Muscle Tissue I and II Flashcards
what are the 3 types of muscle?
skeletal, cardiac and smooth
what are other terms used for muscle fibers?
muscle cell, myocyte
what do muscle fibers do? what are they surrounded by?
produce force, movement and heat
surrounded by connective tissue matrix, bounded by external lamina
MUSCLES ONLY PULL CANNOT PUSH
what makes up muscle fibers?
-sarcolemma —> plasma membrane
-sarcoplasm –> cytoplasm
-sarcoplasmic reticulum (SR) –> sER
what is contraction?
the interaction of cytoplasmic protein chains (myofilaments)
actin and myosin
what causes conformational change?
Calcium
causes actin and myosin to move relative to each other
what types of muscle are striated?
skeletal and cardiac
what type of muscle makes up NONstriated muscle?
smooth muscle
describe some general information about skeletal muscle?
-has multinucleated adult cells —> b/c they join together
-has ABUNDANCE of MITOCHONDRIA, GLYCOGEN, MYOGLOBIN
how is skeletal muscle organized?
tendon –> muscle –> fascicle (muscle fiber bundles) –> muscle fiber –> myofibrils
myofibrils: long rows of myofilaments (contractile thread)
what are the dark bands? the light one? what is the dark line in the light band?
dark bands: A bands
light bands: I bands
dark line: Z disk/Z line
what makes up the sarcomere?
area from one Z disk to another Z disk
is the smallest contractile unit
what is the sliding filament theory?
the Z lines are brought closer together as myofilaments slide past each other
IMPORTANT: myofilaments do not change length
what are transverse tubules (t tubules)?
extension of plasma membrane so the rods inside can receive excitement
what are triads?
2 terminal cisternae + 1 t tubule
are located at junction of A and I bands
what does the all or none principle of contraction mean?
every one (need to specify) will contract or none will
what is a motor unit?
motor neuron and the muscle fiber it innervates
what is the synonymous name for a terminal bouton?
synaptic knob
what does the golgi tendon organ do?
keeps track of how much contraction is happening and if “bad” things are happening
what do muscle spindles do?
are non contractile
keeps track of what is going on in the muscle
PROPRIOCEPTION
what is limited hyperplasia in skeletal muscle?
one response to stress
adding cells
-no mitosis
-satellite cells may give rise to myoblasts if external lamina is intact
what is the primary response in skeletal muscles to stress?
HYPERTROPHY - cells that you have get bigger
myocytes enlarge by addition of proteins
satellite cells fuse with muscle fibers
what are the general characteristics of cardiac muscle?
STRIATED SARCOMERES
autorhythmic contractions –> beats by itself
-modulated by autonomic neurons
-propagated by gap junctions (same as epithelial)
HAS SINGLE, CENTRALLY LOCATED NUCLEUS —> cardiac muscle fibers branch
what are intercalated disks and why are they important?
dark-staining line where intercellular junctions occur
HOW YOU CAN TELL ITS CARDIAC AND NOT SKELETAL
describe the general intercalated disk characteristics
EM: very irregular
transverse portion (where the strength comes from): fascia adherens and desmosomes
longitudinal portion: gap junctions and has less mechanical stress
describe cardiac muscle fibers and the general characteristics?
can be branched or arranged in layers
mononucleated, central nucleus
have HIGH QUANTITY of mitochondria and myoglobin
intercalated discs with gap junctions
large t tubules, spare SR, source of calcium, diad at the Z disc, has sarcomeres and myofibrils
how does cardiac muscle respond to stress?
hyperplasia is negligible
hypertrophy is in response to mechanical stressed (addition of proteins but no satellite cells)
what happens to cardiac muscle in the event of an injury?
cell death and fibrosis (scar tissue)
b/c less contractile than before
describe some general smooth muscle characteristics
-is found in hollow organs, blood vessels, dermis and respiratory passages
NO T TUBULES AND VERY LITTLE SR (calcium source —> mainly extracellular)
what are calveolae?
membrane invaginations that facilitate intake of calcium
slowest contractions
what is this? what shape is it?
smooth muscle
single, central nucleus
NOT STRIATED
why are there crisscross patterns of the myofilaments in smooth muscle?
facilitates contraction of fusiform shape
where is actin anchored at in smooth muscle?
what does it do?
anchored at dense bodies
function similar to Z lines
stabilized by intermediate filaments
what type of nucleus does smooth muscle have?
corkscrew nuclei —> cell twists as it contracts
what are the two types of smooth muscle contraction?
1) multiunit contraction
2) single unit (unitary) contractoin
what is multiunit contraction in smooth muscle?
-muscle functions as multiple units of cells
-each unit innervated by single ANS neuron
-no/few gap junctions
axon terminals in CT, no direct junction with muscle cells
what is single unit (unitary) contraction in smooth muscle?
-all cells contract together as a single unit b/c cells linked by gap junctions
-contractions initiated by mechanical/chemical stimuli and modulated by ANS
-slow, energy efficient contractions
axon terminals in CT, no direct junction with muscle cells
