 Muscle •  Controlled muscle contrac<on allows –  Purposeful movement of the whole body or parts of the body –  Manipula<on of external objects –  Propulsion of contents through various hollow internal organs –  Emptying of contents of certain organs to external environment 6 Skeletal Muscle Contrac<on Fig. 8 ­13; pg. 268 7 Structure of Skeletal Muscle •  Muscle consists a number of muscle fibers lying parallel to one another and held together by connec<ve <ssue. •  Single skeletal muscle cell is known as a muscle fiber: –  Mul<nucleated –  Large, elongated, and cylindrically shaped –  Fibers usually extend en<re length of muscle 8 Structure of Skeletal Muscle •  Myofibrils –  Contrac<le elements of muscle fiber –  Regular arrangement of thick and thin filaments •  Thick filaments – myosin (protein) •  Thin filaments – ac<n (protein) •  Sarcomere –  Func<onal unit of skeletal muscle –  Found between two Z lines (connects thin filaments of two adjoining sarcomeres) 9 Structure of Skeletal Muscle Fig. 8 ­2ab; pg. 259 10 Structure of Skeletal Muscle 2 Kinds of Protein Contrac1le Regulatory Fig. 8 ­2cd; pg. 259 11 Myosin •  Component of thick filament •  Protein molecule consis<ng of two iden<cal subunits shaped somewhat like a golf club –  Tail ends are intertwined around each other –  Globular heads project out at one end •  Tails oriented toward center of filament and globular heads protrude outward at regular intervals –  Heads form cross bridges between thick and thin filaments •  Cross bridge has two important sites cri<cal to contrac<le process –  An ac<n ­binding site –  A myosin ATPase (ATP ­splifng) site 12 Structure and Arrangement of Myosin Molecules Within Thick Filament Fig. 8 ­4; pg. 260 13 Ac<n •  Primary structural component of thin filaments •  Spherical in shape •  Thin filament also has two other proteins –  Tropomyosin and troponin •  Each ac<n molecule has special binding site for aOachment with myosin cross bridge –  Binding results in contrac<on of muscle fiber 14 Ac<n & Myosin •  Ac<n and myosin are ohen called contrac<le proteins. Neither actually contracts. •  Ac<n and myosin are not unique to muscle cells, but are more abundant and more highly organized in muscle cells. 15 Tropomyosin and Troponin •  Ohen called regulatory proteins •  Tropomyosin –  Thread ­like molecules that lie end to end alongside groove of ac<n spiral –  In this posi<on, covers ac<n sites blocking interac<on that leads to muscle contrac<on –  Made of three polypep<de units •  One binds to tropomyosin •  One binds to ac<n •  One can bind with Ca2+ •  Troponin 16 Composi<on of a Thin Filament Fig. 8 ­5; pg. 261 17 Tropomyosin and Troponin •  Troponin –  When not bound to Ca2+, troponin stabilizes tropomyosin in blocking posi<on over ac<n’s cross ­bridge binding sites –  When Ca2+ binds to troponin, tropomyosin moves away from blocking posi<on –  With tropomyosin out of way, ac<n and myosin bind, interact at cross ­bridges –  Muscle contrac<on results 18 Role of Calcium in Cross ­Bridge Forma<on Fig. 8 ­6; pg. 262 19 Sliding Filament Mechanism •  Cross ­bridge interac<on between ac<n and myosin brings about muscle contrac<on by means of the sliding filament mechanism. 20 Sliding Filament Mechanism •  Increase in Ca2+ starts filament sliding •  Decrease in Ca2+ turns off sliding process •  Thin filaments on each side of sarcomere slide inward over sta<onary thick filaments toward center of A band during contrac<on •  As thin filaments slide inward, they pull Z lines closer together •  Sarcomere shortens •  All sarcomeres throughout muscle fiber’s length shorten simultaneously •  Contrac<on is accomplished by thin filaments from opposite sides of each sarcomere sliding closer together between thick filaments 21 Changes in Sarcomere During Shortening Fig. 8 ­8; pg. 263 22 ...
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