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Chapter 8Muscular System

Definition: Three Types (definition & example)

Functions: Examples:

MuscularSystem

(Muscles) - Organs composed of specialized cells that use the chemical energy stored in nutrients to contract.

1-Skeletal – attaches to bones and is under conscious control2-Smooth – within blood vessels and hollow organs (involuntary)3-Cardiac – heart (involuntary)

•Provide forces that move body parts•Maintain posture•Generate heartbeat•Main source of body heat•Muscle tone•Propel body fluids and food

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Introduction:Introduction:

A. All movements require muscle

B. Three types of muscle

1. skeletal, smooth, and cardiac muscle.

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Structure of a Skeletal MuscleStructure of a Skeletal Muscle

A.A. Each muscle is an organ, comprised of Each muscle is an organ, comprised of skeletal skeletal muscle tissue, connective tissues, muscle tissue, connective tissues, nervous nervous tissue, and blood.tissue, and blood.

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B.B. Connective Tissue Coverings Connective Tissue Coverings

1.1. Layers of dense connective tissue, Layers of dense connective tissue, fasciafascia,, surround surround and separate each muscle.and separate each muscle.

2.2. This connective tissue gives rise to This connective tissue gives rise to tendonstendons and and are fused to the periosteum of bones.are fused to the periosteum of bones.

3.3. EpimysiumEpimysium - - layer around each whole muscle layer around each whole muscle

4. 4. PerimysiumPerimysium - - surrounds individual surrounds individual bundles (bundles (fascicles)fascicles) within each muscle within each muscle

5. 5. EndomysiumEndomysium – covers each muscle cell – covers each muscle cell (fiber)(fiber)

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Study AnalogyStudy Analogy

Pretend you are going to play a joke on someonePretend you are going to play a joke on someone and give them 100 pencils. The pencils will and give them 100 pencils. The pencils will represent muscle fibers. First you wrap each represent muscle fibers. First you wrap each individual pencil in tissue paper (dense tissue paperindividual pencil in tissue paper (dense tissue paper of course!). This would be of course!). This would be endomysium.endomysium. Then Then you take about 10 pencils in a bundle (a you take about 10 pencils in a bundle (a fasciclefascicle) ) and wrap them in paper (and wrap them in paper (perimysiumperimysium). After that). After that you take all the bundles and wrap them in gift wrap you take all the bundles and wrap them in gift wrap

((epimysiumepimysium). But you are going to mail this joke, ). But you are going to mail this joke, so you also have to wrap it in brown paper so you also have to wrap it in brown paper representing the representing the fasciafascia..

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C.C. Skeletal Muscle Fibers Skeletal Muscle Fibers

1.1. Single, long, cylindrical muscle cell.Single, long, cylindrical muscle cell.2.2. Under the Under the sarcolemmasarcolemma (cell membrane) (cell membrane) lies lies sarcoplasmsarcoplasm (cytoplasm) the (cytoplasm) the sarcoplasm contains sarcoplasm contains myofibrils.myofibrils.

a. a. ThickThick filaments of myofibrils are made filaments of myofibrils are made up up of the protein of the protein myosinmyosin..

b. b. ThinThin filaments of myofibrils are made filaments of myofibrils are made up of up of the protein the protein actinactin..

c. The organization of these filaments c. The organization of these filaments produces striations.produces striations.

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Muscle Striations

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3.3. A A sarcomere sarcomere extends from Z line to Z line.extends from Z line to Z line.a.a. I bandsI bands = actin filaments (thin) = actin filaments (thin)b.b. A bandsA bands = overlapping thick and thin = overlapping thick and thin filaments.filaments.c.c. H zoneH zone (center of A bands) = myosin (center of A bands) = myosin filaments filaments (thick)(thick)

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http://health.howstuffworks.com/adam-200006.htm

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D.D. Neuromuscular JunctionNeuromuscular Junction 1.1. The site where the motor neuron and The site where the motor neuron and

muscle fiber meet is the muscle fiber meet is the neuromuscular neuromuscular junction.junction.

