Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
132 Cards in this Set
- Front
- Back
|
actin-binding protein
comprises Z disc |
alpha-actinin
|
|
|
band where actin and myosin overlap
|
A-band
|
|
|
appearance depends on direction
|
anisotropic
|
|
|
thin filaments
attach to myosin during contraction |
actin
|
|
|
band with myosin but no actin
|
H-band
|
|
|
appears the same from different directions
|
isotropic
|
|
|
just actin
|
I-band
|
|
|
attachment of myosin molecules
|
M-line
|
|
|
thick filaments of the A band
attach to actin during contraction |
Myosin
|
|
|
possibly regulates actin filament length during sarcomere assembly
|
nebulin
|
|
|
largest known protein 3000kD
helps maintain the resting length of the sarcomere |
titin
|
|
|
attachment of the actin filaments
division between sarcomeres |
Z-disk
|
|
|
actin filament is a
|
alpha-actin double stranded polymer
|
|
|
regulates the binding of myosin head groups in actin
|
tropomyosin
|
|
|
heterotrimer TnT TnC and Tnl
|
troponin
|
|
|
binds to tropomyosin
|
TnT
|
|
|
binds Ca
|
Tnc
|
|
|
binds to actin and inhibits contraction
|
TnI
|
|
|
how many heavy chains is myosin composed of
|
2 intertwined
|
|
|
3 regions of heavy chain
|
tail hinge head
|
|
|
how many light chains are in myosin
|
4
2 alkali 2 regulatory |
|
|
what do alkali light chains do
|
stabilize the head region
|
|
|
what do regulatory light chains do
|
regulate the ATPase activity of myosin
|
|
|
where to head groups of myosin attach
|
binding sites on actin
|
|
|
same length of muscle
tension varies M = muscle |
isometric
|
|
|
same amount of tension
muscle can contract and shorten T = Tension |
isotonic
|
|
|
no overlap of actin and myosin
|
I band
|
|
|
muscle cells contain _ that consist of repeating units called _
|
myofibrils
sarcomeres |
|
|
muscles made up of these fascicles that go the _ length from _ to _
|
entire
ligament to ligament |
|
|
do any filaments get shorter during contraction?
|
NO
|
|
|
what are they doing in contracted state
|
sliding over one another
|
|
|
what brings action potential into the muscle cell
|
T tubules
|
|
|
SR close proximity to T tubule responds to AP by
|
opening up Ca channels
Ca moves from higher concentration inside SR to inside the cell cytoplasm |
|
|
Ca allows what to occur
|
interaction b/w myosin and actin filaments
contraction |
|
|
what concludes contraction
|
Ca pumped back into SR
|
|
|
Ca binds actin in a
|
troponin complex with 3 subunits
|
|
|
in absence of Ca _ covers the myosin binding site
|
TnI
|
|
|
Ca binds to _ affinity site on TnC
|
low
|
|
|
what does this do
|
conformational change that uncovers the binding site
|
|
|
Ca is removed from cell, _ release the bound Ca
|
low affinity sites on TnC
|
|
|
Cycle of actin and myosin
|
1. attached state - then ATP will bind to myosin head causes dissociation of actin from myosin
2. ATP is hydrolyzed into ADP and phosphate, causes myosin head to return to resting conformation ALSO CALLED COCKED STATE 3. cross bridge forms b/w actin and myosin but on a new position (moved up) 4. phosphate released causes myosin head group to change conformation with resulting power stroke 5. ADP is released to get back to starting |
|
|
what causes dissociation of actin-myosin complex
|
ATP binding
|
|
|
what moves the actin and myosin in relation to eachother
|
power stroke
|
|
|
myosin head's resting conformation
|
cocked state
|
|
|
termination of contraction requires
|
reuptake of Ca
|
|
|
most important mechanism by which cell returns intracellular [Ca] to resting levels
|
reuptake into SR
|
|
|
principal Ca-binding protein in skeletal muscle
|
calsequestrin
|
|
|
found in smooth muscle
Ca binding protein |
Calreticulin
|
|
|
minor mechanism for Ca removal from the cytoplasm
what 2 are they? |
extrusion of Ca across the cell membrane
Na-Ca exchanger Ca-H pump (requires ATP) |
|
|
Ca pump on SR requires
|
ATP
|
|
|
why is SR major mechanism for Ca
|
keep Ca in cell for immediate use
|
|
|
no overlap b/w myosin and actin
|
no tension
|
|
|
typical length of sarcomere
|
1.5-3 micrometers
|
|
|
T/F shorter the sarcomere is getting, more its contracting, more tension getting within sarcomere
|
TRUE
|
|
|
MAX tension develops when?
