Muscle tissue. Types. Functions. Cardiac, Smooth, and Skeletal

Transcription

1 Types Cardiac, Smooth, and Skeletal Functions movements posture and body position Support soft tissues Guard openings body temperature nutrient reserves Muscle tissue

2 Special Characteristics of Muscle Tissue Excitability: responsiveness Contractility: shortening Extensibility: streching Elasticity: recoil to resting length 2013 Pearson Education, Inc.

3 Skeletal Muscle Anatomy Macroscopic & Microscopic

4 connective tissues Tendon vs. aponeurosis Epimysium Perimysium Endomysium

5 Bone Tendon Epimysium Epimysium Perimysium Endomysium Muscle fiber Blood vessel Perimysium Endomysium Muscle fiber Fascicle Perimysium 2013 Pearson Education, Inc.

6 Myofibrils vs. Sarcomeres Z-lines I band: Extends from A band to A band A band M line: Connects thick filament H band: Lighter region around M line

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8 Myofilament Structure Thin filaments G-actin vs. F-actin Regulatory proteins: Tropomyosin and Troponin Thick filaments Myosin tails Myosin heads ATPase Binding sites for ATP Binding sites for actin

9 Figure 9.3 Composition of thick and thin filaments. Longitudinal section of filaments within one sarcomere of a myofibril Thick filament Thin filament Thick filament. Each thick filament consists of many myosin molecules whose heads protrude at oppositeends of the filament. Portion of a thick filament In the center of the sarcomere, the thick filaments lack myosin heads. Myosin heads are present only in areas of myosin-actin overlap. Thin filament A thin filament consists of two strands of actin subunits twisted into a helix plus two types of regulatory proteins (troponin and tropomyosin). Portion of a thin filament Myosin head Tropomyosin Troponin Actin Actin-binding sites Heads ATPbinding site Flexible hinge region 2013 Pearson Education, Inc. Myosin molecule Tail Actin subunits Actin subunits Active sites for myosin attachment

10 Specialized parts of muscle cells Sarcoplasmic reticulum tubular network around myofibrils T tubule + terminal cisternae = triad

11 Sarcoplasmic reticulum (SR) Ca 2+ Gated calcium channel (closed) Sarcoplasm Calcium ion pump The membrane of the sarcoplasmic reticulum, which contains calcium ion pumps

12 Specialized parts of muscle cells Sarcolemma Maintains distribution of (+) and (-) charges = Transmembrane potential transmembrane potential changes transmitted along entire muscle cell surface travel along T tubules to cell interior

13 sliding filament model of muscle contraction during contraction Sarcomere shortening thin filaments slide past thick filaments

14 sliding filament model 14

15 For skeletal muscle to contract Phase 1) Activation Action potential ACh Exocytosis Ion permeability of sarcolemma Electrical events Local depolarization => Action potential (AP) Phase 2) Excitationcontraction coupling AP travels along sarcolemma & T-tubules Release of Ca2+ Sliding filament mechanism

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19 Activation: Phases of Action Potential

20 Activation: Events in Generation of an Action Potential 1) Depolarization reduction in membrane potential End plate potential spreads to adjacent areas VG Na + -channels open Na + influx Change in Membrane voltage Threshold = critical voltage

21 Activation: Events in Generation of an Action Potential 2) AP spreads across sarcolemma VG Na+ channels open in adjacent patch depolarize to threshold 2013 Pearson Education, Inc.

22 Activation: Events in Generation of AP 3) Repolarization restoring electrical conditions membrane potential VG K + channels open refractory period Fiber cannot be stimulated until repolarization completes Na + -K + pump Restores ionic conditions of resting state

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24 Motor neuron Acetylcholine 1 release of acetylcholine at the neuromuscular junction causes an electrical impulse to be generated Electrical impulse 2 The electrical impulse ( ) T tubule Sarcoplasmic reticulum 3 triggers the release of Ca 2+ Muscle cell plasma membrane Myofibrils Z-line Figure 6.6

25 Excitation-Contraction (E-C) Coupling Excitation Events that transmit AP along sarcolemma contraction sliding of myofilaments Latent period

26 Cross Bridge Cycle series of events during which myosin heads pull thin filaments toward the center of the sarcomere Dependent on Ca2+ ATP 2013 Pearson Education, Inc.

27 Cross Bridge Cycle

28 Homeostatic Imbalance Rigor mortis 3 4 hours post-mortem Peaking at 12 hours post mortem 2013 Pearson Education, Inc.