How do Muscles Work?How do Muscles Work? Muscles serve FOUR Muscles serve FOUR

functions for us:functions for us: -- motion; they move us-- motion; they move us -- stability and posture -- stability and posture -- controlling organ function-- controlling organ function -- generate body heat-- generate body heat

Characteristics of Muscle Characteristics of Muscle TissueTissue

ExcitabilityExcitability – ability of the muscles to – ability of the muscles to be stimulated by nervesbe stimulated by nerves

ContractilityContractility – muscles can contract – muscles can contract ExtensibilityExtensibility – muscles lengthen – muscles lengthen ElasticityElasticity – after shortening or – after shortening or

lengthening, muscle can return to its lengthening, muscle can return to its original shapeoriginal shape

Muscles Muscles PULLPULL, they never push!, they never push!

Roman Ship Analogy…Roman Ship Analogy… Muscles work much like an old roman Muscles work much like an old roman

ship that used a galley of slaves ship that used a galley of slaves roaring the oars in unison.roaring the oars in unison.

Each slave had only so much Each slave had only so much strength, but together gave the strength, but together gave the ship’s oars incredible power.ship’s oars incredible power.

Muscles need help…Muscles need help…

Muscles need to be connected to the rest Muscles need to be connected to the rest of the bodyof the body

-- they need motor nerves-- they need motor nerves

-- they need energy and O-- they need energy and O22

-- H-- H220, CO0, CO22 waste & glucose transport waste & glucose transport Requires nerves, blood vessels, andRequires nerves, blood vessels, and the lymphatic system to carry themthe lymphatic system to carry them These are held in connective tissues calledThese are held in connective tissues called FASCIAFASCIA

Fascia Galore!Fascia Galore!

Fascia is connective Fascia is connective tissue that surrounds tissue that surrounds musclesmuscles

Provides protection Provides protection and stabilityand stability

Superficial FasciaSuperficial Fascia

Closest to the skin and holds muscle Closest to the skin and holds muscle to the skinto the skin

Also contains adipose tissueAlso contains adipose tissue Stores fat and water, provides Stores fat and water, provides

insulation from heat loss, protects, insulation from heat loss, protects, and is a place for vessels and nerves and is a place for vessels and nerves to carry things in and out of musclesto carry things in and out of muscles

Deep FasciaDeep Fascia

Separates muscle groupsSeparates muscle groups Allows muscles to contract without Allows muscles to contract without

interference from other musclesinterference from other muscles Each muscle has its own outer fascia Each muscle has its own outer fascia

called called epimysiumepimysium which is then which is then surrounded by deep fasciasurrounded by deep fascia

Individual muscle fibers are called Individual muscle fibers are called myofibers (muscle cells)myofibers (muscle cells)

Arranged in groups of 10-100 Arranged in groups of 10-100 myofibers and these groups are myofibers and these groups are called called fasciclesfascicles

PerimysiumPerimysium surrounds fascicles surrounds fascicles EndomysiumEndomysium surrounds individual surrounds individual

myofibersmyofibers

Myofibers

Myofibrils (actin & myosin)Myofibrils (actin & myosin) Proteins are arranged in a thread-like Proteins are arranged in a thread-like

appearance in the sarcoplasmappearance in the sarcoplasm Give skeletal and cardiac muscle Give skeletal and cardiac muscle

tissue their striationstissue their striations

muscle cell

Skeletal Muscle Fiber ContractionSkeletal Muscle Fiber Contraction““Sliding Filament Theory”Sliding Filament Theory”When muscle fibers are stimulated When muscle fibers are stimulated to contract, to contract, myomyofilamentsfilaments (actin an (actin an myosin) slide past one another.myosin) slide past one another.

This causes This causes sarcomeressarcomeres (muscle (muscle units) to shorten and the whole units) to shorten and the whole muscle fiber shortens.muscle fiber shortens.

Sarcomere

Sarcomere

Sarcomere

Whole Muscle ContractionWhole Muscle Contraction

The whole length of The whole length of oneone muscle fiber muscle fiber must contract; however, the whole must contract; however, the whole muscle does not have to contact.muscle does not have to contact.

The number of muscle fibers The number of muscle fibers contracting determines the strength contracting determines the strength of the contraction.of the contraction.

The Effect of ExerciseThe Effect of Exercise A regular exercise program will bring A regular exercise program will bring

about about 1.1. Increased endurance Increased endurance 2.2. Increased strength of muscles. Increased strength of muscles. Muscle enlarge, Muscle enlarge, notnot due to increase in due to increase in

number of muscle fibers, number of muscle fibers, butbut increased increased amounts of actin and myosin amounts of actin and myosin myofibrils inside each muscle fiber myofibrils inside each muscle fiber making them bigger and stronger.making them bigger and stronger.

““Use it or lose it !”Use it or lose it !”

Arnold….then and now!Arnold….then and now!

Exercise increases muscle size, Exercise increases muscle size, strength, and endurancestrength, and endurance– Aerobic (endurance) exercise (biking, Aerobic (endurance) exercise (biking,

jogging) results in stronger, more jogging) results in stronger, more flexible muscles with greater resistance flexible muscles with greater resistance to fatigueto fatigueMakes body metabolism more efficientMakes body metabolism more efficient Improves digestion, coordinationImproves digestion, coordination

Resistance exercise like weight lifting increases muscle size and strength

Effect of Exercise on MusclesEffect of Exercise on Muscles