lecture 10 skeletal muscle tissue Flashcards
primary tissue in
heart, walls of hollow organs and skeletal
muscle
my-filaments are responsible for shortening of muscle cells
-actin and myosin are two type of myofilaments
contractility
nerve signals excite muscle cells, causing electrical impulses to travel along the sarcolemma
excitability
- contraction of a skeletal muscle stretches the opposing muscle
- smooth muscle is stretched by substances within that hollow organ
extensibility
recoils after being stretched
elasticity
plasma membrane of muscle cells
sarcolemma
cytoplasm of muscle cells
sarcoplasm
attached to skeleton
-moves body by moving the bones
skeletal muscle
squeezes fluids and other substances through hollow organs
smooth muscle
function as valves
- open to allow passage of a substance
- contract to close the passageway
sphincters
- enables the body to remain sitting or standing
- muscle tone helps stabilize many synovial joints
maintain posture and stabilize joints
- muscle contractions produce heat
- helps maintain normal body temperature
heat generation
- packaged into skeletal muscles
- makes up 40% of body weight
- cells are striated
skeletal muscle tissue
- occurs only in the walls of the heart
- straited
- involuntary
cardiac muscle tissue
- occupies the walls of hollow organs
- lack striations
- involuntary
smooth muscle tissue
dense regular connective tissue surrounding entire muscle
epimysium
surrounds each fascicle
perimysium
group of muscle fibers
fascicle
a fine sheath of connective tissue wrapping each muscle cell
endomysium
-most skeletal muscles run from one bone to another
muscle attachments
less movable attachment
origin
more movable attachment
insertion
CT fibers are short
fleshy attachments
CT forms a tendon or aponeurosis
indirect attachements
bone markings present where tendons meet bones
tubercles, trochanters, and crests
- fibers are long cylindrical
- huge cells
- several centimeters
- each cell formed by fusion of embryonic cells
- multinucleate
skeletal muscle fiber
- long rods within cytoplasm
- make up 80% of cytoplasm
myofibrils
long row of repeating segments
sarcomeres
boundaries of each sarcomere
z disc (line)
extend from Z disc toward center of sercomere
thin actin filaments
located in the center of the sarcomere
- overlap inner ends of the thin filaments
- contain ATP enzymes
thick (myosin) filaments
- full length of the thick filament
- includes inner end of thin filaments
A bands
center part of A band where no thin filaments occur
H zone
A and I bands refract polarized light differently
A bands ; anisotropic
I bands ; isotropic
- in center of H zone
- contains tiny rods that hold thick filaments together
M line
- region with only thin filaments
- lies within two adjacent sarcomeres
I Band
- springlike molecule that resists overstretching
- extend from z disc to thick filaments to M line
Titin
A specialized smooth ER
-interconecting tubules surround each myofibril
sarcoplasmic reticulum
some tubules form cross-channels
terminal cisterns
released when muscle is stimulated to contract
calcium ions
deep invaginations of sarcolemma
t tubules
t tubule flanked by two terminal cisterns
triad
2 major types of contractions
concentric contraction
eccentric contraction
muscle shortens to do work
concentric contraction
muscle generates force as it lengthens
eccentric contraction
-muscle is stretched by a movement opposite that which contracts it
muscle extension
-point where nerve ending and muscle fiber meet
neuromuscular junction
located at ends of axons
-stores neurotransmitters
terminal boutons
space between axon terminal and sarcolemma
synaptic cleft
produce ATP aerobically
oxidative fibers
produce ATP anaerobically by glycolysis
Glycolytic fibers
skeletal muscle fibers divided into 3 classes
- slow oxidative fibers
- fast glycolytic fibers
- fast oxidative fibers
- red slow oxidative fibers
- obtain energy from aerobic metabolic reactions
- contain large number of mitochondria
- contract slow and resistant to fatigue
slow oxidative fibers
white fast glycolytic fibers
-contract rapidly and tire quickly
fast glycolytic fibers
intermediate fibers
- contract quickly
- fatigue resistant
fast oxidative fibers
-group of inherited muscle destroying disease
-affected muscles enlarge with fat and connective tissue
-muscles degenerate
-types ;
ducheene muscular dystrophy
myotonic dystrophy
muscular dystrophy
pain caused by tightened bands of muscle fibers
myofascial pain syndrome
- mysterious chronic-pain syndrome
- affects mostly women
- symptons ; fatigue, sleep abnormalities, severe musculoskeletal pain, and headache
fibromyalgia
muscle tissue develops from
myoblasts
muscle wasting
sarcopenia