Muscles Lecture - Skeletal, Smooth & Cardiac Muscle PDF

LECTURE 3 Muscular Tissues - Properties - Types Skeletal Muscle - Gross anatomy - Microanatomy - Contraction  Basic Properties of Muscle 1. Excitability M · The ability to respond toStimuli: 2. Contractility ability...

LECTURE 3 Muscular Tissues - Properties - Types Skeletal Muscle - Gross anatomy - Microanatomy - Contraction  Basic Properties of Muscle 1. Excitability M · The ability to respond toStimuli: 2. Contractility ability to shortenf Loading… z · The exert a guil or tension 3. Extensibility to contract of resting lengths st · The ability over a range 4. Elasticity The ability to rebound to its original length · N Muscle Types  Cardiac Muscle (striated involuntary muscle) only associated with the heart Cells are short branched & stricted , , one nucleus Cells connected by intercalated dises Loading… Pulsating/rythmic contractions Can not regenerate * Lab Cardiac Muscle (striated involuntary muscle) Card u iac mus cle cells Nuc D lei Mate In Intercal ated nu discs Striations Figure 3.22b  Smooth Muscle (nonstriated involuntary muscle) non stricted centre nucleus I · Cells are short , spindle shaped , , one Can divide & regenerate I · ⑳ Base of hair follicles, walls of blood vessels, lining the urinary bladder, respiratory, circulatory, digestive, & reproductive tracts A lab Smooth Muscle (nonstriated involuntary muscle) Nucle uS us auf M Smo · oth musc e le cells  Skeletal Muscle (striated voluntary muscle) Incapable of cell reproduction *Myosatellite cells can reproduce for muscle repair* Cells are long cylindrical , , - strictedIn multinucleated Voluntarily the skeleton moves - - LM × 180 Striations Nuclei Muscle fiber  Functions of Skeletal Muscles 1. I Produce Skeletal movement Af. 2. Maintain posture and body position ↑ 2. 3. 3. Support of soft tissue I 4. 5. 4. 5. Regulate entering and exiting of material Maintain body temp. + Gross Anatomy of Skeletal Muscle Connective tissueSKELETAL MUSCLE Surrounded by: Muscle Epimysium Contains: Muscle fascicles Muscle fasicle Muscle fibre Loading… MUSCLE FASCICLE Surrounded by: Perimysium Contains: Muscle fibers I MUSCLE FIBER Surrounded by: Endomysium Contains: Myofibril s Figure 9.5  Connective Tissue Tendon: Attaches muscle to bone Each muscle has 3 layers: 1. Epimysium: Surrounds entire muscic 2. Perimysium: Divides muscle into sections called fasicles 3. Endomysium: Surrounds induvidual muscie fibres  EpimysiuM m nume Muscie Fasicle Muscle Muscle fibers a fascicle Endomysium Perimysium SKELETAL MUSCLE (organ) Perimysium Muscle fiber Endomysium Epimysiu m Blood vessels and nerves MUSCLE FASCICLE (bundle of cells) Capillary Mitochondria Endomysium Endomysium Sarcolemm a Myosatellite Tendon cell Myofibril Perimysiu Axon Sarcoplas Nucleus m m MUSCLE FIBER (cell) Figure 9.1 Microanatomy of Skeletal Muscle Fibers Muscle Fiber MUSCLE FIBER Surrounded by: Endomysium Contains: Myofibril Myofibril s Sarcomeres MYOFIBRI L r Surrounded by: myofilaments Sarcoplasmic reticulum Consists of: Sarcomeres (Z line to Z line) · SARCOMER EI A a band band Contains: Thick filaments Thin filaments Z M line Titin Z line H line band  Muscle Fiber (muscle cell) Can be 30–40 cm in length h ⑳ Multinucleate (each muscle cell has hundreds of nuclei) · · Nuclei under the sarcoleman Muscle fibers run parallel to each other & Myosatellite cells (assist in repair and regeneration) (right under the sarcolemma)  External Organization of muscle · Stores calcium fiber *TRIAD  Myofibrils Highly organized bundles of contractile protein majority of the volume in a muscle fibre (cell) Surrounded by sarcoplasmic reticulum Where force generation