Exam 4: Muscular System Flashcards
functions of muscular system (4)
movement
support
protection
thermoregulation
components of muscular system (2)
skeletal muscle
tendons
tendons
attach muscle to bone
2 ways to classify muscle tissue
structure and function
2 ways to classify muscle tissue by structure
striated and smooth
striated muscle tissue types (3)
skeletal: attached to bone, multinucleated
visceral: identical to skeletal, but restricted to soft tissue
cardiac: heart muscle , one nucleus
smooth muscle tissue
makes up majority of visceral organs
- always one nucleus
all tissue has contractile units in them, ______ gives them pattern
arrangement of cells
2 function types of muscle tissue
voluntary and involuntary
voluntary muscle tissue
skeletal
visceral striated
involuntary muscle tissue
smooth: cannot control blood vessel walls or digestive system or bladder (sphincters in bladder are visceral striated - voluntary)
cardiac
muscle fiber
individual cell
endomysium
wraps around each individual muscle cell
fassicle
bundle of muscle cells - protective connective tissue
perimysium
wraps around perimeter of muscle cells
epimysium
connective tissue around entire functioning organ
why are tendons so strong, do not rip?
- has endomysium, perimysium, epimysium throughout the ENTIRE organ
- connective tissue throughout entire thing, wrapping all the way through it
- have extensions from all cells
what stimulates transformation of mesenchymal cells into myoblasts
myogenic regulating factors (MRFs)
MRF4
blocks the ones that do final differentiation into type of muscle cell you will be
- keep getting lots of myoblasts
7th week embryology
- starting to get endochondral bone formation
- get condensation of myoblasts
(cannot form bones until endochondral bone formation with perichondral - need dense bone tissue) - once start forming limbs myoblasts migrate to where arms and legs will be
myoblasts are spindle-shaped cells that fuse together forming…
multi-nucleated myotubes
initial myotubes formed by myoblasts migrating to….
connective tissue fibers
fusion of myoblasts stimulates the production of ____
myofibrils
what does initial migration and myotube formation provide for the muscle?
primary framework
what increases muscle size?
innervation of primary fibers causes small contractions which attracts more myoblasts and activated fusion which inc muscle
2 things needed to get a good muscle
innervation and a good blood supply
poland syndrome
occurs when there is a disruption in blood supply to embryonic tissue
- results in missing or abnormal pectoralis major muscle
- losing muscle
why would poland syndrome be unilateral?
can have blood supply to one side but it can also sill reach other side
- recognized at birth (congenital)
not genetic
why in Poland syndrome severe cases can you get incomplete formation of limb?
bad blood flow
bones are highly vascular
- not getting signal or blood supply can cause bone to be compromised
myosatelite cells
quiescent
- when there is damage they are activated with growth factors, can help repair damage
thick filament in sarcomere
myosin
thin filament in sarcomere
actin
Binding role of myosin
- can bind 2 things but not at same time (actin and ATP)
- when it binds ATP, it has enzymatic ability and can hydrolyze and release high energy bond allowing for movement (pivot of the head)
2 ways myosin is stabilized
- titin
2. myomeseum
one long molecule from z line through the filament to another z line
- anchors to both sides of sarcomere
titin
protein down the center, secured at the M line
myomesium
structure of actin
2 strings of actin twisted in helix around itself
how is actin anchored to the Z line?
actinin
- does not go through whole molecule, only attached at one end
- hooks to Z line
what is the anchor of actin?
nebulin - hooks to Z line
how are actin and myosin regulated?
tropomyosin and troponin
tropomyosin
blocks interaction of actin and myosin
when muscle is relaxed what form is tropomyosin in?
blocking position
what happens with tropomyosin when you want to contract a muscle?