E.E. Motor Units Motor Units 1. A motor neuron and the muscle fibers it 1. A motor neuron and the muscle fibers it controls make up a motor unit; when controls make up a motor unit; when

stimulated to do so, the muscle fibers of the stimulated to do so, the muscle fibers of the motor unit contract all at once. motor unit contract all at once.

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Skeletal Muscle ContractionSkeletal Muscle Contraction A.A. Muscle contraction result in the shortening Muscle contraction result in the shortening

of sarcomeres,of sarcomeres, and the pulling of and the pulling of the muscle the muscle against its attachments.against its attachments.

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B.B. Role of Myosin and Actin Role of Myosin and Actin 1.1. MyosinMyosin consists of two twisted strands consists of two twisted strands with globular cross-bridges projected outward with globular cross-bridges projected outward along the strands.along the strands.2.2. ActinActin is a globular protein with myosin is a globular protein with myosinbinding sitesbinding sites

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How do muscles contract?1.1. Motor neuron releases acetylcholineMotor neuron releases acetylcholine

2.2. Acetylcholine binds to receptors on muscle fiberAcetylcholine binds to receptors on muscle fiber

3.3. Muscle fiber is stimulated and passes impulse to Muscle fiber is stimulated and passes impulse to sarcoplasmic reticulumsarcoplasmic reticulum

4.4. Ca binds to troponin moleculesCa binds to troponin molecules

5.5. Troponin and Tropomyosin interact and expose Troponin and Tropomyosin interact and expose binding sites on actinbinding sites on actin

6.6. Actin and Myosin linkActin and Myosin link

7.7. Myosin pull actin inwardMyosin pull actin inward

8.8. Muscle fiber shortens and creates contractionMuscle fiber shortens and creates contraction

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How do muscles relax?1.1. Muscle fiber is destimulated by acetylcholineMuscle fiber is destimulated by acetylcholine

2.2. Ca is transported into sarcoplasmic reticulumCa is transported into sarcoplasmic reticulum

3.3. ATP breaks links between actin and myosinATP breaks links between actin and myosin

4.4. Troponin and Trypomyosin block binding sites Troponin and Trypomyosin block binding sites on actin on actin

5.5. Muscle fiber relaxesMuscle fiber relaxes

6.6. ATP breaks down, getting myosin ready for next ATP breaks down, getting myosin ready for next contractioncontraction

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http://health.howstuffworks.com/muscle2.htm

http://www.mhhe.com/biosci/esp/2001_gbio/folder_structure/an/m5/s5/anm5s5_8.htm

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C.C. Stimulus for ContractionStimulus for Contraction

1.1. The motor neuron must release the The motor neuron must release the neurotransmitter neurotransmitter acetylcholineacetylcholine for muscle for muscle contraction.contraction.

D. Energy Sources for ContractionD. Energy Sources for Contraction

1. Energy for contraction comes from 1. Energy for contraction comes from ATPATP. .

ATP – Adenosine TriphosphateATP – Adenosine Triphosphate

2.2. Creatine phosphateCreatine phosphate, which stores excess , which stores excess energy is present to regenerate ATP from ADP energy is present to regenerate ATP from ADP and phosphate.and phosphate.

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Skeletal Muscle ActionsSkeletal Muscle Actions A.A. Origin and InsertionOrigin and Insertion

1. The immovable end of a muscle is the 1. The immovable end of a muscle is the originorigin, while the movable end is the , while the movable end is the

insertion; insertion; contraction pulls the contraction pulls the insertioninsertion toward the toward the origin.origin.

2.Some muscles have more than one 2.Some muscles have more than one insertion insertion or origin.or origin.

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B.B. Interaction of Skeletal MusclesInteraction of Skeletal Muscles

1.1. Of a group of muscles, the one Of a group of muscles, the one doing the doing the majority of the work is the majority of the work is the prime moverprime mover..

2.2. Helper muscles are called Helper muscles are called synergistssynergists; ; opposing muscles are called opposing muscles are called antagonistsantagonists. .

Examples:??Examples:??

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Muscle Movement

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Steroid use

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