|
every myosin head group able to bind to actin
|
|
|
do you get any more tension after max?
does it still shorten? |
NO
YES |
|
|
what can happen to tension with too much shortening of sarcomere
|
decrease
|
|
|
bone contain _ salt?
|
70%
|
|
|
major salt?
whats it made up of? |
hydroxyapatite
calcium and phosphate Ca10(PO4)6(OH)2 |
|
|
Is Ca or P regulated tighter?
|
Ca
due to cell signaling functions phosphate fluctuates through the day - after meals |
|
|
Ca and P homeostasis tied to each other via?
|
hydroxyapatite
regulated by same hormones: PTH calcitrol calcitonin |
|
|
which one increases blood calcium levels and activates osteoclasts
|
PTH
|
|
|
which one decreases blood calcium levels and activates osteoblasts
|
calcitonin
|
|
|
inhibits hydroxyapatite crystals to form in other tissues besides bone despite states of supersaturation of the ions?
|
pyrophosphate
|
|
|
major dietary source of Ca
|
dairy products
|
|
|
in plasma Ca exists in 3 forms
|
1. 45% free, ionized
2. 45% ions associated with proteins 3. 10% bound to low molecular weight organic ions (citrate and oxalate) |
|
|
how much Ca coming in through diet
|
1000 mg/day
|
|
|
how much absorbed through gut
|
500 mg/day
|
|
|
how much total removed via feces
|
825 mg/day
|
|
|
ECF concentration of calcium
Bone pool of calcium |
1000 mg/day
1000 GRAMS |
|
|
how much Ca used in formation and resorption of bone per day
|
BOTH 280 mg/day
same form as resorb |
|
|
ECF calcium is recycled through _
how many times/day |
kidneys
10 total filtered is 10,000 mg/day |
|
|
how much is reabsorbed through kidneys?
how much actually excreted through urine? total amount excreted? total amount entering? |
9825 mg/day
175 mg/day 1000 mg/day 1000 mg/day |
|
|
major source of dietary phosphates
|
dairy products
|
|
|
how does phosphates in soft tissue exist?
|
phospholipids, phosphoproteins, nucleic acids, and nucleotides
|
|
|
how much phosphate enters body?
how much excreted from body? how much excreted from urine? from feces? |
1400 mg/day
1400 mg/day 900 mg/day 500 mg/day |
|
|
out of 1400 entering body how much is absorbed through gut
|
1100 mg/day
|
|
|
how much goes to bone formation?
how much goes to bone resorption? |
210 mg/day
210 mg/day |
|
|
ECF phosphate pool
Bone pool of phosphate |
500 mg/day
600 GRAMS |
|
|
filtered through kidneys?
reabsorbed through kidneys? |
7000 mg/day
6100 mg/day |
|
|
form by which it is filtered
|
plasma
|
|
|
how much phosphate is soft tissues?
|
100 GRAMS
|
|
|
average long bone (compact, cortical) contains
|
70% salts
30% matrix |
|
|
Matrix
|
90-95% collagen
remainder is gelatinous medium with ECF and proteoglycans (chondroitan sulfate and hyaluronic acid) |
|
|
secrete matrix (osteoid)
|
osteoblasts
|
|
|
lining cells
|
quiescent osteoblasts
|
|
|
surrounded by osteoid
|
osteocytes (were osteoblasts)
|
|
|
osteocytes are connected by _ which allows cellular communication through _
|
canaliculi
gap junctions |
|
|
trabecular has how much more surface area then cortical region
|
5X
|
|
|
repeating units within cortex
|
osteons
|
|
|
center of osteons
|
haversian canal
contains blood vessels |
|
|
when can rate of deposition exceed rate of absorption?
