CHAPTER 9 MUSCLE TISSUE
Muscle
•skeletalvoluntary striated 40% of body weight
•cardiacinvoluntaryheart striated branched intercalated discs
•smoothinvoluntaryorgans ; blood vessels
functions
•movement-external=locomotion
•movement-internal
•posture ; balance
•joint stabilization
•heat maintenance
characteristics of muscle
•contractilityable to shorten
•excitabilityable to be stimulated by environment can transmit electrical impulse
•extensibilitycan be stretched
•elasticitycan stretch and recoil
specialization
•shape of cells
•cell membrane
•receptors
•many nuclei and mitochondria
•proteins- contractile
muscle organ
•each muscle is an organ
•several tissues
•muscle
•nerve
•connective tissue
•blood vessels
gross anatomy
•muscle cell = muscle fiber
•fascicle = bundlemany fibers
•musclemany bundles
•sarcomere lengthwise units
connective tissue
•endomysiumsurrounds each fiber (cell)
•perimysiumsurrounds each fascicle (bundle)
•epimysiumsurrounds entire muscle
tendons
•connect muscle to bone
•origin
•insertion
muscle cell = fiber
•sarcolemmacell membrane
•T tubulesinward folds of sarcolemma
•myofibrilsrod shaped contractile organelles
muscle cell = fiber
•sarcoplasmic reticulumstores Calcium
•terminal cisternathickened SR at T tubules
•triadT tubule + 2 terminal cisternae
sarcomere
•= unit of contraction
•lengthwise in myofibril
•myofilamentscontractile proteins
•myosinthick filament
•actinthin filament
•Z discends of each sarcomere
•A banddark bandsmostly myosin
•I bandlight bandsonly actin
how muscles contract
•sliding filament theory
•myosin and actin slide past each other
•filaments don’t “contract”
•
•Calcium – stimulates binding of myosin and actin
•sarcomere shortens
–I bands shorten
–A bands don’t shorten
–Z bands closer
neuromuscular junction
• = end of neuron + synapse + sarcolemma
•axon terminalend of neuron
•synapsespace
•motor end platesarcolemma
•receptorsfor acetylcholine; on sarcolemma
•one axon per muscle fiber
motor unit
•= neuron + muscle fibers it supplies
•nerve = many neurons
•fine muscle control-small motor units
•strong muscle-large motor units
•alternation and fatigue
muscle tone
•muscle tone = slight contraction of all skeletal muscles
–maintain posture
–protect joints
–heat production
types of skeletal muscle fibers
•slow oxidative fibers (type I)
–aerobic (cell respiration)
–myoglobin ; mitochondriared
–slow , prolonged contraction
•fast glycolytic fibers (type II x)
–anaerobic
–little myoglobin or mitochondria (pale)
–fast contraction ; quick fatigue
•fast oxidative fibers (type II a)
–intermediate speed, strength, and fatigue
exercise
•endurance exercise
–more efficient metabolism
•increased mitochondria
•increased capillaries
•increased myoglobin and glycogen
–less fatigue
–no increase muscle mass
•resistance exercise
–increased myofibrils
•“split ends” theory
•glycogen storage
–increased connective tissue
cardiac muscle
• = myocardium
•striated (sarcomeres)
•intercalated discs
–gap junctions transmit Calcium between cells
•more mitochondriaresistant to fatigue
•more ATP and O2 dependant than skeletal musc
smooth muscle
•walls of all hollow organs
•wall of blood vessels
•2 layerscircular ; longitudinal
•peristalsis
•no sarcomeres ; but has sliding filaments
•gap junctions- contract in unison
•slower contraction than skeletal
•no fatiguerequires much less ATP
•
types of muscle contractions
•isotonicmuscle length changes
–concentricmuscle shortens
–eccentricmuscle lengthens
•isometricmuscle length doesn’t change
Aging
•no mitosis
•receptors
•neurotransmitters
•nutrition
•oxygen
•decreased muscle sense
•decreased position sense