PP18 Muscle Anatomy Chapter 2 pg 21-41 ANS 3043 University of Florida Dr. Michael J. Fields.

PP18PP18Muscle AnatomyMuscle Anatomy

Chapter 2 pg 21-41Chapter 2 pg 21-41

ANS 3043ANS 3043University of FloridaUniversity of FloridaDr. Michael J. FieldsDr. Michael J. Fields

Muscle FunctionMuscle Function

MovementMovement– Locomotion, digestion, breathing, vision, Locomotion, digestion, breathing, vision,

circulationcirculation– Due to unique ability of muscles to contract and Due to unique ability of muscles to contract and

shortenshorten– Conversion of chemical energy to mechanical Conversion of chemical energy to mechanical

energyenergy 20-25% efficient20-25% efficient Remainder of energy lost as heat (i.e. shivering)Remainder of energy lost as heat (i.e. shivering)

Direct Function : Voice Related StructuresDirect Function : Voice Related Structures Indirect Function : Body Movements (road Indirect Function : Body Movements (road

rage finger)rage finger)

Muscle FunctionMuscle Function

Maintains body temperature in warm Maintains body temperature in warm blooded animals (cold climate causes blooded animals (cold climate causes energy use to keep warm)energy use to keep warm)

Food source for other animals and Food source for other animals and humans (high in protein, minerals humans (high in protein, minerals and protein)and protein)

Types of MuscleTypes of Muscle

Based on microstructure and Based on microstructure and manner of contractionmanner of contraction

1.1. Smooth : blood vessels, GI tract, repro Smooth : blood vessels, GI tract, repro tissuestissues

2.2. Cardiac : heartCardiac : heart

3.3. Skeletal : striatedSkeletal : striated

Cross Section

Longitudinal Section

Note striations and nucleus

Anatomy of Skeletal MuscleAnatomy of Skeletal Muscle

GeneralGeneral– Multinucleated with voluntary neural inputMultinucleated with voluntary neural input– Each cell has its own nerve, artery and veinEach cell has its own nerve, artery and vein– Striated : consist of sliding filaments that Striated : consist of sliding filaments that

contract and apply force to musclecontract and apply force to muscle– Large cells harnessed in a network of Large cells harnessed in a network of

connective tissue (Figure 2.22)connective tissue (Figure 2.22) Acts as a harness to transmit contractile force to Acts as a harness to transmit contractile force to

bone or other tissuesbone or other tissues


MacrostructureMacrostructure– Epimysium : connective tissue that surrounds Epimysium : connective tissue that surrounds

entire muscleentire muscle Separates individual muscles into distinct unitsSeparates individual muscles into distinct units Avenue for blood vessels and nerves to enter Avenue for blood vessels and nerves to enter

musclemuscle

– PerimysiumPerimysium Muscle bundles contain 20 to 40 muscle fibersMuscle bundles contain 20 to 40 muscle fibers Enmeshes and supports major blood vesselsEnmeshes and supports major blood vessels Intramuscular fat (marbling) deposited within Intramuscular fat (marbling) deposited within

perimysium (white flecks of fat in membrane)perimysium (white flecks of fat in membrane)


3.3. Endomysium : connective tissue that Endomysium : connective tissue that surounds individual muscle fiberssurounds individual muscle fibers– Lies immediately adjacent to muscle cell Lies immediately adjacent to muscle cell

membranemembrane– Major connective tissue responsible for meat Major connective tissue responsible for meat

tenderness (increases with age)tenderness (increases with age)

Microstructure : contains multiple Microstructure : contains multiple fibrils responsible for contractionfibrils responsible for contraction

1.1. Muscle fibers or myofiber : structural unit of Muscle fibers or myofiber : structural unit of muscle (Figure 2.23, 2.24)muscle (Figure 2.23, 2.24)


Microstructure : contains multiple fibrils Microstructure : contains multiple fibrils responsible for contractionresponsible for contraction

1.1.Muscle fibers or myofiber : structural unit of Muscle fibers or myofiber : structural unit of muscle (Figure 2.23, 2.24)muscle (Figure 2.23, 2.24)– May extend total length of muscle but normally May extend total length of muscle but normally

extends partial length of muscleextends partial length of muscle– Growth in fiber length, increase in number of fiber Growth in fiber length, increase in number of fiber

and girth of muscleand girth of muscle– Encased by sarcolemma (basement membrane)Encased by sarcolemma (basement membrane)

