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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
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
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