How do Muscles How do Muscles Work?Work?

Muscles serve FOUR functions for us:

-- motion; they move our skeleton

-- stability and posture -- controlling organ

function -- 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 people ship that used a galley of people rowing the oars in unison.rowing the oars in unison.

Each person had only so much Each person had only so much strength, but together, they gave the strength, but together, they 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 of the body -- they need motor nerves -- they need energy and O2

-- H20, CO2 waste & glucose transport

Requires nerves, blood vessels, and

the lymphatic system to carry them

These are held in connective tissues called

FASCIAMuscles need to use sugar

available in blood for energy

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 to the skin

Also contains adipose tissue

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

Deep FasciaDeep Fascia Separates muscle groups

Allows muscles to contract without interference from other muscles

Each muscle has its own outer fascia called epimysium which is then surrounded by deep fascia

Superficial Fascia

Deep Fascia

Individual muscle fibers are

called myofibers (muscle cells)

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

Perimysium surrounds fascicles

Endomysium surrounds individual myofibers

Myofibers

MyofibrilsMyofibrils Proteins are arranged in a thread-like Proteins are arranged in a thread-like

appearance within a muscle cellappearance within a muscle cell 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, filaments slide past to contract, filaments slide past each other getting shorter.each other getting shorter.– Myofilaments Myofilaments = = actin and myosinactin and myosin

These filaments are arranged in These filaments are arranged in small bundles called small bundles called sarcomeressarcomeres

Sarcomere

Sarcomere

Sarcomere

Whole Muscle Whole Muscle ContractionContraction

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

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

1. Electrical signals from the brain travel through the nervous system to the muscle

2. Calcium is released inside the muscle cells and binds to troponin C causing contraction.

3. Acitin and myosin filaments slide past each other, causing the muslcle to contract

4. ATP provides chemical energy needed for this process.

Events of Sarcomere 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