Flashcards in LEC43: Muscle Tissue Deck (111):
3 types of muscle tissue
smooth, skeletal, cardiac
general functions of muscle tissue
2) maintenance of posture
3) joint stabilization
4) heat generation
special functional characteristics of muscle
muscle only has 1 action: to shorten
shortening generates pulling force
muscle can be excited; nerve fibers cause electrical impulse to travel
muscle can stretch w/ contraction of an opposing muscle
muscle recoils passively after being stretched
skeletal muscle location
attach to, move skeleton
how much of body weight does skeletal muscle comprise?
are skeletal muscle contractions voluntary or involuntary?
which muscle types are striated?
where is cardiac muscle found?
only in wall of the heart
are cardiac muscle contractions voluntary or involuntary?
where is smooth muscle found?
walls of hollow organs
are smooth muscle contractions voluntary or involuntary?
..although some voluntary as well
what does each skeletal muscle have associated w/ it?
1 nerve, 1 artery, 1 vein, which branch repeatedly
what do skeletal muscles connect
1 bone to another
what do skeletal muscles span
at least 1 movable joint, but can span 2 or more joints
where is skeletal muscle origin/insertion re: movement?
origin: the less movable attachment
insertion: pulled toward the origin
do both bones move when skeletal muscle contracts?
no, usually 1 bone moves other remains fixed
where is origin re: insertion (proximal, distal)
origin is proximal to insertion
what is biarticular muscle?
multijoint muscle, when muscles span 2 or more joints, cause movements at 2 joints
what are "fleshy" attachments?
aka direct attachment
attachment so short muscle appears to attach directly to bone
what is indirect attachment?
when connective tissue extends well beyond the muscle
what do most skeletal muscles have attached to them?
tendonous attachment - cordlike
characteristics of skeletal muscle
1) moves skeleton
2) voluntary/conscious control
3) limited regeneration
muscle cell plasma membrane?
sarcolema / plasmalemma
muscle cell ER?
muscle cell cytoplasm?
what comprises a skeletal muscle's motor unit?
1 motor nerve + all the muscle fibers it innervates
how many fibers in a muscle cell?
how is skeletal muscle nucleus?
multinucleated, nuclei are peripherally located, surrounded by endomysium
arrangement of skeletal muscle fiber
fiber surrounded by endomysium
how are skeletal muscle fibers bundled?
fibers grouped into fasicles; surrounded by perimysium
how are several skeletal muscle fasicles grouped?
bundles of fasicles make up a muscle, surrounded by epimysium
what are endomysium, perimysium, epimysium made of?
what is a muscle cell made of?
what are myofibrils made of?
bundles of myofilaments (thin-actin, thick-myosin), organized into sarcomeres
which tissue types are present in a skeletal muscle
- arteries/veins have endothelial cell lining
- nerves have nervous tissue
- CT surrounds muscle cell fibers
what is connective tissue function re: skeletal muscle?
necessary for muscle function, continuous with tendons, muscle attachments distributing force of muscle to bone, skin, etc
what surrounds myofibril?
what are A and I bands named for?
how they rotate polarized light
I: isotropic: same in all drxns
A: anisotropic: diff in all drxns
basic unit of a muscle/myofiber, what allows us to flex
segment between 2 neighboring Z lines
subdivisions of sarcomere?
A band, I band, Z line, H band, M line
actin, myosin filaments
bisects I band
anchors actin, defines border of adjacent sarcomeres
light band, bisects A band
dark line, bisects H band
what type of filaments make up myofibrils?
structure of myosin
2 light chains + ATPase domain + actin-binding domain
how does myosin filament assemble? what is rod structure?
self-assembles into a-helical tail, large bipolar aggregate or filament
what does troponin connect? what is troponin complex made of?
connects to actin a-helices, to tropomyosin between actin filaments
1) calcium binding part
2) inhibitory part-troponin I
3) troponin T, binds to tropomyosin
what covers actin's myosin-binding site?
what is driving force for movement in myosin?
myosin II heads, thru ATPase activity move along actin filament
what connects actin to Z disc?
what connects myosin to Z disc?
where is a-actinin?
incorporated into Z disk
attaches actin to the disk
what is sarcoplasmic reticulum made of?
sarcoplasmic reticulum function?
store Ca++, release it when muscle stimulated to contract
what is continuous with sarcolemma? what is the result?
therefore whole muscle contracts simultaneously (including deep parts)
what are terminal cisternae
cross-channels in sarcoplasmic reticulum
what makes troponins change conformation?
what binds to troponin in muscle contraction? what is result?