takes place Made up of sarcomeres joined end to end Sarcoplasmic reticulum  The Myofibril Fibr C e Wh Myofibril Sarcomere  Sarcomere smallest functional unit of skeletal muscle made of myofilaments Actin-thin protein filaments filaments Myosin-thick protein -  Myofilaments ACTIN MYOSIN D 8o Make up the thin and thick filaments…the contractile machinery of the muscle cell  Sarcomere - thin - thick · thin filaments  The Sarcomere M-line: centre of A-band where myosin filaments are held together * Z-disc: centre of I-band where actin filaments are held together I-band: made of only of actin filaments (light region) A-band: myosin filaments with overlapping actin filaments at edges (dark region) Figure 9.4b * The Sarcomere I-band A-band Z-disc M-line H-Zone Figure 9.4b  SKELETAL MUSCLE Surrounded by: Summary Epimysium Contains: Muscle fascicles Skeletal muscles consist of muscle fascicles MUSCLE FASCICLE Surrounded by: Perimysium Muscle fascicles consist of muscle fibers Contains: Muscle fibers ↑ Muscle fibers consist - C of myofibrils MUSCLE FIBER Surrounded by: Endomysium Contains: Myofibril s Myofibrils consist of sarcomeres almmmmt MYOFIBRI L Sarcomeres consist of myofilaments 1( Surrounded by: Sarcoplasmic reticulum Consists of: Sarcomeres (Z line to Z line) Myofilaments are made of actin · A and myosin SARCOMER EI A band band Contains: mmm Thick filaments Thin filaments Z M line Titin Z Figure 9.5 line H band line  Contraction of a Muscle Fiber Excitation-Contraction Coupling: 1. Excitation phase 2. Contraction phase  Contraction Phase Muscle shortens in length caused by interactions between thick & thin filaments in the sarcomere Triggered by the presence of calcium ions Requires ATP When a muscle contracts, actin filaments slide toward each other – Sliding Filament Theory Myosin and actin interaction: ATP to ADP 2+ Mg An 2+ O Cast m Ca W 2+ Dr. Rene Vandenboom  Sliding Filament Theory I-band Upon contraction: Hand f I band get smaller zone of overlap gets larger 2 linesmore closer together Myosin filaments do not move ⑭ H-Zone Actin filaments slide on myosim Titin limits length of sarcomere  Contractile cycle s 1. ↑ Rigor State S Myosim head is tightly bound to activ active site g ↓ d ATP bound the myosin & There is ne to Cross-bridge is at 45° relative to the filaments Loading… · S 2 M 45 ° Myosin filament Myosin ATP binding binding sites site 2 3 4 1 Actin molecule Figre 9.7  Contractile Cycle t 1.. 2 Myosin Release · ATP binds to Myosin head I Affinity of Myosin for Actin is decreased · Cross-bridge is broken ATP 1 2 3 4  Contractile Cycle Get 1. 3 ATP Hydrolysis. ATP is broken down S Energy released allows myosin head to move down actin filament into “cocked” position ADP P i 1 2 3 4  Contraction Cycle G 1. 4. Myosin Reattaches to the activ active site Myosin head binds weakly · occurs oneltwa positions away from 1st · Binding & The myosin head is still in it’s “cocked” position 90° P i 1 2 3 4  Contraction Cycle g 1. 5. Power Stroke P: released from myosin head is ↳ - & This strengthens the bond between actin and myosin head towards the M-line with · Myosim head swings , pulling actio it P i 1 2 3 4 5 Actin filament moves toward M line.  Contraction Cycle A 1. 