- need to get tropomyosin out of the way
- conformational change in tropomyosin by release of Calcium
- troponin binds Ca and changes shape
- since troponin attached to tropomyosin shape is changes and tropomyosin slides out of the way
A band
length of thick filament
- should not change with contraction bc thick filament dos not change in length
I band
z line down center
thin filament not overlapped by thick
- bigger when not contracting
what happens to H and I bands when muscle contracts
they get smaller bc they overlap
H zone/band
down the center is the M line
on either side is myosin - not overlapped
if not contracting, less thick band has thin pulled over it
just see thick filament!!
How do we get the sarcomere to contract? - a few steps
- get nerve impulse to muscle, depolarizing the membrane which releases internal store of calcium
- Ca binds troponin
- conformational changes in troponin moves tropomyosin out of blocking position
- myosin binding site exposed
Cross bridge formation - may steps
- binding site available, myosin heads have ATP, it hydrolyzes ATP giving it a power stroke, the head comes up and gets closer, eventually get connection
- myosin heads bind to actin forming cross bridge
- myosin cross bridges rotate to center of sarcomere
- as myosin heads bind ATP, the cross bridges detach from actin
cross bridge formation: once movement arc done, it will have inc affinity for ATP and release ____ is ATP available
it will bind ATP and the head will go back down and have a higher affinity for ____
myosin
actin
are the heads on the filament synchronized?
NO
- if they were you would not get any movement
the stringer the nerve impulse…
the longer Ca can remain, the longer sites are available for binding, tight contraction
when you relax muscles, the signal stops and what happens to the Ca?
it goes back into storage
where is Ca stored during muscle relaxation?
terminal cisternae
when muscle is stimulated, action potential transmitted to sarcomere by_____
transverse tubule (T tubule)
when calcium is released from terminal cisternae, what does it travel to to get to the sarcomere?
open-ended longitudinal tubules
sarcoplasmic reticulum
Ca storage
Ca pumps in the membrane
- released so much Ca it cannot pull it back in at once
- when depolarization stops, pumps recapture Ca and put back into storage in terminal cisternae - active transport to restore Ca
cardiac muscle vs. skeletal muscle
- cardiac = branched
- cardiac is stored in enlarged T-tubules (no triad formation)
- Cardiac requires BOTH intracellular and extracellular sources
triad
fusion of T-tubules
2 terminal cisternae and 1 t tubule
is cardiac considered part of the muscle system?
no
if high or low Ca in danger of…
heart attack
cardiac has no individual innervation
troponin in heart binds bc of shape one less Ca than in skeletal muscle - can do blood test to see if heart attack - cells die and release contents into blood
2 main diff between cardiac and skeletal muscle
- how it stores/uses Ca
- troponin diff no innervation in cardiac
smooth muscle vs. skeletal muscle
- intermediate filaments, vimentin and desmin, connect sarcomeres to dense bodies and desmosomes
- troponin replaced with caldesmon (does not directly bind Ca)
- Ca stored in caveoli (no other sarcoplasmic structures exist)
- smooth contraction dependent on influx of extracellular Ca
smooth muscle vs. skeletal muscle
- intermediate filaments, vimentin and desmin, connect sarcomeres to dense bodies and desmosomes
- troponin replaced with caldesmon (does not directly bind Ca)
- Ca stored in caveoli (no other sarcoplasmic structures exist)
- smooth contraction dependent on influx of extracellular Ca
vimentin and desmin
help connect to dense bodies
hold sarcomere together
- not z lines but similar
What do calveoli do when depolarized in smooth muscle?
release calcium into cytoplasm
NOT directly into sarcomere
- second messenger system binds Ca
How is caldesmon diff than troponin?
it is removed off tropomyosin by second messengers like calmodulin
which muscle type is the influx of calcium bound by calmodulin?
smooth muscle
what are the 2 actions of the calcium-calmodulin complex?
- complex activated myosin light chain kinase (MLCK) and removes caldesmon from tropomyosin
- MLCK activates ATPase activity in myosin head ad cross-bridge formation occurs
which muscle type is the only one with individual innervation?
skeletal