|
mechanical stresses signal the need for more bone
|
|
|
rate of absorption exceeds rate of deposition?
|
microgravity or disuse
|
|
|
average amount of bone surfaces (internal and external) being remodeled at any given time
|
4%
|
|
|
where does most of bone remodeling take place
|
trabecular bone (has osteoblasts and osteoclasts on surface)
|
|
|
when osteocytes sense mechanical stress on bone what do they secrete?
|
growth factors that stimulate osteoblasts and lining cells
|
|
|
what other role do they play
|
transfer of mineral from interior of bone to growth surface
|
|
|
what acts on osteoblasts that causes them to release macrophage stimulating factor
|
vitamin D
PTH |
|
|
what does this factor do
|
differentiation of stem cells into osteoclast precursors which then become mononuclear osteoclasts then multinuclear osteoclasts
|
|
|
what stimulates osteoclasts
|
IL-6
RANK ligand |
|
|
degradation of bone by osteoclasts is done by?
|
acid (H)
proteases (lysosomal enzymes) phosphatases (TRAP) |
|
|
what is involved in sealing osteoclasts to bone
|
integrins on osteoblast
binds to vitronectin on bone |
|
|
inhibits bone resorption?
promotes bone resorption? |
PKA
cytokines |
|
|
osteoclasts exists in small masses that eat at bone for how long?
|
2-3 weeks
|
|
|
osteoclasts build?
osteoblasts infiltrate and do what? |
tunnels 0.2-1 mm in diameter
deposit new bone in successive layers |
|
|
bone-remodeling units
|
osteons
|
|
|
how often are they replaced
|
6-9 months
|
|
|
T/F Haversian canal at center of osteon is remodeled as well
|
FALSE
remains untouched |
|
|
percent of total adult bone mass turns over each year
|
10%
|
|
|
which bone turns over more slowly
|
cortical 4%
trabecular is quicker 28% |
|
|
what cleans up material digested by osteoclasts
|
macrophages
|
|
|
life span of osteoclasts?
osteoblasts? osteocytes? |
2 weeks
3 months 20 years |
|
|
what gives rise to osteoclasts?
|
hematopoietic stem cells
(also give rise to monocytes) |
|
|
what gives rise to osteoblasts?
|
mesenchymal cells
|
|
|
Calcium salts on surface of collagen fibers form what?
|
small nidi
nodes 2nd step |
|
|
nodes grow over days to weeks into finished product which is?
|
hydroxyapatite crystals
|
|
|
T/F initial calcium salts are hydroxyapatite?
|
FALSE
amorphous non-crystalline mixture of calcium, phosphate, and water |
|
|
processes that reshape salts into hydroxyapatite crystals
|
addition and substitution
|
|
|
what neutralizes the pyrophosphate inhibitor and what secretes it
|
osteoblasts secrete a substance into osteoid
|
|
|
3 types of MS lever systems
|
1st, 2nd, 3rd classes
|
|
|
rigid bar that moves (bone)
|
lever
|
|
|
fixed point (joint)
|
fulcrum
|
|
|
applied force used to move a resistance (muscle)
|
effort
|
|
|
resistance
|
load
|
|
|
Ex of 1st class
where is the fulcrum? |
skull on vertebral column
fulcrum is in the middle b/w the effort and load |
|
|
Ex of 2nd class
|
ankle
load is in b/w the effort and fulcrum |
|
|
Ex of 3rd class
|
elbow
effort is b/w the fulcrum and load |
|
|
amount of effort depends on
|
relative positions of load, fulcrum, and effort
|
|
|
equation for lever systems
|
effort x distance to fulcrum = load x distance to fulcrum
|
|
|
what class works as a mechanical disadvantage
|
3rd
|
|
|
which work as mechanical advantage
|
1st and 2nd
|
|
|
what would require you to exert less effort with a 3rd class
|
move effort toward the load
less distance between them |
