PowerPoint ® Lecture Slide Presentation by Patty Bostwick-Taylor, Florence-Darlington Technical College Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PART A 6 The Muscular System

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Muscular System  Muscles are responsible for all types of body movement  Three basic muscle types are found in the body  Skeletal muscle  Cardiac muscle  Smooth muscle

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Characteristics of Muscles  Skeletal and smooth muscle cells are elongated (muscle cell = muscle fiber)  Contraction of muscles is due to the movement of microfilaments  All muscles share some terminology  Prefixes myo and mys refer to “muscle”  Prefix sarco refers to “flesh”

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Comparison of Skeletal, Cardiac, and Smooth Muscles Table 6.1 (1 of 2)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Characteristics  Most are attached by tendons to bones  Cells are multinucleate  Striated—have visible banding  Voluntary—subject to conscious control

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Connective Tissue Wrappings of Skeletal Muscle  Cells are surrounded and bundled by connective tissue  Endomysium—encloses a single muscle fiber  Perimysium—wraps around a fascicle (bundle) of muscle fibers  Epimysium—covers the entire skeletal muscle

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Connective Tissue Wrappings of Skeletal Muscle Figure 6.1

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Attachments  Epimysium blends into a connective tissue attachment  Tendons—cord-like structures  Mostly collagen fibers  Often cross a joint due to toughness and small size  Aponeuroses—sheet-like structures  Attach muscles indirectly to bones, cartilages, or connective tissue coverings

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings

Skeletal Muscle Attachments  Sites of muscle attachment  Bones  Cartilages  Connective tissue coverings

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle Characteristics  Lacks striations  Spindle-shaped cells  Single nucleus  Involuntary—no conscious control  Found mainly in the walls of hollow organs

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle Characteristics Figure 6.2a

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Muscle Characteristics  Striations  Usually has a single nucleus  Branching cells  Joined to another muscle cell at an intercalated disc  Involuntary  Found only in the heart

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Muscle Characteristics Figure 6.2b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Functions  Produce movement  Maintain posture  Stabilize joints  Generate heat

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle  Sarcolemma—specialized plasma membrane  Myofibrils—long organelles inside muscle cell  Sarcoplasmic Reticulum- sacs that contain Calcium  T-tubules  Channels that carry a nerve impulse  Not found in smooth muscle  Cisternae- part of the SR next to the t-tubule  2 cisternae and one t-tubule form a triad  Allows electrical impulse to travel quickly

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle  Thick filaments = myosin filaments  Composed of the protein myosin  Has ATPase enzymes  Myosin filaments have heads (extensions, or cross bridges)  Myosin and actin overlap somewhat

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle  Thin filaments = actin filaments  Composed of the protein actin  Anchored to the Z disc (line)  Have troponin and tropomyosin  Keep muscles from contracting  Can be removed by calcium

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle  Myofibrils are aligned to give distinct bands  I band = light band  Contains only thin filaments  A band = dark band  Contains the entire length of the thick filaments

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle  Sarcomere—contractile unit of a muscle fiber  Basic unit of muscle  Segment between two z lines  Makes muscles look striated  Organization of the sarcomere  Myofilaments  Thick filaments = myosin filaments  Thin filaments = actin filaments

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle Figure 6.3a

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle Figure 6.3b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle Figure 6.3c

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle Figure 6.3d

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Sacromere  A band- band of myosin and actin  I band- composed of only actin  H zone- contains only myosin  Z lines- borders of a sarcomere

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Stimulation and Contraction of Single Skeletal Muscle Cells  Excitability (also called responsiveness or irritability)—ability to receive and respond to a stimulus  Contractility—ability to shorten when an adequate stimulus is received  Extensibility—ability of muscle cells to be stretched  Elasticity—ability to recoil and resume resting length after stretching

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Nerve Stimulus and Action Potential  Skeletal muscles must be stimulated by a motor neuron (nerve cell) to contract  Motor unit—one motor neuron and all the skeletal muscle cells stimulated by that neuron  Motor neuron is a nerve cell  Motor endplate- folded muscle fiber

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 6.4a The Nerve Stimulus and Action Potential

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Nerve Stimulus and Action Potential Figure 6.4b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Nerve Stimulus and Action Potential  Neuromuscular junction  Association site of axon terminal of the motor neuron and muscle  Junction between a nerve and a muscle

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Nerve Stimulus and Action Potential Figure 6.5a

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Nerve Stimulus and Action Potential  Synaptic cleft  Gap between nerve and muscle  Nerve and muscle do not make contact  Area between nerve and muscle is filled with interstitial fluid

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Nerve Stimulus and Action Potential Figure 6.5b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Nerve Impulse to Muscle  Neurotransmitter—chemical released by nerve upon arrival of nerve impulse  The neurotransmitter for skeletal muscle is acetylcholine (ACh)  Acetylcholine attaches to receptors on the sarcolemma  Sarcolemma becomes permeable to sodium (Na+)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Nerve Impulse to Muscle Figure 6.5c

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Nerve Impulse to Muscle  Sodium rushes into the cell generating an action potential  Once started, muscle contraction cannot be stopped

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Nerve Impulse to Muscle Figure 6.6

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Sliding Filament Theory of Muscle Contraction  Activation by nerve causes myosin heads (cross bridges) to attach to binding sites on the thin filament  Myosin heads then bind to the next site of the thin filament and pull them toward the center of the sarcomere  This continued action causes a sliding of the myosin along the actin  The result is that the muscle is shortened (contracted)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Steps of a Muscle Contraction  Nerve impulse is transmitted by a motor nerve to the muscle  Neurotransmitter is Ach  Ach goes across the gap (synapse or synaptic cleft) to the sarcolemma  Travels up the T-tubule  SR releases Ca ions  Ca binds with troponin and tropomyosin and exposes actin

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Steps of a Muscle Contraction  Myosin crossbridges interact with actin  Crossbridges form  Pull in  Break  Repeat  Contraction is complete when z lines are all the way in.

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Relaxation of a Muscle Cell  Ach is deomposed by cholinesterase  Ca goes back to the SR  Cross bridges break  Sarcomere returns to resting length  Actin and myosin slide past each other  Troponin and tropomyosin attach to actin

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings

Botulinum  Bacteria clostridium botulinum produces a poison called botulinum toxin that can prevent the release of Ach from motor neurons at neuromuscular junctions causing botulism  Botulism is a very serious food poisoning  Caused by eating food that has not been heated enough to kill the bacteria or to inactivate the toxin  Botulism toxin blocks the simulation of muscle fibers, paralyzing muscles, including those responsible for breathing.  Fatal without medical treatment

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Botox injections  Inject botulism toxin into the facial skin to temporarily smooth wrinkles by preventing local muscles from contracting

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Rigor Mortis  Means the stiffness of death  At time of death, the stimulation of muscle stops  Some muscles may be in the middle of a contraction  Myosin crossbridges still attached to actin  Requires ATP to release them and so they are left stuck

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Stimulation of Muscle  1 nerve can stimulate one muscle or several muscles  If it stimulates 1 muscle- have good control  If 1 nerve stimulates many muscles, you don’t have as much control

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Sliding Filament Theory of Muscle Contraction Figure 6.7a–b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Sliding Filament Theory Figure 6.8a

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Sliding Filament Theory Figure 6.8b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Sliding Filament Theory Figure 6.8c