CHAPTER 9 MUSCLE TISSUE
Muscle
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skeletal
voluntary
striated
40% of body weight
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cardiac
involuntary
striated
branched
intercalated discs
heart
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smooth
involuntary
organs ; blood vessels
functions
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movement
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external =
movement
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internal
locomotion
posture ; balance
joint stabilization
heat maintenance
characteristics of muscle
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contractility
able to shorten
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excitability
able to be stimulated by environment
can transmit electrical impulse
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extensibility
can be stretched
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elasticity
can stretch and recoil
specialization
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shape of cells
cell membrane
receptors
many nuclei and mitochondria
proteins
- contractile
muscle organ
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each muscle is an organ
several tissues
• muscle
• nerve
• connective tissue
• blood vessels
gross anatomy
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muscle cell = muscle fiber
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fascicle = bundle
many fibers
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muscle
many bundles
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sarcomere
lengthwise units
connective tissue
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endomysium
surrounds each fiber (cell)
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perimysium
surrounds each fascicle (bundle)
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epimysium
surrounds entire muscle
tendons
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connect muscle to bone
origin
insertion
muscle cell = fiber
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sarcolemma
cell membrane
T tubules
inward folds of sarcolemma
myofibrils
rod shaped contractile organelles
muscle cell = fiber
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sarcoplasmic reticulum
stores Calcium
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terminal cisterna
thickened SR
at T tubules
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triad
T tubule + 2 terminal cisternae
sarcomere
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= unit of contraction
lengthwise in myofibril
myofilaments
• myosin
• actin
contractile proteins
thick filament
thin filament
Z disc
ends of each sarcomere
A band
dark bands
mostly myosin
I band
light bands
only actin
how muscles contract
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sliding filament theory
myosin and actin slide past each other
filaments don’t “contract”
Calcium – stimulates binding of myosin and actin
sarcomere shortens
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I bands shorten
A bands don’t shorten
Z bands closer
neuromuscular junction
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= end of neuron + synapse + sarcolemma
axon terminal
end of neuron
synapse
space
motor end plate
sarcolemma
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receptors
for acetylcholine; on sarcolemma
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one axon per muscle fiber
motor unit
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= neuron + muscle fibers it supplies
nerve = many neurons
fine muscle control
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small motor units
strong muscle
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large motor units
alternation and fatigue
muscle tone
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muscle tone = slight contraction of all skeletal muscles
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maintain posture
protect joints
heat production
types of skeletal muscle fibers
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slow oxidative fibers (type I)
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aerobic (cell respiration)
myoglobin ; mitochondria
red
slow , prolonged contraction
fast glycolytic fibers (type II x)
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anaerobic
little myoglobin or mitochondria
(pale)
fast contraction ; quick fatigue
fast oxidative fibers (type II a)
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intermediate speed, strength, and fatigue
exercise
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endurance exercise
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more efficient metabolism
• increased mitochondria
• increased capillaries
• increased myoglobin and glycogen
less fatigue
no increase muscle mass
resistance exercise
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increased myofibrils
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increased connective tissue
• “split ends” theory
• glycogen storage
cardiac muscle
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striated
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intercalated discs
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= myocardium
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(sarcomeres)
gap junctions
more mitochondria
transmit Calcium between cells
resistant to fatigue
more ATP and O2 dependant than skeletal musc
smooth muscle
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walls of all hollow organs
wall of blood vessels
2 layers
circular ; longitudinal
peristalsis
no sarcomeres ; but has sliding filaments
gap junctions -
contract in unison
slower contraction than skeletal
no fatigue
requires much less ATP
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types of muscle contractions
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isotonic
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muscle length changes
concentric
muscle shortens
eccentric
muscle lengthens
isometric
muscle length doesn’t change
Aging
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no mitosis
receptors
neurotransmitters
nutrition
oxygen
decreased muscle sense
decreased position sense