Ca++ moves tropomyosin out of the way, bonds to troponin
allows myosin to bind to actin, muscle contraction
what happens if [Ca++] is low?
troponin returns to standard conformation
tropomyosin blocks myosin
no muscle contraction
role of neurotransmitters in muscle contraction, re: calcium?
1) neurotransmitters from motor end plate cause depolarization of sarcollema, including T-tubules
2) depolarization extends to membranes of sarcoplasmic reticulum
3) Ca++ released into sarcoplasm
what happens when Ca++ in sarcoplasm?
binds to Tpn C, separates Tpn I from actin, exposes myosin binding site, contraction cycle begins
what surrounds T tubule and skeletal muscle?
2 terminal cisternae
what makes up the "triad" of the sarcoplasm? where is it?
2 terminal cisternea + T tubule
at the A-I junction
what is the nature of the "triad" in cardiac muscle?
it is a diad
motor end-plate function?
motor end plate of neuromuscular junction impinges on muscle fiber
what happens to A-I band length when muscle contracts?
what kind of movement when actin-myosin bind?
cause of contraction of muscle fiber?
1) Ca++ influx
2) ATP hydrolyzed to ADP + Pi
role of satellite cell in skeletal muscle?
lie within basal lamina
migrate up, make filaments to fill in damaged areas when skeletal muscle damaged
what is myasthenia gravis?
antibodies against Ach receptor bind to receptor, prevent Ach from binding to it, blocks normal nerve-muscle interaction, no muscle firing
clinically, ppl suffer from progressive muscular weakness
how are the fibers in cardiac muscle?
position of nucleus in cardiac muscle?
1-2 central nuclei
do cardiac muscles have satellite cells?
what are features within cardiac muscles?
1) intercalated disks
2) T-tubules at Z lines
how many cells make up a cadiac muscle?
where do cardiac muscle cells join
what is a cardiac muscle "fiber"
long row of joined cardiac muscle cells
what is myocardium
thick bundles of cardiac muscle
what is inherent rhythmicity?
characteristic of cardiac muscle whereby each muscle cell beats separately, without stimulation
cardiac muscle cells are interconnected by specialized membranes with gap junctions which are synchronized electrically in an action potential
how is terminal cisternae arrangement in cardiac muscle?
diad of terminal cisternae join with T tubule at Z line
how does intercalated disc join together cardiac muscle cells?
1) macula adherens
2) gap junction
3) fascia adherens
6 major locations of smooth muscle
1) inside eye
2) walls of vessels
3) respiratory tubes
4) digestive tubes
5) urinary organs
6) reproductive organs
shape of smooth muscle cells?
how many nuclei in smooth muscle cell?
how are smooth muscle cells grouped?
into sheets; often run perpendicular to each other
how do smooth muscles move?
slow, sustained contractions that're resistant to fatigue
which type of muscles do peristalsis?
what stimulates smooth muscle to contract?
can be stretching, hormones; doesn't have to be nervous signal
where is myenteric plexus, what kinds of cells found there?
neuronal ganglion cells
what feature of smooth muscle takes in calcium?
surface caveolae, endocytotic vesicles
what does calcium bind w/ in smooth muscle?
how does smooth muscle contraction cascade work?
Ca-calmodulin complexes > phosphorylation of myosin light chain kinase of myosin rod > conformational change exposing actin binding site of myosin > myosin binds actin > contraction
what are dense bodies?
analogous to z-disks, but in smooth muscle
where are dense bodies?
in smooth muscle
beneath plasma membrane, in cytoplasm's intercytoplasmic surface
what do dense bodies contain?
alpha actinin site of insertion of actin filaments - holds actin in place
does smooth muscle have myosin filaments?
what must occur for myosin to be able to bind actin?
myosin light chain kinase phosphorylates light chains; tail extends; forms bipolar myosin filaments, myosin heads can now bind actin
which muscle tissue type cannot regenerate in adults?
can skeletal muscle tissue regenerate?
nuclei cannot undergo mitosis; tissue can undergo limited regeneration
what in skeletal muscle allows regeneration?
can smooth muscle tissue regenerate?
i.e. uterus enlarges during pregnancy
how many known actin genes?
at least 4
1) cardiac actin
2) skeletal muscle actin
3) vascular smooth muscle actin
4) visceral smooth muscle actin
what causes myopathies
changes in actin gene structure