6. ADP Release · During power stroke ADD is released & Cross-bridge is returned to rigor state awaiting ATP and next cycle ADP 1 2 3 4 5  Contraction Cycle The rigor state is a strong bond As long as cat" is present , myosin will be able to bind Allows a series of cycles to cause large contractions Neuromuscular Junction Fig. 9- 8  Neuromuscular Junction Neuromuscular synapse Skeletal muscle fiber Axon Nerve LM x 230 SEM x 400 a A neuromuscular synapse as seen b Colorized SEM of a neuromuscular on a muscle fiber of this fascicle synapse Figure 9.2  Excitation Phase An impulse travels down the of 1. axon merve a 2. Acetylcholine mo is released from the end of the axon into the neuromuscular synapse 3. This causes an action potential and ultimately causes the sarcoplasmic reticulum to release its stored calcium ions 4. Calcium binds to active site on activ 5. the contraction of the muscic Begins  Neuromuscular Junction R&K Fig 5.4 or W&C Fig 1.8 Triad: SR and T-Tubules STEPS IN INITIATING MUSCLE CONTRACTION STEPS IN MUSCLE RELAXATION Synapti C Motor c Alt end plate T tubule Sarcolemm terminal a 2 Action 1 ACh released, binding 6 potential ACh removed by to receptors reaches AChE T tubule 3 Sarcoplasmic 7 Sarcoplasmic reticulum reticulum releases Ca2+ recaptures Ca2 t Ca2+ + · 4 Active-site Actin 8 Active sites exposure, cross- covered, no bridge Myosi cross-bridge formation n interaction 9 Contractio n 5 Contractio ends n begins 1 Relaxation occurs, 0 passive return to resting length Figure 9.9  Excitation-Contraction Coupling The excitation of the sarcolemma and T-tubules leads to release of Ca2+ from SR Thus excitation and contraction are “coupled” Neural signal conveyed to the contractive machinery  Skeletal Muscle Fiber Organization Muscles can be classified based on shape or by the arrangement of the fibers – Parallel muscle fibers – Convergent muscle fibers -start wide converge , narrow – Pennate muscle fibers tendon along muscle running angular - , Unipennate muscle fibers Bipennate muscle fibers Multipennate muscle fibers – Circular muscle fibers  Parallel Muscles Convergent Muscles a Parallel muscle b Parallel muscle with c Wrapping d Convergent muscle (Biceps brachii muscle) tendinous bands muscle (Pectoralis muscles) (Rectus abdominis (Supinator) muscle) Tendon Base of muscle (h) Fascicle (d) Cross (g) section Body (a) (belly) (b) Cross section (e) (c) (f) Pennate Muscles Circular Muscles e Unipennate f Bipennate g Multipennate muscle h Circular muscle Muscle (Extensor muscle (Deltoid muscle) (Orbicularis oris muscle) digitorum muscle) (Rectus femoris muscle) Contracted Tendons Extended tendon Relaxed Cross section Figure 9.12 © 2015 Pearson Education, Inc.  FACTORS INFLUENCING THE MOTION AND POWER OF MUSCLES 1. Shape of the muscle of muscle Fibers 2. # immun 3. Size of muscle Fibers 4. Orientation Da of muscle cells relative to their & tendon  Muscle Action Terminology Muscles can be grouped according to their primary actions: & 1. Y Prime movers (agonists) 2. Antagonists: - Actions oppose the action of the agonist 3. ↑ Synergists: Assist the prime mover in performing an action 4. Fixators: Agonist & antagonist muscles F contracting at the same - time to stabilize a joint Muscle Action Terminology  Levers and Pulleys: Movement Most of the time, upon contraction, a muscle causes action D % This action is applied to a lever (a bone) This lever moves on a fixed point called the fulcrum (joint) The action of the lever is opposed by a force acting in the opposite direction 28  Three classes of levers First class: The fulcrum (joint) lies between the agplied force& the resistance force lapped force)  Three classes of levers Second class: The resistance is located between the applied Force & the Fulcrum (joint)  Three Classes of Levers Third class: The force is applied between the resistance of the fulcrum  - - Pulleys Sometimes, a tendon may loop around a bony projection (i.e. lateral malleolus or platella) direction of force & Changing Ease & efficiency F Patella Lateral malleolus of fibulla Figure 9.13 The Muscular System Not is this class……………………… The END!