Muscle bundle

MuscleMuscle Bundle Muscle Fiber/MyofiberMyofibril

Z ZMyosin


2.2. Myofibrils (Fig 2.26 – 2.29) Myofibrils (Fig 2.26 – 2.29) – Functional contractile unit of muscle composed Functional contractile unit of muscle composed

of microfilamentsof microfilaments– Extends entire length of muscle cellExtends entire length of muscle cell– Bathed in cytoplasm, which is high in proteinBathed in cytoplasm, which is high in protein– Contains Contains SarcomeresSarcomeres : muscle unit : muscle unit

3.3. SarcomeresSarcomeres– ““z line” to “z line”z line” to “z line”– Repeating contractile unit of muscle that Repeating contractile unit of muscle that

represents organization of myofibrilsrepresents organization of myofibrils– ““Z lines :” outer demarcation of each sarcomereZ lines :” outer demarcation of each sarcomere– Elongation of muscle occurs by addition of Elongation of muscle occurs by addition of

sarcomeres near bone attachmentsarcomeres near bone attachment


4.4. Myosin : Thick Filament (Figure 2.28)Myosin : Thick Filament (Figure 2.28)– Located in center of sarcomere and overlaps Located in center of sarcomere and overlaps

actinactin– Major component of muscle contraction and Major component of muscle contraction and

sarcomere shorteningsarcomere shortening– Heavy (contain head) and light chains held Heavy (contain head) and light chains held

together by C-proteinstogether by C-proteins– Bi-directional arrangement (head on both ends)Bi-directional arrangement (head on both ends)– Head of heavy chain has ATPase activity : binds Head of heavy chain has ATPase activity : binds

to actin and serves to “rachet” or pull actin to actin and serves to “rachet” or pull actin filaments together contracting musclefilaments together contracting muscle


4.4. Myosin : Thick Filament (Figure 2.28)Myosin : Thick Filament (Figure 2.28)– Adjacent myosin molecules attached Adjacent myosin molecules attached

together at center by m-protein (skelemin), together at center by m-protein (skelemin), which forms m-linewhich forms m-line

– Isoforms of myosin, which are basis for Isoforms of myosin, which are basis for different muscle fiber typesdifferent muscle fiber types


5.5. Actin : Thin Filament (Figure 2.30)Actin : Thin Filament (Figure 2.30)– Consists of subunit called globular (G) actinConsists of subunit called globular (G) actin

– 400 G-actin molecules, which form double helical 400 G-actin molecules, which form double helical structure of the filamentous (F) actinstructure of the filamentous (F) actin

– Tropomyosin : occupies F-actin groove and is Tropomyosin : occupies F-actin groove and is necessary for development of cross bridges necessary for development of cross bridges during muscle contraction and serves as myosin during muscle contraction and serves as myosin binding sitebinding site

– Troponin T, I, C : Trimeric protein that binds to F-Troponin T, I, C : Trimeric protein that binds to F-actin and tropomyosin to regulate cross-bridge actin and tropomyosin to regulate cross-bridge development during muscle contractiondevelopment during muscle contraction

Surrounds muscle fiber/myofiber


6.6. Intrasarcomeric Proteins Intrasarcomeric Proteins a.a. within myofibril to provide organization to within myofibril to provide organization to

sarcomeresarcomere Titin : maintains structure of the half sarcomere Titin : maintains structure of the half sarcomere

by being associated with myosin by being associated with myosin – responsible for resting tension of muscle (spring-like)responsible for resting tension of muscle (spring-like)

Nebulin : associated with actin andmay serve as Nebulin : associated with actin andmay serve as template for building actin and maintaining F-template for building actin and maintaining F-actinactin

b.b. outside myofibril (Figure 2.33)outside myofibril (Figure 2.33) Desmin : protein responsible for tying myofibrils Desmin : protein responsible for tying myofibrils

together like a raft made of logstogether like a raft made of logs


7.7. CostameresCostameres– Anchors myofibrils to sarcolemmaAnchors myofibrils to sarcolemma– Transfers force generated from Transfers force generated from

contracting myofibrils to cell contracting myofibrils to cell membranemembrane

– Consist of several aggregated Consist of several aggregated proteins : filamin, viniculin, talinproteins : filamin, viniculin, talin

Ultrastructure

Muscle Fiber/Myofiber


UltrastructureUltrastructure1.1. Transverse tubules : continuous tubule Transverse tubules : continuous tubule

system extending from plasma membrane system extending from plasma membrane into interior of muscle fiber to transmit into interior of muscle fiber to transmit action potential to initiate contraction of the action potential to initiate contraction of the fiberfiber

2.2. Sarcoplasmic reticulum (SR) : system of Sarcoplasmic reticulum (SR) : system of tubules surrounding myofibrils tubules surrounding myofibrils – Make up terminal cisternae and fenestrated Make up terminal cisternae and fenestrated

collarcollar– Serve as a storage unit during muscle relaxationServe as a storage unit during muscle relaxation


