Sk/ Sm Musc, Bones, Joints Flashcards
smooth muscle is arranged in…
layered sheets that contract in waves
myogenesis
formation of skeletal muscle
muscle fibers form thru the fusion of precursor ______ into multinucleated fibers called _______
myoblasts; myotubes
1st stage of myogenesis
cell cycle exit and commencement of expression of differentiation genes; commitment of stem (satellite) cells into myoblasts
2nd step of myogenesis
alignment of myoblasts
3rd step of myogenesis
cell fusion of myoblasts into myotubes
epimysium surrounds
muscle bundle
perimysium surrounds
fascicle
endomysium surrounds
muscle fiber
sarcoplasmic reticulum surrounds
myofibril
smallest unit of skeletal muscle
sarcomere
skeletal muscle thin filament composed of 3 proteins:
actin, tropomyosin, troponin
G-actin vs F-actin
G-actin: globular protein composing F
F-actin: filamentous, helices
tropomyosin
filamentous protein, blocks myosin binding site at rest, regulator of muscle contraction
troponin general function
the sensor; tells other components when Ca2+ is present
troponin T
attaches troponin to tropomyosin
troponin I
inhibitory; inhibit interaction of actin/myosin by covering myosin binding site
troponin C
calcium binding site; changes conformation to allow actin/myosin binding
thick filaments composed of
myosin
myosin head domain
binds to actin, uses ATP hydrolysis to generate force and “walk” along filament
myosin neck domain
links head and tail, lever arm
myosin tail domain
contains binding sites that determine specific activities of a particular myosin
which filament is anchor? which is moveable scaffold?
anchor= thin
moveable scaffold= thick
Z-disk
end of sarcomere, in center of I-band
A- band
span length of thick filament, some thin filament overlap
I-band
SHORTENS; thin filament and protein only with z-disk in middle
bare zone/ H-zone
no thin filament, M-line in middle
M-line
center of bare zone, connects thick filaments
cytoskeletal proteins (4)
establish architecture of myofibrils; dystrophin, titin, nebulin, alpha actinin
dystrophin
actin binding protein anchors entire myofibril array to cell membrane; defective in muscular dystrophy
titin
extends from z-disc to m-line thru thick filament; has elasticity near z-disc (prevent overcontraction)
nebulin
spans length of thin filament; helps sarcomere have proprioception of thick/thin filaments
alpha actinin
anchors thin filament to z-disk
where is Ca2+ ATPase (SERCA) found?
membrane of SR
function of SERCA
keep intracellular Ca2+ low when muscle at rest
what mechanism translates muscle AP into production of tension
excitation-contraction coupling
how many Ca2+ ions can bind to trop C?
up to 4, each Ca incr trop C’s affinity
what is a crossbridge?
intermolecular bonds between actin and myosin
rigor
actin and myosin tightly bound at rest, rigid
is ATP bound to myosin at beginning of cycle?
no
ATP is hydrolyzed into
ADP and Pi
how far does each cross-bridge move the myosin head?
10nm
what determines amt of tension that a muscle fiber can produce?
number of cross-bridges
which protein is like a rubber band?
titin; must be stretched (delay in force of contraction and relaxation)
single twitch
muscle fiber restimulated after relaxation; 2nd twitch is same magnitude as 1st
twitch summation
if a fiber is restimulated before complete relaxation; 2nd twitch adds to 1st
tetanus
fiber is stimulated so rapidly that it cannot relax at all; maximal sustained contraction
passive tension
tension developed from simply stretching
total tension
when muscle is stimulated to contract at different preloads; sum of active and passive
active tension
force developed during cross-bridge cycling; subtracting passive from total tension
pre-load
position/stretching of muscle prior to contraction
force-velocity relationship is determined by…
allowing the muscle to shorten
weight of the object=
preload
force needed to lift the object against gravity is
afterload
maximal tension
when thick and thin filaments overlap to the greatest degree
we classify muscle based on the _____________
specific myosin heavy chain protein
smooth muscle is found
in the walls of hollow organs: GI tracts, bladder, uterus, vasculature, ureters, bronchioles, eye muscles
2 functions of smooth muscle
produce motility; maintain tension
shape of smooth muscle cells
spindle
what are the 2 intermediate filaments and protein found in dense bodies?
alpha-actinin; vimentin and desmin
where is unitary smooth muscle found
GI tract, bladder, uterus, ureter
where is combination unitary/multiunit smooth muscle found
vasculature
where is multiunit smooth muscle found
iris, ciliary muscles of lens, vas deferens
does unitary or multiunit sm muscle have more precise control during contraction?
multiunit
thin filaments in smooth muscle
calponin and caldesmon
the amount of tension in smooth muscle cells is proportional to ….
amt of intracellular Ca2+
what provides tensile strength between sarcomeres in cardiac muscle?
desmosomes
is cardiac muscle slow or fast twitch?
slow, but cannot be tetanized
are cardiac cells more similar to skeletal or smooth muscle?
skeletal; similar sarcomeres
_______ and _______ regulate levels of calcium and phosphorus by resorption
parathyroid hormone; vitamin D
fluoride provides what kind of strength of bones?
tensile
hydroxyapatite provides _____ strength while collagen provides ______ strength
compressive; tensile
2 types of bone tissue
lamellar, woven
does spongy or compact bone comprise more of the body’s bones?
compact is 80% of bone tissue
which marrow is “mature” marrow?
yellow
what is a growth plate
“physis” - transverse cartilage plate in juvenile bones
how do growth plates add to bone length?
add cartilage to side near joint, other side of plate ossifies; endochondral ossification
epiphysis
cap of spongy bone, usually widest part, from growth plate to articular surface
metaphysis
funnel shaped area of spongy bone connecting growth plate to diaphysis
diaphysis
shaft of bone
long bones are primarily in
extremities
short and flat bones
make up feet, hands, skull, ribs, pelvis, scapula, spine
irregular bones
no easily characterized shape
sesamoid bones
small; commonly found embedded in muscle or tendon near joint surfaces
periosteum
tough cartilaginous membrane covering bone; contains osteoblasts, nerves, blood vessels
components of osteoid
bone matrix and protein fibers
lacunae
tiny pores, osteoblasts get stuck in them and become osteocytes
canaliculi
channels linking osteocytes
which types of bone cells are regulated by parathyroid and vitamin D
osteoclasts and osteoblasts
appositional growth
method by which bones grow; at interface of one surface with another
synarthrosis
no movement (skull)
amphiarthrosis
limited twisting or sliding (vertebrae)
diarthrosis
allows full motion (fingers)
fibrous joints
synarthroses join bone by fibrous tissue; no space
cartilaginous joints
amphiarthroses join bones by cartilage; no space, limited movement
synovial joints
diarthroses join bones by ligaments (joint space, large range of motion)
where is bursae found (2)
between tendon/bone;
between skin/bony protuberance
