Muscle fibers & tissueMuscle fibers & tissueWhere chemical energy is used to produce force & movement

Types of muscleTypes of muscle• Identified based on structure, result

of contraction, & control.• Skeletal – attached to bone &

responsible for supporting & moving the skeleton, neurons cause movement & is voluntary

• Smooth – surround organs & tubes, contraction changes diameter or propels fluids, controlled by ANS, hormones & other chemical messengers

• Cardiac- heart, contractions propel blood, regulated by ANS

MuscleMuscleBundle of muscle fibers bundled

together by connective tissue.Most fibers do not extend the entire

length of a muscle

Striated (skeletal) muscleStriated (skeletal) muscleUnder a microscope looks like a

series of light and dark bands going across the muscle. Looks like it has different bands.

Results from thin & thick filaments of the myofibrils

http://www.scienceclarified.com/images/uesc_07_img0385.jpg

Muscle fiberMuscle fiberSingle skeletal muscle cellCan be as long as 20 cm

nvo.com

MyofibrilsMyofibrils Occupies most of the cytoplasm

Long “filaments” that stretch the length of a muscle fiber (cell)

Bundled togetherSarcomere is a

single unit inside the myofibril, they are lined up end to end repeating along the length of the myofibril.

SarcomereSarcomereMade of alternating thick & thin filamentsThick filament made of myosinThin filament made of actinDuring contraction these filaments work to

shorten the length of the sarcomere by “sliding” along one another.

bodyplusmind.co.uk

Damage to fibersDamage to fibersIf destroyed cannot be replaced

by other muscle fibers, but by undifferentiated cells near the muscle fibers. These do not have the capacity to rebuild severe damage.

Most of restoration of strength comes from increasing the size of remaining fibers.

CalciumCalciumCalcium in the cytoplasm is

important for muscle contractionThe electrical stimulation provided

to the muscle increases the concentration of Ca in the cytoplasm

Increased levels of Ca make muscle contraction possible.

Relaxation begins as Ca is pumped out of the cytoplasm

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/

Neuromuscular junctionNeuromuscular junction Area of muscle fiber under the axon terminal. ACh released into this junction ACh acts to open Ca channels to allow Ca into the

cytoplasm. Can be re-stimulated before contraction ends, results

in tetany (sustained muscle contraction)http://fig.cox.miami.edu/~cmallery/150/neuro/neuromuscular-sml.jpg

Rigor MortisRigor MortisThe stiffening of skeletal muscles

after deathComplete by 12 hours post mortemFilaments are stuck in position &

cannot slideRigor mortis starts to disappear

about 48 hours after deathDisappears due to decomposition

of muscle tissue

tendonstendonsConnect muscles to bones

http://www.medical-look.com/systems_images/Skeletal_Muscle_Fibers.gif

Moving bonesMoving bonesAnalogy people pulling on a ropeEach fiber is analogous to a

personRope is analogous to the

connective tissue & tendonhttp://www.argosymedical.com/fl

ash/armflex/landing.html

Smooth muscleSmooth muscleSingle nucleusAble to divide to produce more cellsUnder a microscope does not have bandsInnervated by autonomic nervous systemStill uses actin, myosin and Ca for

contractions.Fibers have a smaller diameter than skeletal

fibersHas the ability to stretch a great deal w/o

affecting function (bladder)class.kmu.edu.tw

Smooth Muscle Smooth Muscle ContractionContractionActin & myosin are not organized

Can have 2X as much actin as myosinCa acts on a different molecule that results in

contractionNot as much ATP is required to, contraction is

slower, but does not fatigue.Can maintain contraction for long period of time.

cytochemistry.net

Smooth muscle Smooth muscle innervationinnervationAxon forms many branches and

access many areas along the same muscle fiber

Some neurotransmitters excite others relax

http://www.mfi.ku.dk/PPaulev/chapter2/images/n2-11.jpg

Gap junctionsGap junctionsContraction may be stimulated by the

contraction/excitation of surrounding fibersChannels between fibers allow flow of ions

which conducts the impulse to the next cellExamples: Intestines, blood vessels, uterus

Cardiac muscleCardiac muscleCombines

properties of skeletal and smooth muscle

Cells are striated, short, and have branching

Has specialized cells responsible for conducting starting the heart beat and quickly spreading the contraction throughout the heart muscle

http://webanatomy.net/histology/cardiac/cardiac_muscle.jpg

Cardiac innervationCardiac innervationReceives signals from the

sympathetic and parasympathetic system

Sympathetic releases norepinephrine (responsible for racing heart)

Parasympathetic releases ACh which inhibits contractions

Refractory periodRefractory periodPeriod when a muscle cannot be

excitedExtremely long in cardiac muscleCardiac muscle cannot

experience tetany

PotassiumPotassiumPotassium also plays a role in

muscle contractionDifferences exist in the amount

of K let back into the cell during contraction