3.3. Combined, T-tubules and SR form the Combined, T-tubules and SR form the tubular network that acts in the tubular network that acts in the coupling of excitation, contraction and coupling of excitation, contraction and relaxation of the musclerelaxation of the muscle– Combined with voltage sensing receptors, Combined with voltage sensing receptors,

allows for calcium flow into cytoplasmallows for calcium flow into cytoplasm– Calcium pumps : pump calcium back into Calcium pumps : pump calcium back into

SR where Ca binds with a protein know as SR where Ca binds with a protein know as calsequestrincalsequestrin


Other important componentsOther important components1.1. Nuclei Nuclei

– Muscle fibers are multinucleatedMuscle fibers are multinucleated– Elliptical and located on periphery beneath Elliptical and located on periphery beneath

sarcolemmasarcolemma

2.2. Mitochondria (powerhouse of the cell)Mitochondria (powerhouse of the cell)– Responsible for generating energy substrates for the Responsible for generating energy substrates for the

cellcell– Contain enzymes associated with oxidative Contain enzymes associated with oxidative

metabolismmetabolism– If not enough oxygen muscle switches to anaerobic If not enough oxygen muscle switches to anaerobic

metabolism and produces lactic acidmetabolism and produces lactic acid– Clustered around periphery of cellClustered around periphery of cell– Generates ATP resulting in phosphorylating or Generates ATP resulting in phosphorylating or

tropomyosin and troponin leading to contractiontropomyosin and troponin leading to contraction

Cardiac MuscleCardiac Muscle

CharacteristicsCharacteristics– Mono and multinucleated with nucleus Mono and multinucleated with nucleus

in center of cellin center of cell– Striated but decreased and not as Striated but decreased and not as

organized compared to skeletal muscleorganized compared to skeletal muscle– Actin : Myosin filaments (2:1)Actin : Myosin filaments (2:1)

Not cylindrical nor in discrete units like Not cylindrical nor in discrete units like skeletal muscleskeletal muscle

Joined together and variable in numberJoined together and variable in number

Cardiac Muscle

Nuclei

Z line

Cardiac Muscle

Z line

Cardiac MuscleCardiac Muscle

– Contractions : involuntary neural inputContractions : involuntary neural input Intercalated discs – connections between Intercalated discs – connections between

cardiocytes (muscle fibers)cardiocytes (muscle fibers) Run perpendicular to long axis of muscleRun perpendicular to long axis of muscle Allows for electrical impulses to migrate Allows for electrical impulses to migrate

through each cellthrough each cell Cardiac myofibrils attached directly to discs Cardiac myofibrils attached directly to discs

to allow heart to act as a groupto allow heart to act as a group

Smooth MuscleSmooth Muscle

DescriptionDescription– Sheet-like muscle masses surrounding Sheet-like muscle masses surrounding

various organsvarious organs Functions and location in bodyFunctions and location in body

– Extreme elasticity and pliability but still Extreme elasticity and pliability but still allow for contractionsallow for contractions Uterus : very think in non-gravid uterus but Uterus : very think in non-gravid uterus but

thin during pregnancythin during pregnancy

– Allows for fluid movement through blood Allows for fluid movement through blood vessels and intestinal tractvessels and intestinal tract

Smooth muscle

Smooth MuscleSmooth Muscle

CharacteristicsCharacteristics– Mononucleated with centrally located cigar Mononucleated with centrally located cigar

shaped nucleusshaped nucleus– Non-striatedNon-striated

Myofilaments not aligned into myofibrils and repeating Myofilaments not aligned into myofibrils and repeating units like skeletal muscleunits like skeletal muscle

Actin : Myosin (15:1)Actin : Myosin (15:1)– Attached to cell membranes and strategically located Attached to cell membranes and strategically located

throughout cellthroughout cell– Contraction allows for the generation of force in several Contraction allows for the generation of force in several

(unorganized) directions(unorganized) directions

Contracts by involuntary neural input and/or Contracts by involuntary neural input and/or stimulation by hormones/chemicalsstimulation by hormones/chemicals

– Slow prolonged contractionsSlow prolonged contractions

Fibers scattered throughout cell

Water 75% (65 – 80%)

Nitrogenous20.5%

Lipid 2.5%(1.5 - 13.0%)

CHO 1.0%

Inorganic 1.0%

Muscle- chemical composition

Glycogen stored in muscle

PP18 Muscle Anatomy Chapter 2 pg 21-41 ANS 3043 University of Florida Dr. Michael J. Fields.

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Transcript of PP18 Muscle Anatomy Chapter 2 pg 21-41 ANS 3043 University of Florida Dr. Michael J. Fields.