what are t tubules
extensions of plasma membrane justaposed with terminal cisternae
part of the sarcoplasmic reticulum
what type of muscle has a triad
1 t tubule and 2 terminal cisternae in skeletal muscle
what type of muscle has a diad
1 t tubule and 1 terminal cisternae in cardiac muscle
roel of t tubule in muscle contraction pelase
after ach released from opening of vg Ca in presynaptic and binds on post synaptic membranes causing cell depol in the motor end plate - depolarization travels along muscle cell and dowon the t tubule
whats the roel of the dihydropyridine receptors in muscle contraction
are activated by depol from t tubules = mechanically couples to the ryanodine receptors ont eh SR – results in conformational change in teh RYR that causes Ca release from teh SR
what happens after RYR receptors permit Ca out of the SR
release Ca binds to troponin C = leads to conformational change that moves torpomyosin out of the myoisn binding groove on actin filaments
why cany myosin and actin interact when there is no calcium around
troponin C and Ca move tropomyosin out of the myosin binding grooves on the actin filaments
what happens when myosin release ADP and organic Pi
displacement of myosin on the actin filamemt - poser stroke = contraction
what changes size in contraction
NOT THE A BAND H band I band length or sarcomere Z lines move towards the M line
what happens when new ATP binds myosin
causes detachement of myosin head from actin
what happens when ATP hydrolyzes to form ADp and Pi bound to mysoin
resets into cocked/high energy position ready for the next contraction cytle
what happens when mysoin releases ADP and PI
power stroke, release from high energy state/cocked position and causes contraction
describe role of ATP and myosin head
ATP bound = detaches myosin from actin
ATP hydrolyzes to form ADP and PI that are still bound to myosin = assumes high energy/cocked position
ADP and PI leave myosin - binds to actin and causes contraction leaving the high energy/cocked position.
list the components of a sarcomere and what each represents pelase
H band- part of A band/mysoin heavy chains that is not interacting with actin chains
I band - width of actin not interacting with myosin. contains the Z line
A band - width of myosin heavy chainns, contains the mysoin chains and the H band and the M line
M line = connection of myosin heavy chaings
I line - connection of actin heavy chaings
H band decreases as more mysoin is interacting with actin
I band decreases as more actin is interacting with mysoin
A band - samezees
boundaries of the sarcomere
Z line to Z line. hurah.
on Em describe apperance of sarcomere
Z lines - darkest
I band - lighest area on both sides of Z line
H band - pale region around medium gray M line
M line - medim gray in middle of A band
A band - medium gray with H band and M line between I band.
type 1 or type 2 fibres: slow twitch
one
type 1 or type 2 fibres: fast twitch
two
type 1 or type 2 fibres: red
one
type 1 or type 2 fibres: white
two
type 1 or type 2 fibres: lots of mitochondria
one
type 1 or type 2 fibres: lots of myoglobin
one
type 1 or type 2 fibres: oxidative phosphorylation
one
type 1 or type 2 fibres: anaerboic glycosylation
two
type 1 or type 2 fibres: increased at weight lifiting
hypertrophy of two
type 1 or type 2 fibres: sustained contraction
one
one slow ox
type one
describe the relaxation of smooth muscle
NO - causes GC to convert GTP to cGMP - causes activation of MLCP - MLCP dephosphorylates myosin = relxation
describe the contraction of smooth muscle
action potential opens L tyep vg CA channels - increases intracellualr calcium - complex of CA and calmodulin forms - causes activation of MLCK - phosphorylates myosine - myopsin-p + action = contraction via cross bidging
what is endochondral ossification
cartilaginous modle of bones first made by chondrocytes – osteoblasts and clasts then replace with woven bone and then remodel that to lamellar bone
what bones undergo endochondral ossification
axial and appendicular skeleton and base of skull
what pathos has woven boneÉ
pagets disease - woven bone - pathologica fractures
what is membranous ossification
no cartiliginous modle. woven bone is formed directly and is then converted to lamellar bone.
what bones undergo membranous ossification
calvarium and facial bones
name that bone cell: secrete collagen and catalyze mineralization
osteoblasts
name that bone cell: multinucleated cells
osteoclasts
name that bone cell: seceted acid and collagenases
osteoclasts
name that bone cell: differentiate from mesenchyme in stem cells of periostem
osteoblasts
name that bone cell: diffferentiated from monocytes/macropahges
osteoclasts
what effect does PTH have on bone at low, intermittent levels
exerts anabolic effects/building of bone on osteoblasts and clasts (indirectly)
what happens when PTH levels are chronically elevated
cause catabolic effects ie osteitis fibrosa cystica in primary hyperparathyroidisim
effect of estrogen on bone
inhibits apoptosis of blasts
allows apoptosis of clasts
what happens to bone when estrogen is def
surgery or post menopausal
excess cycles of remodelling and bone resorption = osteoporosis.